Overlapping Systems

During design workflows, multiple responsible parties may collaborate on the design of a single physical Entity. There are a wide variety of potential collaboration workflows involving the PhysicalElement modeling that physical Entity. We examine how BIS addresses this issue using the example of an architect and a structural engineer collaborating on the design of a load-bearing wall…

There are situations in which both the architect and structural engineer must be able to express differing “opinions” regarding the wall’s design. When using iModels, we hope to solve most of these cases via “branching” and a “pull-request” workflow—each party can make “suggested changes” to a given Element in their own branch and then make a “pull-request” for the other party to review, approve, pull, and merge the suggested changes.

There may still be cases where we need to temporarily allow the architect and the structural engineer to each have their own LoadBearingWall Element in their own Model, both modeling the same physical load-bearing wall Entity. The architect can use his/her Element to represent a “suggestion” to the structural engineer.

We must maintain clarity on which Element is the authoritative LoadBearingWall (in this case, the one in the structural Model). The authoritative LoadBearingWall may have a non-null FederationGUID and CodeValue, while the non-authoritative one should have NULL for those properties. There will also be a PhysicalElementIsANonAuthoritativeDuplicateOfPhysicalElement relationship to indicate which LoadBearingWall is a Non-Authoritative Duplicate (NAD) of the other.

When the collaboration is “done”, and both Elements are consistent, the non-authoritative LoadBearingWall should be deleted. The LoadBearingWall in the structural Model would be related to the architectural System via PhysicalElementIncludesPhysicalElement and related to a CompoundWall via AssemblyIncludesPhysicalElement. Any relationships that were pointing to the non-authoritative LoadBearingWall should be re-mapped to the authoritative one.

Consistency checks can ensure that all NADs are eliminated before designs are finalized and published for use in construction or operations, where redundant modeling of the same physical Entity creates problems.


Next: Physical Models and Elements

Last Updated: 13 August, 2019