In general, the geometry will be identified by the autocad_entity.
For more information, see Feature Representation.
Geometry Traits
In a number of Civil3D feature types such as Alignments, the geometry of a feature can be quite complicated and make use of a number of different entities, each with its own purpose. Since FME currently restricts a feature to having only one geometric element, the Civil3D Reader constructs an aggregate out of the different geometry properties that a given feature has. At each level of geometry hierarchy, a geometry contains a geometry trait called Name which identifies it.
An example taken from an Alignment element shows the Name trait in question.
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Geometry Type: IFMEAggregate
Number of Geometries: 23
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Geometry Number: 0
Geometry Type: IFMEMultiPoint
Name(fme-system): aec_align_begin_points'
Number of Points: 1
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Point Number: 0
Geometry Type: IFMEPoint
Coordinate Dimension: 2
(20039.54386238,20618.287148300002)
[rest of geometry omitted]
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Geometry Traits are also used to tie properties of a geometry to that geometry rather than the FME feature which contains that geometry. Due to aggregation of geometry on FME features read by the Civil3D Reader, the following Feature attributes may be stored on either as attribute on a Feature, or as traits on a geometry.