In order to solve the problem of automation of control in the automated control system, there was a need for a system description of the management process, including decision making. One of the first models in this direction were the so-called Forrester models. Later, the methodology of automation (Structures Analysis Design Technique) SADT, based on which CASE-technology was built.
Model components of CASE-technology (Figure 3.5) are the components of ERD, DFD, STD. Their place in the system description of the control process is shown in Fig. 3.6.
CASE-technology is a system of methods for describing, designed to use computers when creating a database. Computer-Aided Software/System Engineering (CASE-technology) - a set of methodologies for the analysis, design, development and maintenance of complex software systems, supported by a set of interrelated automation tools. CASE is a tool for system analysts, developers and programmers.
Fig. 3.5. Classification of CASE-methods:
There are a lot of elements; B - description of the elements; UCH - educational process; DFD - Data Flow Diagram; ERD - Entity Relationship Diagram; STD - State Transaction Diagram
Fig. 3.6. Description of the process in the system
CASE-technology is based on the methodology of system analysis. System analysis is understood as a scientific discipline that develops general principles for the study of complex objects and processes, taking into account their systemic nature. Its main goal is to focus on the initial stages of development.
In the framework of CASE-technology, system analysis is designed for the separation of design from programming. In the development in accordance with CASE-technology, the architecture is selected and its subsequent implementation, therefore the system analysis is called structural system analysis or simply structural analysis.
The most important (basic) principles are division (decomposition) and subsequent hierarchical ordering. They are complemented by the following principles:
1. The principle of abstracting from nonessential details (with their "hiding") with control for the presence of unnecessary elements.
2. The principle of formalization.
3. Principle of conceptual community (structural analysis - structural programming - structural testing). Hence the methodology of structural analysis - the method of research from a general overview through detailing to a hierarchical structure with an increasing number of levels.
4. The principle of consistency is the justification and consistency of the elements.
5. The principle of logical and physical independence of data.
6. The principle of direct access (without programming) to the end user.
This technology is the basis for the implementation of software CASE-tools.
A formal charting tool is the chart system (see Figure 3.5): ER diagrams, data flow diagrams (DFDs), state transition diagrams (STDs), process specifications that will be discussed separately.
Two cases are possible in the description of processes: complex and simple processes. In the second case, it is more convenient to develop a database using the concept of "attitude". Let's consider therefore only complex processes, considering that CASE-technology was developed for it.
From Fig. 3.6 it can be seen that, in fact, the first variety of methods of the CASE-model system was Chen's ER-models, considered in detail in the previous section. Here we only note its version - the Barker model (Figure 3.7). It specifies the name of the entity, the degree of multiplicity (for example, EM), the binding (- - -) or the optional (......................) connection.
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