Meta-process modeling

Meta-process modeling

Definition

The term Meta-process modeling as described here belongs to the context of Information System Development, in specific to the discipline of ‘Method Engineering’ / ‘Situational Method Engineering’, or ‘Process Engineering’.

Method Engineering “represents the effort to improve the usefulness of systems development methods by creating an adaptation framework whereby methods are created to match specific organisational situations” [Colland – A Primer]. Meta-process models are a mean to achieve this goal. They support the effort of creating flexible process models, also known as Situational Method Engineering.

Meta-process modeling focuses on and supports the process of construction process models. Its main concern is to improve process models and to make them evolve, which in turn, will support the development of systems [Rolland1998]. This is important due to the fact that “processes change with time and so do the process models underlying them. Thus, new processes and models may have to be built and existing ones improved” [Rolland1998]. “The focus has been to increase the level of formality of process models in order to make possible their enactment in process-centred software environments” [Rolland1999] referring to [Finkelstein1994].

A process meta-model is a meta-model, “a description at the type level of a process model. A process model is, thus, an instantiation of a process meta-model. [..] A meta-model can be instantiated several times in order to define various process models. A process meta-model is at the meta-type level with respect to a process.” [Rolland1998]

Abstraction level for processes [Rolland1993]

Purpose

The purpose of process models is to

• Document and communicate processes
• Enhance the reuse of processes

Thus, processes can be better taught and executed. Results of using meta-process models are an increased productivity of process engineers and an improved quality of the models they produce. [Rolland1998]

Techniques (Formalism / Notation)

There different techniques for constructing process models. “Construction techniques used in the information systems area have developed independently of those in software engineering. In information systems, construction techniques exploit the notion of a meta-model and the two principal techniques used are those of instantiation and assembly. In software engineering the main construction technique used today is language-based. However, early techniques in both, information systems and software engineering were based on the experience of process engineers and were, therefore, ad-hoc in nature.” [Rolland1998]

Instantiation

For reusing processes a meta-process model identifies “the common, generic features of process models and represents them in a system of concepts. Such a representation has the potential to 'generate' all process models that share these features. This potential is realised when a generation technique is defined whose application results in the desired process model.” [Rolland1998]

Process models are then derived from the process meta-models through instantiation. Rolland [Rolland1998] associates a number of advantages with the instantiation approach:

1. The exploitation of the meta-model helps to define a wide range of process models.
2. It makes the activity of defining process models systematic and versatile.
3. It forces to look for and introduce, in the process meta-model, generic solutions to problems and this makes the derived process models inherit the solution characteristics.

“The instantiation technique has been used, for example, in NATURE [Rolland1993], [Rolland1994], [Rolland1996]. The process engineer must define the instances of contexts and relationships that comprise the process model of interest.” [Rolland1998]

Assembly

The assembly technique is based on the idea of a process repository from which process components can be selected. [Rolland1998] lists two selection strategies:

1. Promoting a global analysis of the project on hand based on contingency criteria

(Example [VanSlooten1996])

1. Using the notion of descriptors [Antonellis1991] as a means to describe process chunks. This eases the retrieval of components meeting the requirements of the user / matching with the situation at hand. [Rolland1996b]

(Example [Plihon1995] in NATURE and repository of scenario based approaches accessible on Internet in the CREWS project [Rolland1998b])

“For the assembly technique to be successful, it is necessary that process models are modular. If the assembly technique is combined with the instantiation technique then the meta-model must itself be modular.” [Rolland1998]

Language

[Rolland1998] lists numerous languages for expressing process models used by the software engineering community (E3 [19], various Prolog dialects for EPOS [28], Oikos [1], and PEACE [19], PS-Algol for PWI [19]) as well as further computational paradigms (Petri nets in EPOS [28] and SPADE [3], rule based paradigm in MERLIN [16], ALF [5], Marvel [33], EPOS [28], and triggers in ADELE [4] and MVP-L [19]).

“Languages are typically related to process programs whereas instantiation techniques have been used to construct process scripts.” [Rolland1998]

Ad-hoc

“Traditional process models are expressions of the experiences of their developers. Since this experience is not formalised and is, consequently, not available as a fund of knowledge, it can be said that these process models are the result of an ad-hoc construction technique. This has two major consequences: it is not possible to know how these process models were generated, and they become dependent on the domain of experience. If process models are to be domain independent and if they are to be rapidly generable and modifiable, then we need to go away from experience based process model construction. Clearly, generation and modifiability relate to the process management policy adopted (see Usage World). Instantiation and assembly, by promoting modularization, facilitate the capitalisation of good practice and the improvement of given process models.” [Rolland1998]

Tool support

The Meta-modeling process is often supported through software tools, called CAME tools (Computer Aided Method Engineering) or Meta-CASE tools (Computer Assisted Software Engineering tools on a Meta-level). Often the instantiation technique “has been utilised to build the repository of Computer Aided Method Engineering environments” [Rolland1998] (referring to [Kelly1996], [Harmsen1995], [Merbeth1991], [Si-Said1996]).

Example tools for meta-process modeling are:

• Maestro II [Merbeth1991]
• MetaEdit+ [Kelly1996]
• Mentor [Si-Said1996]

[Rolland1997]

Example: “Multi-model view”

In [Rolland1999] Colette Rolland provides an example of a meta-process model which utilizes the instantiation and assembly technique. In the paper the approach is called “Multi-model view” and was applied on the CREWS-L’Ecritoire method. The CREWS-L’Ecritoire method represents a methodical approach for Requirements Engineering, “the part of the IS development that involves investigating problems and requirements of the users community and developing a specification of the future system, the so-called conceptual schema.” ([Rolland1993], referring to [Hagelstein1988] and [Dubois1989]).

Besides the CREWS-L’Ecritoire approach, the multi-model view has served as a basis for representing [Rolland1999]: (a) the three other requirements engineering approaches developed within the CREWS project (Real World Scenes approach [38], SAVRE approach for scenario exceptions discovery [39], and the scenario animation approach [40]) (b) for integrating approaches ([41] one with the other and with the OOSE approach [15])

Furthermore, the CREWS-L’Ecritoire utilizes process models and meta-process models in order to achieve flexibility for the situation at hand. The approach is based on the notion of a labelled graph of intentions and strategies called a map as well as its associated guidelines [Rolland1999]. Together, map (process model) and the guidelines form the method. The main source of this explanation is the elaboration of Colette Rolland in [Rolland1999].

Process model / Map

The map is “a navigational structure which supports the dynamic selection of the intention to be achieved next and the appropriate strategy to achieve it”; it is “a process model in which a nondeterministic ordering of intentions and strategies has been included. It is a labelled directed graph with intentions as nodes and strategies as edges between intentions. The directed nature of the graph shows which intentions can follow which one.” [Rolland1999]

The map of the CREWS-L’Ecritoire method looks as follow:

Process model of the CREWS-L’Ecritoire method [Rolland1999]

The map consists of goals / intentions (marked with ovals) which are connected by strategies (symbolized through arrows). An intention is a goal, an objective that the application engineer has in mind at a given point of time. A strategy is an approach, a manner to achieve an intention. The connection of two goals with a strategy is also called section. [Rolland1999].

A map “allows the application engineer to determine a path from Start intention to Stop intention. The map contains a finite number of paths, each of them prescribing a way to develop the product, i.e. each of them is a process model. Therefore the map is a multi-model. It embodies several process models, providing a multi-model view for modelling a class of processes. None of the finite set of models included in the map is recommended ‘a priori’. Instead the approach suggests a dynamic construction of the actual path by navigating in the map. In this sense the approach is sensitive to the specific situations as they arise in the process. The next intention and strategy to achieve it are selected dynamically by the application engineer among the several possible ones offered by the map. Furthermore, the approach is meant to allow the dynamic adjunction of a path in the map, i.e. adding a new strategy or a new section in the actual course of the process. In such a case guidelines that make available all choices open to handle a given situation are of great convenience. The map is associated to such guidelines” [Rolland1999].

Guidelines

A guideline “helps in the operationalisation of the selected intention” [Rolland1999]; it is “a set of indications on how to proceed to achieve an objective or perform an activity” [RobertDict1995]. The description of the guidelines is based on the NATURE project’s contextual approach [NATURE, 23, 30] and its corresponding enactment mechanism [14, 31].

Three types of guidelines can be distinguished:

• Intention Selection Guidelines (ISG) identify the set of intentions that can be achieved in the next step and selects the corresponding set of either IAGs (only one choice for an intention) or SSGs (several possible intentions).
• Strategy Selection Guidelines (SSG) guide the selection of a strategy, thereby leading to the selection of the corresponding IAG.
• Intention Achievement Guidelines (IAG) aim at supporting the application engineer in the achievement of an intention according to a strategy, are concerned with the tactics to implement these strategies, might offer several tactics, and thus may contain alternative operational ways to fulfil the intention.

In our case, the following guidelines – which correspond with the map displayed above – need to be defined:

Intention Selection Guidelines (ISG)

1. ISG-1 Progress from Elicit a goal
2. ISG-2 Progress from Conceptualize a Scenario
3. ISG-3 Progress from Write a scenario
4. ISG-4 Progress from Start

The following graph displays the details for the Intention Selection Guideline 1 (ISG-1).

Example of an Intention Selection Guideline 1 (ISG-1) [Rolland1999]

Strategy Selection Guidelines (SSG)

1. SSG-1 Progress to Elicit a goal
2. SSG-2 Progress to Conceptualize a Scenario
3. SSG-3 Progress to Write a scenario
4. SSG-4 Progress to Elicit a goal
5. SSG-5 Progress to Stop

The following graph displays the details for the Strategy Selection Guideline 1 (SSG-1).

Example of an Strategy Selection Guideline 1 (SSG-1) [Rolland1999]

Intention Achievement Guidelines (IAG)

1. IAG-1 Elicit a goal with case-based strategy
2. IAG-2 Elicit a goal with composition strategy
3. IAG-3 Elicit a goal with alternative strategy
4. IAG-4 Elicit a goal with refinement strategy
5. IAG-5 Elicit a goal with linguistic strategy
6. IAG-6 Elicit a goal with template-driven strategy
7. IAG-7 Write a scenario with template-driven strategy
8. IAG-8 Write a scenario in free prose
9. IAG-9 Conceptualize a Scenario with computer support strategy
10. IAG-10 Conceptualize a Scenario manually
11. IAG-11 Stop with completeness strategy

The following graph displays the details for the Intention Achievement Guideline 8 (IAG-8).

Example of an Intention Achievement Guideline 8 (IAG-8) [Rolland1999]

Meta-process map

In the multi-model view as presented in the paper of C. Rolland, the meta-process (the instance of the meta-process model) is “a process for the generation of a path from the map and its instantaneous enactment for the application at hand.” [Rolland1999]

While the meta-process model can be represented in many different ways, a map was chosen again as a means to do so. It is not to be mixed up with the map for the process model as presented above.

Meta-process model of the CREWS-L’Ecritoire method [Rolland1999]

Colette Rolland describes the meta-model as follow [Rolland1999]: (Meta-intentions are in bold, meta-strategies in italic – in green in the map).

“The Start meta-intention starts the construction of a process by selecting a section in the method map which has map intention Start as source. The Choose Section meta-intention results in the selection of a method map section. The Enact Section meta-intention causes the execution of the method map section resulting from Choose Section. Finally, the Stop meta-intention stops the construction of the application process. This happens when the Enact Section meta-intention leads to the enactment of the method map section having Stop as the target. As already explained in the previous sections, there are two ways in which a section of a method map can be selected, namely by selecting an intention or by selecting a strategy. Therefore, the meta-intention Choose Section has two meta-strategies associated with it, select intention and select strategy respectively. Once a method map section has been selected by Choose Section, the IAG to support its enactment must be retrieved; this is represented in [the graph] by associating the meta-strategy automated support with the meta-intention, Enact Section.”

Sample process: Eliciting requirements of a Recycling Machine

This sample process is about a method for designing the requirements of recycling facilities. The recycling facilities are meant for customers of a supermarket. The adequate method is obtained though instantiation of the meta-process model on the process model.

The following table displays the stepwise trace of the process to elicit requirements for the recycling machine:

• • COMING SOON**

Source: [Rolland1999]