Information Technology Reference
In-Depth Information
1.3.1.1  Enterprise Architecture and Systems Architecture
Architecture is a multidimensional practice. Challenges facing the architect include
paradox, dichotomies, balancing a multitude of tasks, deadlines, conflicting prem-
ises, constraints, uncertainty with existing information, and missing information.
Critical architectural decisions may include many assumptions (a professional
euphemism for guesses ). A structured approach to architecture provides a method
to minimize assumption uncertainty. An effective architectural approach addresses
enterprise architecture (the big picture) as well as systems architecture (the pieces
comprising the big picture).
GEAO describes enterprise architecture as follows:
The way in which an enterprise vision is expressed in the structure and
dynamics of an Enterprise. It provides, on various architecture abstrac-
tion levels, a coherent set of models, principles, guidelines, and policies,
to translate, align, and evolve the systems that exist within the scope
and context of an Enterprise.
An EA process is a methodology that aligns solutions (business, technical, oper-
ations, etc.) with organizational core mission and strategic direction in terms of
to-be , target architecture; as-is , current architecture; and transition , migration plan
from as-is to to-be .
Understanding that systems comprise the greater enterprise, there is a distinc-
tion between enterprise architecture and systems architecture. A system may or may
not be a computer system, but is by definition an entity that accepts input, performs
a process, generates output, and reacts to feedback (e.g., nervous system, economic
system, or computer system). Based on the GEAO definition of enterprise architec-
ture, system architecture is defined as follows:
Systems architecture refers to the way in which a system vision is
expressed in the structure and dynamics of the system and often in
context of a collection of systems. It provides, on various architecture
abstraction levels, a coherent set of models, principles, guidelines, and
policies, used for the translation, alignment, and evolution of the com-
ponents that exist within the scope and context of a system.
Enterprise architecture and system architecture are complex practices of abstrac-
tion that provide guidelines to develop business solutions without regard to spe-
cific services or mechanisms. Information assurance architecture is itself a complex
practice of abstraction requiring a melding of architectural concepts, information
Global Enterprise Architecture Organization (www.geao.org).
 
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