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Paraplegia, the loss of sensation and voluntary motor control after serious spinal cord damage, may be accompanied by girdle pain at the level of the spinal cord damage, visceral pain evoked by a filling bladder or bowel, or, in five to ten per cent of paraplegics, phantom body pain in areas of complete sensory loss. This phantom body pain is initially described as burning or tingling but may evolve into severe crushing or pinching pain, or the sensation of fire running down the legs or of a knife twisting in the flesh. Onset may be immediate or may not occur until years after the disabling injury. Surgical treatment rarely provides lasting relief.
People with long-term pain frequently display psychological disturbance, with elevated scores on the Minnesota Multiphasic Personality Inventory scales of hysteria, depression and hypochondriasis (the "neurotic triad"). Some investigators have argued that it is this neuroticism that causes acute pain to turn chronic, but clinical evidence points the other way, to chronic pain causing neuroticism. When long-term pain is relieved by therapeutic intervention, scores on the neurotic triad and anxiety fall, often to normal levels. Self-esteem, often low in chronic pain patients, also shows improvement once pain has resolved.
Breakthrough pain is transitory acute pain that comes on suddenly and is not alleviated by the patient's normal pain management. It is common in cancer patients who often have background pain that is generally well-controlled by medications, but who also sometimes experience bouts of severe pain that from time to time "breaks through" the medication. The characteristics of breakthrough cancer pain vary from person to person and according to the cause. Management of breakthrough pain can entail intensive use of opioids, including fentanyl.
Although unpleasantness is an essential part of the IASP definition of pain, it is possible to induce a state described as intense pain devoid of unpleasantness in some patients, with morphine injection or psychosurgery. Such patients report that they have pain but are not bothered by it; they recognize the sensation of pain but suffer little, or not at all. Indifference to pain can also rarely be present from birth; these people have normal nerves on medical investigations, and find pain unpleasant, but do not avoid repetition of the pain stimulus.
A much smaller number of people are insensitive to pain due to an inborn abnormality of the nervous system, known as "congenital insensitivity to pain". Children with this condition incur carelessly-repeated damage to their tongues, eyes, joints, skin, and muscles. Some die before adulthood, and others have a reduced life expectancy.[citation needed] Most people with congenital insensitivity to pain have one of five hereditary sensory and autonomic neuropathies (which includes familial dysautonomia and congenital insensitivity to pain with anhidrosis). These conditions feature decreased sensitivity to pain together with other neurological abnormalities, particularly of the autonomic nervous system. A very rare syndrome with isolated congenital insensitivity to pain has been linked with mutations in the SCN9A gene, which codes for a sodium channel (Nav1.7) necessary in conducting pain nerve stimuli.
In 1644, René Descartes theorized that pain was a disturbance that passed down along nerve fibers until the disturbance reached the brain, a development that transformed the perception of pain from a spiritual, mystical experience to a physical, mechanical sensation[citation needed]. Descartes's work, along with Avicenna's, prefigured the 19th-century development of specificity theory. Specificity theory saw pain as "a specific sensation, with its own sensory apparatus independent of touch and other senses". Another theory that came to prominence in the 18th and 19th centuries was intensive theory, which conceived of pain not as a unique sensory modality, but an emotional state produced by stronger than normal stimuli such as intense light, pressure or temperature. By the mid-1890s, specificity was backed mostly by physiologists and physicians, and the intensive theory was mostly backed by psychologists. However, after a series of clinical observations by Henry Head and experiments by Max von Frey, the psychologists migrated to specificity almost en masse, and by century's end, most textbooks on physiology and psychology were presenting pain specificity as fact.
In 1955, DC Sinclair and G Weddell developed peripheral pattern theory, based on a 1934 suggestion by John Paul Nafe. They proposed that all skin fiber endings (with the exception of those innervating hair cells) are identical, and that pain is produced by intense stimulation of these fibers. Another 20th-century theory was gate control theory, introduced by Ronald Melzack and Patrick Wall in the 1965 Science article "Pain Mechanisms: A New Theory". The authors proposed that both thin (pain) and large diameter (touch, pressure, vibration) nerve fibers carry information from the site of injury to two destinations in the dorsal horn of the spinal cord, and that the more large fiber activity relative to thin fiber activity at the inhibitory cell, the less pain is felt. Both peripheral pattern theory and gate control theory have been superseded by more modern theories of pain[citation needed].
In 1968 Ronald Melzack and Kenneth Casey described pain in terms of its three dimensions: "sensory-discriminative" (sense of the intensity, location, quality and duration of the pain), "affective-motivational" (unpleasantness and urge to escape the unpleasantness), and "cognitive-evaluative" (cognitions such as appraisal, cultural values, distraction and hypnotic suggestion). They theorized that pain intensity (the sensory discriminative dimension) and unpleasantness (the affective-motivational dimension) are not simply determined by the magnitude of the painful stimulus, but "higher" cognitive activities can influence perceived intensity and unpleasantness. Cognitive activities "may affect both sensory and affective experience or they may modify primarily the affective-motivational dimension. Thus, excitement in games or war appears to block both dimensions of pain, while suggestion and placebos may modulate the affective-motivational dimension and leave the sensory-discriminative dimension relatively undisturbed." (p. 432) The paper ends with a call to action: "Pain can be treated not only by trying to cut down the sensory input by anesthetic block, surgical intervention and the like, but also by influencing the motivational-affective and cognitive factors as well." (p. 435)
Wilhelm Erb's (1874) "intensive" theory, that a pain signal can be generated by intense enough stimulation of any sensory receptor, has been soundly disproved. Some sensory fibers do not differentiate between noxious and non-noxious stimuli, while others, nociceptors, respond only to noxious, high intensity stimuli. At the peripheral end of the nociceptor, noxious stimuli generate currents that, above a given threshold, begin to send signals along the nerve fiber to the spinal cord. The "specificity" (whether it responds to thermal, chemical or mechanical features of its environment) of a nociceptor is determined by which ion channels it expresses at its peripheral end. Dozens of different types of nociceptor ion channels have so far been identified, and their exact functions are still being determined.
The pain signal travels from the periphery to the spinal cord along an A-delta or C fiber. Because the A-delta fiber is thicker than the C fiber, and is thinly sheathed in an electrically insulating material (myelin), it carries its signal faster (5–30 m/s) than the unmyelinated C fiber (0.5–2 m/s). Pain evoked by the (faster) A-delta fibers is described as sharp and is felt first. This is followed by a duller pain, often described as burning, carried by the C fibers. These first order neurons enter the spinal cord via Lissauer's tract.
Spinal cord fibers dedicated to carrying A-delta fiber pain signals, and others that carry both A-delta and C fiber pain signals up the spinal cord to the thalamus in the brain have been identified. Other spinal cord fibers, known as wide dynamic range neurons, respond to A-delta and C fibers, but also to the large A-beta fibers that carry touch, pressure and vibration signals. Pain-related activity in the thalamus spreads to the insular cortex (thought to embody, among other things, the feeling that distinguishes pain from other homeostatic emotions such as itch and nausea) and anterior cingulate cortex (thought to embody, among other things, the motivational element of pain); and pain that is distinctly located also activates the primary and secondary somatosensory cortices. Melzack and Casey's 1968 picture of the dimensions of pain is as influential today as ever, firmly framing theory and guiding research in the functional neuroanatomy and psychology of pain.
In his book, The Greatest Show on Earth: The Evidence for Evolution, biologist Richard Dawkins grapples with the question of why pain has to be so very painful. He describes the alternative as a simple, mental raising of a "red flag". To argue why that red flag might be insufficient, Dawkins explains that drives must compete with each other within living beings. The most fit creature would be the one whose pains are well balanced. Those pains which mean certain death when ignored will become the most powerfully felt. The relative intensities of pain, then, may resemble the relative importance of that risk to our ancestors (lack of food, too much cold, or serious injuries are felt as agony, whereas minor damage is felt as mere discomfort). This resemblance will not be perfect, however, because natural selection can be a poor designer. The result is often glitches in animals, including supernormal stimuli. Such glitches help explain pains which are not, or at least no longer directly adaptive (e.g. perhaps some forms of toothache, or injury to fingernails).
Differences in pain perception and tolerance thresholds are associated with, among other factors, ethnicity, genetics, and sex. People of Mediterranean origin report as painful some radiant heat intensities that northern Europeans describe as nonpainful. And Italian women tolerate less intense electric shock than Jewish or Native American women. Some individuals in all cultures have significantly higher than normal pain perception and tolerance thresholds. For instance, patients who experience painless heart attacks have higher pain thresholds for electric shock, muscle cramp and heat.
A person's self-report is the most reliable measure of pain, with health care professionals tending to underestimate severity. A definition of pain widely employed in nursing, emphasizing its subjective nature and the importance of believing patient reports, was introduced by Margo McCaffery in 1968: "Pain is whatever the experiencing person says it is, existing whenever he says it does". To assess intensity, the patient may be asked to locate their pain on a scale of 0 to 10, with 0 being no pain at all, and 10 the worst pain they have ever felt. Quality can be established by having the patient complete the McGill Pain Questionnaire indicating which words best describe their pain.
The Multidimensional Pain Inventory (MPI) is a questionnaire designed to assess the psychosocial state of a person with chronic pain. Analysis of MPI results by Turk and Rudy (1988) found three classes of chronic pain patient: "(a) dysfunctional, people who perceived the severity of their pain to be high, reported that pain interfered with much of their lives, reported a higher degree of psychological distress caused by pain, and reported low levels of activity; (b) interpersonally distressed, people with a common perception that significant others were not very supportive of their pain problems; and (c) adaptive copers, patients who reported high levels of social support, relatively low levels of pain and perceived interference, and relatively high levels of activity." Combining the MPI characterization of the person with their IASP five-category pain profile is recommended for deriving the most useful case description.
When a person is non-verbal and cannot self-report pain, observation becomes critical, and specific behaviors can be monitored as pain indicators. Behaviors such as facial grimacing and guarding indicate pain, as well as an increase or decrease in vocalizations, changes in routine behavior patterns and mental status changes. Patients experiencing pain may exhibit withdrawn social behavior and possibly experience a decreased appetite and decreased nutritional intake. A change in condition that deviates from baseline such as moaning with movement or when manipulating a body part, and limited range of motion are also potential pain indicators. In patients who possess language but are incapable of expressing themselves effectively, such as those with dementia, an increase in confusion or display of aggressive behaviors or agitation may signal that discomfort exists, and further assessment is necessary.
The experience of pain has many cultural dimensions. For instance, the way in which one experiences and responds to pain is related to sociocultural characteristics, such as gender, ethnicity, and age. An aging adult may not respond to pain in the way that a younger person would. Their ability to recognize pain may be blunted by illness or the use of multiple prescription drugs. Depression may also keep the older adult from reporting they are in pain. The older adult may also quit doing activities they love because it hurts too much. Decline in self-care activities (dressing, grooming, walking, etc.) may also be indicators that the older adult is experiencing pain. The older adult may refrain from reporting pain because they are afraid they will have to have surgery or will be put on a drug they might become addicted to. They may not want others to see them as weak, or may feel there is something impolite or shameful in complaining about pain, or they may feel the pain is deserved punishment for past transgressions.
Cultural barriers can also keep a person from telling someone they are in pain. Religious beliefs may prevent the individual from seeking help. They may feel certain pain treatment is against their religion. They may not report pain because they feel it is a sign that death is near. Many people fear the stigma of addiction and avoid pain treatment so as not to be prescribed potentially addicting drugs. Many Asians do not want to lose respect in society by admitting they are in pain and need help, believing the pain should be borne in silence, while other cultures feel they should report pain right away and get immediate relief. Gender can also be a factor in reporting pain. Sexual differences can be the result of social and cultural expectations, with women expected to be emotional and show pain and men stoic, keeping pain to themselves.
The International Association for the Study of Pain advocates that the relief of pain should be recognized as a human right, that chronic pain should be considered a disease in its own right, and that pain medicine should have the full status of a specialty. It is a specialty only in China and Australia at this time. Elsewhere, pain medicine is a subspecialty under disciplines such as anesthesiology, physiatry, neurology, palliative medicine and psychiatry. In 2011, Human Rights Watch alerted that tens of millions of people worldwide are still denied access to inexpensive medications for severe pain.
Sugar taken orally reduces the total crying time but not the duration of the first cry in newborns undergoing a painful procedure (a single lancing of the heel). It does not moderate the effect of pain on heart rate and a recent single study found that sugar did not significantly affect pain-related electrical activity in the brains of newborns one second after the heel lance procedure. Sweet oral liquid moderately reduces the incidence and duration of crying caused by immunization injection in children between one and twelve months of age.
A number of meta-analyses have found clinical hypnosis to be effective in controlling pain associated with diagnostic and surgical procedures in both adults and children, as well as pain associated with cancer and childbirth. A 2007 review of 13 studies found evidence for the efficacy of hypnosis in the reduction of chronic pain in some conditions, though the number of patients enrolled in the studies was low, bringing up issues of power to detect group differences, and most lacked credible controls for placebo and/or expectation. The authors concluded that "although the findings provide support for the general applicability of hypnosis in the treatment of chronic pain, considerably more research will be needed to fully determine the effects of hypnosis for different chronic-pain conditions."
Pain is the most common reason for people to use complementary and alternative medicine. An analysis of the 13 highest quality studies of pain treatment with acupuncture, published in January 2009, concluded there is little difference in the effect of real, sham and no acupuncture. However other reviews have found benefit. Additionally, there is tentative evidence for a few herbal medicine. There is interest in the relationship between vitamin D and pain, but the evidence so far from controlled trials for such a relationship, other than in osteomalacia, is unconvincing.
Physical pain is an important political topic in relation to various issues, including pain management policy, drug control, animal rights or animal welfare, torture, and pain compliance. In various contexts, the deliberate infliction of pain in the form of corporal punishment is used as retribution for an offence, or for the purpose of disciplining or reforming a wrongdoer, or to deter attitudes or behaviour deemed unacceptable. In some cultures, extreme practices such as mortification of the flesh or painful rites of passage are highly regarded.
The most reliable method for assessing pain in most humans is by asking a question: a person may report pain that cannot be detected by any known physiological measure. However, like infants (Latin infans meaning "unable to speak"), animals cannot answer questions about whether they feel pain; thus the defining criterion for pain in humans cannot be applied to them. Philosophers and scientists have responded to this difficulty in a variety of ways. René Descartes for example argued that animals lack consciousness and therefore do not experience pain and suffering in the way that humans do. Bernard Rollin of Colorado State University, the principal author of two U.S. federal laws regulating pain relief for animals, writes that researchers remained unsure into the 1980s as to whether animals experience pain, and that veterinarians trained in the U.S. before 1989 were simply taught to ignore animal pain. In his interactions with scientists and other veterinarians, he was regularly asked to "prove" that animals are conscious, and to provide "scientifically acceptable" grounds for claiming that they feel pain. Carbone writes that the view that animals feel pain differently is now a minority view. Academic reviews of the topic are more equivocal, noting that although the argument that animals have at least simple conscious thoughts and feelings has strong support, some critics continue to question how reliably animal mental states can be determined. The ability of invertebrate species of animals, such as insects, to feel pain and suffering is also unclear.
The presence of pain in an animal cannot be known for certain, but it can be inferred through physical and behavioral reactions. Specialists currently believe that all vertebrates can feel pain, and that certain invertebrates, like the octopus, might too. As for other animals, plants, or other entities, their ability to feel physical pain is at present a question beyond scientific reach, since no mechanism is known by which they could have such a feeling. In particular, there are no known nociceptors in groups such as plants, fungi, and most insects, except for instance in fruit flies.
A database management system (DBMS) is a computer software application that interacts with the user, other applications, and the database itself to capture and analyze data. A general-purpose DBMS is designed to allow the definition, creation, querying, update, and administration of databases. Well-known DBMSs include MySQL, PostgreSQL, Microsoft SQL Server, Oracle, Sybase, SAP HANA, and IBM DB2. A database is not generally portable across different DBMSs, but different DBMS can interoperate by using standards such as SQL and ODBC or JDBC to allow a single application to work with more than one DBMS. Database management systems are often classified according to the database model that they support; the most popular database systems since the 1980s have all supported the relational model as represented by the SQL language.[disputed – discuss] Sometimes a DBMS is loosely referred to as a 'database'.
Formally, a "database" refers to a set of related data and the way it is organized. Access to these data is usually provided by a "database management system" (DBMS) consisting of an integrated set of computer software that allows users to interact with one or more databases and provides access to all of the data contained in the database (although restrictions may exist that limit access to particular data). The DBMS provides various functions that allow entry, storage and retrieval of large quantities of information and provides ways to manage how that information is organized.
Physically, database servers are dedicated computers that hold the actual databases and run only the DBMS and related software. Database servers are usually multiprocessor computers, with generous memory and RAID disk arrays used for stable storage. RAID is used for recovery of data if any of the disks fail. Hardware database accelerators, connected to one or more servers via a high-speed channel, are also used in large volume transaction processing environments. DBMSs are found at the heart of most database applications. DBMSs may be built around a custom multitasking kernel with built-in networking support, but modern DBMSs typically rely on a standard operating system to provide these functions. from databases before the inception of Structured Query Language (SQL). The data recovered was disparate, redundant and disorderly, since there was no proper method to fetch it and arrange it in a concrete structure.[citation needed]
A DBMS has evolved into a complex software system and its development typically requires thousands of human years of development effort.[a] Some general-purpose DBMSs such as Adabas, Oracle and DB2 have been undergoing upgrades since the 1970s. General-purpose DBMSs aim to meet the needs of as many applications as possible, which adds to the complexity. However, the fact that their development cost can be spread over a large number of users means that they are often the most cost-effective approach. However, a general-purpose DBMS is not always the optimal solution: in some cases a general-purpose DBMS may introduce unnecessary overhead. Therefore, there are many examples of systems that use special-purpose databases. A common example is an email system that performs many of the functions of a general-purpose DBMS such as the insertion and deletion of messages composed of various items of data or associating messages with a particular email address; but these functions are limited to what is required to handle email and don't provide the user with all of the functionality that would be available using a general-purpose DBMS.
Many other databases have application software that accesses the database on behalf of end-users, without exposing the DBMS interface directly. Application programmers may use a wire protocol directly, or more likely through an application programming interface. Database designers and database administrators interact with the DBMS through dedicated interfaces to build and maintain the applications' databases, and thus need some more knowledge and understanding about how DBMSs operate and the DBMSs' external interfaces and tuning parameters.
The relational model, first proposed in 1970 by Edgar F. Codd, departed from this tradition by insisting that applications should search for data by content, rather than by following links. The relational model employs sets of ledger-style tables, each used for a different type of entity. Only in the mid-1980s did computing hardware become powerful enough to allow the wide deployment of relational systems (DBMSs plus applications). By the early 1990s, however, relational systems dominated in all large-scale data processing applications, and as of 2015[update] they remain dominant : IBM DB2, Oracle, MySQL and Microsoft SQL Server are the top DBMS. The dominant database language, standardised SQL for the relational model, has influenced database languages for other data models.[citation needed]
As computers grew in speed and capability, a number of general-purpose database systems emerged; by the mid-1960s a number of such systems had come into commercial use. Interest in a standard began to grow, and Charles Bachman, author of one such product, the Integrated Data Store (IDS), founded the "Database Task Group" within CODASYL, the group responsible for the creation and standardization of COBOL. In 1971 the Database Task Group delivered their standard, which generally became known as the "CODASYL approach", and soon a number of commercial products based on this approach entered the market.
IBM also had their own DBMS in 1966, known as Information Management System (IMS). IMS was a development of software written for the Apollo program on the System/360. IMS was generally similar in concept to CODASYL, but used a strict hierarchy for its model of data navigation instead of CODASYL's network model. Both concepts later became known as navigational databases due to the way data was accessed, and Bachman's 1973 Turing Award presentation was The Programmer as Navigator. IMS is classified[by whom?] as a hierarchical database. IDMS and Cincom Systems' TOTAL database are classified as network databases. IMS remains in use as of 2014[update].
In this paper, he described a new system for storing and working with large databases. Instead of records being stored in some sort of linked list of free-form records as in CODASYL, Codd's idea was to use a "table" of fixed-length records, with each table used for a different type of entity. A linked-list system would be very inefficient when storing "sparse" databases where some of the data for any one record could be left empty. The relational model solved this by splitting the data into a series of normalized tables (or relations), with optional elements being moved out of the main table to where they would take up room only if needed. Data may be freely inserted, deleted and edited in these tables, with the DBMS doing whatever maintenance needed to present a table view to the application/user.
The relational model also allowed the content of the database to evolve without constant rewriting of links and pointers. The relational part comes from entities referencing other entities in what is known as one-to-many relationship, like a traditional hierarchical model, and many-to-many relationship, like a navigational (network) model. Thus, a relational model can express both hierarchical and navigational models, as well as its native tabular model, allowing for pure or combined modeling in terms of these three models, as the application requires.
For instance, a common use of a database system is to track information about users, their name, login information, various addresses and phone numbers. In the navigational approach all of this data would be placed in a single record, and unused items would simply not be placed in the database. In the relational approach, the data would be normalized into a user table, an address table and a phone number table (for instance). Records would be created in these optional tables only if the address or phone numbers were actually provided.
Linking the information back together is the key to this system. In the relational model, some bit of information was used as a "key", uniquely defining a particular record. When information was being collected about a user, information stored in the optional tables would be found by searching for this key. For instance, if the login name of a user is unique, addresses and phone numbers for that user would be recorded with the login name as its key. This simple "re-linking" of related data back into a single collection is something that traditional computer languages are not designed for.
Just as the navigational approach would require programs to loop in order to collect records, the relational approach would require loops to collect information about any one record. Codd's solution to the necessary looping was a set-oriented language, a suggestion that would later spawn the ubiquitous SQL. Using a branch of mathematics known as tuple calculus, he demonstrated that such a system could support all the operations of normal databases (inserting, updating etc.) as well as providing a simple system for finding and returning sets of data in a single operation.
Codd's paper was picked up by two people at Berkeley, Eugene Wong and Michael Stonebraker. They started a project known as INGRES using funding that had already been allocated for a geographical database project and student programmers to produce code. Beginning in 1973, INGRES delivered its first test products which were generally ready for widespread use in 1979. INGRES was similar to System R in a number of ways, including the use of a "language" for data access, known as QUEL. Over time, INGRES moved to the emerging SQL standard.
Another approach to hardware support for database management was ICL's CAFS accelerator, a hardware disk controller with programmable search capabilities. In the long term, these efforts were generally unsuccessful because specialized database machines could not keep pace with the rapid development and progress of general-purpose computers. Thus most database systems nowadays are software systems running on general-purpose hardware, using general-purpose computer data storage. However this idea is still pursued for certain applications by some companies like Netezza and Oracle (Exadata).
IBM started working on a prototype system loosely based on Codd's concepts as System R in the early 1970s. The first version was ready in 1974/5, and work then started on multi-table systems in which the data could be split so that all of the data for a record (some of which is optional) did not have to be stored in a single large "chunk". Subsequent multi-user versions were tested by customers in 1978 and 1979, by which time a standardized query language – SQL[citation needed] – had been added. Codd's ideas were establishing themselves as both workable and superior to CODASYL, pushing IBM to develop a true production version of System R, known as SQL/DS, and, later, Database 2 (DB2).
The 1980s ushered in the age of desktop computing. The new computers empowered their users with spreadsheets like Lotus 1-2-3 and database software like dBASE. The dBASE product was lightweight and easy for any computer user to understand out of the box. C. Wayne Ratliff the creator of dBASE stated: "dBASE was different from programs like BASIC, C, FORTRAN, and COBOL in that a lot of the dirty work had already been done. The data manipulation is done by dBASE instead of by the user, so the user can concentrate on what he is doing, rather than having to mess with the dirty details of opening, reading, and closing files, and managing space allocation." dBASE was one of the top selling software titles in the 1980s and early 1990s.
The 1990s, along with a rise in object-oriented programming, saw a growth in how data in various databases were handled. Programmers and designers began to treat the data in their databases as objects. That is to say that if a person's data were in a database, that person's attributes, such as their address, phone number, and age, were now considered to belong to that person instead of being extraneous data. This allows for relations between data to be relations to objects and their attributes and not to individual fields. The term "object-relational impedance mismatch" described the inconvenience of translating between programmed objects and database tables. Object databases and object-relational databases attempt to solve this problem by providing an object-oriented language (sometimes as extensions to SQL) that programmers can use as alternative to purely relational SQL. On the programming side, libraries known as object-relational mappings (ORMs) attempt to solve the same problem.
XML databases are a type of structured document-oriented database that allows querying based on XML document attributes. XML databases are mostly used in enterprise database management, where XML is being used as the machine-to-machine data interoperability standard. XML database management systems include commercial software MarkLogic and Oracle Berkeley DB XML, and a free use software Clusterpoint Distributed XML/JSON Database. All are enterprise software database platforms and support industry standard ACID-compliant transaction processing with strong database consistency characteristics and high level of database security.
In recent years there was a high demand for massively distributed databases with high partition tolerance but according to the CAP theorem it is impossible for a distributed system to simultaneously provide consistency, availability and partition tolerance guarantees. A distributed system can satisfy any two of these guarantees at the same time, but not all three. For that reason many NoSQL databases are using what is called eventual consistency to provide both availability and partition tolerance guarantees with a reduced level of data consistency.
The first task of a database designer is to produce a conceptual data model that reflects the structure of the information to be held in the database. A common approach to this is to develop an entity-relationship model, often with the aid of drawing tools. Another popular approach is the Unified Modeling Language. A successful data model will accurately reflect the possible state of the external world being modeled: for example, if people can have more than one phone number, it will allow this information to be captured. Designing a good conceptual data model requires a good understanding of the application domain; it typically involves asking deep questions about the things of interest to an organisation, like "can a customer also be a supplier?", or "if a product is sold with two different forms of packaging, are those the same product or different products?", or "if a plane flies from New York to Dubai via Frankfurt, is that one flight or two (or maybe even three)?". The answers to these questions establish definitions of the terminology used for entities (customers, products, flights, flight segments) and their relationships and attributes.
Having produced a conceptual data model that users are happy with, the next stage is to translate this into a schema that implements the relevant data structures within the database. This process is often called logical database design, and the output is a logical data model expressed in the form of a schema. Whereas the conceptual data model is (in theory at least) independent of the choice of database technology, the logical data model will be expressed in terms of a particular database model supported by the chosen DBMS. (The terms data model and database model are often used interchangeably, but in this article we use data model for the design of a specific database, and database model for the modelling notation used to express that design.)
The final stage of database design is to make the decisions that affect performance, scalability, recovery, security, and the like. This is often called physical database design. A key goal during this stage is data independence, meaning that the decisions made for performance optimization purposes should be invisible to end-users and applications. Physical design is driven mainly by performance requirements, and requires a good knowledge of the expected workload and access patterns, and a deep understanding of the features offered by the chosen DBMS.
While there is typically only one conceptual (or logical) and physical (or internal) view of the data, there can be any number of different external views. This allows users to see database information in a more business-related way rather than from a technical, processing viewpoint. For example, a financial department of a company needs the payment details of all employees as part of the company's expenses, but does not need details about employees that are the interest of the human resources department. Thus different departments need different views of the company's database.
The conceptual view provides a level of indirection between internal and external. On one hand it provides a common view of the database, independent of different external view structures, and on the other hand it abstracts away details of how the data are stored or managed (internal level). In principle every level, and even every external view, can be presented by a different data model. In practice usually a given DBMS uses the same data model for both the external and the conceptual levels (e.g., relational model). The internal level, which is hidden inside the DBMS and depends on its implementation, requires a different level of detail and uses its own types of data structure types.
Database storage is the container of the physical materialization of a database. It comprises the internal (physical) level in the database architecture. It also contains all the information needed (e.g., metadata, "data about the data", and internal data structures) to reconstruct the conceptual level and external level from the internal level when needed. Putting data into permanent storage is generally the responsibility of the database engine a.k.a. "storage engine". Though typically accessed by a DBMS through the underlying operating system (and often utilizing the operating systems' file systems as intermediates for storage layout), storage properties and configuration setting are extremely important for the efficient operation of the DBMS, and thus are closely maintained by database administrators. A DBMS, while in operation, always has its database residing in several types of storage (e.g., memory and external storage). The database data and the additional needed information, possibly in very large amounts, are coded into bits. Data typically reside in the storage in structures that look completely different from the way the data look in the conceptual and external levels, but in ways that attempt to optimize (the best possible) these levels' reconstruction when needed by users and programs, as well as for computing additional types of needed information from the data (e.g., when querying the database).
Database access control deals with controlling who (a person or a certain computer program) is allowed to access what information in the database. The information may comprise specific database objects (e.g., record types, specific records, data structures), certain computations over certain objects (e.g., query types, or specific queries), or utilizing specific access paths to the former (e.g., using specific indexes or other data structures to access information). Database access controls are set by special authorized (by the database owner) personnel that uses dedicated protected security DBMS interfaces.
This may be managed directly on an individual basis, or by the assignment of individuals and privileges to groups, or (in the most elaborate models) through the assignment of individuals and groups to roles which are then granted entitlements. Data security prevents unauthorized users from viewing or updating the database. Using passwords, users are allowed access to the entire database or subsets of it called "subschemas". For example, an employee database can contain all the data about an individual employee, but one group of users may be authorized to view only payroll data, while others are allowed access to only work history and medical data. If the DBMS provides a way to interactively enter and update the database, as well as interrogate it, this capability allows for managing personal databases.
Database transactions can be used to introduce some level of fault tolerance and data integrity after recovery from a crash. A database transaction is a unit of work, typically encapsulating a number of operations over a database (e.g., reading a database object, writing, acquiring lock, etc.), an abstraction supported in database and also other systems. Each transaction has well defined boundaries in terms of which program/code executions are included in that transaction (determined by the transaction's programmer via special transaction commands).
A database built with one DBMS is not portable to another DBMS (i.e., the other DBMS cannot run it). However, in some situations it is desirable to move, migrate a database from one DBMS to another. The reasons are primarily economical (different DBMSs may have different total costs of ownership or TCOs), functional, and operational (different DBMSs may have different capabilities). The migration involves the database's transformation from one DBMS type to another. The transformation should maintain (if possible) the database related application (i.e., all related application programs) intact. Thus, the database's conceptual and external architectural levels should be maintained in the transformation. It may be desired that also some aspects of the architecture internal level are maintained. A complex or large database migration may be a complicated and costly (one-time) project by itself, which should be factored into the decision to migrate. This in spite of the fact that tools may exist to help migration between specific DBMSs. Typically a DBMS vendor provides tools to help importing databases from other popular DBMSs.
Sometimes it is desired to bring a database back to a previous state (for many reasons, e.g., cases when the database is found corrupted due to a software error, or if it has been updated with erroneous data). To achieve this a backup operation is done occasionally or continuously, where each desired database state (i.e., the values of its data and their embedding in database's data structures) is kept within dedicated backup files (many techniques exist to do this effectively). When this state is needed, i.e., when it is decided by a database administrator to bring the database back to this state (e.g., by specifying this state by a desired point in time when the database was in this state), these files are utilized to restore that state.
Static analysis techniques for software verification can be applied also in the scenario of query languages. In particular, the *Abstract interpretation framework has been extended to the field of query languages for relational databases as a way to support sound approximation techniques. The semantics of query languages can be tuned according to suitable abstractions of the concrete domain of data. The abstraction of relational database system has many interesting applications, in particular, for security purposes, such as fine grained access control, watermarking, etc.
Tucson (/ˈtuːsɒn/ /tuːˈsɒn/) is a city and the county seat of Pima County, Arizona, United States, and home to the University of Arizona. The 2010 United States Census put the population at 520,116, while the 2013 estimated population of the entire Tucson metropolitan statistical area (MSA) was 996,544. The Tucson MSA forms part of the larger Tucson-Nogales combined statistical area (CSA), with a total population of 980,263 as of the 2010 Census. Tucson is the second-largest populated city in Arizona behind Phoenix, both of which anchor the Arizona Sun Corridor. The city is located 108 miles (174 km) southeast of Phoenix and 60 mi (97 km) north of the U.S.-Mexico border. Tucson is the 33rd largest city and the 59th largest metropolitan area in the United States. Roughly 150 Tucson companies are involved in the design and manufacture of optics and optoelectronics systems, earning Tucson the nickname Optics Valley.
Tucson was probably first visited by Paleo-Indians, known to have been in southern Arizona about 12,000 years ago. Recent archaeological excavations near the Santa Cruz River have located a village site dating from 2100 BC.[citation needed] The floodplain of the Santa Cruz River was extensively farmed during the Early Agricultural period, circa 1200 BC to AD 150. These people constructed irrigation canals and grew corn, beans, and other crops while gathering wild plants and hunting. The Early Ceramic period occupation of Tucson saw the first extensive use of pottery vessels for cooking and storage. The groups designated as the Hohokam lived in the area from AD 600 to 1450 and are known for their vast irrigation canal systems and their red-on-brown pottery.[citation needed]
Jesuit missionary Eusebio Francisco Kino visited the Santa Cruz River valley in 1692, and founded the Mission San Xavier del Bac in 1700 about 7 mi (11 km) upstream from the site of the settlement of Tucson. A separate Convento settlement was founded downstream along the Santa Cruz River, near the base of what is now "A" mountain. Hugo O'Conor, the founding father of the city of Tucson, Arizona authorized the construction of a military fort in that location, Presidio San Agustín del Tucsón, on August 20, 1775 (near the present downtown Pima County Courthouse). During the Spanish period of the presidio, attacks such as the Second Battle of Tucson were repeatedly mounted by Apaches. Eventually the town came to be called "Tucson" and became a part of Sonora after Mexico gained independence from Spain in 1821.
Arizona, south of the Gila River was legally bought from Mexico in the Gadsden Purchase on June 8, 1854. Tucson became a part of the United States of America, although the American military did not formally take over control until March 1856. In 1857 Tucson became a stage station on the San Antonio-San Diego Mail Line and in 1858 became 3rd division headquarters of the Butterfield Overland Mail until the line shut down in March 1861. The Overland Mail Corporation attempted to continue running, however following the Bascom Affair, devastating Apache attacks on the stations and coaches ended operations in August 1861.[citation needed]
From 1877 to 1878, the area suffered a rash of stagecoach robberies. Most notable, however, were the two holdups committed by masked road-agent William Whitney Brazelton. Brazelton held up two stages in the summer of 1878 near Point of Mountain Station approximately 17 mi (27 km) northwest of Tucson. John Clum, of Tombstone, Arizona fame was one of the passengers. Brazelton was eventually tracked down and killed on Monday August 19, 1878, in a mesquite bosque along the Santa Cruz River 3 miles (5 km) south of Tucson by Pima County Sheriff Charles A. Shibell and his citizen's posse. Brazelton had been suspected of highway robbery not only in the Tucson area, but also in the Prescott region and Silver City, New Mexico area as well. Brazelton's crimes prompted John J. Valentine, Sr. of Wells, Fargo & Co. to send special agent and future Pima County sheriff Bob Paul to investigate. Fort Lowell, then east of Tucson, was established to help protect settlers from Apache attacks. In 1882, Frank Stilwell was implicated in the murder of Morgan Earp by Cowboy Pete Spence's wife, Marietta, at the coroner's inquest on Morgan Earp's shooting. The coroner's jury concluded that Spence, Stilwell, Frederick Bode, and Florentino "Indian Charlie" Cruz were the prime suspects in the assassination of Morgan Earp. :250 Deputy U.S. Marshal Wyatt Earp gathered a few trusted friends and accompanied Virgil Earp and his family as they traveled to Benson for a train ride to California. They found Stilwell lying in wait for Virgil in the Tucson station and killed him on the tracks. After killing Stilwell, Wyatt deputized others and rode on a vendetta, killing three more cowboys over the next few days before leaving the state.
By 1900, 7,531 people lived in the city. The population increased gradually to 13,913 in 1910. At about this time, the U.S. Veterans Administration had begun construction on the present Veterans Hospital. Many veterans who had been gassed in World War I and were in need of respiratory therapy began coming to Tucson after the war, due to the clean dry air. Over the following years the city continued to grow, with the population increasing to 20,292 in 1920 and 36,818 in 1940. In 2006 the population of Pima County, in which Tucson is located, passed one million while the City of Tucson's population was 535,000.
The city's elevation is 2,643 ft (806 m) above sea level (as measured at the Tucson International Airport). Tucson is situated on an alluvial plain in the Sonoran desert, surrounded by five minor ranges of mountains: the Santa Catalina Mountains and the Tortolita Mountains to the north, the Santa Rita Mountains to the south, the Rincon Mountains to the east, and the Tucson Mountains to the west. The high point of the Santa Catalina Mountains is 9,157 ft (2,791 m) Mount Lemmon, the southernmost ski destination in the continental U.S., while the Tucson Mountains include 4,687 ft (1,429 m) Wasson Peak. The highest point in the area is Mount Wrightson, found in the Santa Rita Mountains at 9,453 ft (2,881 m) above sea level.
Tucson is located 118 mi (190 km) southeast of Phoenix and 60 mi (97 km) north of the United States - Mexico border. The 2010 United States Census puts the city's population at 520,116 with a metropolitan area population at 980,263. In 2009, Tucson ranked as the 32nd largest city and 52nd largest metropolitan area in the United States. A major city in the Arizona Sun Corridor, Tucson is the largest city in southern Arizona, the second largest in the state after Phoenix. It is also the largest city in the area of the Gadsden Purchase. As of 2015, The Greater Tucson Metro area has exceeded a population of 1 million.
Interstate 10, which runs southeast to northwest through town, connects Tucson to Phoenix to the northwest on the way to its western terminus in Santa Monica, California, and to Las Cruces, New Mexico and El Paso, Texas toward its eastern terminus in Jacksonville, Florida. I-19 runs south from Tucson toward Nogales and the U.S.-Mexico border. I-19 is the only Interstate highway that uses "kilometer posts" instead of "mileposts", although the speed limits are marked in miles per hour instead of kilometers per hour.
At the end of the first decade of the 21st century, downtown Tucson underwent a revitalization effort by city planners and the business community. The primary project was Rio Nuevo, a large retail and community center that has been stalled in planning for more than ten years. Downtown is generally regarded as the area bordered by 17th Street to the south, I-10 to the west, and 6th Street to the north, and Toole Avenue and the Union Pacific (formerly Southern Pacific) railroad tracks, site of the historic train depot and "Locomotive #1673", built in 1900. Downtown is divided into the Presidio District, the Barrio Viejo, and the Congress Street Arts and Entertainment District. Some authorities include the 4th Avenue shopping district, which is set just northeast of the rest of downtown and connected by an underpass beneath the UPRR tracks.
As one of the oldest parts of town, Central Tucson is anchored by the Broadway Village shopping center designed by local architect Josias Joesler at the intersection of Broadway Boulevard and Country Club Road. The 4th Avenue Shopping District between downtown and the University and the Lost Barrio just East of downtown, also have many unique and popular stores. Local retail business in Central Tucson is densely concentrated along Fourth Avenue and the Main Gate Square on University Boulevard near the UA campus. The El Con Mall is also located in the eastern part of midtown.
Tucson's largest park, Reid Park, is located in midtown and includes Reid Park Zoo and Hi Corbett Field. Speedway Boulevard, a major east-west arterial road in central Tucson, was named the "ugliest street in America" by Life magazine in the early 1970s, quoting Tucson Mayor James Corbett. Despite this, Speedway Boulevard was awarded "Street of the Year" by Arizona Highways in the late 1990s. According to David Leighton, historical writer for the Arizona Daily Star newspaper, Speedway Boulevard derives its name from an old horse racetrack, known as "The Harlem River Speedway," more commonly called "The Speedway," in New York City. The street was called "The Speedway," from 1904 to about 1906 before the word "The" was taken out.
Central Tucson is bicycle-friendly. To the east of the University of Arizona, Third Street is bike-only except for local traffic and passes by the historic homes of the Sam Hughes neighborhood. To the west, E. University Boulevard leads to the Fourth Avenue Shopping District. To the North, N. Mountain Avenue has a full bike-only lane for half of the 3.5 miles (5.6 km) to the Rillito River Park bike and walk multi-use path. To the south, N. Highland Avenue leads to the Barraza-Aviation Parkway bicycle path.
South Tucson is actually the name of an independent, incorporated town of 1 sq mi (2.6 km2), completely surrounded by the city of Tucson, sitting just south of downtown. South Tucson has a colorful, dynamic history. It was first incorporated in 1936, and later reincorporated in 1940. The population consists of about 83% Mexican-American and 10% Native American residents. South Tucson is widely known for its many Mexican restaurants and the architectural styles which include bright outdoor murals, many of which have been painted over due to city policy.
A combination of urban and suburban development, the West Side is generally defined as the area west of I-10. Western Tucson encompasses the banks of the Santa Cruz River and the foothills of the Tucson Mountains, and includes the International Wildlife Museum, Sentinel Peak, and the Marriott Starr Pass Resort & Spa, located in the wealthy enclave known as Starr Pass. Moving past the Tucson Mountains, travelers find themselves in the area commonly referred to as "west of" Tucson or "Old West Tucson". A large undulating plain extending south into the Altar Valley, rural residential development predominates, but here you will also find major attractions including Saguaro National Park West, the Arizona-Sonora Desert Museum, and the Old Tucson Studios movie set/theme park.
On Sentinel Peak (also known as "'A' Mountain"), just west of downtown, there is a giant "A" in honor of the University of Arizona. Starting in about 1916, a yearly tradition developed for freshmen to whitewash the "A", which was visible for miles. However, at the beginning of the Iraq War, anti-war activists painted it black. This was followed by a paint scuffle where the "A" was painted various colors until the city council intervened. It is now red, white and blue except when it is white or another color decided by a biennial election. Because of the three-color paint scheme often used, the shape of the A can be vague and indistinguishable from the rest of the peak. The top of Sentinel Peak, which is accessible by road, offers an outstanding scenic view of the city looking eastward. A parking lot located near the summit of Sentinel Peak was formerly a popular place to watch sunsets or view the city lights at night.
Also on the north side is the suburban community of Catalina Foothills, located in the foothills of the Santa Catalina Mountains just north of the city limits. This community includes among the area's most expensive homes, sometimes multimillion-dollar estates. The Foothills area is generally defined as north of River Road, east of Oracle Road, and west of Sabino Creek. Some of the Tucson area's major resorts are located in the Catalina Foothills, including the Hacienda Del Sol, Westin La Paloma Resort, Loews Ventana Canyon Resort and Canyon Ranch Resort. La Encantada, an upscale outdoor shopping mall, is also in the Foothills.
The expansive area northwest of the city limits is diverse, ranging from the rural communities of Catalina and parts of the town of Marana, the small suburb of Picture Rocks, the affluent town of Oro Valley in the western foothills of the Santa Catalina Mountains, and residential areas in the northeastern foothills of the Tucson Mountains. Continental Ranch (Marana), Dove Mountain (Marana), and Rancho Vistoso (Oro Valley) are all masterplanned communities located in the Northwest, where thousands of residents live.
The community of Casas Adobes is also on the Northwest Side, with the distinction of being Tucson's first suburb, established in the late 1940s. Casas Adobes is centered on the historic Casas Adobes Plaza (built in 1948). Casas Adobes is also home to Tohono Chul Park (a nature preserve) near the intersection of North Oracle Road and West Ina Road. The attempted assassination of Representative Gabrielle Giffords, and the murders of chief judge for the U.S. District Court for Arizona, John Roll and five other people on January 8, 2011, occurred at the La Toscana Village in Casas Adobes. The Foothills Mall is also located on the northwest side in Casas Adobes.
East Tucson is relatively new compared to other parts of the city, developed between the 1950s and the 1970s,[citation needed] with developments such as Desert Palms Park. It is generally classified as the area of the city east of Swan Road, with above-average real estate values relative to the rest of the city. The area includes urban and suburban development near the Rincon Mountains. East Tucson includes Saguaro National Park East. Tucson's "Restaurant Row" is also located on the east side, along with a significant corporate and financial presence. Restaurant Row is sandwiched by three of Tucson's storied Neighborhoods: Harold Bell Wright Estates, named after the famous author's ranch which occupied some of that area prior to the depression; the Tucson Country Club (the third to bear the name Tucson Country Club), and the Dorado Country Club. Tucson's largest office building is 5151 East Broadway in east Tucson, completed in 1975. The first phases of Williams Centre, a mixed-use, master-planned development on Broadway near Craycroft Road, were opened in 1987. Park Place, a recently renovated shopping center, is also located along Broadway (west of Wilmot Road).
Near the intersection of Craycroft and Ft. Lowell Roads are the remnants of the Historic Fort Lowell. This area has become one of Tucson's iconic neighborhoods. In 1891, the Fort was abandoned and much of the interior was stripped of their useful components and it quickly fell into ruin. In 1900, three of the officer buildings were purchased for use as a sanitarium. The sanitarium was then sold to Harvey Adkins in 1928. The Bolsius family Pete, Nan and Charles Bolsius purchased and renovated surviving adobe buildings of the Fort – transforming them into spectacular artistic southwestern architectural examples. Their woodwork, plaster treatment and sense of proportion drew on their Dutch heritage and New Mexican experience. Other artists and academics throughout the middle of the 20th century, including: Win Ellis, Jack Maul, Madame Cheruy, Giorgio Belloli, Charels Bode, Veronica Hughart, Edward and Rosamond Spicer, Hazel Larson Archer and Ruth Brown, renovated adobes, built homes and lived in the area. The artist colony attracted writers and poets including beat generation Alan Harrington and Jack Kerouac whose visit is documented in his iconic book On the Road. This rural pocket in the middle of the city is listed on the National Register of Historic Places. Each year in February the neighborhood celebrates its history in the City Landmark it owns and restored the San Pedro Chapel.
Southeast Tucson continues to experience rapid residential development. The area includes Davis-Monthan Air Force Base. The area is considered to be south of Golf Links Road. It is the home of Santa Rita High School, Chuck Ford Park (Lakeside Park), Lakeside Lake, Lincoln Park (upper and lower), The Lakecrest Neighborhoods, and Pima Community College East Campus. The Atterbury Wash with its access to excellent bird watching is also located in the Southeast Tucson area. The suburban community of Rita Ranch houses many of the military families from Davis-Monthan, and is near the southeastern-most expansion of the current city limits. Close by Rita Ranch and also within the city limits lies Civano, a planned development meant to showcase ecologically sound building practices and lifestyles.
Catalina Highway stretches 25 miles (40 km) and the entire mountain range is one of Tucson's most popular vacation spots for cycling, hiking, rock climbing, camping, birding, and wintertime snowboarding and skiing. Near the top of Mt. Lemmon is the town of Summerhaven. In Summerhaven, visitors will find log houses and cabins, a general store, and various shops, as well as numerous hiking trails. Near Summerhaven is the road to Ski Valley which hosts a ski lift, several runs, a giftshop, and nearby restaurant.
Tucson has a desert climate (Köppen BWh), with two major seasons, summer and winter; plus three minor seasons: fall, spring, and the monsoon. Tucson averages 11.8 inches (299.7 mm) of precipitation per year, more than most other locations with desert climates, but it still qualifies due to its high evapotranspiration; in other words, it experiences a high net loss of water. A similar scenario is seen in Alice Springs, Australia, which averages 11 inches (279.4 mm) a year, but has a desert climate.
The monsoon can begin any time from mid-June to late July, with an average start date around July 3. It typically continues through August and sometimes into September. During the monsoon, the humidity is much higher than the rest of the year. It begins with clouds building up from the south in the early afternoon followed by intense thunderstorms and rainfall, which can cause flash floods. The evening sky at this time of year is often pierced with dramatic lightning strikes. Large areas of the city do not have storm sewers, so monsoon rains flood the main thoroughfares, usually for no longer than a few hours. A few underpasses in Tucson have "feet of water" scales painted on their supports to discourage fording by automobiles during a rainstorm. Arizona traffic code Title 28-910, the so-called "Stupid Motorist Law", was instituted in 1995 to discourage people from entering flooded roadways. If the road is flooded and a barricade is in place, motorists who drive around the barricade can be charged up to $2000 for costs involved in rescuing them. Despite all warnings and precautions, however, three Tucson drivers have drowned between 2004 and 2010.
Winters in Tucson are mild relative to other parts of the United States. Daytime highs in the winter range between 64 and 75 °F (18 and 24 °C), with overnight lows between 30 and 44 °F (−1 and 7 °C). Tucson typically averages one hard freeze per winter season, with temperatures dipping to the mid or low-20s (−7 to −4 °C), but this is typically limited to only a very few nights. Although rare, snow has been known to fall in Tucson, usually a light dusting that melts within a day. The most recent snowfall was on February 20, 2013 when 2.0 inches of snow blanketed the city, the largest snowfall since 1987.
At the University of Arizona, where records have been kept since 1894, the record maximum temperature was 115 °F (46 °C) on June 19, 1960, and July 28, 1995, and the record minimum temperature was 6 °F (−14 °C) on January 7, 1913. There are an average of 150.1 days annually with highs of 90 °F (32 °C) or higher and an average of 26.4 days with lows reaching or below the freezing mark. Average annual precipitation is 11.15 in (283 mm). There is an average of 49 days with measurable precipitation. The wettest year was 1905 with 24.17 in (614 mm) and the driest year was 1924 with 5.07 in (129 mm). The most precipitation in one month was 7.56 in (192 mm) in July 1984. The most precipitation in 24 hours was 4.16 in (106 mm) on October 1, 1983. Annual snowfall averages 0.7 in (1.8 cm). The most snow in one year was 7.2 in (18 cm) in 1987. The most snow in one month was 6.0 in (15 cm) in January 1898 and March 1922.
At the airport, where records have been kept since 1930, the record maximum temperature was 117 °F (47 °C) on June 26, 1990, and the record minimum temperature was 16 °F (−9 °C) on January 4, 1949. There is an average of 145.0 days annually with highs of 90 °F (32 °C) or higher and an average of 16.9 days with lows reaching or below the freezing mark. Measurable precipitation falls on an average of 53 days. The wettest year was 1983 with 21.86 in (555 mm) of precipitation, and the driest year was 1953 with 5.34 in (136 mm). The most rainfall in one month was 7.93 in (201 mm) in August 1955. The most rainfall in 24 hours was 3.93 in (100 mm) on July 29, 1958. Snow at the airport averages only 1.1 in (2.8 cm) annually. The most snow received in one year was 8.3 in (21 cm) and the most snow in one month was 6.8 in (17 cm) in December 1971.
As of the census of 2010, there were 520,116 people, 229,762 households, and 112,455 families residing in the city. The population density was 2,500.1 inhabitants per square mile (965.3/km²). There were 209,609 housing units at an average density of 1,076.7 per square mile (415.7/km²). The racial makeup of the city was 69.7% White (down from 94.8% in 1970), 5.0% Black or African-American, 2.7% Native American, 2.9% Asian, 0.2% Pacific Islander, 16.9% from other races, and 3.8% from two or more races. Hispanic or Latino of any race were 41.6% of the population. Non-Hispanic Whites were 47.2% of the population in 2010, down from 72.8% in 1970.
Much of Tucson's economic development has been centered on the development of the University of Arizona, which is currently the second largest employer in the city. Davis-Monthan Air Force Base, located on the southeastern edge of the city, also provides many jobs for Tucson residents. Its presence, as well as the presence of the US Army Intelligence Center (Fort Huachuca, the largest employer in the region in nearby Sierra Vista), has led to the development of a significant number of high-tech industries, including government contractors, in the area. The city of Tucson is also a major hub for the Union Pacific Railroad's Sunset Route that links the Los Angeles ports with the South/Southeast regions of the country.
The City of Tucson, Pima County, the State of Arizona, and the private sector have all made commitments to create a growing, healthy economy[citation needed] with advanced technology industry sectors as its foundation. Raytheon Missile Systems (formerly Hughes Aircraft Co.), Texas Instruments, IBM, Intuit Inc., Universal Avionics, Honeywell Aerospace, Sunquest Information Systems, Sanofi-Aventis, Ventana Medical Systems, Inc., and Bombardier Aerospace all have a significant presence in Tucson. Roughly 150 Tucson companies are involved in the design and manufacture of optics and optoelectronics systems, earning Tucson the nickname "Optics Valley".
Since 2009, the Tucson Festival of Books has been held annually over a two-day period in March at the University of Arizona. By 2010 it had become the fourth largest book festival in the United States, with 450 authors and 80,000 attendees. In addition to readings and lectures, it features a science fair, varied entertainment, food, and exhibitors ranging from local retailers and publishers to regional and national nonprofit organizations. In 2011, the Festival began presenting a Founder's Award; recipients include Elmore Leonard and R.L. Stine.
For the past 25 years, the Tucson Folk Festival has taken place the first Saturday and Sunday of May in downtown Tucson's El Presidio Park. In addition to nationally known headline acts each evening, the Festival highlights over 100 local and regional musicians on five stages is one of the largest free festivals in the country. All stages are within easy walking distance. Organized by the Tucson Kitchen Musicians Association, volunteers make this festival possible. KXCI 91.3-FM, Arizona's only community radio station, is a major partner, broadcasting from the Plaza Stage throughout the weekend. In addition, there are numerous workshops, events for children, sing-alongs, and a popular singer/songwriter contest. Musicians typically play 30-minute sets, supported by professional audio staff volunteers. A variety of food and crafts are available at the festival, as well as local micro-brews. All proceeds from sales go to fund future festivals.
Another popular event held in February, which is early spring in Tucson, is the Fiesta de los Vaqueros, or rodeo week, founded by winter visitor, Leighton Kramer. While at its heart the Fiesta is a sporting event, it includes what is billed as "the world's largest non-mechanized parade". The Rodeo Parade is a popular event as most schools give two rodeo days off instead of Presidents Day. The exception to this is Presidio High (a non-public charter school), which doesn't get either. Western wear is seen throughout the city as corporate dress codes are cast aside during the Fiesta. The Fiesta de los Vaqueros marks the beginning of the rodeo season in the United States.
The Procession, held at sundown, consists of a non-motorized parade through downtown Tucson featuring many floats, sculptures, and memorials, in which the community is encouraged to participate. The parade is followed by performances on an outdoor stage, culminating in the burning of an urn in which written prayers have been collected from participants and spectators. The event is organized and funded by the non-profit arts organization Many Mouths One Stomach, with the assistance of many volunteers and donations from the public and local businesses.
The accomplished and awarded writers (poets, novelists, dramatists, nonfiction writers) who have lived in Tucson include Edward Abbey, Erskine Caldwell, Barbara Kingsolver and David Foster Wallace. Some were associated with the University of Arizona, but many were independent writers who chose to make Tucson their home. The city is particularly active in publishing and presenting contemporary innovative poetry in various ways. Examples are the Chax Press, a publisher of poetry books in trade and book arts editions, and the University of Arizona Poetry Center, which has a sizable poetry library and presents readings, conferences, and workshops.
Tucson is commonly known as "The Old Pueblo". While the exact origin of this nickname is uncertain, it is commonly traced back to Mayor R. N. "Bob" Leatherwood. When rail service was established to the city on March 20, 1880, Leatherwood celebrated the fact by sending telegrams to various leaders, including the President of the United States and the Pope, announcing that the "ancient and honorable pueblo" of Tucson was now connected by rail to the outside world. The term became popular with newspaper writers who often abbreviated it as "A. and H. Pueblo". This in turn transformed into the current form of "The Old Pueblo".
The University of Arizona Wildcats sports teams, most notably the men's basketball and women's softball teams have strong local interest. The men's basketball team, formerly coached by Hall of Fame head coach Lute Olson and currently coached by Sean Miller, has made 25 straight NCAA Tournaments and won the 1997 National Championship. Arizona's Softball team has reached the NCAA National Championship game 12 times and has won 8 times, most recently in 2007. The university's swim teams have gained international recognition, with swimmers coming from as far as Japan and Africa to train with the coach Frank Busch who has also worked with the U.S. Olympic swim team for a number of years. Both men and women's swim teams recently[when?] won the NCAA National Championships.
The Tucson Padres played at Kino Veterans Memorial Stadium from 2011 to 2013. They served as the AAA affiliate of the San Diego Padres. The team, formerly known as the Portland Beavers, was temporarily relocated to Tucson from Portland while awaiting the building of a new stadium in Escondido. Legal issues derailed the plans to build the Escondido stadium, so they moved to El Paso, Texas for the 2014 season. Previously, the Tucson Sidewinders, a triple-A affiliate of the Arizona Diamondbacks, won the Pacific Coast League championship and unofficial AAA championship in 2006. The Sidewinders played in Tucson Electric Park and were in the Pacific Conference South of the PCL. The Sidewinders were sold in 2007 and moved to Reno, Nevada after the 2008 season. They now compete as the Reno Aces.
Tracks include Tucson Raceway Park and Rillito Downs. Tucson Raceway Park hosts NASCAR-sanctioned auto racing events and is one of only two asphalt short tracks in Arizona. Rillito Downs is an in-town destination on weekends in January and February each year. This historic track held the first organized quarter horse races in the world, and they are still racing there. The racetrack is threatened by development. The Moltacqua racetrack, was another historic horse racetrack located on what is now Sabino Canyon Road and Vactor Ranch Trail, but it no longer exists.
The League of American Bicyclists gave Tucson a gold rating for bicycle friendliness in late April 2007. Tucson hosts the largest perimeter cycling event in the United States. The ride called "El Tour de Tucson" happens in November on the Saturday before Thanksgiving. El Tour de Tucson produced and promoted by Perimeter Bicycling has as many as 10,000 participants from all over the world, annually. Tucson is one of only nine cities in the U.S. to receive a gold rating or higher for cycling friendliness from the League of American Bicyclists. The city is known for its winter cycling opportunities. Both road and mountain biking are popular in and around Tucson with trail areas including Starr Pass and Fantasy Island.
In general, Tucson and Pima County support the Democratic Party, as opposed the state's largest metropolitan area, Phoenix, which usually supports the Republican Party. Congressional redistricting in 2013, following the publication of the 2010 Census, divided the Tucson area into three Federal Congressional districts (the first, second and third of Arizona). The city center is in the 3rd District, represented by Raul Grijalva, a Democrat, since 2003, while the more affluent residential areas to the south and east are in the 2nd District, represented by Republican Martha McSally since 2015, and the exurbs north and west between Tucson and Phoenix in the 3rd District are represented by Democrat Ann Kirkpatrick since 2008. The United States Postal Service operates post offices in Tucson. The Tucson Main Post Office is located at 1501 South Cherrybell Stravenue.
Both the council members and the mayor serve four-year terms; none face term limits. Council members are nominated by their wards via a ward-level primary held in September. The top vote-earners from each party then compete at-large for their ward's seat on the November ballot. In other words, on election day the whole city votes on all the council races up for that year. Council elections are severed: Wards 1, 2, and 4 (as well as the mayor) are up for election in the same year (most recently 2011), while Wards 3, 5, and 6 share another year (most recently 2013).