This chapter describes the Information Systems Architectures for an architecture project, including the development of Data and
Application Architectures.
Figure 9-1: Phase C: Information Systems Architectures
9.1 Objectives
The objective of Phase C is to develop Target Architectures covering either or both (depending on project scope) of the data and
application systems domains.
Information Systems Architecture focuses on identifying and defining the applications and data considerations that support an
enterprise's Business Architecture; for example, by defining views that relate to information, knowledge, application services,
etc.
9.2 Approach
9.2.1 Development
Phase C involves some combination of Data and Application Architecture, in either order. Advocates exist for both sequences. For
example, Steven Spewak's Enterprise Architecture Planning (EAP) recommends a data-driven approach.
On the other hand, major applications systems - such as those for Enterprise Resource Planning (ERP), Customer Relationship
Management (CRM), etc. - often provide a combination of technology infrastructure and business application logic, and some
organizations take an application-driven approach, whereby they recognize certain key applications as forming the core underpinning
of the mission-critical business processes, and take the implementation and integration of those core applications as the primary
focus of architecture effort (the integration issues often constituting a major challenge).
9.2.2 Implementation
Implementation of these architectures may not necessarily follow the same order. For example, one common implementation approach
is top-down design and bottom-up implementation:
Design:
Business Architecture design
Data (or Application) Architecture design
Application (or Data) Architecture design
Technology Architecture design
Implementation:
Technology Architecture implementation
Application (or Data) Architecture implementation
Data (or Application) Architecture implementation
Business Architecture implementation
An alternative approach is a data-driven sequence, whereby application systems that create data are implemented first, then
applications that process the data, and finally applications that archive data.
9.3 Inputs
This section defines the inputs to Phase C.
9.3.1 Reference Materials External to the Enterprise
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organization wishing to use TOGAF 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 G091.