Intensional Couplings in Variable-Structure Models

Abstract

In modular, hierarchical modeling, couplings (connections) describe and constrain the communication, and thus interaction, between model components. Defining couplings between a large set of components in an extensional manner—listing all existing couplings individually—often proves to be rather tedious. Moreover, if models change their structure, that is, composition and interaction patterns and, in some cases, even their interfaces during simulation, questions about the consistency of the couplings arise. For instance, an extensionally defined coupling may refer to a model that no longer exists. Instead, an intensional coupling definition, based on attributes of the components to couple and dynamically translated into concrete couplings during simulation, promises to alleviate these problems. We propose a concept that combines a flexible, yet expressive, definition of couplings that rests on component interfaces announcing attributes of interest. However, intensional couplings come at a price, as they need to be translated during simulation; in variable-structure models, this translation has to happen frequently. We illuminate our concept based on a revision of the modeling formalism Multilevel Discrete Event System Specification ( ML - DEVS ). Developed for multilevel modeling and simulation, ML - DEVS exhibits another alternative to intensional couplings, that is, sharing parts of model states for up- and downward causation. The intricate interplay between these different types of couplings is revealed in the abstract simulator of ML - DEVS .

Emergence at the Fundamental Systems Level: Existence Conditions for Iterative Specifications

“…After much progress in understanding how dynamic structure can be managed in DEVS-based simulations [14][15][16], a framework that incorporates several insights has recently been developed [17]. This framework, formulated in the DEVS formalism, can be extended to iterative specifications and investigated for conditions of existence as done here.…”

“…The results are shown in the first two columns of Table E2. They seem to show that TMs break into two classes-those that halt within a small number of steps (e.g., 16) and those that do not halt. Indeed, the data in the table suggest that approximately one-third of the sampled TMs halt, while two-thirds do not.…”

Emergence at the Fundamental Systems Level: Existence Conditions for Iterative Specifications

“…After much progress in understanding how dynamic structure can be managed in DEVS-based simulations [2,3,11], a framework that incorporates several insights has recently been developed [8]. This framework, formulated in the DEVS formalism, can be extended to iterative specifications and investigated for conditions of existence as done here.…”

Some Modeling & Simulation Perspectives on Emergence in System-of-Systems

“…Strong dynamic structure capabilities are needed to specify and exibly control the changes in components and their coupling to be able to adequately model adaptation, evolution and emergence in ways that include the possibility of genuine surprise. A next generation of dynamic structure formalisms have been recently under development in the DEVS community [9,11,10].…”

“…In [11], Steiniger denes a concept of intensional coupling specication distinct from the explicit (extensional) coupling they specify. Biological cellular level modeling similarly motivated this development with the same implications for emergence modeling.…”