Abstract: The Initial Graphics Exchange Specification (IGES) is one of the most widely used
neutral file standards. The related researches have mainly focused on the translation of single parts,
however, few of them dealt with the IGES form for assemblies, which appear frequently in design.
In this paper, we first summarize the IGES-file form of assemblies in most popular CAD software
and then propose an IGES data exchange algorithm for assemblies based on Directed Acyclic Graph
(DAG) Representation and Production Rules. This method standardizes the process of analysis of
IGES forms, which enhances its commonality and extensibility. Moreover, the correctness of the
method can be formally verified. With this method, we implement the pre-processor and
post-processor for the multi-file IGES representation for assemblies. The experiments conducted in
our geometry modeling system TiGems 7.0 show that the algorithm is fast and robust.

Key words: IGES, assembly, data exchange, DAG, production rules