Generalized Use of Non-Terminal Symbols for Procedural Modeling

We present the new procedural modeling language G2 (Generalized Grammar) which adapts various concepts from general purpose programming languages in order to provide high descriptive power with well-defined semantics and a simple syntax which is easily readable even by non-programmers. The term "Generalized" reflects two kinds of generalization. On the one hand we extend the scope of previous architectural modeling languages by allowing for multiple types of non-terminal objects with domain-specific operators and attributes. On the other hand the language accepts non-terminal symbols as parameters in modeling rules and thus enables the definition of abstract structure templates for flexible re-use within the grammar. By deriving G2 from the well-established programming language Python, we can make sure that our modeling language has a well-defined semantics. For illustration, we apply G2 to architectural as well as plant modeling in order to demonstrate its descriptive power with some complex examples.