Procedure Description

 

A generic procedure description model

In automation technology, controllable processes appear in various different application fields and on different levels. The planned control sequences are also called procedures. Examples of such procedures are simple engine control systems, starting up and shutting down plants, executing batch-recipes, carrying out maintenance services or monthly production planning. This very general idea can basically be applied to entire industrial plants, general technical systems, social systems, organizational systems, software systems and many others. From a procedure-based perspective, each available functionality is part of the system including in particular those functionalities that it can access, such as subordinate control functions, services, human participants, organizational units, etc. The model also indicates that the formulation of a procedure does not only require the process itself, but also the system together with its available interfaces and system functionalities. Procedure descriptions represent the connective link between process knowledge, sequence description, structure and functionality of the available resources and the operational execution context. In the following figure, the structure and characteristics of procedure descriptions are exemplified for an industrial production process.

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Procedure Description

The operational execution of a procedure is thus strictly separated from its description. The different application fields have led to the establishment of various different solutions concerning the procedure descriptions. In the past, the diversity of description forms did not lead to problems, since these application fields were treated completely separately. However, the emergence of Industrie 4.0 as a future project will inevitably have consequences for procedure descriptions. There are technical reasons for the afore-mentioned diversity among procedure descriptions such as the various kinds of actions that can be performed, the different requirements for integrating human beings into procedure control and action execution, but also the different ways of coupling procedure descriptions to PLS-programming languages. Additionally, one has to deal with the separate historical developments in the individual application fields that eventually led to the different procedure description languages.

Components of a general procedure description

A general procedure description model must take different concepts into consideration and make appropriate statements with regard to these concepts.

Structure: The structure model describes the basic elements that are part of a procedure description and places these elements into conceptual relationships. The main elements of this model are e.g. steps, transitions or actions.

Abstraction and Allocation: This model provides a basis for managing and maintaining procedures during the entire use phase including the first draft, the subsequent engineering and the operational running. With regard to procedures there are multiple variations of how they can be systematically specialized from generic and abstract descriptions and then realized operationally. The abstraction- and allocation model describes the required steps and stages of concretization. In some cases, the specifications are not made until runtime. During runtime, only structurally consistent transformations shall be permitted.

Actions and Activities: The action- and activity model describes the integration of the procedure system into the environment. Procedures actively influence the target system. The central aspect with regard to this model is an understanding of the concept action request as a specialized service. Actions are technologically timeless procedures, while activities have a specific duration.

Hierarchy- and Networking: The simple base pattern of an operational structure is a terminating linear chain. In many cases though, operational structures are more complicated. They typically contain branches, macro steps, hierarchical sub-chains and other constituents. The hierarchy- and networking model describes the patterns and rules for designing these interconnected operational structures.

Execution Control: A procedure does not only include the fully automated sequence that applies to normal operations, since procedure sequences can also be controlled semi-automatically or manually. However, the procedure control must react to disturbances and interruptions according to a standardized pattern. The description of these concepts is assumed by the execution control model.

Implementation: The target followed by the implementation model is the specification of a landscape of description languages that enable continuous transformations and refinements of the generic master model, the domain-specific engineering models and the programming languages of the realization systems. For flexibility reasons, the model also requires a language for the description of reconfiguration processes at runtime.

Additional Information

For additional information, please contact Andreas Schüller. The text you find on this page is a translation of sections from the following article:

Andreas Schüller, Ulrich Epple: Ein Referenzmodell zur Prozedurbeschreibung: Eine Basis für Industrie 4.0, Berlin / De Gruyter, at - Automatisierungstechnik, Band: 63, Ausgabe: 2, Seite(n): 87-98, (2015) . Weiterleitung

For further information on this topic, you may consult the following papers.

Andreas Schüller, Ulrich Epple: Ein einheitliches Prozedurbeschreibungsmodell als Basis der domänenübergreifenden Verständigung, Entwurf komplexer Automatisierungssysteme - EKA 2014 : Beschreibungsmittel, Methoden, Werkzeuge und Anwendungen ; 13. Fachtagung mit Tutorium, 14. bis 15. Mai 2014 in Magdeburg / Ulrich Jumar; Christian Diedrich (Hrsg.) Weiterleitung

Andreas Schüller, Ulrich Epple, Jürgen Elger, Andreas Müller-Martin, Ulrich Löwen: Geschäftsprozesse und technische Prozesse - Ein Ebenenmodell zur Integration, Berlin / De Gruyter, at - Automatisierungstechnik, Band: 62, Ausgabe: 9, Seite(n): 665-675 , (2014) Weiterleitung