Recognises a chasm trap

K-525 · Skill knobit · Activity: Derive the logical data model · Competence: Data modelling

A path exists, but an optional relationship on it breaks it for some instances, so they silently drop out of every query that follows the path.

Can AI do this?

Not tested yet

No AI benchmark covers this knobit yet. New results are announced in the Can AI Do the Job? newsletter.

What it looks like in practice

Expected result: The path, the optional relationship on it, and the instances that drop out

How it is assessed: Flags the deficient case and passes the acceptable one. Deficient: Branch 1:N Account Manager 1:N Account with Account → Account Manager optional: accounts opened online have no path to a branch and vanish from branch totals (row 24's fix can create this) Acceptable: A direct Account → Branch relationship, or a direct-channel branch, so every account reaches exactly one

Also known as: Chasm trap (logical model)

Related knobits

Builds on

• K-569 Explains the connection, fan and chasm traps

Needed for

• K-628 Recognises a nullable foreign key on a reporting join path

All 56 knobits of Derive the logical data model.

Source: Review checklist 05-logical, row 25; Howe; C&B