Bridging the gap between enterprise architectures and software architectures

The US Federal Agencies’ Chief Information Officer Council in its guide to Federal Enterprise Architecture has defined an Enterprise Architecture (EA) to be “a strategic information asset base, which defines the mission, the information necessary to perform the mission and the technologies necessary to perform the mission, and the transitional processes for implementing new technologies in response to changing mission needs”. An EA is an architecture, and hence by definition the EA serves as the “blueprint” for all information systems developed in an organization. In other words, we may consider the EA as capturing the information technology architecture of an organization including hardware, software, and networking standardizations, if any, that serves as the basis for all information systems developed within an organization. This viewpoint enables us to put EA in proper business perspective: the EA is derived from, and closely aligned with, the Strategic Enterprise Plan (SEP) of the organization where the SEP captures the high level business objectives and goals for the organization for the next 3 to 5 years. The Strategic Information Systems Plan (SISP), usually developed by the Information Systems business unit of the organization, is derived from the SEP, and prioritizes the information systems development projects that will be undertaken in the near term (next 3 to 5 years) by the organization that will help achieve the business goals of the organization set in the SEP. Any information system that is approved for development by the SISP usually, after another round of approvals by the executive sponsors, goes through the typical system development process whose initial phases include scope definition, problem analysis and requirements analysis. During the requirements analysis phase the requirements of the new system are elicited from the stakeholders and analyzed — the analysis includes the development of system architectures (SysA) which considers allocation of the requirements between hardware, software and the network. Selection of the optimal SA from among the candidate system architectures is an important part of system development, since the quality of the system architecture has an effect on the quality of the final system — generally, a high quality system architecture results in a high quality final system. Usually the system requirements drive the selection of the system architecture from among competing architectures — but this approach ignores the effects of the EA on SysA that ensures that the system architecture meets the requirements set by the EA, such as satisfying the requirements of the chosen enterprise technology. Therefore, it will be extremely useful to the organization to have an understanding of the extent to which the SysA satisfies the EA — this traceability will ensure that the chosen system architecture meets the goals of the enterprise architecture as well. Once the optimal system architecture is selected, the next step is to develop the hardware, software and the network elements of the system almost independently of each other. Among these elements, software development is usually the most important, since the development of software seems to consume most resources in terms of budget, schedule, and manpower. The requirements pertaining to software are used to design the software subsystem, and the first step in the design is usually the development of the software architecture (SwA) for the system. The SwA is the high level viewpoint of the software to be developed and consists of components, connectors, constraints, styles, patterns, and the like. Most of the properties of the final software are considered to have been designed into the software at the software architectural design stage itself, hence, in general, high quality software architecture being expected to result in the development of a high quality software system. Like for the SysA, SwA selection is driven not only by the software requirements but also by the SysA, and since the SysA is influenced by the EA, we can see that the SwA is influenced by the EA as well.