ASCEND - AN OBJECT-ORIENTED COMPUTER ENVIRONMENT FOR MODELING AND ANALYSIS - THE MODELING LANGUAGE

ASCEND (Advanced System for Computations in ENgineering Design) is a new rapid model building environment for complex models comprising large sets of simultaneous nonlinear algebraic equations. In ASCEND the definition of a model is separated from the solving of it. This paper presents the ASCEND modeling language; a companion paper will describe the tools available to aid in debugging and solving models. The ASCEND language is a type definition language that uses and extends object-oriented concepts, including refinement hierarchies, generalized arrays, part/whole modeling, partial and complete merging, deferred binding and universal types. Dimensional consistency is required among all the equations. This paper discusses the need for a modeling environment like ASCEND to aid the design process, comparing its functional requirements to earlier approaches. It then presents an informal definition of the syntax and associated semantics for the language. An example for solving mixed sets of ordinary differential and algebraic equations using a two-point boundary value approach illustrates the modeling power of the language.