41. Architecture Repository

Chapter Contents
41.1 Overview | 41.2 Architecture Landscape | 41.3 Reference Library | 41.4 Standards Information Base | 41.5 Governance Log | 41.6 The Enterprise Repository | 41.7 External Repositories

41.1 Overview

Operating a mature Architecture Capability within a large enterprise creates a huge volume of architectural output. Effective management and leverage of these architectural work products require a formal taxonomy for different types of architectural asset alongside dedicated processes and tools for architectural content storage.

This section of TOGAF provides a structural framework for an Architecture Repository that allows an enterprise to distinguish between different types of architectural assets that exist at different levels of abstraction in the organization. This Architecture Repository is one part of the wider Enterprise Repository, which provides the capability to link architectural assets to components of the Detailed Design, Deployment, and Service Management Repositories.

At a high level, six classes of architectural information are expected to be held within an Architecture Repository:

The relationships between these areas of the Architecture Repository are shown in Figure 41-1.

Figure 41-1: Overview of Architecture Repository

This section of TOGAF describes the structure and content of the repository areas that hold the output of projects, namely the Architecture Landscape, the Reference Library, the Standards Information Base, and the Governance Log.

This section also discusses requirements to be considered when selecting tools to manage an Architecture Repository.

41.2 Architecture Landscape

The Architecture Landscape holds architectural views of the state of the enterprise at particular points in time. Due to the sheer volume and the diverse stakeholder needs throughout an entire enterprise, the Architecture Landscape is divided into three levels of granularity:

  1. Strategic Architectures (see Part I, 3.70 Strategic Architecture) show a long-term summary view of the entire enterprise. Strategic Architectures provide an organizing framework for operational and change activity and allow for direction setting at an executive level.
  2. Segment Architectures (see Part I, 3.62 Segment Architecture) provide more detailed operating models for areas within an enterprise. Segment Architectures can be used at the program or portfolio level to organize and operationally align more detailed change activity.
  3. Capability Architectures (see Part I, 3.27 Capability Architecture) show in a more detailed fashion how the enterprise can support a particular unit of capability. Capability Architectures are used to provide an overview of current capability, target capability, and capability increments and allow for individual work packages and projects to be grouped within managed portfolios and programs.

41.3 Reference Library

41.3.1 Overview

The Reference Library provides a repository to hold reference materials that should be used to develop architectures. Reference materials held may be obtained from a variety of sources, including:

The Reference Library should contain:

The terms reference architecture and reference model are not used carefully in most literature. Reference architecture and reference model have the same relationship as architecture and model. Either can exist as either generic or an organization-specific state. Typically, a generic reference architecture provides the architecture team with an outline of their organization-specific reference architecture that will be customized for a specific organization. For example, a generic reference architecture may identify that there is a need for data models. An organization that selects the TMF's SID as a reference data model is creating an organization-specific reference architecture.

In order to segregate different classes of architecture reference materials, the Reference Library can use the Architecture Continuum as a method for classification.

Figure 41-2: Architecture Continuum

The Architecture Continuum, as shown in Figure 41-2, can be viewed as a Reference Library classification scheme. As such it illustrates how reference architectures can be organized across a range - from Foundation Architectures, and Industry-Specific Architectures, to an Organization-Specific Architecture.

The enterprise needs and business requirements are addressed in decreasing abstraction from left to right. The architect will typically find more re-usable architectural elements toward the left of the range. When elements are not found, the requirements for the missing elements are passed to the left of the range for incorporation.

Through this exercise it is important to keep in mind the concepts of levels and partitions. At different levels of granularity there may exist reference materials appropriate to the level, and partitions within the Architecture Landscape can be expected to use different reference material (see 40. Architecture Partitioning and Part III, 20. Applying the ADM across the Architecture Landscape).

41.4 Standards Information Base

41.4.1 Overview

The Standards Information Base provides a repository area to hold a set of specifications, to which architectures must conform. Establishment of a Standards Information Base provides an unambiguous basis for architectural governance because:

41.4.2 Types of Standard

Standards typically fall into three classes:

41.4.3 Standards Lifecycle

Standards do not generally exist for all time. New standards are identified and managed through a lifecycle process. Typically, standards pass through the following stages:

All standards should be periodically reviewed to ensure that they sit within the right stage of the standards lifecycle. As a part of standards lifecycle management, the impact of changing the lifecycle status should be addressed to understand the landscape impact of a standards change and plan for appropriate action to address it.

41.4.4 Standards Classification within the Standards Information Base

Standards within the Standards Information Base are categorized according to the building blocks within the TOGAF content metamodel. Each metamodel entity can potentially have standards associated with it (e.g., Business Service, Technology Component).

Standards may relate to "approved" building blocks (e.g., a list of standard Technology Components) or may specify appropriate use of a building block (e.g., scenarios where messaging infrastructure is appropriate, application communication standards are defined).

At the top level, standards are classified in line with the TOGAF architecture domains, including the following areas:

41.5 Governance Log

41.5.1 Overview

The Governance Log provides a repository area to hold shared information relating to the ongoing governance of projects. Maintaining a shared repository of governance information is important, because:

41.5.2 Contents of the Governance Log

The Governance Log should contain the following items:

41.6 The Enterprise Repository

While the Architecture Repository holds information concerning the enterprise architecture and associated artifacts there are a considerable number of enterprise repositories that support the architecture. These include the Requirements Repository storing requirements and the Solutions Repository storing Solution Building Blocks (SBBs). See Figure 41-1.

The business outcomes for requirements will be reflected in the Solutions Repository over time. When this occurs the requirements are met and archived for audit purposes.

41.6.1 Requirements Repository

The Requirements Repository is used by the Requirements Management Phase of the Architecture Development Method (ADM) to record and manage all information relevant to the architecture requirements. The requirements address the many types of architecture requirements; i.e., strategic, segment and capability requirements which are the major drivers for the enterprise architecture.

Requirements can be gathered at every stage of the architecture development lifecycle and need to be approved through the various phases and governance processes.

41.6.2 Solutions Repository

The Solutions Repository holds the Solution Building Blocks (SBBs).

41.7 External Repositories

41.7.1 External Reference Models

There are many industry reference models available which may assist in understanding the role of and developing the Reference Architectures. Examples include MDA from OMG, FEA for US Government, TMF from the Telecoms Industry, SOA reference models from OASIS and The Open Group.

41.7.2 External Standards

These relate to industry, best practice, or formal defined standards used by leading organizations. Examples include ISO, IEEE, and Government standards.

41.7.3 Architecture Board Approvals

Decisions made by the Architecture Board which affect the enterprise architecture are often recorded in the minutes of meetings. These minutes are often held in documentation archives which are excluded from the Architecture Repository for legal or regulatory reasons.
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Downloads of TOGAF®, an Open Group Standard, are available under license from the TOGAF information web site. The license is free to any organization wishing to use the TOGAF standard entirely for internal purposes (for example, to develop an information system architecture for use within that organization). A book is also available (in hardcopy and pdf) from The Open Group Bookstore as document G116.