This article explores intraindividual microvariation in dialect syntax. We argue that in many cases the speaker has internalized a different (sub)grammar for each dialectal variety, in line with the hypothesis of universal bilingualism and parallel grammars argued for by Roeper (1999 et seq.). We discuss the question of how we can distinguish parallel grammars from optionality within one grammar, suggesting that the identification of correlating contextual factors might be a promising criterion. However, we also explore a more subtle type of variation, namely cases where a standard variety influences a potentially more vulnerable non-standard variety in a way that makes it exceedingly difficult for the language user and even for a trained linguist to discern what is what. We discuss whether or not these properties should be analysed as properties of another subgrammar (the standard grammar) or as fully integrated (albeit acquired) properties of the non-standard dialect.

Shape grammars come in a variety of forms. Algebras of shapes have been defined for spatial elements of different kinds, as well as for shapes augmented with varying attributes, allowing for grammar forms to be expressed in terms of a direct product of basic algebras. This algebraic approach is extended here to the algebraic derivation of combinations of basic shape algebras with attribute algebras. This algebraic abstraction at the same time serves as a procedural abstraction, giving insights into the modular implementation of a general shape grammar interpreter for different grammar forms. In addition, we consider practical limitations on algebraic compositions of basic shape algebras with attribute algebras and identify a complication with respect to solving the matching problem for parallel and compound shape grammars, suggesting a way to address this complication.