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Copy pasted text from Memoranda 97-16 (Information Technology Architectures) + some further explanations |
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In a way the NIST Enterprise Architecture Model was ahead of his time. According to Zachman (1993) in the 1980s the "architecture" was acknowledged as a topic of interest, but there was still little consolidated theory concerning this concept.<ref>J.A Zachman (1993) ''[http://www.ies.aust.com/pdf-papers/zachman3.pdf Concepts for Framework for EA - Enterprise Architecture Resources]''. Zachman International, Inc. paper. p. 1</ref> [[Software architecture]], for example. become an important topic not until the second half of the nineties.<ref>Leonor Barroca, Jon Hall and Patrick Hall (200) "[http://mcs.open.ac.uk/lmb3/introduction.pdf An Introduction and History of Software Architectures, Components, and Reuse]" in: ''Software Architectures'', 2000 p. 1</ref>
To support the NIST Enterprise Architecture Model in the 1990s, it was widely promoted within the [[Federal government of the United States|U.S. federal government]] as Enterprise Architecture management tool.<ref name="CIOC99"/>.
== NIST Enterprise Architecture Model topics ==
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* Data Delivery Systems level: Technical implementation level of software, hardware, and communications that support the data architecture.
A sample elements of how the [[Enterprise Architecture]] can be described in more detail is shown in the illustration.
=== Information Technology Architecture ===
The "Memoranda 97-16 (Information Technology Architectures)" gave the following definition of enterprise architecture:<ref name="M-97-16"/>
:''The Enterprise Architecture is the explicit description of the current and desired relationships among business and management process and information technology. It describes the "target" situation which the agency wishes to create and maintain by managing its IT portfolio.''
:''The documentation of the Enterprise Architecture should include a discussion of principles and goals.1 For example, the agency's overall management environment, including the balance between centralization and decentralization and the pace of change within the agency, should be clearly understood when developing the Enterprise Architecture. Within that environment, principles and goals set direction on such issues as the promotion of interoperability, open systems, public access, end-user satisfaction, and security.''
In this guidance the five component model of the NIST was adopted and further explained. Agencies were permitted to identify different components as appropriate and to specify the organizational level at which specific aspects of the components will be implemented. Although the substance of these components, sometimes called "architectures" or "sub-architectures," must be addressed in every agency's complete Enterprise Architecture, agencies have great flexibility in describing, combining, and renaming the components, which consist of<ref name="M-97-16"/>:
* ''Business Processes'': This component of the Enterprise Architecture describes the core business processes which support the organization's missions. The Business Processes component is a high-level analysis of the work the agency performs to support the organizations's mission, vision, and goals, and is the foundation of the ITA. Analysis of the business processes determine the information needed and processed by the agency. This aspect of the ITA must be developed by senior program managers in conjunction with IT managers. Without a thorough understanding of its business processes and their relation to the agency missions, the agency will not be able to use its ITA effectively. <br>Business processes can be described by decomposing the processes into derivative business activities. There are a number of methodologies and related tools available to help agencies decompose processes. Irrespective of the tool used, the model should remain at a high enough level to allow a broad agency focus, yet sufficiently detailed to be useful in decision-making as the agency identifies its information needs. Agencies should avoid excessive emphasis on modeling business processes, which can result in a waste of agency resources.<ref>The US Department of Defense includes aspects of the Business Processes element in its Operational Architecture; the US Department of Treasury incorporates it into its business view.</ref>
* ''Information Flows and Relationships'': This component analyzes the information utilized by the organization in its business processes, identifying the information used and the movement of the information within the agency. The relationships among the various flows of information are described in this component. These information flows indicate where the information is needed and how the information is shared to support mission functions.<ref>The US Department of Agriculture has incorporated this component into its Business Architecture, while the US Department of Defense and Treasury have built it into their Operational Architectures. </ref>
* ''Applications'' : The Applications component identifies, defines, and organizes the activities that capture, manipulate, and manage the business information to support mission operations. It also describes the logical dependencies and relationships among business activities.<ref>The US Department of Energy incorporates Business Applications into its Applications Subarchitecture, while the US Department of Treasury includes them in its Functional Architecture. </ref>
* ''Data Descriptions'': This component of the Enterprise Architecture identifies how data is maintained, accessed, and used. At a high level, agencies define the data and and describe the relationships among data elements used in the agency's information systems. The Data Descriptions and Relationships component can include data models that describe the data underlying the business and information needs of the agency. Clearly representing the data and data relationships is important for identifying data that can be shared corporately, for minimizing redundancy, and for supporting new applications<ref>The US Department of Agriculture has included in this element in its Business/Data Architecture, while the US Department of Treasury incorporates it in its Information Architecture. </ref>
* ''Technology Infrastructure'' : The Technology Infrastructure component describes and identifies the physical layer including, the functional characteristics, capabilities, and interconnections of the hardware, software, and communications, including networks, protocols, and nodes. It is the "wiring diagram" of the physical IT infrastructure.<ref>The US Department of Agriculture had incorporated this architecture into its Technical Standard and Telecommunications Architectures. US DoD uses its System Architecture, and US Treasury its Infrastrucsture to describe the physical layer. </ref>
With the exception of the Business Processes component, the interrelationships among and priorities of these components are not prescribed by this guidance; there is no hierarchy of relationships implied. Furthermore, agencies should document not only their current environment for each of these components, but also the target environment that is desired.<ref name="M-97-16"/>
== Applications ==
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