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Extended FOM Module Merging Capabilities

SISO SIWzie award winner

ABSTRACT: The HLA Evolved specification describes a number of FOM Module merging principles whereby classes, data types, etc. from different modules can be merged into the FOM of a federation. Based upon practical experiences with FOM modules, this paper proposes three additional capabilities for the next HLA version. They are particularly useful, and in some cases necessary, when reusing and extending standardized FOMs, for example the RPR FOM. They can also be designed so that backwards compatibility is maintained.


The first capability is to enable a module to add attributes to an already existing object class. This enables federations to extend object classes of a reference FOM without modifying the reference FOM.

The second capability is to enable a module to add DDM dimensions to an already existing attribute or interaction class. This enables federations to use DDM filtering for concepts described in a reference FOM. An even more powerful approach would be to not require dimensions to be explicitly specified in the FOM for attributes and interactions classes, which would increase flexibility.


The third capability is a development time rather than runtime FOM merging capability. An enumerated data type in a FOM should be able to reference and include a separately stored list of enumerated values. This would simplify the usage of enumerations in the RPR FOM, where several enumerations, with a large number of values, are shared with the DIS standard.

These three capabilities are presented in detail for discussion and possibly inclusion in the next version of HLA.

Authors: Björn Möller, Andy Bowers, Mikael Karlsson, Björn Löfstrand
Publication: Proceedings of 2013 Spring Simulation Interoperability Workshop, 13S-SIW-004, Simulation Interoperability Standards Organization, April 2013.

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