Patterns INCOSE MBSE WG 2014 02 27 Copyright

1. Overview 1. What are patterns? 2. An approach to documenting patterns 3. Candidate

1. What are patterns? < “A pattern describes a problem which occurs over and over again in our environment, and then describes the core of the solution to that problem, in such a way that you can use this solution a million times over, without ever doing it the same way twice". - Christopher Alexander, ‘A Pattern Language’, 1977 < Original ideas from (building) architecture but adopted by software engineering OO community - Made more widely known through “Gang of Four Book” (1995) < Ideas spread to analysis and data modelling through books by Fowler (1997) and Day (1996) < Now being adopted in the wider systems engineering community Copyright © 2014 Atego. 3

Architectural vs. Enabling Patterns < On the COMPASS project (http: //www. compass-research. eu) we use the terms architectural pattern and enabling pattern < Architectural patterns - Describe specific system architectures, in terms of both structure and behaviour, which address particular needs of the system < Enabling patterns - Specific constructs of modelling elements whose combination and subsequent use enables a number of systems engineering applications - E. g. one used for the definition of interfaces or one used to ensure traceability throughout a model of a system < See COMPASS Deliverable D 22. 3 ‘Report on Modelling Patterns for So. S Architectures’ - Available from http: //www. compass-research. eu/deliverables. html Copyright © 2014 Atego. 4

2. An approach to documenting patterns < When defining patterns it is important to use a consistent model-based approach < One such approach is based on around the ideas of ontology, viewpoints and framework < Ontology - Define concepts and relationships between them < Viewpoints and Framework - Define viewpoints organised into a framework - Viewpoints can only use concepts from the ontology < Originally developed by Brownsword, Holt and Perry (2011) - Further refined by Holt & Perry (2013) (the Framework for Architectural Frameworks – FAF) - Adopted in the COMPASS project (FAF adopted into COMPASS as the CAFF) Copyright © 2014 Atego. 5

The COMPASS Architectural Framework (CAFF) < The CAFF was initially developed to improve the definition of Architectural Frameworks (AFs) - Applicable to the definition of patterns < Consists of: - An ontology - Six viewpoints - Supporting processes < Described in COMPASS Deliverable D 21. 2 ‘Initial Report on Guidelines for Architectural Level So. S Modelling’ - Available from http: //www. compass-research. eu/deliverables. html Copyright © 2014 Atego. 6

The CAFF Ontology Copyright © 2014 Atego. 7

The CAFF Viewpoints < AF Context Viewpoint (AFCV) - Defines the context for the AF - Represents the AF concerns in context, establishing why the AF is needed < Ontology Definition Viewpoint (ODV) - Defines the ontology for the AF - Derived from the AF Context Viewpoint & and defines concepts that can appear on a Viewpoint < Viewpoint Relationships Viewpoint (VRV) - Shows the relationships between the Viewpoints that make up an AF - Groups them into perspectives. It is derived from the Ontology Definition Viewpoint Copyright © 2014 Atego. 8

The CAFF Viewpoints continued < Viewpoint Context Viewpoint (VCV) - Defines the context for a particular Viewpoint - Represents the Viewpoint concerns in context for a particular Viewpoint, establishing why the Viewpoint is needed. It is derived from the AF Context Viewpoint < Viewpoint Definition Viewpoint (VDV) - Defines a particular Viewpoint - Shows the Viewpoint Elements (and hence the Ontology Elements) that appear on the Viewpoint < Rules Definition Viewpoint (RDV) - Defines the various rules that constrain the AF Copyright © 2014 Atego. 9

The CAFF Viewpoints Copyright © 2014 Atego. 10

The CAFF Viewpoints – an example of use for the Traceability Pattern Copyright ©

3. Candidate patterns < Defined by Atego - Interface Definition - Traceability - Testing - Life Cycle - Epoch < In development by Atego - Connection - Context - Description < What others are of interest? - Patterns workshop next session Copyright © 2014 Atego. 17

4. Summary < Patterns are now seen as a useful and powerful tool in model-based systems engineering < Patterns (and their extensions, Architectural Frameworks) need to be described in a consistent fashion < Work has been undertaken (and is continuing) on the COMPASS project in the collection and definition of appropriate architectural and enabling patterns < The COMPASS Architectural Framework, though initially developed to help in the consistent definition of AFs can also be used in the definition of patterns Copyright © 2014 Atego. 18

5. References < Alexander, C. S. , Ishikawa, M. , Silverstein, M. , Jacobson, M. , Fiksdahl. Ling, I. & Angel, S. ‘A Pattern Language’. New York: Oxford University Press; 1977 < Gamma, E. , Helm, R. , Johnson, R. & Vlissides, J. ‘Design Patterns – Elements of Reusable Object Oriented Software. ’ Boston, MA: Addison. Wesley; 1995 < Hay, D. ‘Data Model Patterns: Conventions of Thought’. New York: Dorset House; 1996 < Fowler, M. ‘Analysis Patterns: Reusable Object Models’. Boston, MA: Addison-Wesley; 1997 Copyright © 2014 Atego. 19

References continued < COMPASS. ‘D 22. 3 – Report on Modelling Patterns for So. S Architectures’; COMPASS Project; 2013 < COMPASS. ‘D 21. 2 – Initial Report on Guidelines for Architectural Level So. S Modelling’. COMPASS Project; 2013 < Holt, J, Perry, S & Brownsword, M. ‘Model-Based Requirements Engineering’. IET Publishing, 2011 < Holt, J & Perry, S. ‘Sys. ML for Systems Engineering; 2 nd Edition: A modelbased approach’. London: IET Publishing; 2013 Copyright © 2014 Atego. 20