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Thursday, 13 June 2013 11:34

Change Patterns

Companies increasingly adopt process-aware information systems (PAISs), which offer promising perspectives for more flexible enterprise computing. The emergence of different process support paradigms and the lack of methods for comparing existing approaches enabling PAIS changes have made the selection of adequate process management technology difficult. We suggest a set of 18 change patterns and 7 change support features to foster the systematic comparison of existing process management technology in respect to process change support. While the proposed patterns are all based on empirical evidence from several large case studies, the suggested change support features constitute typical functionalities provided by flexible PAISs. Based on the proposed change patterns and features, we provide a detailed analysis and evaluation of selected approaches from both academia and industry. The presented work will not only facilitate the selection of technologies for realizing flexible PAISs, but can also be used as a reference for implementing flexible PAISs.

patterns

Adaption Patterns

Adaptation patterns allow users to structurally change process schemes. In general, the application of an adaptation pattern transforms a process schema S into another process schema S'. For this, two different options exist, which can be both found in existing systems.

On the one hand, structural adaptations can be realized based on a set of change primitives like add node, remove node, add edge, remove edge, and move edge. Following this approach, the realization of a particular adaptation (e.g., to delete an activity or to add a new one) usually requires the application of multiple change primitives. Specifying structural adaptations at this low level of abstraction, however, is a complex and error-prone task. Further, when applying a single change primitive, soundness of the resulting process schema (e.g., absence of deadlocks) cannot be guaranteed. Therefore, for more complex process meta models it is not possible to associate formal pre-/post-conditions with the application of single primitives. Instead, correctness of a process schema has to be explicitly checked after applying the respective set of primitives.

On the other hand, structural adaptations can be based on high-level change operations (e.g., to insert a process fragment between two sets of nodes), which abstract from the concrete schema transformations to be conducted. Instead of specifying a set of change primitives the user applies one or more high-level change operations to realize the desired process schema adaptation. Approaches following this direction often associate pre- and post-conditions with the high-level operations, which allows the PAIS to guarantee soundness when applying the respective operations. Note that soundness will become a fundamental issue if changes are to be applied by end-users or – even more challenging – by automated software components (i.e., software agents). For these reasons we only consider high-level operations as adaptation patterns; more precisely, an adaptation pattern comprises exactly one high-level operation. Furthermore, its application to a given process schema will preserve soundness of this schema if certain pre-conditions are met.

Furthermore there are two general design choices, which are valid for all 14 adaptation patterns and which can be used for their parametrization. Additional design choices, only relevant in the context of a specific adaptation pattern, are provided with the description of the respective patterns

Patterns for Changes in Predefined Regions

Patterns for changes in predefined regions allow for better dealing with uncertainty by deferring decisions regarding the exact control-flow to run-time. Instead of requiring a process model to be fully specified prior to execution, parts of the model can remain unspecified. In contrast to adaptation patterns, whose application is not restricted a priori to a particular process part, patterns for changes in predefined regions define constraints concerning the parts of a process schema that can be changed or expanded. In this category we have identified 4 patterns: Late Selection (PP1), Late Modeling (PP2) and Late Composition of Process Fragments (PP3) and Multi-Instance Activity (PP4). These four patterns differ regarding the parts that can remain unspecified resulting in a different degree of freedom during run-time.

Change Support Features

supportfeatures

So far, we have introduced a set of change patterns which can be used to accomplish changes at the process type or process instance level. However, simply looking at the supported patterns and counting their number is not sucient to analyze how well a system can deal with process change. In addition, change support features must be considered to make change patterns useful in practice. Relevant change support features include Schema Evolution, Version Control and Instance Migration (F1), Support for Instance-Speci c Changes (F2), Correctness of Change (F3), Traceability and Analysis of Changes (F4), Access Control for Changes (F5), Change Reuse (F6), and Change Concurrency Control (F7). As illustrated above, the described change support features are not equally important for both process type level and process instance level changes. Version control, for example, is primarily relevant for changes at the type level (T), while change reuse is particularly useful at the instance level (I).

 

Support of Change Patterns

Publications

2013

icon pdf Reichert, Manfred and Weber, Barbara (2013) Process Change Patterns: Recent Research, Use Cases, Research Directions. Springer, In: Seminal Contributions to Information Systems Engineering - 25 Years of CAiSE. pp. 398-404

2008

icon pdf Rinderle-Ma, Stefanie and Reichert, Manfred and Weber, Barbara (2008) On the Formal Semantics of Change Patterns in Process-aware Information Systems. In: Proc. 27th Int'l Conference on Conceptual Modeling (ER'08), Barcelona, Spain, October 2008, LNCS 5231, Springer, pp. 279-293

icon pdf Weber, Barbara and Reichert, Manfred and Rinderle-Ma, Stefanie(2008) Change Patterns and Change Support Features - Enhancing Flexibility in Process-Aware Information Systems. Data and Knowledge Engineering, 66(3): 438-466, Elsevier Science.

2007

icon pdf Weber, Barbara and Rinderle, Stefanie and Reichert, Manfred (2007) Change Patterns and Change Support Features in Process-Aware Information Systems. In: Proc. 11th Int'l Conf. on Advanced Information Systems Engineering (CAiSE'07), Trondheim, Norway, LNCS 4495, Springer, pp. 574-588

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