IDEF3 - IDEF3 Basic Concepts - Descriptions and Models

Descriptions and Models

The distinction between descriptions and models, though subtle, is an important one in IDEF3, and both have a precise technical meaning.

  • The term description is used as a reserved technical term to mean records of empirical observations; that is, descriptions record knowledge that originates in or is based on observations or experience.
  • The term model is used to mean an idealization of an entity or state of affairs. That is, a model constitutes an idealized system of objects, properties, and relations that is designed to imitate, in certain relevant respects, the character of a given real-world system. Frictionless planes, perfectly rigid bodies, the assumption of point mass, and so forth are representative examples of models.

The power of a model comes from its ability to simplify the real-world system it represents and to predict certain facts about that system by virtue of corresponding facts within the model. Thus, a model is a designed system in its own right. Models are idealized systems known to be incorrect but assumed to be close enough to provide reliable predictors for the predefined areas of interest within a domain. A description, on the other hand, is a recording of facts or beliefs about something within the realm of an individual’s knowledge or experience. Such descriptions are generally incomplete; that is, the person giving a description may omit facts that he or she believes are irrelevant, or which were forgotten in the course of describing the system. Descriptions may also be inconsistent with respect to how others have observed situations within the domain. IDEF3 accommodates these possibilities by providing specific features enabling the capture and organization of alternative descriptions of the same scenario or process, see figure.

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Famous quotes containing the words descriptions and/or models:

    Matter-of-fact descriptions make the improbable seem real.
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    Friends broaden our horizons. They serve as new models with whom we can identify. They allow us to be ourselves—and accept us that way. They enhance our self-esteem because they think we’re okay, because we matter to them. And because they matter to us—for various reasons, at various levels of intensity—they enrich the quality of our emotional life.
    Judith Viorst (20th century)