@article{ref1,
title="What is a system?",
journal="Social networks",
year="1981",
author="Harary, Frank and Batell, Mark F.",
volume="3",
number="1",
pages="29-40",
abstract="A new definition and model of a system is presented utilizing graph theoretic concepts and introducing nested graphs. By a comprehensive search of the literature, this abstract formulation of a system is shown to incorporate extant theory. The approach of Emery and Trist using open and closed systems, the system-environment model of Cartwright and Harary, and the structural role system of Oeser and Harary are all subsumed as special cases. The value of such a theory is discussed in statistical terms by considering correlational problems and Simpson's paradox. A general problem-solving algorithm is presented, using this model of a system, suggested by a simultaneous generalization of the statistical procedures of cluster analysis and stagewise regression. An example is interpreted in the nested network framework, illustrating the applicability of the model to empirical situations.<p />",
language="",
issn="0378-8733",
doi="10.1016/0378-8733(81)90003-4",
url="http://dx.doi.org/10.1016/0378-8733(81)90003-4"
}