ABSTRACT
This chapter describes the original basis of the Reticular Action Model (RAM) approach
to structural equation modeling (SEM). The RAM rules were initially presented
(1978-1981) to simplify and unify structural equation models based on path analysis
graphics. The mathematical representation of RAM is presented as a second-order
moment structure model that includes two parameter matrices, one of which is a
patterned inverse. The graphic representation of RAM is presented through a series of
definitions and axioms that provide a complete and concise isomorphism between
graphics and algebra. Comparisons to other traditional models, such as those of multiple
linear regression, path analysis, and factor analysis, show how these models may be
easily and economically represented using RAM rules. Two other general modeling
foundations, LISREL and COSAN, are presented as special cases and, somewhat
paradoxically, as generalizations of RAM. These results are then used to develop some
important technical features of the RAM rules, including efficient algorithmic estimation
procedures and the further development of statistical indicators. Issues of conceptual
representation are provided from a general systems perspective. Finally, some of the
current limitations and benefits of the RAM rules are considered.
