Architecture Frameworks Further information There are many resources covering topics in architecture. In recent years there have been several significant attempts to Here are a few you might find useful: provide assistance to architects,particularly in relation to what ■ The INCOSEUK Chapter’s Architecture Working Group Z8 kind of system descriptions might be relevant for Issue 1.1 wiki pages:www.ukawg.org system architecture. This assistance is usually expressed July 2020 ■ The UK Ministry of Defence’s Architecture Framework through Architecture Frameworks, which serve to structure (MODAF):www.mod.uk/modaf and organise architectural descriptions. (Other techniques ■ The Open Group’s Architecture Framework (TOGAF): and tools are relevant in the ‘implementation domain’ www.opengroup.org/togaf but cannot be covered here.) System Architecture ■ The ISO/IEC standard on Architecture Descriptions (ISO/IEC42010): www.iso.org Architecture Frameworks define a set of viewpoints on to ■ The UK Department for Transport’sArchitecture Framework What is System Architecture? an underlying architecture and they may be supported by a (TRAK),originally created by London Underground: metamodel (a precise definition of what can be described in Architecture is a popular and evidently useful http://trak-community.org the architecture through each of the viewpoints). The emerging concept, with many practical benefits (seePage 4) - ■ The US Department of Defense’s Architecture Framework international standard ISO/IEC42010 addresses architecture (DoDAF):http://cio-nii.defense.gov/sites/dodaf20 unfortunately for the novice and the unwary there are descriptions and architecture frameworks. ■ The original IT-inspired Architecture Framework from many different interpretations in widespread use. John Zachman: www.zifa.com Examples of widely used architecture frameworks include: ■ The book by Maier and Rechtin gives a particular perspective Drawing on a variety of such interpretations, the Zachman, MODAF, DoDAF and TOGAF (see Page 6). on architecture: M. W. Maier and E. Rechtin. 2009. The Art of following is our summary definition that captures Note that some Architecture Frameworks focus more Systems Architecting. ISBN:978-1420079135 on the architecting process and others focus more on the majority of the common ground: architecture products. “The architecture of a system is its fundamental A visual representation of types of views in MODAF structure – which may include principles applying to is shown below: This leaflet the structure as well as specific structures.” This leaflet is intended to be a simple introductory guide to system architecture and architecting, particularly as practised Some authors broaden the definition of architecture in the UK. It is one of a series of introductory guides produced to include, for example, principles associated with the by the INCOSE UK Chapter. realisation of the system (how it is implemented) or governing its evolution over time.

Technical Strategic Views For further information, advice and links to helpful websites go to: www.incoseuk.org What fundamental means in practice is found to be Download copies of this leaflet and other Systems Engineering context dependent. The identification of fundamental l Views All Operational Views Views Aquisition resources online at: www.incoseuk.org tnadViews Standard types of structure usually depends on the nature of the For more information about the worldwide Systems Engineering professional community, go to www.incose.org system as well as on the purpose of the architecture. Service Views Structure that is judged not to be fundamental should Z8 lead author: Mike Wilkinson (Atkins) be excluded from the architecture.

System Views INCOSE UK Ltd @incoseuk The architecture of a systemi s its Z8 Issue 1.1 July 2020 fundamental structure © 2020 INCOSE UK ltd.

5 6 1 What is architectural structure? What is the role of architecture?

Define A typical system architecture will not usually be described structuring In use, architectural descriptions will usually have a by a single type of structure – it is likely to include logical principles primary role (or purpose) and a multitude of secondary (functional) structure, behaviour (process) structure, physical Define structure and potentially other types of structure (eg financial architecture ones. Some examples are: options or commercial). What needs to be included depends on what is judged to be fundamental, as discussed earlier. Analyse ■ Acting as a vehicle for communications between architecture options stakeholders Select ■ Establishing context architecture options ■ Capturing key business and technical concepts Produce ■ Providing a decision/tradeframework architecture ■ Providing guidance to the creation of detailed designs descriptions ■ Handling complexity and uncertainty Illustrative architecting process ■ Supporting re-use of system elements ■ Supporting extension, enhancement or scaling Behaviour (process) description ■ Dealing with transformation or evolution of systems over time System Architecting is the process of creating a system architecture A well crafted architecture should deliver the desirable outcomes (benefits) associated with each of its primary Logical (functional) description and secondary roles. What are the different types How is architecting related to Physical (layout) description of architecture? Illustrative architecture elements Systems Engineering? There are many types of architecture in use, each of What is system architecting? which may be focused on a particular topic of interest, There are many and diverse beliefs about the answer or on a specific purpose, or on a specific set of systems. to this question. System architecting is simply the process of creating (and describing) a system architecture, which we regard as Some examples of architectures with a focus on Some system architects regard Architecting as a subset a process within Systems Engineering (see Page 4). It may specific topics are: Operational; Programme; Security; of Systems Engineering, whereas others – particularly be motivated by a variety of factors; for example, ‘forward Information. those from the IT world and those involved in applying architecting’ aims to provide a basis for more detailed design, whereas ‘reverse architecting’ captures an existing system Some examples of architectures with specific purposes systems thinking at the business level – tend to regard architecture for analysis. are: Integration; Problem Domain Definition; Architecting as providing something missing from Systems Engineering, which they see as applying Architecting can be more or less systematic but typically Design-Controlling. involves: understanding context; exploration of alternatives; only at the physical level. Some examples of architectures addressing a specific understanding trades; supporting decision making; and so on. An illustrative architecting process is shown on Page 3 – set of systems are: System of Systems; Product Family; The answer to the question clearly depends on how in practice the precise form of the architecting process will Enterprise. one defines Systems Engineering. In the UK, Systems depend on the purpose and context of the architecture. Some practitioners regard each type of architecture as Engineering has historically been considered broadly, There are many good guiding principles for architecting, a viewpoint on to a single underlying architecture applying at all levels and embracing both synthetic including modularity, high cohesion, loose coupling, etc. (i.e. a single system could have a security architecture and analytical methods. Hence, we advocate the view As an overall principle, we paraphrase Saint-Exupéry: that Architecting is best regarded as a subset of a “An architect knows he has achieved perfection not when and an information architecture, etc) – more on this in there is nothing left to add, but when there is nothing left the section on Architecture Frameworks (see Page 5). broadly drawn Systems Engineering. to take away.” 2 3 4