Database Designing Procedure, User Interface, Application Algorithm - Databases

Database design procedure

In the database implementation, as noted earlier, the computer creation of the database itself, user interface and application algorithm (conversion algorithm).

Creating a database itself involves using the SQL or QBE programming language for:

• Building a table structure (specifying a table name and a list of fields with the appropriate data types, specifying keys, indexes, and constraints on individual fields or a group of fields);

• establishing links between tables, taking into account the referential integrity;

• filling tables with data.

In the filling of the tables, the following are distinguished: initial filling - for testing the operation of the database; business filling. Filling can be done manually (most convenient for small tables and initial filling) or programmatically (when borrowing data from other electronic sources).

Manual populating is possible in two ways:

• directly the table itself (including through the corresponding utilities);

• through specially created forms related to the user interface and being in some way analogous to the string "paper" table along the ruler, laid on this row of the table.

User Interface

The user interface [45] refers to the aggregate of the information model (MI) of the problem area, the means and ways the user interacts with this model, as well as the components that support the formation of MIs in the course of the software system operation. The interface plays a critical role in survival rates developed software products.

Note that the task of designing the user interface is multivariant, while the selection procedure is largely informal. Due to this informality, it is necessary to streamline the design procedure by introducing a set of rules-principles. Let's list the main ones.

1. Orientation to the user's requirements (rather than to the developer's skill) - User_centred Design.

2. Consistency (using single-valued commands in a production environment).

3. The presence of feedback from the computer (signal about the perception of the command).

4. The simplicity of the interface is to provide only those controls that are needed at this stage of the session of working with the software product. By session ( session ) means the time interval from the launch of the product to the exit from it.

5. The flexibility of the interface is the ability to take into account the level of user training.

6. Accounting for aesthetic requirements, which include the time of mastering the interface, the time of solving the problem, subjective satisfaction with the convenience of the interface.

7. Accounting for the traditions of the domain.

8. Iterative character of interface development taking into account user preferences.

9. Accounting for software and hardware capabilities.

10. The ability to take into account the psychological characteristics of the user: the left hemisphere of the brain perceives the text better, the right one - images, images.

11. Accounting for the possibilities of simplifying programming.

12. Short computer response time: if the interval from the request to the answer of the computer exceeds 20 seconds, the system is not considered interactive.

The listed requirements are sometimes contradictory, but they should be taken into account.

The user interface is based on a control system in conjunction with forms and reports.

As a synchronizing object in the user interface, use either a (head) menu or a button form.

Application Algorithm

In the traditional approach, an algorithm is developed for the direct conversion of data from source tables to output documents. The output documents (tables) are requests and reports. Queries are generated using the SQL or QBE programming language. The reports are actually inquiries, provided with additional explanations. Reports can be implemented with the help of various designers (with actually manual creation) or with the help of wizards (in semi-automatic mode).

The application algorithms in the modern approach differ from the application algorithms with more complex computations with the possible formation of intermediate objects. The application algorithm can be written in various programming languages ​​- for example, Visual Basic for Applications (VBA), Object Pascal, SQL. In the latter case, it is performed in the form of stored procedures, generators, and triggers.

In conclusion, it should be noted that the design process is iterative: requirements in TK, components of DB design and implementation can be constantly changed.

The design and implementation processes are covered in two examples - the "Learning process" and "Job recruitment", a condensed description of which is given in examples 2.1 and 2.2.

The implementation of the databases described in the examples is carried out on the Access and InterBase databases (within the Delphi software product).

A number of special features of these databases are devoted to special individual publications [27-36, 41]. The development of opportunities, as experience has shown, is expedient to carry out in two stages:

1) consideration of the main branch of implementation technology for a specific example (DB) using a limited range of DBMS capabilities;

2) detailed development - by detailed descriptions [27-36, 41] - named DBMS, taking into account their numerous private opportunities.

Works in the second stage after a thorough study of the technology at the first stage, as practice shows, does not cause any special difficulties. At the same time, the description of numerous private procedures of the second stage, as it appears from [17-36], occupies a volume exceeding this publication. In this regard, in this paper, we highlight only the first stage.

The procedure for creating data warehouses just started to be formed. Currently, there are two options:

• the complete one, described in Ch. 2;

• truncated & quot ;, which consists in the periodic transfer to archive tables of data from operational tables. Links between archival tables are most often absent.

The second variant is given in [32] and considered in § 15.4 of this paper.

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