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.