init: README with 26 splits (00=2000 .. 25=2025)

README.md

@@ -1 +1,108 @@
-.
+---
+license: other
+language:
+- en
+tags:
+- perplexity
+- evaluation
+- news
+- time-isolated
+configs:
+- config_name: default
+  data_files:
+  - split: "00"
+    path: "data/00.parquet"
+  - split: "01"
+    path: "data/01.parquet"
+  - split: "02"
+    path: "data/02.parquet"
+  - split: "03"
+    path: "data/03.parquet"
+  - split: "04"
+    path: "data/04.parquet"
+  - split: "05"
+    path: "data/05.parquet"
+  - split: "06"
+    path: "data/06.parquet"
+  - split: "07"
+    path: "data/07.parquet"
+  - split: "08"
+    path: "data/08.parquet"
+  - split: "09"
+    path: "data/09.parquet"
+  - split: "10"
+    path: "data/10.parquet"
+  - split: "11"
+    path: "data/11.parquet"
+  - split: "12"
+    path: "data/12.parquet"
+  - split: "13"
+    path: "data/13.parquet"
+  - split: "14"
+    path: "data/14.parquet"
+  - split: "15"
+    path: "data/15.parquet"
+  - split: "16"
+    path: "data/16.parquet"
+  - split: "17"
+    path: "data/17.parquet"
+  - split: "18"
+    path: "data/18.parquet"
+  - split: "19"
+    path: "data/19.parquet"
+  - split: "20"
+    path: "data/20.parquet"
+  - split: "21"
+    path: "data/21.parquet"
+  - split: "22"
+    path: "data/22.parquet"
+  - split: "23"
+    path: "data/23.parquet"
+  - split: "24"
+    path: "data/24.parquet"
+  - split: "25"
+    path: "data/25.parquet"
+---
+
+# TheFinAI/ppl — Per-Year News Corpus for Perplexity Evaluation
+
+A held-out news corpus for evaluating per-year perplexity of time-isolated
+language models (TILE / MoE per-year experts).
+
+## Structure
+
+- One split per year, named `00` (= 2000) through `25` (= 2025).
+- Each split contains ~2000 news articles sampled month-stratified
+  (~167/month) from The Guardian Open Platform.
+- Sections kept: world, us-news, uk-news, business, politics, technology,
+  science, environment, society, education, media, law, etc.
+  (Sport, lifestyle, food, fashion, film, books, travel, games dropped.)
+- All articles passed `token_count >= 50` (cl100k_base) filter.
+
+## Schema
+
+| column        | dtype  | note                                  |
+|---------------|--------|---------------------------------------|
+| `source`      | str    | constant `"guardian"`                 |
+| `date`        | int32  | year, e.g. `2003`                     |
+| `pub_date`    | str    | publication date `YYYY-MM-DD`         |
+| `section`     | str    | guardian sectionId                    |
+| `headline`    | str    | webTitle                              |
+| `url`         | str    | webUrl                                |
+| `text`        | str    | full article body (`bodyText`)        |
+| `token_count` | int32  | tiktoken `cl100k_base` token count    |
+
+## Usage
+
+```python
+from datasets import load_dataset
+ds = load_dataset("TheFinAI/ppl", split="03")  # year 2003
+```
+
+## Notes
+
+- Cross-year fairness: all years drawn from the same source pipeline, same
+  section filter, same length filter, same tokenizer. PPL comparisons
+  across years should not be biased by corpus shift.
+- Single-source: only Guardian. For multi-outlet eval, supplement with NYT
+  metadata (`TheFinAI/ppl_nyt` if/when added).