13.4 The Enterprise Continuum and the TOGAF 10 Architecture Repository

13.4 The Enterprise Continuum and the TOGAF 10 Architecture Repository

The Enterprise Continuum and the Architecture Repository appear in the Level 1 "Concepts" and "Architecture Content" areas. The Level 2 outcomes ask you to know how a repository can be structured using the TOGAF repository, what to expect in a well-run Architecture Repository, and how architecture levels organize the Architecture Landscape. This section uses the TOGAF Standard, 10th Edition names. Older material still describes six repository classes with a Standards Information Base and a Governance Log.

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The Enterprise Continuum

TOGAF describes the Enterprise Continuum as a view of the Architecture Repository that shows the evolution of related architectures from generic to specific, from abstract to concrete, and from logical to physical. It is a way of classifying architecture and solution assets so architects can find and reuse them, and it gives a common language for discussing them.

It has two related continua:

Moving left to right (from Foundation to Organization-Specific), architectures address enterprise needs in decreasing abstraction. Architects typically find more reusable elements toward the Foundation end. When an element is missing, the requirement is passed back toward the generic end so that it can be incorporated there for future reuse. The Architecture Continuum also serves as a classification scheme for the Reference Library. The Solutions Continuum classifies the solutions that realize architectures. Within each level of the Architecture Landscape, the Architecture Continuum divides architectures by abstraction.

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The Architecture Repository

TOGAF explains that a mature Architecture Capability produces a huge volume of output. Managing and reusing it requires a formal taxonomy of architectural assets plus processes and tools for storing them. The Architecture Repository is one part of the wider Enterprise Repository, which also links to detailed design, deployment, and service management repositories.

The Eight Classes of Information

Inside the Key Areas

Architecture Landscape. The landscape is divided into three levels of granularity:

• Strategic Architectures show a long-term summary view of the entire enterprise and support direction setting at an executive level.
• Segment Architectures give more detailed operating models for areas within the enterprise and are used at program or portfolio level.
• Capability Architectures show in more detail how the enterprise can support a particular unit of capability: current capability, target capability, and capability increments, so that work packages and projects can be grouped into portfolios and programs.

Reference Library. Materials come from standards bodies, product and service vendors, industry communities and forums, standard templates, and enterprise best practice. It should contain reference architectures, reference models, a viewpoint library, and templates. TOGAF notes that reference architecture and reference model have the same relationship as architecture and model, and that either can be generic or organization-specific. Its examples include the IT4IT Reference Architecture and the TM Forum eTOM and SID.

Standards Library. Standards are classed as legal and regulatory obligations, industry standards, and organizational standards. They move through a lifecycle: Proposed, Provisional (Trial), Standard (Active), Phasing-Out (Deprecated), and Retired (Obsolete). They are classified by the building blocks of the Enterprise Metamodel and by domain: business, data, applications, and technology standards (Section 7.2).

Governance Repository. It holds a decision log (product selections, justifications for major architectural features, standards deviations, standards lifecycle changes, Change Request evaluations, and reuse assessments), compliance assessments, capability assessments, a calendar of in-flight projects and reviews, the project portfolio under governance, and performance measurement for the architecture function.

Architecture Requirements Repository. It is used by all ADM phases and managed by Requirements Management. Requirements are held at strategic, segment, and capability levels, and once their business outcomes are reflected in the Solutions Landscape they are archived for audit.

Solutions Landscape. It holds the SBBs (products or services) that support the specified ABBs, categorized by the Enterprise Continuum or as Strategic, Segment, or Capability SBBs. It does not include the information and data that the solutions themselves produce.

TOGAF also mentions external repositories: external reference models, external standards (ISO, IEEE, government), and Architecture Board approvals. Board minutes are often held in documentation archives outside the Architecture Repository for legal or regulatory reasons.

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Continuum Versus Repository

• The Enterprise Continuum is a classification view: it organizes assets from generic to specific, abstract to concrete, and logical to physical.
• The Architecture Repository is the store that holds the assets, organized into the eight classes above.

The Reference Library uses the Architecture Continuum as its classification scheme, and the Architecture Landscape uses levels plus the Architecture Continuum. That is why the two concepts are often taught together.

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Common Exam Traps

• Using TOGAF 9 names. In the 10th Edition the store of standards is the Standards Library, and governance records live in the Governance Repository.
• Putting industry reference models in the Architecture Landscape. Generic or industry reference material belongs in the Reference Library; the Landscape holds the enterprise's own architectures at points in time.
• Forgetting the Solutions Landscape and Requirements Repository. The 10th Edition repository has eight classes, not six.
• Confusing the Architecture Capability area with the Architecture Metamodel area. The Capability area holds the parameters, structures, and processes that govern the repository; the Metamodel area holds the tailored method and content metamodel.