Simultaneous Equations in the Model System With an Application to Econometric Modelling
This report describes modifications to the MODEL language and processor to facilitate automatic implementation of solution procedures for systems of simultaneous equations. MODEL is a very high level nonprocedural language for specifying computational tasks. The MODEL processor compiles a specification in the MODEL language into a computer program in PL/I . The purpose of the current modifications is to allow users with relatively little programming expertise to solve complex mathematical systems involving sets of simultaneous equations quickly and efficiently using an automatic program generation approach to modelling. The primary application which has motivated these modifications is that of Project LINK, an international econometric model composed of independent constituent country/region models which are linked together into a complex network of simultaneous equations. This report presents the rationale behind these modifications, describes the syntax, semantics, scheduling and code generation of specifications containing simultaneous equations, and illustrates these facilities in applications to two small national models from the LINK system and to a novel linkage mechanism used to simulate trade among the national models.