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Copyright © 2000 Essential Strategies, Inc.
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The Zachman Framework
David C. Hay
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Introduction The System Development Life Cycle
Many methodologies are organized around the "system development life cycle," an organization of the steps required to develop systems. Oracle's is shown in Figure 1, expressed specifically as consisting of:
Notice that each of these steps addresses issues of data and function. Data and functions are typically addressed as separate topics, although ideally, they are addressed together.
Most methodologies portray the system development life cycle in terms approximating these. Some go so far as to give it the acronym "SDLC."
- Strategy The planning of an organization's overall systems development effort. This includes determining the overall set of things of significance to a business, the application areas to be addressed, and the priorities to apply to those priorities.
- Analysis The detailed definition of requirements for a particular area of the business. At this point, the data structures are mapped in detail, the functions of the business are described thoroughly, and the areas to be automated are defined.
- Design The specific application of technology to the requirements defined during analysis. Here the data structures become database designs and the function definitions become program specifications. At this point attention is paid to the human interface, in the interest of defining the behavior of a prospective system.
- Construction The actual building of the system.
- Documentation Preparation of the user manuals, reference manuals, etc. to describe the system.
- Transition The implementation of the system, so as to make it part of the infrastructure of the organization. This involves education, training, definition of new organizational structures and roles, and the conversion of existing data.
- Production The ongoing monitoring of the system to ensure that it continues to meet the needs of the organization.
Figure 1: The System Development Life Cycle
The Zachman Framework
In 1987, John Zachman published a different approach to the elements of system
development. Instead of representing the process as a series of
steps, he organized it around the points of view taken by the various players. These players
included (1) the CEO or whoever is setting the agenda and strategy for an organization,
(2) the business people who run the organization, (3) the systems analyst who wants to represent
the business in a disciplined form, (4) the designer, who applies specific technologies
to solve the problems of the business, and finally, (5) the system itself. Mr. Zachman
represents each of these perspectives as a row in his matrix.
He then defined columns in the matrix to represent the kinds of things people should be looking at. These include functions and data, as addressed by most methodologies. In addition, however, Mr. Zachman has set up columns to represent locations (where business is conducted), the people and organizations involved, events which cause things to happen, and the motivations and constraints which determine how the business behaves.
John Zachman's "framework for information systems architecture" is diagrammed in Figure 2. The rows represent the points of view of different players in the systems development process, while columns represent different aspects of the process. The players are:
The columns in the Zachman framework represent different areas of interest for each perspective. The columns describe
the dimensions of the systems development effort. As shown in Figure 2, these are:
- Scope (Ballpark view): Definition of the enterprise's direction and business purpose. This is necessary to establish the context for any system development effort.
- Model of the business (Owner's view): This defines in business terms the nature of the business, including its structure, functions, organization, and so forth.
- Model of the information system (Architect's view): This defines the business described in step 2, but in more rigorous information terms. Where row two described business functions, for example, as perceived by the people performing them, row three describes them specifically as transformations of data. Where row two described all the things of interest to the enterprise, row three describes those things about which the organization wishes to collect and maintain information, and begins to describe that information.
- Technology model (Designer's view): This describes how technology may be used to address the information processing needs identified in the previous rows. Here relational databases are chosen over network ones (or vice versa), kinds of languages are selected and program structures are defined, user interfaces are described, and so forth.
- Detailed representations (Builder's view): Here a particular language is chosen, and the program listings, database specifications, networks, and so forth are all produced.
- Functioning system: Finally, a system is implemented and made part of an organization.
- Data: Each of the rows in this column address understanding of and dealing with an enterprise's data. This begins in row one with an list of the things that concern the company and affect its direction and purpose. Row two, is a contiguous model of the things seen by the participants in the business. Many-to-many and n-ary relationships may be present, reflecting the way the business views them. Also, relationships may be shown which themselves have attributes. Row three provides more of an information-based perspective, resolving many-to-many and n-ary relationships, along with relationships containing their own attributes. Indeed, attributes are more exhaustively defined, and unique identifiers are specified. Entities are generalized to more closely reflect the underlying structure of the business and its relationships. In row four, entities are converted to table definitions, object classes, hierarchy segments, or whatever is appropriate for the kind of data base management system to be used. This is tantamount to creating the data definition language statements. In row five, the tables are actually implemented on physical disk drives, using the underlying organization of the database management system. This is where tablespaces are defined, disk packs are allocated, and so forth. The actual database itself is created and initial data are converted and loaded for row six.
- Function: The rows in the function column describe the process of translating the mission of the enterprise into successively more detailed definitions of its operations. Where row one is a list of the kinds of activities the enterprise conducts, row two describes these activities in a contiguous model. Row three portrays them in terms of data transforming processes, described exclusively in terms of the conversion of input data into output data. The technology model in row four then converts these data conversion processes into the definition of program modules and how they interact with each other. Pseudo-code is produced here. Row five then converts these into source and object code. Row six is where the code is linked and converted to executable programs.
Note that in the object-oriented approach, functions and data tend to be addressed together.
- Network: This column is concerned with the geographical distribution of the enterprise's activities. At the strategic level (row one), this is simply a listing of the places where the enterprise does business. At row two, this becomes a more detailed communications chart, describing how the various locations interact with each other. Row three produces the architecture for data distribution, itemizing what information is created where and where it is to be used. In row four, this distribution is translated into the kinds of computer facilities that are required in each location, and in row five, these facilities requirements are translated into specification of particular computers, protocols, communications facilities, and the like. Row six describes the implemented communications facilities.
- People: The fourth column describes who is involved in the business and in the introduction of new technology. The row one model of people is a simple list of the organizational units and each unit's mission. In row two, this list is fleshed out into a full organization chart, linked to the function column. Here also, requirements for security are described in general terms. In row three, the potential interaction between people and technology begins to be specified, specifically in terms of who needs what information to do his job. What roles do each play and what data are necessary for those roles? Along with this are specific definitions of security requirements, in terms of who (which role) is permitted access to what. In row four, the actual interface between each person and the technology is designed. In this row, issues of interface graphics, navigation paths, security rules and presentation style are addressed. In row five, this design is converted into the outward appearance of each program, as well as the definitions of access permissions in terms of specific tables and/or columns each user can have access to. In row six, you have trained people, using the new system.
- Time: The fifth column describes the effects of time on the enterprise. It is difficult to describe or address this column in isolation from the others, especially column two. At the strategic (row one) level, this is a description of the business cycle and overall business events. In the detailed model of the business (row two), the time column defines when functions are to happen and under what circumstances. Row three defines the business events which cause specific data transformations and entity state changes to take place. In the technology model (row four), the events become program triggers and messages, and the information processing responses are designed in detail. In row five, these designs become specific programs. In row six business events are correctly responded to by the system.
- Motivation: As Mr. Zachman describes it, this is concerned with the translation of business goals and strategies into specific ends and means. This can be expanded to include the entire set of constraints that apply to an enterprise's efforts. In row one, the enterprise identifies its goals and strategies in general, common language terms. In row two, these are translated into the specific rules and constraints that apply to an enterprise's operation.
n row three, business rules may be expressed in terms of information that is and is not permitted to exist. This includes constraints on the creation of rows in a database as well as on the updating of specific values.
In row four, these business rules will be converted to program design elements, and in row five they will become specific programs. In row six, business rules are enforced.