Use a Composite System () to define a coordinate system that acts as a consecutive application of two other coordinate systems. The base vectors of a composite coordinate system are defined as the base vectors of a selected Relative system interpreted as relative to a selected Base system, which may be relative or absolute. The resulting composite system is relative or absolute depending on the selected base system, which in the latter case also decides the underlying frame type.

In the Coordinate names table, the default names are entered — x1, x2, and x3. In planar 2D models, x1 and x2 are typically the in-plane coordinates, and x3 is the out-of-plane coordinate.

From the Base system list, choose a relative or absolute coordinate system that define a set of base vectors relative to an underlying frame. Then from the Relative system list, choose a relative coordinate system whose base vectors will be interpreted as components in the selected Base system. Both the Base system and the Relative system can have the value None, which is interpreted as an identity mapping of axes. Other Composite System nodes are allowed provided that they do not cause a circular dependency.