Bipartite hop — Linnainmaa 1976 citation histogram vs OSTI SAND-91-7095 structured date: no shared entity; the real overlap is 'database field as witness', and it exposes a granularity gap in the OSTI 'January 1992' claim

bipartiteembedding-false-friendbridge-investigationbibliometricsostisemantic-scholarmetadata-granularitysand-91-7095linnainmaa

Sibling check (bridge-seed discipline): grep of 10-inbox/raw/ for captures naming both claim-linnainmaa-1976-citation-histogram and claim-osti-structured-metadata-confirms-sand91-7095-january-1992 found none (the first appears in three captures, the second in one; no file contains both). This is a first investigation of the pair. Related prior tests of the same kind: observation-greenhalgh-2003-klensin-romberg-1989-cosine-pairing-is-embedding-false-friend, observation-gates-jevons-cosine-pairing-is-embedding-false-friend, observation-ml-ad-en-gedi-cosine-pairing-is-embedding-false-friend.

Verdict in one line: at the object level a false friend (no person, document, institution or dataset joins them), but the pairing is not empty — both notes rest a claim on a bibliographic database's structured field, and reading them side by side surfaces a granularity question the OSTI note does not answer.

Claim: No entity, document or dataset connects the two notes (object-level false friend)

• claim_type: historical/structural (uncontested; Tier 1 record reads below)
• The Linnainmaa note concerns a 1976 paper in BIT (DOI 10.1007/BF01931367, title "Taylor expansion of the accumulated rounding error") and per-year counts of papers citing it; the OSTI note concerns a 1992 Sandia report by Sulsky, Chen and Schreyer on the material point method. The OSTI record's author/lab fields (Sulsky, Chen, Schreyer; Sandia National Labs., Albuquerque) contain no Linnainmaa or automatic-differentiation link. In the Semantic Scholar citation list for the Linnainmaa paper, entries are identified only by opaque paperId and year (the query requested fields=year), so this session could not test whether SAND-91-7095 or any Sulsky/Schreyer paper is among the 305 citing papers. [unverified — could not confirm or deny after search: whether any citing paperId is a material-point-method paper; would need a second API call with fields=title,authors.]
• source_url: https://api.semanticscholar.org/graph/v1/paper/DOI:10.1007/BF01931367/citations?fields=year&limit=1000
• source_sha: 43b3efdd5bd90cc697a78269b0f5c05e234c334973c50712f3a3c78e3579fa66
• source_title: (API response; no document title — the queried paper is "Taylor expansion of the accumulated rounding error")
• source_author: Semantic Scholar Graph API (Allen Institute for AI)
• source_date: queried 2026-09-26
• source_venue: Semantic Scholar Academic Graph API
• source_tier: 2 (an aggregator's derived database of others' metadata; the vault's earlier note grades it 1 by house convention — graded conservatively here)
• source_quote: {"citingPaper": {"paperId": "218a7f84a4048b4b8cd14ba1f5b326d9b5089bfd", "year": null}} (structure of the record: id + year only)
• The OSTI half: source_url https://www.osti.gov/biblio/5900384, source_sha f96ee695…a953a160e (above), source_title "The application of a material-spatial numerical method to penetration", source_tier 1, source_quote: "Report Number(s):SAND-91-7095".
• verifies: (no named question stem supplied for this topic)

Claim: The genuine shared mechanism is 'a database's year/date field used as the witness', and the two databases use it at different granularities

• claim_type: technical-mechanism (Tier 1 record reads; the inference is flagged)
• Semantic Scholar's citation records carry a bare integer year per citing paper, with some null — the histogram is therefore built on year-level data only, which is adequate for a per-decade table. I re-tallied 1978–2009 by hand from the fetched response and got 51 dated citations (1970s 3, 1980s 6, 1990s 25, 2000s 17), matching the existing note's pre-2010 figures. I did not re-tally 2010 onward. I counted ten null-year entries at the tail of the list by eye, where the existing note says nine undated [unverified-quant — hand count of a 27 KB JSON, needs a scripted recount; possible one-off discrepancy, or an artifact of the live index having changed since 2026-07-07].
• OSTI's record exposes a month (month = {01}) and a full timestamp ("Technical Report·Wed Jan 01 00:00:00 EST 1992"). But a different, unrelated OSTI record (OSTI ID 4024824, an Illinois Univ. Materials Research Lab report) exports the identical pattern for 1971: "Technical Report·Fri Jan 01 00:00:00 EST 1971" and year = {1971}, month = {01}. Two records agreeing on "01 Jan 00:00" is what a year-only placeholder would also produce. So the OSTI note's "January 1992" is confirmed as what OSTI's export says, not yet as what the report's date is; the year 1992 is unaffected. The cross-reference sidebar value "Tue Dec 31 19:00:00 EST 1991" equals 1992-01-01 00:00 UTC, consistent with the earlier note's UTC-rendering reading — one instant, rendered two ways.
• [unverified-mechanism -- needs primary]: that OSTI fills unknown months/days with 01/01. Only one comparison record was inspected; a search-engine summary asserted this practice but is a summarising layer and is not relied on. I read the OSTI FAQ (sha 4ee05d82…6198a) through its opening sections (metadata fields are collected via the E-Link submission system, with a PDF metadata table); the passage on date semantics, if any, was not reached. The metadata-table PDF linked from that FAQ is the likely primary.
• source_url: https://www.osti.gov/biblio/4024824
• source_sha: 45a819b6f23de86af39d827863246a25aaca054f17d08522c61afafc808a3ab8
• source_title: "ANNUAL PROGRESS REPORT."
• source_author: Illinois Univ. (Materials Research Lab., Urbana), per OSTI catalog
• source_date: 1971 (OSTI catalog); read 2026-09-26
• source_venue: OSTI.GOV, Technical Report COO-1198-808
• source_tier: 1 (for what OSTI's catalog records)
• source_quote: "Technical Report·Fri Jan 01 00:00:00 EST 1971"
• Second source_quote (SAND-91-7095 record, sha f96ee695…): "Technical Report·Wed Jan 01 00:00:00 EST 1992"

Claim: The resemblance does not transfer evidence in either direction

• claim_type: definitional/structural
• The Linnainmaa histogram supports a claim about citation volume by year and says nothing about report dating; the OSTI export supports a claim about a catalog's recorded year and says nothing about citation behaviour. The vault's ML/AD-communities-mutual-unawareness note claim-ml-and-ad-communities-mutually-unaware and the Sandia cluster (entity-howard-schreyer, entity-deborah-sulsky, entity-zhen-chen, claim-schreyer-bibliography-confirms-1992-asme-publication) sit in separate fields; claim-linnainmaa-field-numerical-analysis places Linnainmaa in numerical analysis, the neighbouring field to computational mechanics, but no citation or author link between them was found. [unverified — could not confirm or deny a hidden connection after search.]
• Source: the two vault notes above (Tier 1 as house convention for vault-recorded facts; not independently re-fetched beyond the primary records cited in the previous claims).

Safety flags

None fired. All fetched pages (osti.gov record pages, OSTI FAQ, Semantic Scholar API JSON) were plain record/reference text with no addressed-to-AI, override, authority, credential or file-system content. The web search summary was treated as a lead only.

Further leads

• Re-run the Semantic Scholar query with fields=title,authors,year and script the per-decade tally, including a null-year count check (10 vs 9): https://api.semanticscholar.org/graph/v1/paper/DOI:10.1007/BF01931367/citations
• OSTI E-Link "Metadata Table (PDF)" linked from https://www.osti.gov/faqs — likely primary for how partial dates are stored.
• Sample more pre-1995 OSTI technical reports with known month-level dates (cover pages) to see whether month ever varies from 01 — would confirm or kill the placeholder hypothesis. Cover-page date of SAND-91-7095 itself remains unfound.
• Search results surfaced other OSTI year-only-looking records (e.g. https://www.osti.gov/biblio/4626960) — not read.

Entity candidates

• Seppo Linnainmaa — person — the foundational figure whose 1976 paper the histogram measures; the priority claim rests on him.
• Semantic Scholar Graph API — term — source of the citation counts; its year-only field defines the histogram's grain.
• OSTI E-Link — term — DOE's submission system for citation metadata; determines what date fields OSTI records mean.
• OSTI.GOV — term — U.S. DOE catalog; the venue of record for SAND-91-7095's metadata.
• Deborah Sulsky — person — SAND-91-7095 author, the report's material-point-method lineage.
• Howard Schreyer — person — SAND-91-7095 co-author.
• Zhen Chen — person — SAND-91-7095 co-author.
• Metadata granularity / placeholder dates — concept — year-only records rendered as Jan 1 00:00; affects any "month" claim from catalog exports.
• Material point method — concept — subject of SAND-91-7095; separate field from automatic differentiation.
• Citation histogram / bibliometric resurrection curve — concept — the Linnainmaa note's core artifact.