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Negative Match

The Negative Match page at /mdm/negative-match lists "do-not-match" rules — pairs or groups of records the matcher would otherwise consolidate but stewards have explicitly marked as different entities.

Why negative match​

Even well-tuned match rules produce false positives:

  • Twins with the same name and address
  • A customer and their adult child with the same email and phone
  • Two business entities with very similar names but distinct legal structures
  • A renamed entity that re-appears in source as a "new" record but mustn't merge with the legacy

Lowering the match threshold to avoid these breaks legitimate matches. Negative match is the surgical fix: keep rules tuned for the common case, blacklist exceptions explicitly.

Rule types​

TypeNotes
PairTwo specific entity IDs that must not merge
GroupA set of entity IDs that must remain separate from each other
PatternRule predicate (e.g. "records with same email but different last_name suffix never match")

Authoring​

The most common path is via Stewardship: when a steward rejects a match, the case offers a checkbox to Add to negative match. Selecting it captures the pair as a permanent exception.

Manual authoring:

type: pair
entity_a_id: ent_abc
entity_b_id: ent_xyz
reason: "Twin sisters - same name, address, phone, but distinct individuals"
created_by: steward@acme.com

Pattern rules:

type: pattern
predicate: |
  a.email = b.email
  AND a.last_name = b.last_name
  AND (a.suffix IS NOT NULL OR b.suffix IS NOT NULL)
  AND a.suffix IS DISTINCT FROM b.suffix
reason: "Senior/Junior with shared email"

Enforcement​

When the matcher computes pairs, it checks each candidate match against the negative list. Matches blocked by negative match are recorded in the run log with the rule ID for audit.

Review​

The page lists all negative-match rules with:

  • Entity IDs (clickable to Golden Records)
  • Reason
  • Created by + when
  • Match attempts blocked (count)
  • Status (active / inactive)

Stewards can deactivate a rule if circumstances change (e.g. it turns out the records really are duplicates).

API​

GET    /mdm/negative-match
POST   /mdm/negative-match
PATCH  /mdm/negative-match/{id}     # activate / deactivate
DELETE /mdm/negative-match/{id}