README.md

---
license: cc-by-4.0
task_categories:
  - text-retrieval
language:
  - en
size_categories:
  - 1K<n<10K
tags:
  - table-retrieval
  - keyword-search
  - data-discovery
  - tables
  - wikipedia
pretty_name: WikiTables
configs:
  - config_name: metadata
    data_files:
      - split: all
        path: metadata.csv
  - config_name: queries
    data_files:
      - split: all
        path: queries.csv
  - config_name: qrels
    data_files:
      - split: all
        path: qrels.csv
---

# WikiTables

## Dataset Summary

WikiTables is a dataset for **keyword search over tables (KWS-over-tables)**:
given a short natural-language keyword query (e.g., *"2008 beijing olympics"*),
a retrieval system must rank the tables in a corpus by their relevance to the
query. The task is the table analog of text retrieval — instead of returning
documents, the system returns structured tables.

The corpus is a downsampled subset of the WikiTables corpus, a large
collection of HTML tables extracted from Wikipedia and originally assembled
for entity linking research. Tables in this corpus do **not** have schema-style
table names; instead, each table is identified by an opaque `table_id` and
described by the column names plus surrounding Wikipedia context (page title,
section title, caption).

Relevance judgments are **graded on a 0–2 scale** (`0` = non-relevant,
`1` = related, `2` = relevant), inherited unchanged from the original
WikiTables benchmark. This differs from the binary positive-only convention
used by the other datasets in the Polaris suite.

WikiTables is one of six datasets in an evaluation suite for the KWS-over-tables
task; each dataset is published as its own Hugging Face repo following a
shared schema (with the per-dataset variations noted below).

## How to Use

WikiTables is an **evaluation-only** benchmark — there is no train/test split.
All rows live in a single split named `all`. (Hugging Face's `datasets`
library requires every config to declare a split; `all` is used here in place
of the default `train` label to avoid implying training data.)

```python
from datasets import load_dataset

# Tables, queries, and graded relevance judgments
metadata = load_dataset("anhaidgroup/wikitables", "metadata", split="all")  # 3,361 tables
queries  = load_dataset("anhaidgroup/wikitables", "queries",  split="all")  # 60 queries
qrels    = load_dataset("anhaidgroup/wikitables", "qrels",    split="all")  # 3,120 judgments
```

For methods that consume tuple-level data, download the per-table tuples
archive separately:

```python
from huggingface_hub import hf_hub_download
import zipfile, pandas as pd

zip_path = hf_hub_download("anhaidgroup/wikitables", "tuples.zip", repo_type="dataset")
with zipfile.ZipFile(zip_path) as z:
    with z.open("Tuples/table-0001-249.csv") as f:
        df = pd.read_csv(f)
```

Methods that retrieve over table metadata (column names and Wikipedia
context) only need `metadata`, `queries`, and `qrels`. Methods that retrieve
over actual tuple values additionally need `tuples.zip`.

## Dataset Structure

### Files

| file | size | purpose |
|---|---|---|
| `metadata.csv` | 3,361 rows | one row per table; identifier, column names, Wikipedia context |
| `queries.csv` | 60 rows | one row per query; identifier and query text |
| `qrels.csv` | 3,120 rows | graded relevance judgments (0/1/2) |
| `tuples.zip` | 3,361 inner CSVs | per-table tuple data, one CSV per table |

### Schema

`metadata.csv`

| column | type | description |
|---|---|---|
| `table_id` | str | unique identifier, e.g., `table-0001-249` |
| `column_names` | str | JSON-encoded list of column names; parse with `json.loads` |
| `table_context` | str | JSON-encoded object with Wikipedia context for the table; commonly contains `pgTitle` (page title), `secondTitle` (section title), and `caption`; parse with `json.loads` |

There is no `table_name` column. Wikipedia tables are not named in the source
data — the role usually played by a table name is filled by `table_context`,
which carries the page and section the table came from.

`queries.csv`

| column | type | description |
|---|---|---|
| `query_id` | int | unique identifier, e.g., `1`, `2`, ..., `60` |
| `query` | str | natural-language keyword query |

Note that `query_id` is an integer here, in contrast to the string form
(`q1`, `q2`, ...) used by the other Polaris datasets. This matches the
original WikiTables release.

`qrels.csv` — graded relevance, **not** positive-only.

| column | type | description |
|---|---|---|
| `query_id` | int | foreign key to `queries.csv` |
| `table_id` | str | identifier from the original WikiTables corpus (see note below) |
| `relevance_score` | int | `0` = non-relevant, `1` = related, `2` = relevant |

`tuples.zip` — archive of per-table CSV files.
- Inner layout: `Tuples/<table_id>.csv` (one file per table).
- Each inner CSV: header on row 0 (matching the `column_names` entry in
  `metadata.csv` for that `table_id`), tuples on subsequent rows, RFC 4180
  quoting.
- Headers may contain duplicate or empty strings (Wikipedia tables sometimes
  have repeated or unnamed columns). Use a CSV parser that returns headers
  verbatim; `pandas.read_csv` will auto-suffix duplicates (`Foo` → `Foo.1`)
  and rename blanks (`""` → `Unnamed: 0`).

### Statistics

- **3,361** tables, after corpus downsampling (see below).
- **60** keyword queries (the full original WikiTables query set).
- **3,120** graded judgments: 2,269 non-relevant (`0`), 474 related (`1`),
  377 relevant (`2`).
- Per-query judgment counts range from 39 to 62 (median 52).

## Dataset Creation

### Source Data

The corpus is a downsampled subset of the WikiTables corpus, a collection of
roughly 1.6M HTML tables extracted from English Wikipedia, originally
assembled for entity linking research. The 60 keyword queries and the graded
(0–2) relevance judgments used here are from the ad hoc table retrieval
benchmark introduced by Zhang and Balog (2018) over that corpus. Tables
carry column names and surrounding page context (page title, section title,
caption) but no schema-style table names.

### Downsampling

Generating LLM enrichments for the full 1.6M-table corpus is prohibitively
expensive. To make LLM-based KWS evaluation tractable while preserving task
difficulty, the corpus is downsampled as follows:

> For each query, retrieve the top-50 tables via BM25 and take the union
> with all tables judged relevant for that query. This focuses the corpus on
> hard cases (BM25-retrievable distractors) without removing relevant
> material.

This procedure yields **3,361 retained tables**, listed in `metadata.csv`,
with their full tuple content in `tuples.zip`.

### Annotations

Relevance judgments are inherited unchanged from the Zhang and Balog (2018)
ad hoc table retrieval benchmark and were produced by manual inspection. The
0–2 scale reflects three judgment levels (non-relevant / related / relevant)
and is preserved as-is in `qrels.csv` rather than being collapsed to binary,
so users can replicate prior published numbers and compute graded-relevance
metrics (e.g., nDCG) directly.

## Considerations for Using the Data

### Why `qrels.csv` references some tables not in `metadata.csv`

The original WikiTables qrels file contains 3,120 (query, table) judgments
covering tables in the full 1.6M-table source corpus. After downsampling,
3,361 of those tables remain in `metadata.csv`. To preserve the full source
qrels file as published, **`qrels.csv` retains all 3,120 original rows**,
including rows whose `table_id` is not present in `metadata.csv`.

In practice:

- All `relevance_score = 1` and `relevance_score = 2` rows reference tables
  that *are* in `metadata.csv`. Every relevant table was kept by the
  downsampling procedure (it is in the union of "BM25 top-50 ∪ all relevant
  tables").
- Rows whose `table_id` is *not* in `metadata.csv` all have
  `relevance_score = 0`. These judgments concern tables that were dropped
  from the corpus during downsampling and cannot be retrieved by any system
  evaluated on this release.

This is a deliberate choice to preserve the original WikiTables qrels file
verbatim. It does mean that **`qrels.csv` does not satisfy a strict foreign-key
constraint with `metadata.csv`**. Code that joins the two files should either
use a left join (and treat the gap as expected) or filter to in-corpus
judgments before evaluation:

```python
import pandas as pd
md = pd.read_csv("metadata.csv")
ql = pd.read_csv("qrels.csv")
ql_in_corpus = ql[ql.table_id.isin(md.table_id)]   # 1,141 rows: 290 zeros + 474 ones + 377 twos
```

For most retrieval evaluations the in-corpus subset is the right one to use,
since a system cannot retrieve a table that is not in the corpus.

### Why `queries.csv` retains all 60 queries

Three queries (`12` *running shoes*, `52` *erp systems price*, `53` *cats
life span*) have no `relevance_score >= 1` row anywhere in the WikiTables
qrels file — i.e., they had no relevant tables even in the full 1.6M-table
source corpus. We retain these queries in `queries.csv` to preserve the
original WikiTables query set. Users who want to evaluate only on queries
with at least one relevant table in the downsampled corpus should filter:

```python
qr = pd.read_csv("queries.csv")
ql = pd.read_csv("qrels.csv")
md = pd.read_csv("metadata.csv")
qids_with_relevant = ql[(ql.relevance_score >= 1) & (ql.table_id.isin(md.table_id))].query_id.unique()
qr_eval = qr[qr.query_id.isin(qids_with_relevant)]   # 57 queries
```

### Tuple downsampling

This release additionally caps each table's tuples at 500,000 rows
(`df.head(500_000)` against the source); tables with fewer rows are
unaffected. WikiTables tables are typically small (extracted from
single-page HTML), so this cap binds rarely if at all.

`metadata.csv` and `qrels.csv` were produced against the un-capped corpus.
Methods that rely only on metadata are unaffected; methods that inspect
tuple values may produce a slightly deflated score relative to the same
method evaluated on the un-capped corpus.

## License

The dataset is released under
[CC-BY-4.0](https://creativecommons.org/licenses/by/4.0/). You are free to
share and adapt the material with attribution.

The source WikiTables corpus is derived from English Wikipedia content;
attribution should be given to Wikipedia and to the original WikiTables
release.

## Citation

A citation for this dataset release will be added once the associated paper
is published.

<!-- TODO: replace with BibTeX entry on publication -->

The queries and graded relevance judgments are from:

> Zhang, S., and Balog, K. (2018). Ad hoc table retrieval using semantic
> similarity. In *Proceedings of the 2018 World Wide Web Conference* (WWW '18),
> pp. 1553–1562.

```bibtex
@inproceedings{zhang2018adhoc,
  author    = {Zhang, Shuo and Balog, Krisztian},
  title     = {Ad Hoc Table Retrieval using Semantic Similarity},
  booktitle = {Proceedings of the 2018 World Wide Web Conference},
  series    = {WWW '18},
  year      = {2018},
  pages     = {1553--1562}
}
```

## Authors

Minh Phan, Ting Cai, AnHai Doan.