docs/limitations.md

Known limitations: CodeMixCheck v2.2.1

1. Mostly synthetic. 6,910 of the 7,254 released rows are template-generated. Their labels are correct by construction within a simulated world, and no human checked them row by row. They are not real-world fact-checks.
2. No evidence corpus. evidence_explanation states the (simulated) evidence in one sentence. A RAG system cannot retrieve it from anywhere.
3. Semantic overlap across splits (release audit, no rows removed):
   • fact_verification: 84 claim cores (228 rows) recur across splits under different framing (D01). There are 73 near-duplicate cross-split pairs at fuzz.ratio ≥ 90, mostly template siblings with a different entity.
   • sentiment (synthetic): 36 train/validation near-duplicate pairs.
   • abuse_detection: 57 cross-split near-duplicate pairs (train, validation and test are typo/emoji variants of a small set of base comments).
   • Implication: synthetic validation/test scores overestimate generalisation. Use the strict filter (587 of 661 test_synthetic rows) and test_curated.
4. Generator artefacts. Emoji, hashtags, typo patterns and frame templates repeat. Models may pick up surface cues. Rows with an unparsed frame are mostly True (589 of 845).
5. Small auxiliary tasks. Public sentiment has 128 rows (train 98 / validation 30, no test split; the human-collected test set is not released). Abuse has 122 rows (67 / 27 / 28). Neither is representative of naturally occurring sentiment or abuse.
6. Curated test label skew. Hearsay is 100% Unverifiable and health/lifestyle is 90% True. Across test_curated there are only 30 False and 15 Partially True rows. Report results per eval_subset.
7. Missing explanations. 129 curated rows have no evidence_explanation after the v2.2.1 relabel.
8. No source references for curated claims (paraphrased; sources not recorded).
9. Incomplete version history. 782 retired IDs have no recorded reason.
10. Narrow coverage. The data is Tamil Nadu-centric, and Romanisation follows one set of conventions. Sri Lankan, Malaysian, Singaporean and diaspora Tamil are not represented.
11. Single annotator. There is no inter-annotator agreement study.