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Thursday, 13 June 2013 11:09

Pattern PP2: Late Modeling of Process Fragments

This pattern offers more freedom and allows for modeling selected parts of the process schema at run-time. Prior to execution only a placeholder activity has to be provided, its implementation is modeld during run-time. Design Choice A specifies which building blocks can be used for late modeling. Building blocks can either be all process fragments from the repository, a constraint-based subset of the fragments from the repository, or newly defined activities or process fragments. Design Choice B describes whether the user may apply the same modeling constructs during build-time or more restrictions apply. Late modeling can take place upon creation of the process instance, when the placeholder activity is enabled, or when a particular state in the process is reached (Design Choice C). Depending on the pattern variant users start late modeling with an empty template or they take a predefined template as a starting point and adapt it as required (Design Choice D).

Description

Parts of the process schema have not been defined at build-time, but are modeled separately during run-time for each process instance. For this purpose, placeholder activities are provided, which are modeled and executed during run-time. The modeling of the placeholder activity must be completed before the respective process fragment can be executed.

Example

The exact treatment process of a particular patient is composed out of existing process fragments at run-time.

Problem

Not all parts of the process schema can be completely specified at build time.

Design Choices 

  1. What are the basic building blocks for late modeling?
    1. All process fragments from the repository can be chosen.
    2. A constraint-based subset of the process fragments from the repository can be chosen.
    3. New activities or process fragments can be defined.
  2. What is the degree of freedom regarding late modeling?
    1. Same modeling constructs and change patterns can be applied as for modeling at the process type level. Which of the adaptation patterns are supported within the placeholder activity is determined by the expressiveness of the modeling language.
    2. More restrictions apply than for modeling at the process type level.
  3. When does late modeling take place?
    1. When a new process instance is created.
    2. When the placeholder activity is instantiated.
    3. When a particular state in the process (preceding the instantiation of the placeholder activity) is reached.
  4. Does the modeling start from scratch?
    1. Starts with an empty template.
    2. Starts with a predefined template which can be adapted.

PP2

Implementation

After having modeled the placeholder activity with the process editor during run-time, the fragment is stored in the repository and deployed afterwards. Then, the process fragment is dynamically invoked as a sub process. The assignment of the respective process fragment to the placeholder activity is done through late binding.

Related Patterns

Late Selection of Process Fragments (PP1)

Animation

View Animation

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