README.md

---
license: cc-by-4.0
language:
- ja
- en
pretty_name: "Japan Construction Cost Database (JCCDB)"
tags:
- construction
- cost-estimation
- consumer-protection
- japan
- taxonomy
- open-data
size_categories:
- 10K<n<100K
task_categories:
- text-classification
- feature-extraction
---

# Japan Construction Cost Database (JCCDB)

**A public, structured taxonomy of 65,729 construction cost line-items across 398 categories — item names, categories, and units only (no prices).**

JCCDB is the first openly published, machine-readable taxonomy of construction and renovation cost line-items for the Japanese market. It is designed to give homeowners, researchers, and developers a neutral, standardized vocabulary for construction cost items — addressing the structural information asymmetry between contractors (who know prices) and homeowners (who do not).

This release contains **item names, category classifications, and units of measurement only. It contains no prices.** Pricing is intentionally excluded; the database is a *naming and classification layer*, not a price list.

---

## Abstract

In residential construction and renovation, homeowners face a persistent information asymmetry: estimates are frequently presented as opaque "lump-sum" (一式) line-items with no breakdown of quantity, unit, or unit price. This opacity is a structural enabler of overcharging. A precondition for any neutral cost-verification system is a shared, standardized taxonomy of construction line-items — yet no such open, machine-readable taxonomy has existed for the Japanese market.

The Japan Construction Cost Database (JCCDB) addresses this gap. It is a publicly released taxonomy of 65,729 construction cost line-items organized into 398 categories, specifying for each item its standardized name, category, and unit of measurement. Prices are deliberately excluded; JCCDB defines *what* is being built and *how it is measured*, not *what it costs*. This separation allows the taxonomy to serve as neutral public infrastructure that any party — homeowner, contractor, researcher, or third-party verifier — can reference without commercial bias.

We describe the construction of the taxonomy, its category structure, and its intended role as a foundational layer for transparent cost estimation and consumer-protection applications in the construction domain. The database is released under CC-BY-4.0 and is permanently archived with content-addressed integrity proofs.

---

## Dataset Structure

| Field | Description |
|-------|-------------|
| **item name** | Standardized name of the construction cost line-item |
| **category** | One of 398 construction work categories |
| **unit** | Unit of measurement (e.g., ㎡, m, 個, 式, 人工) |

- **Total items:** 65,729
- **Categories:** 398
- **Contains prices:** No — names, categories, and units only

### What this dataset is *not*
JCCDB is a **naming and classification layer**. It is intentionally distinct from any pricing dataset. Pricing for HORIZON SHIELD's diagnostic services is maintained in a separate, independent layer ("souba-db", 170 categories) and is **not** part of this release.

---

## Intended Use

- A standardized vocabulary for describing construction/renovation work
- A classification target for parsing or normalizing real-world estimates
- Research on construction-cost transparency and consumer protection
- A neutral reference layer for third-party cost-verification systems

### Out-of-scope / cautions
- This dataset provides **no prices** and must not be represented as a price reference.
- It does not constitute legal, financial, or construction advice.

---

## Provenance & Permanent Archival

This dataset and its accompanying paper are permanently archived and identified across multiple independent systems for integrity and citation:

| System | Identifier |
|--------|-----------|
| **SSRN** | abstract_id = 6738701 |
| **engrXiv** | DOI: 10.31224/7007 |
| **Zenodo** | (archived) |
| **GitHub** | ogasurfproject-jpg/japan-construction-cost-database |
| **Bitcoin (OpenTimestamps)** | Block #949356 |

Content integrity is anchored to the Bitcoin blockchain via OpenTimestamps, providing an independent, tamper-evident proof of the dataset's existence at a fixed point in time.

**WPC (Weighted Price Coefficient) reference value: 1.0935** *(methodological constant published with the accompanying paper; not a price.)*

---

## Citation

If you use this dataset, please cite:

```bibtex
@misc{oga2026jccdb,
  title        = {Japan Construction Cost Database (JCCDB):
                  An Open Taxonomy of Construction Cost Line-Items
                  for Transparency and Consumer Protection},
  author       = {Oga, Toshikatsu},
  year         = {2026},
  doi          = {10.31224/7007},
  note         = {SSRN abstract 6738701; archived on Zenodo and
                  Bitcoin block 949356},
  howpublished = {Hugging Face Datasets: ogasurfproject/jccdb}
}
```

---

## License

Released under **Creative Commons Attribution 4.0 International (CC-BY-4.0)**.
You may share and adapt the material for any purpose, including commercially, provided you give appropriate credit.

---

## Author

**Toshikatsu Oga (大賀 俊勝)**
Founder & Representative Director, The HORIZ音s株式会社 / HORIZON SHIELD
ORCID: 0009-0000-9180-903X
30+ years in construction (carpenter → site supervisor → construction manager → AI engineer)

Project: https://shield.the-horizons-innovation.com/presentation.html