This page would look a lot spiffier if you downloaded a standards compliant web browser.

Elements that Follow Your Rules: Constraint Based CAD layout
    Proceedings of Association for Computer Aided Design in Architecture (ACADIA) 96 Tuscon, AZ, pp. 115-122 1996
    The paper reports on CKB (Construction Kit Builder) -a prototype CAD program that designers can program with
    positioning and assembly rules for layout of building elements. The program's premise is that designing can be
    understood as a process of making and following rules for the selection, position, and dimension of built and space elements. CKB operates at two distinct levels of design: the technical system designer, who makes the rules, and the end designer, who lays out the material and space elements to make a design. CKB supports two kinds of rules with constraint based programming techniques: grid and zone based position rules, and assembly rules that position elements with respect to one another. The paper discusses the rational for CKB and describes its implementation.