Fabric of the Universe


This section briefly describes the few core concepts that form the foundation for all of BIS. All information in a BIS Repository is defined using Elements, ElementAspects, Models and relationships. We refer to these core concepts a “the fabric of the universe”.

BIS is expressed using the EC Information Modeling Language (aka “using ECSchemas”). However BIS imposes additional rules, naming conventions, and other restrictions. It is assumed that the reader is familiar with ECObjects. See ECSchema.

Most of the concepts below are defined as ECClasses in the “BisCore” domain schema, which has the alias “bis”, and thus we write “{ClassName}” to denote an ECClass defined in BisCore.


An Element is an object in the digital world that represents some entity in the real world, e.g. pumps, beams, contracts, companies, etc.). Elements are contained in Models. Elements are defined through ECProperties. Elements are the finest-grained object in BIS that can be individually identified and locked.

See Element Fundamentals for a more detailed discussion.


An ElementAspect is a set of ECProperties that “belong” to a particular Element, but which have an independent lifecycle (they may come and go over the lifetime of the Element). ElementAspect instances are owned a single Element; ElementAspects are never shared by more than one Element. An ElementAspect is considered part of the Element and therefore can not be the target of any “incoming” relationships (other than from the single Element that owns it.) There are ElementUniqueAspects that have a maximum of one instance per Element and ElementMultiAspects that may potentially have many instances per Element.

See ElementAspect Fundamentals for a more detailed discussion of ElementAspects.


A Model is a “container” of Elements that provides a context (and a Modeling Perspective) for the contained Elements.

See Model Fundamentals for a more detailed discussion of Models.


Various ECRelationship classes are defined in BisCore to relate Models, Elements and ElementAspects. See Relationship Fundamentals for a more detailed discussion of Relationships.

No other Data Types

All BIS information is defined using the Element, ElementAspect, Model classes or by using relationships. BIS domain schemas (other than BisCore) can only define classes that (directly or indirectly) subclass classes defined in the BisCore domain.

Next: Element Fundamentals

Last Updated: 06 December, 2018