Migration and Long-Lived Systems: The Key Principles
Enterprise Focus
Open-System, Standards-Based Development
Component-Based, Distributed Computing Environment
Planning for Change
Architecture-Influenced Decisions
Enterprise Focus
Long-lived systems require that IT design and implementation decisions be made in a broad context, considering the entire Enterprise. Consequences of decisions must be assessed against long-term goals, special interests, and currently available resources. Appropriate tradeoffs are made within this context. For flexibility in making these tradeoffs and minimization of imposed constraints, the scope should be as large as possible.
The Enterprise figure depicts the notion of an Enterprise and its boundaries. This Enterprise scope establishes the boundary where the Enterprise has control over its technology and business decisions. This is reflected in the Enterprise's business and IT delivery and support processes. The boundary helps to identify the immediate and wider environments of interest in which the Enterprise participates. The boundary is used to identify the roles that participate directly or indirectly in the Enterprise processes. Within the Enterprise, alignment is necessary between the Enterprise's overall business strategy and the IT strategy. The IT Planning and Management Guides assume the HS Agency as the Enterprise scope, which may include several programs (e.g., TANF, CSE, Food Stamps, Medicaid, Child Welfare, and Child Care) and their respective IT Divisions. The individuals and groups associated with the environments are described in the role model.
Open-System, Standards-Based Development
An Open system approach unifies technical and business strategy to establish a rational structure in which to make key AIS design and product purchasing decisions. The primary goal is to promote interoperability and integration of technology within and external to the HS Agency. Portability may also be a significant design goal, particularly for portions of the applications that interact with the user. This may be driven by innovation in the types of user interface devices, such as information appliances , and wireless or mobile computing.
Open system concepts guide long-term evolution of technology in use by the HS Agency. Nonproprietary, commercially supported specifications and standards with broad industry support are the basis of defining each HS Agency's unique technology interfaces, formats, protocols, products, practices, and tools.
The principle of Enterprise standardization is similar to that stated in RFC 2026 Bradner 1996 ). Standardization is not a set of absolute constraints. It represents guidelines that can be adapted by IT projects , under control of the HS Agency architects, to manage project IT life-cycle costs, deployment schedule, and performance tradeoffs. Standards are usually selected (see profile ) to implement a TRM appropriate for the HS Agency's business-technology environment.
Component-Based, Distributed Computing Environment
Monolithic applications, statically configured and linked, are giving way to highly distributed, loosely-coupled applications based on technologies such as COM+ , J2EE , and CORBA Applications and their constituent parts are considered reusable resources that, once introduced into the run-time environment, can be used in novel ways to compose additional applications.
AIS's built with these techniques are capable of exhibiting the scalability and malleability needed to adapt in a rapidly changing world. Components may provide general services, be application-specific, or support specific vertical markets. They can be developed in-house, purchased, or leased as a Web service .
Planning for Change
A rapid rate of change in the business and technology environments is a compelling reason to consider not only satisfying current needs as quickly as possible but anticipating future needs and changes. IT planning decisions must be influenced by an understanding of trends in the HS Agency business and technological environments. Uncertainty related to future business and technology factors will influence approaches used to select, adapt, develop, and use technology. Technology decisions made today should not severely limit future choices.
Planning for change affects and interacts with the other principles. For example, the architects may establish interfaces to isolate and abstract applications on some computer systems, allowing them to be replaced in the future with limited impact (e.g., wrappers). The scope of integration and interoperability can likewise be established to give the HS Agency influence over decisions before they become levied as constraints, such as working with partner organizations on common network protocols or message formats. The considerations and barriers described in the WRIT report ( ACF 2000 provide information on common risks and aversion strategies for the TANF program.
Architecture-Influenced Decisions
HS Agency strategic direction provides the basis for the technology vision. Decisions on the future use of existing IT resources provide the context. Those decisions reflect the need to keep, discard, revamp, or reengineer the existing IT inventory, as well as to add new or modified applications and capabilities. This combination of the technology vision and resource decisions is used to identify the basic technology elements that the HS Agency must include in its inventory. These elements and their relationship to one another constitute the Agency's Technical Architecture. Documentation to describe the elements and the processes by which they are produced and used then guides the individual project and application system technical decisions - throughout their complete life cycle. The four foundational principles then guide the generation of this technical blueprint, which controls the evolution of the technology and technology-related entities.