  We propose the use of hyperedge replacement graph grammars for factor graphs,
or factor graph grammars (FGGs) for short. FGGs generate sets of factor graphs
and can describe a more general class of models than plate notation, dynamic
graphical models, case-factor diagrams, and sum-product networks can. Moreover,
inference can be done on FGGs without enumerating all the generated factor
graphs. For finite variable domains (but possibly infinite sets of graphs), a
generalization of variable elimination to FGGs allows exact and tractable
inference in many situations. For finite sets of graphs (but possibly infinite
variable domains), a FGG can be converted to a single factor graph amenable to
standard inference techniques.
