Representing Design Objects in SORAC

Abstract

In this paper, we apply our experience in developing ArchObjects, an intelligent architectural design system, towards the development of a general data modeling language appropriate for design representations. An adequate design representation language is crucial to the ability to reason about designs. Current object-oriented and semantic data models are not well-suited to complex design domains, however. The built-in relationship types of the traditional semantic data models do not adequately support the needs of design applications nor do they provide adequate behavioral support. Although object-oriented models are popular, and provide encapsulation of behavior, these do not support built-in relationships or reuse of relationship semantics. Neither model includes constraints, which are a fundamental concept in ArchObjects and other intelligent design systems. To solve these problems, we are building SORAC, an object-oriented model with semantic relationships and constraints. This model has several major features. Relationships are represented as objects, with a relationship class hierarchy. In addition, relationship classes are derived from a core set of semantic relationships by selecting certain semantic options. Complex constraints are also represented as objects; these are constraints over several relationships and can represent domain knowledge such as fire safety codes. First, we discuss the requirements imposed on this data model from the design domain. Next, we present the core semantic relationships of SORAC, optional semantics, and an overview of the data modeling language. Finally, some examples of using relationship semantics to simplify triggering and evaluation of domain constraints are presented.