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The term '''process model''' is used in various contexts. For example, in [[business process modeling]] the enterprise process model is often referred to as the ''business process model''.
[[Image:Meta-levels.svg|thumb|right|300px|Abstraction level for processes<ref name="Rolland1993">
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== Classification of process models ==
=== By coverage ===
There are five types of coverage where the term process model has been defined differently:<ref name="Dowson1988">M. Dowson (1998). ''Iteration in the Software Process, Proc 9th Int. Conf. on Software Engineering''.</ref>
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Various frameworks were developed to help in understanding quality of process modeling techniques, one example is Quality based modeling evaluation framework or known as Q-Me framework which argued to provide set of well defined quality properties and procedures to make an objective assessment of this properties possible.<ref name=hommes/>
This framework also has advantages of providing uniform and formal description of the model element within one or different model types using one modeling techniques<ref name=hommes>BJ Hommes, V Van Reijswoud, Assessing the Quality of Business Process Modeling Techniques -Proceedings of the 33rd Hawaii International Conference on System Sciences – 2000</ref>
In short this can make assessment of both the product quality and the process quality of modeling techniques with regard to a set of properties that have been defined before.
Quality properties that relate to business process modeling techniques discussed in <ref name=hommes/> are:
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* Effectiveness: the degree to which the modeling process achieves its goal.
To asses the quality of Q-ME framework; it is used to illustrate the quality of the dynamic essentials modeling of the organisation (DEMO) business modeling techniques.
It is stated that the evaluation of the Q-ME framework to the DEMO modeling techniques has revealed the shortcomings of Q-ME. One particular is that it does not include quantifiable metric to express the quality of business modeling technique which makes it hard to compare quality of different techniques in an overall rating.
There is also a systematic approach for quality measurement of modeling techniques known as complexity metrics suggested by Rossi et al. (1996). Techniques of Meta model is used as a basis for computation of these complexity metrics. In comparison to quality framework proposed by Krogstie, quality measurement focus more on technical level instead of individual model level.<ref name="ReferenceA">Bart-Jan Hommes, The evaluation of business process modeling techniques, 2000</ref>
Authors (Cardoso, Mendling, Neuman and Reijers, 2006) used complexity metrics to measure the simplicity and understandability of a design. This is supported by later research done by Mendling ''et al.'' who argued that without using the quality metrics to help question quality properties of a model, simple process can be modeled in a complex and unsuitable way. This in turn can lead to a lower understandability, higher maintenance cost and perhaps inefficient execution of the process in question.<ref name="MendlingMoserBPM">J. Mendling, M. Moser, G. Neumann, H. Verbeek, B. Dongen, W. van der Aalst, A Quantitative Analysis of Faulty EPCs in the SAP Reference Model, BPM Center Report BPM-06-08, BPMCenter.org, 2006.</ref>
The quality of modeling technique is important in creating models that are of quality and contribute to the correctness and usefulness of models.
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Enormous number of research has been done on quality of models but less focus has been shifted towards the quality of process models. Quality issues of process models cannot be evaluated exhaustively however there are four main guidelines and frameworks in practice for such. These are: top-down quality frameworks, bottom-up metrics related to quality aspects, empirical surveys related to modeling techniques, and pragmatic guidelines.<ref>{{cite journal |first=J. |last=Mendling |first2=H. A. |last2=Reijers |first3=W. M. P. |last3=van der Aalst |title=Seven process modeling guidelines (7PMG) |journal=Information and Software Technology |volume=52 |issue=2 |year=2010 |pages=127–136 |doi=10.1016/j.infsof.2009.08.004 }}</ref>
Hommes quoted Wang ''et al.'' (1994)<ref name=ReferenceA/> that all the main characteristic of quality of models can all be grouped under 2 groups namely correctness and usefulness of a model, correctness ranges from the model correspondence to the phenomenon that is modeled to its correspondence to syntactical rules of the modeling and also it is independent of the purpose to which the model is used.
Whereas the usefulness can be seen as the model being helpful for the specific purpose at hand for which the model is constructed at first place. Hommes also makes a further distinction between internal correctness (empirical, syntactical and semantic quality) and external correctness (validity).
A common starting point for defining the quality of conceptual model is to look at the linguistic properties of the modeling language of which syntax and semantics are most often applied.
Also the broader approach is to be based on semiotics rather than linguistic as was done by Krogstie using the top-down quality framework known as SEQUAL.<ref name=krogstie/><ref>{{cite journal |first=O. |last=Lindland |first2=G. |last2=Sindre |first3=A. |last3=Sølvberg |title=Understanding quality in conceptual modeling |journal=IEEE Software |volume=11 |issue=2 |year=1994 |pages=42–49 |doi=10.1109/52.268955 }}</ref> It defines several quality aspects based on relationships between a model, knowledge Externalisation, ___domain, a modeling language, and the activities of learning, taking action, and modeling.
The framework does not however provide ways to determine various degrees of quality but has been used extensively for business process modeling in empirical tests carried out <ref>D. Moody, G. Sindre, T. Brasethvik and A. Sølvberg, Evaluating the quality of process models: empirical testing of a quality framework. In: S. Spaccapietra, S.T. March and Y. Kambayashi, Editors, Conceptual Modeling – ER 2002, 21st International Conference on Conceptual Modeling, Tampere, Finland, October 7–11, 2002, Proceedings, Lecture Notes in Computer Science vol. 2503, Springer (2002), pp. 380–396.</ref>
According to previous research done by Moody ''et al.''<ref>Daniel L. Moody, G. Sindre, T. Brasethvik, A. Sølvberg. Evaluating the Quality of Process Models: Empirical Testing of a Quality Framework</ref> with use of conceptual model quality framework proposed by Lindland ''et al.'' (1994) to evaluate quality of process model, three levels of quality<ref>{{cite book |last=Morris |first=C. W. |year=1970 |title=Foundations of the Theory of Signs |___location=Chicago |publisher=Chicago University Press }}</ref> were identified:
* Syntactic quality: Assesses extent to which the model conforms to the grammar rules of modeling language being used.
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This framework is called SEQUEL framework by Krogstie ''et al.'' 1995 (Refined further by Krogstie & Jørgensen, 2002) which included three more quality aspects.
* Physical quality: whether the
* Empirical quality: whether the model is modeled according to the established regulations regarding a given language.
* Social quality: This regards the agreement between the stakeholders in the modeling ___domain.
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Modeling Domain is the set of all statements that are relevant and correct for describing a problem ___domain, Language Extension is the set of all statements that are possible given the grammar and vocabulary of the modeling languages used. Model Externalization is the conceptual representation of the problem ___domain.
It is defined as the set of statements about the problem ___domain that are actually made. Social Actor Interpretation and Technical Actor Interpretation are the sets of statements that actors both human model users and the tools that interact with the model, respectively ‘think’ the conceptual representation of the problem ___domain contains.
Finally, Participant Knowledge is the set of statements that human actors, who are involved in the modeling process, believe should be made to represent the problem ___domain. These quality dimensions were later divided into two groups that deal with physical and social aspects of the model.
In later work, Krogstie et al.<ref name=krogstie/> stated that while the extension of the SEQUAL framework has fixed some of the limitation of the initial framework, however other limitation remain .
In particular, the framework is too static in its view upon semantic quality, mainly considering models, not modeling activities, and comparing these models to a static ___domain rather than seeing the model as a facilitator for changing the ___domain.
Also, the framework’s definition of pragmatic quality is quite narrow, focusing on understanding, in line with the semiotics of Morris, while newer research in linguistics and semiotics has focused beyond mere understanding, on how the model is used and impact its interpreters.
The need for a more dynamic view in the semiotic quality framework is particularly evident when considering process models, which themselves often prescribe or even enact actions in the problem ___domain, hence a change to the model may also change the problem ___domain directly. This paper discusses the quality framework in relation to active process models and suggests a revised framework based on this.
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The other framework in use is Guidelines of Modeling (GoM) <ref>J. Becker, M. Rosemann and C. Uthmann, Guidelines of business process modeling. In: W. van der Aalst, J. Desel and A. Oberweis, Editors, Business Process Management. Models, Techniques, and Empirical Studies, Springer, Berlin (2000), pp. 30–49</ref> based on general accounting principles include the six principles: Correctness, Clarity deals with the comprehensibility and explicitness (System description) of model systems.
Comprehensibility relates to graphical arrangement of the information objects and, therefore, supports the understand ability of a model.
Relevance relates to the model and the situation being presented. Comparability involves the ability to compare models that is semantic comparison between two models, Economic efficiency; the produced cost of the design process need at least to be covered by the proposed use of cost cuttings and revenue increases.
Since the purpose of organizations in most cases is the maximization of profit, the principle defines the borderline for the modeling process. The last principle is Systematic design defines that there should be an accepted differentiation between diverse views within modeling.
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The two frameworks SEQUAL and GOM have a limitation of use in that they cannot be used by people who are not competent with modeling. They provide major quality metrics but are not easily applicable by non-experts.
The use of bottom-up metrics related to quality aspects of process models is trying to bridge the gap of use of the other two frameworks by non-experts in modeling but it is mostly theoretical and no empirical tests have been carried out to support their use.
Most experiments carried out relate to the relationship between metrics and quality aspects and these works have been done individually by different authors: Canfora et al. study the connection mainly between count metrics (for example, the number of tasks or splits -and maintainability of software process models;<ref>{{cite journal |first=G. |last=Canfora |first2=F. |last2=Garcia |first3=M. |last3=Piattini |first4=F. |last4=Ruiz |first5=C. |last5=Visaggio |title=A family of experiments to validate metrics for software process models |journal=Journal of Systems and Software |volume=77 |issue=2 |year=2005 |pages=113–129 |doi=10.1016/j.jss.2004.11.007 }}</ref> Cardoso validates the correlation between control flow complexity and perceived complexity; and Mendling et al. use metrics to predict control flow errors such as deadlocks in process models.<ref name=MendlingMoserBPM/><ref>J. Mendling, Detection and prediction of errors in epc business process models, Ph.D. thesis, Vienna University of Economics and Business Administration, http://wi.wu-wien.ac.at/home/mendling/publications/Mendling%20Doctoral%20thesis.pdf, 2007.</ref>
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* [http://www.apqc.org/ American Productivity and Quality Center (APQC)], a worldwide organization for process and performance improvement
* [http://www.workflowpatterns.com/documentation/documents/vanderaalst98application.pdf The Application of Petri Nets to Workflow Management], W.M.P. van der Aalst, 1998.
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