A taxonomic structure employed to classify the various possible ways to modelize complex systems.
The "System Entity Structure" has been introduced by B. ZEIGLER (1984 and 1994).
In H. PRAEHOFER's words: "The system entity structure is used to manage a family of models and has to support the representation of decomposition, couplings and taxonomy. Decomposition is used to represent the way real systems are composed into components in a hierarchical manner. Coupling specifications define how these components can be coupled together. Taxonomic knowledge means the representation of different kind of objects (i.e. how they are categorized and subclassified)" (1991, p.301).
This is a good methodological track, well adapted to conventional computers and based on the classical view of systems as pre-ordained hierarchies of components. The key word is here obviously "decomposition", with its somewhat reductionist overtones. But what about networks representation of parallel learning systems?
ZEIGLER defines the structure as a labeled tree, in accordance with the following axioms (as resumed by PRAEHOFER):
"1. Uniformity: Any two nodes that have the same name have identical attached variable types and isomorphic subtrees
"2. Strict hierarchy: No label appears more than once down any path of the tree
"3. Alternating mode: Each node has a mode that is either entity, aspect, or specialization; if the mode of a node is entity, than the modes of its successors are aspects or specialization; if the mode of a node is aspect or specialization, then the modes of its successors are entity. The mode of the root is entity.
"4. Valid brothers: No two brothers have the same label
"5. Attached variables: No two variable types attached to the same item have the same name.
"6. Inheritance: Every entity in a specialization inherits all the variables, aspects, and specializations from the parent of the specialization…
"The best way to represent an entity structure is by a pictorial representation of the tree structure. The nodes of the tree represent entities, aspects and specializations. The arcs of the tree represent the relations between parents and their children. As, depending on the type of the node, we can identify different relations between the nodes, we use different arcs to represent these relations. An aspect relation is depicted by a single line, a multiple decomposition relation by three parallel lines and a specialization relation by a double line arrow" (Ibid., p.302-303).
It would be of much interest to evaluate FORRESTER's systems dynamics models, and other types of formalized models in the light of ZEIGLER's methodology.
Another good subject for research should be the constraints imposed by the nature of digital sequential computer on the methodologies of complex systems modelization.
For graph terminology, as used here, see "graph" and "graph theory".
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Bertalanffy Center for the Study of Systems Science (2020). Title of the entry. In Charles François (Ed.), International Encyclopedia of Systems and Cybernetics (2). Retrieved from www.systemspedia.org/[full/url]
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