"A model is a purposeful representation." (Starfield, Smith and Bleloch, 1990)The most striking common denominator (explicitly or implicitly stated) is that a model is something that represents something else. There is a perceived relationship between two phenomena, in which one of them possesses some undefined quality that makes the observer categorize it as a model of the other phenomenon. The prototype of what is not a model of a given phenomenon is in a sense the phenomenon itself.
"A model is a structure that a system can use to simulate or anticipate the behavior of something else." (Høyte, 1992:18)
"A model is an abstraction externalized in a language." (Krogstie, 1995:476)
"A model is an abstraction of something for the purpose of understanding it before building it." (Rumbaugh et al., 1991:15)
"A model is the explicit expression of one's understanding of a system or situation. 70; A model is a representation of something else." (ISO/ANSI, 1994:11)
Based on this wide characterization of models, the relationships between models, the modeled UoD and the modeler will be discussed next.
Figure 3.2 may be read as follows: Ew is
physical reality that is perceived to exist (in an organization, Ew
refers to the material embodiment of the externalized, organizational reality).
Iw is how the modeler M interprets Ew,
i.e., the meaning attributed to organizational reality. Im
is a deliberate, alternative representation made by M of Iw,
and Em is the expression being a manifestation
of Im, created by M. The pair (Em,
Im) is said to be a model of (Ew,
Iw). Hence, a model is a compound phenomenon (Em,
Im) playing the role depicted in figure 3.2.
|In figure 3.2, the real world phenomenon that is modeled is exemplified by an oil platform. It may equally well be a more intangible construction, e.g., a dialogue between two colleagues. The real world expression of such a dialogue is the sounds and gestures, the impression is the meaning the modeler attributes to these waves and gestures (e.g., interpreting it as a quarrel or a flirt).|
Figure 3.2 is a valid model of models from both an objectivist and constructivist point of view. Still, the nature of expressions and impressions differ substantially based on worldview taken. From an objectivist point of view, the meaning of Ew is given objectively as Iw and can be experienced directly. Likewise, the meaning of Em is given as Im, based on a formally defined syntax and semantics of the modeling language. Hence, one may develop general criteria for estimating the goodness (the quality) of the representation of Iw as Im.
From a constructivist point of view, the meaning of Ew is subjective, but more or less subject to closure following from social construction. The meaning Iw is not inherent to Ew, but relative to a perspective held within the community. The meaning Im of Em is neither objectively given, and both Iw and Im may change over time (from a hermeneutic point of view). Hence, the goodness of the representation of Iw by Im depends on the relationship between the horizons of the model creator and interpreter (as also claimed by Klein and Lyytinen, 1992:214).
Figure 3.3 includes the four concepts Ew, Iw, Im and Em and actors from Figure 3.2. The process of model creation is depicted from left to right, while the process of model interpretation goes from right to left. The loop at the far right can be considered distribution of the model expression as the model creators and the model interpreters may not be the same.
Modeling is seen as embracing three major activities: Sense-making, representation and manifestation. Both model creation and model interpretation involve these three activities. Model creation is described first:
Sense-making Ew => Iw: The model creator attempts to interpret and make sense of the UoD. The sense-making process may not necessarily involve a physical reality (Ew may play a minor role when creating models of UoDs constructed through imagination and not grounded experientially, Lakoff and Johnson, 1980:193).
Representation Iw => Im: The model creator deliberately associates concepts perceived to be a part of the UoD with selected concepts understood to be a part of what might be called a modeling language. Representation is not necessarily direct mapping.
Manifestation Im => Em: The model creator externalizes the representation using a chosen medium, e.g., draws the model on a sheet of paper. The medium might be audio, video, paper, digital computers, etc.
The three activities can be carried out simultaneously. Sense-making, representation and manifestation are integrated activities in the sense that the modeler improves her understanding of the domain by making preliminary and alternative representations and sketches of a model, tacking back and forth between the activities.
The three activities above constitute what is considered the creative side of modeling in this thesis -- to make sense of a domain, deliberately represent it in some way and express the representation using some medium. The three following activities correspond to the use of models, the interpretive side of modeling:
Sense-making Em => Im: The model interpreter attempts to make sense of the model expression by attributing meaning to the model symbols.
Representation Im => Iw: The model interpreter associates something with the model impression, seeking to imagine what the original modeler created a model of, i.e., her UoD.
Manifestation Iw => Ew: The model interpreter might use the understanding gained from interpreting the model, e.g., to construct an artifact. In this sense, manifestation becomes action, externalizing the local reality in speech or deed.
Note that the model expression is just as real as the world expression and that model creation and model interpretation in a sense are symmetric. Hence, one may question what is the difference between the two processes? In principle, the most obvious difference is the purpose -- the deliberate representation of Iw by Im, creating the artifact Em in the first place. Hence, what is world (UoD) and what is model is decided by purpose. In practice (as also seen from several of the definitions of model on page ), abstraction is an essential trait of models.
As for the model concept in section , the modeling concept is valid independently of worldview. However, the perceived challenges of the modeling process (both model creation and interpretation) differ substantially according to the chosen worldview.
From an objectivist point of view, the following can be assumed to hold: