In this document we will avoid the use of special computer jargon as much as possible. However, it is important to introduce a few terms that are crucial to the understanding of Enterprise Integration, Models and methods that are being developed to create a solid base of it. This base is required for mutual understanding and for the education of personnel on all hierarchical levels of the enterprise.
As outlined before, an architecture is a structured plan, a framework on the basis of which a product or an organisation of an enterprise can be constructed. A reference architecture is a generalised architecture, from this, a particular architecture can be defined or be used as an example. Also see the definitions of reference model and particular model for a more elaborate explanation of the terms 'reference' and 'particular'.
A model is a representation of reality. The more characteristics, processes and functions of the real world (real product, flow of actions in a real situation) that can be added to the model, the more information one can retrieve from the model. Examples of models are : scaled down models of ships, trains or aeroplanes, the mock-up of a building or an automobile, the drawing of a new city plan. These physical models lend themselves to the evaluation of the correctness of reality. One can measure the model, subject it to forces, and observe its behaviour under varying circumstances. In all cases, such a physical, miniature, real world "thing" has to be constructed. An approach more and more used, is to "model" a real entity in a computer. This is more difficult because one has to define the 'real thing' in mathematical and algorithmic descriptions. The advantage is that changes to the model can be made directly, without having to build a new physical model. With these types of models it is possible to add so many details and functions that on can be certain of having represented the reality as close as required. Also, the immediate changes that can be made accelerate the design and evolution time. The drawback is that the definition of a computer model is difficult, complex and may take a long time.
Computer models are used today to define, analyse or visualise "things" like the computer itself, communication networks, traffic situations, oil refineries, factory floors and organisational structures. Some of these models need elaborate calculations to verify their correct functioning. However, because of the progress of information technology, and with the aid of computer models, we are capable of designing and manufacturing larger scale integrated circuitry and complex communication networks.
A reference model can be considered a general model that can be used as a base to derive other models from, or as an example that can serve to compose other models. Of course, the reference model is valid for a very specific class of real world entities.
An example of a reference model is the composition of a general quality management system defined the world wide known ISO 9000 Standard. We also use this example in explaining a 'particular model'. ISO 9000 is a framework to assure the orderly operation of all enterprise processes and thereby ascertain conformance to specifications of a product during its entire life cycle to the customer. In addition, it provides a guidelines for quality management systems. As part of the standard series, ISO 9001 defines the requirements of a general quality system for design, development, manufacturing and maintenance in the reference model. From this reference model, more specialised models are derived, by adding , subtracting or detailing elements of the reference model : An ISO 9002 model for manufacturing, assembly and maintenance . An ISO 9003 model for final inspection and test. An ISO 9004 model for software and services.
A particular model will be used in a particular enterprise for operation qualification and can be derived from the reference model. In the above mentioned example, the particular model of a specific quality management system consists of the general standard and specialisations for a particular enterprise. The first part consists of the general requirements, criteria and the steps to set up a quality management system. The second part contains additional requirements - some of which may even exceed the ISO 9001 requirements - of the specific quality management system for the particular enterprise of given size in a certain industry sector.
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