TITLE: ASCEND: An Object-Oriented Computer Environment for Modeling 
and Analysis: The Modeling Language.
AUTHORS: Piela, P., Epperly, T., Westerberg, K. and Westerberg, A.
PUBLICATION: Computers and Chemical Engineering, Vol. 15, No. 1, 53-72
PUBLISHER: Pergamon Press
DATE: 1991
ABSTRACT: 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 language 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.