Semantic Layer Modeling - Chasm trap Issue

Star Schema


Chasm trap is a semantic data modeling issue.

A chasm trap occurs when a semantic layer model suggests the existence of a relationship between entity types, but the pathway does not exist between certain entity occurrences.

This modelling issue is the result of a failure to capture all the relationships that exist in the real world in the model.


  • A Building has one-or-more Rooms, that hold zero-or-more Computers.
  • You would expect to be able to query the model to see all the Computers in the Building.
  • However, Computers not currently assigned to a Room (because they are under repair or somewhere else) are not shown on the list.
  • You need another relation between Building and Computers to capture all the computers in the building.

Documentation / Reference

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