Methodology
The semantic contract of this dataset.
What we observe
venue-access-eu records public observations of trading-venue membership captured from official venue sources. An observation means: "this firm appeared as a member in a specific captured artifact at a specific time." Nothing more is claimed.
What we do not observe
The dataset does not attempt to identify private routing arrangements, DMA/DEA relationships, sponsored-access arrangements unless explicitly published by the venue, contractual broker relationships, or a firm's actual ability to execute a given order. Membership, access, routing, clearing and settlement are distinct concepts; only observed membership is modelled.
Absence semantics
NOT_OBSERVED means: no matching membership was found in a successfully processed source whose documented scope covers the question. It is never rendered as "has no access". When a source is partial, failed, or quarantined, the answer is UNKNOWN — with the reason attached.
Temporal semantics
first_seen_at means "present in a good snapshot taken that day" — not "became a member that day". Sources do not publish valid_from/valid_to for memberships, so we never fabricate them. A disappearance requires two consecutive good snapshots to be CONFIRMED; a single absence is only POSSIBLY_DISAPPEARED. Quarantined snapshots create no absence events.
Identity resolution
Participants are matched to GLEIF legal entities (LEI) by a deterministic, auditable pipeline: source-provided LEI when the venue publishes it, else exact normalized legal-name match corroborated by country/address evidence. Fuzzy matches produce review candidates, never automatic merges. Ambiguous names stay UNRESOLVED. Manual overrides are recorded with reviewer, reason and date.
Provenance
Every public claim traces to: raw artifact bytes (SHA-256), retrieval timestamp, official URL, parser version, normalized record hash, and the identity-resolution method. Snapshots are immutable.
Source quality gates
A snapshot that drops >15% of records or segments versus the previous good snapshot, returns zero rows, fails schema checks, or looks like a block/error page is QUARANTINED. Mass "disappearances" are treated as pipeline failures until proven otherwise.
Known limitations
Coverage v0.1: Xetra, Euronext (7 markets, cash+derivatives), BME equity members, LSE member firm directory. Not covered: Cboe, Aquis, Athens, Nasdaq Nordic/Baltic, SIX, Warsaw, Eurex, CCP membership. GLEIF Level-2 relationships are populated only for resolved LEIs. Snapshots are periodic observations, not a continuous feed.