Three papers lacked abstracts and 1911.00966 was fully degraded (OpenAlex 404
-> empty `Paper(id, title="")` stub). Recovery sources verified, then wired in:
- arxiv.fetch_metadata: resolve an arXiv id to a Paper via the Atom export API
(authoritative for preprints). Used as an ingest fallback on OpenAlex 404,
replacing the empty stub.
- crossref.py (new): fetch_abstract(doi), JATS-stripped, Crossref Polite Pool.
- semanticscholar.fetch_abstract: fetch just the abstract field.
- ingest.py: _recover_abstract() supplements an empty abstract from S2 then
Crossref *before* embedding, so the paper gets a real (non-zero) vector.
Live DB backfill: 1911.00966 fully recovered from arXiv (bibkey
PinkallSpringborn2019, 384-char abstract, its 10 chunks now visible to chunk
search); 10.1007/s00454-019-00132-8 abstract from S2 (1186 chars). Book chapter
10.1007/978-3-642-17413-1_7 has no abstract in OpenAlex/S2/Crossref -> documented
limit. Corpus now has 1 paper without an abstract.
Also documented DQ-5 (not fixed): ingest_paper is not idempotent for DOI papers
(openalex returns full-URL id vs the bare canonical id) -> re-ingest trips
papers_openalex_id_key. Blocks roadmap R-A/R-C; needs a careful _map_paper fix.
Tests: arxiv/crossref/s2 fetchers + ingest recovery paths (342 passing).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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