Structure and construction of information model of a subject domain

Process of creation of information model begins with definition of conceptual requirements of the future users of a DB (workers of military chair, dean's offices and faculties). On fig. 4 the general structure of information model is presented.

Designing of conceptual model is based on the analysis of solved problems on data processing, i.e. storage and processing of curricula of groups, calculation of the academic commissions on chairs, loading distribution on teachers and lesson schedule drawing up. Thus efforts of the developer should be directed basically on structurization of the data belonging to the future users of a DB and revealing of interrelations between them.

Probably, that the interrelations reflected in conceptual model between objects will appear subsequently not realised means chosen subd. It will demand change of conceptual model. The logic model reflects logic communications between attributes without dependence from their maintenance and the environment of storage and can be relational, hierarchical or relational.

To various users in information model there correspond various subsets of its logic model which are called as external models of users. Thus, the external model of the user represents display of conceptual requirements of this user in logic model and corresponds to those representations which the user receives about a subject domain on the basis of logic model. Hence, the external model, how much full is how much well designed and precisely information model displays a subject domain and so full and precisely the automated control system of this subject domain works.

Now distinguish in the basic three types of information models: hierarchical, network and relational.

Hierarchical and network models of data began to be applied in the early sixties. The relational model of data which intended in a DB for the personal computer has been in the early seventies offered.

These three models differ basically with ways of information display of objects and their interrelations. We will accept for base relational model.

Relational DB have the powerful theoretical base based on the mathematical theory of relations. It has been developed by the employee of firm IBM doctor Edgarom Koddom. Language SQL also has been developed For construction of inquiries to relational DB (Structured Query Language, language of the structured inquiries). It has got character of the industrial standard in relational subd. Therefore, passing from one relational base on another, the user and the developer deal with the same language. Other important plus SQL is that this language is focused on vysokourovnevye operations with data. Giving out inquiry, it is possible not to worry about nizkourovnevyh access problems to the data, specific to each DB as interpretation of inquiries in commands of low level lays under the authority of concrete subd.

Between two or more tables of a relational database there can be subordination relations. Subordination relations define, that for each record of the main table (master, named still parental) can exist one or several records in the subordinated table (detail, named still affiliated).

The database is big storehouse on volume in which we place all details used in it and from which various users can receive them, using various appendices.

Such uniform database is represented ideal for all structural divisions of military chair, faculty.

On working out of optimum system of a DB we should put representations of end users in a basis of researches and conceptual requirements to system.
The end user in the work makes of the decision with the account of the information received as a result of access to a database. The overall performance of military chair will depend on efficiency and quality of this information.

By consideration of requirements of end users to a DB it is necessary to take into consideration the following:

1. The DB should satisfy to actual information requirements of the enterprise. And it means, that the organisation of details in a DB should on structure and the maintenance to correspond to problems solved at the enterprise.

2. The DB should provide reception of demanded data for comprehensible time, that is to provide the set productivity.

3. The DB should be calculated on possibility of satisfaction of again arising requirements of end users.

4. The database should be calculated on expansion possibility by reorganisation and subject domain expansion.

5. The DB should change easily at change of the program and hardware environment.

6. The correct data loaded into a DB should remain correct.

7. Data before inclusion in a DB should be checked on reliability.

8. To the data placed in a DB, persons with corresponding powers should have access only.

Design stages of a database with the account considered above aspects are presented on fig. 5. As a result of the analysis of a task in view and

Fig. 5. Database design stages

Processings of requirements of end users the conceptual model is made.

By working out of logic model of a DB, first of all, it is necessary to solve, what model of data most approaches for display of concrete conceptual model of a subject domain.

Transition from conceptual to logic model of data is made as follows. Each rectangle (object) of conceptual model in logic model is represented the table containing its attributes which in the user-friendly form it is displayed by visual means of the personal computer, for example, on the display screen.

Let's consider process of creation of a DB for system of automation of activity of a teaching department of military chair.

For reception of demanded model it is necessary to consider communications of military chair with faculties, high school chairs.
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A source: Dulin V.V.. Pedagogical management of process of preparation of reserve officers on military chairs. 2004

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