Databases in the design and implementation of information systems
When considering a database as one of the key elements of an information system, it is important to identify the place of database development in the design and implementation of information systems. As a rule, the process of developing an information system is represented by four key stages (figure 1.5), which regulate the strict sequence of creating an information system.
Analysis Designing Development Implementation
Fig. 15. The life cycle of the development of the information system
Speaking about the process of developing an information system, developers are constantly raising the issue of data structures that need to be presented in the information system, and information that must be stored and processed. This leads to the idea of the need to develop a database, which can be represented by various options.
For example, for some information systems it is enough to store information in ordinary text files, they assume operative work with data that does not require long-term storage and does not seem to be a complex structure. The use of test files as a means of data storage has long been the only tool for working with simple Internet systems, such as, for example, organizations, e-commerce, product cataloging, etc.
Another presentation of the databases was structured files, which were the prototype of modern databases, but the rules for saving data in them and processing the stored information at the file level were determined by programmers. The main problems of this data processing technology are the complexity of providing efficient data processing, the inability to organize a full-fledged data integrity, inefficient operation with files.
The third option for presenting the database is structuring using DBMS and based on the basic principles of working with databases, usually relational ones. Database standards provided an opportunity to organize the uniformity of storage and processing technologies in databases, which led to the development of unified rules for the development of databases, ensuring correct and high-quality data processing.
As a result, when the task arises of developing an information system, the issue of data storage is one of the key, especially considering that any human activity in the organization involves the processing of data in documents, printed, voice and visual presentations. This forces developers to give serious attention to the development of data structures and databases at all stages of the development of the information system.
Thus, at the analysis stage, the developer-analyst, examining the processes taking place in the considered activity, pays attention to the documents that are formed and processed by the participants in the processes. At the same time, it is not enough to single out these documents, we need to consider their structural composition, which will later correctly organize the data structures represented in the database, as well as determine the objects of activity, information about which should be stored in the database and processed in the information system.
When analyzing the subject area for the purpose of further designing and implementing an automated information system using a database, analysts consider two key components: documents and objects, information about which should be stored in the database. Documentary analysis of the domain is the stage where the attributes of the objects of the domain are distinguished. But the given analysis does not allow to allocate information which should be stored in a database and not presented in documents. Usually this happens when considering individual operations of the domain in which there are no formalized documents or the object of information storage is some action or state of the aggregated object.
A sex is an aggregated object that is an element of the domain, made up of attributes of several objects, forming an object with the characteristics considered
The presence of unformalized documents is of particular complexity, since such documents do not have a sufficient number of clearly identified structural elements (attributes) and the content of documents can vary significantly from document to document. The processing of such documents is a complex intellectual task, and the documents themselves have a sufficiently large number of interpretations that it is practically impossible to provide at the time of analysis.
In this regard, the second most important task of analysis is the selection of objects of the domain, the information about which must be stored in the database. The main factor that makes it possible to distinguish such objects is the necessity of long-term memorization of data on certain actions and objects with the subsequent need to obtain the stored information.
So, if the essence of the work in the domain of the organization's employee is to remember that at some point the action was taken to sell the goods to the customer with subsequent information about the quantity of goods sold or about the customers who bought goods, the analyst will allocate the following objects: customer, sale. In the documents accompanying this task, there is only cash and commodity checks that are issued to the client and remain in the store. The structure of these checks indicates information about the goods, in some cases, about the customers that can be formed on the basis of the discount card.
From this example it is obvious that information about the goods can be submitted on the basis of documents only in terms of name, price and, in some cases, the article. On the client, neither cash nor commodity checks are provided with information, but they can contain information about the client's discount card, from which, if information about it is stored in the database, you can get this information. It is not possible to isolate information about the client from the documents in question (cash and commodity checks). Therefore, there is a need to refer to the subject area or other functions of this subject area in order to determine the client to whom the goods are sold based on the application for the design of the discount card. About the Selling in the documents there is no information at all, except for an indirect indication of the fact of this action, which can be determined only by the value of the transaction, where the positive value will show the fact of sale, and a negative value will reflect the return of the goods. Only a deep analysis of the essence of the operation and the rules of forming the values of the attributes of documents allows you to determine the essence of the previously selected object "Sale."
A brief example illustrates the importance of analyzing documents and their structures, but also illustrates the need for not only structural analysis of documents, but also the semantic and functional analysis of documents and the subject area within the framework of individual functions.
The analysis of the subject area gives the designer the opportunity to determine the structures of the future database, which are represented by the database models at the logical and physical levels. In this process, the database design specialist not only transfers the data obtained in the structure analysis phase to the model, but also optimizes (normalizes) the model obtained, followed by verification (verification) of the correspondence of the domain and tasks for which the information system is created and the database in general data in particular.
Designing a modern database is not limited to building a data structure and representation in a database model. This process involves defining data-processing rules at the database level. To these rules of processing can be attributed two key: the sampling of data and operations for the modification of information. Along with these operations, a number of other operations are designed in databases that determine the correctness of working with data, storing it, protecting it, etc.
Sampling in databases is one of the most important and most frequently used operations, because it allows you to quickly obtain information from the database in any form convenient for further processing and is used when organizing the information system interface, filling out documents, presenting information for analytical processing and etc. Often sampling is needed to perform qualitatively and efficiently data processing operations when they are modified in the database.
Data processing in a database is represented by three basic operations: addition, modification and deletion. These operations provide the majority of users' needs for data modification, but along with them there are operations and constructs that extend the capabilities of the database. These components of data processing are represented on the basis of the programming languages built in the DBMS, the key one being the SQL (Structured Query Language) language. Also, DBMS includes extensions of this language that are represented by independent languages or software modules that provide more efficient methods of data processing, solving complex problems, among which one can distinguish: processing of geographic data, representation and processing of multidimensional data structures, processing of hierarchical structures, etc.
Step implementation The life cycle of the information system also affects the work with the database, which has already been discussed above. As a rule, such work consists of sampling and data processing, but some other procedures related to ensuring the integrity of the structure of the database and content are also included. These operations are based on the same principles, rules and languages as the processing procedures, but have a number of additional limitations and application possibilities.
During the implementation and maintenance phase, working with the database is one of the key. This statement is based on the fact that when implementing in database not only data structures, but also processing, it is required to ensure correct installation, configuration and subsequent support of the database. It is this element of the information system that takes on the basic tasks of working with data, providing the user with the maximum convenience of interaction with the information system. Of course, the database does not solve the interface tasks, but providing the correct data retrieval allows the information system to display the necessary information on the screen to the user in a convenient form, and providing efficient processing and security procedures makes the database an indispensable tool for working with data.
Speaking about database maintenance, you should not forget about the need to monitor the changes in the domain and make changes both in the structure of the database (tables, attributes, links), similar to the usual computer program solutions, and in the software procedures that provide processing and receiving data on user requests.
As a result, taking into account all the above, the database is the most important element of almost any modern information system and is considered at all stages of the life cycle of the development of the information system (Figure 1.6).
Fig. 1.6. The relationship of the database with the stages of the development of the information system
When developing a modern information system, the issue of designing data storage and processing becomes important and, given that business processes are automated, the database is considered an integral part of it. Such a review of the database is based on the need to transfer information in business processes and the need to work with documents. Moreover, many information systems work on the basis of document circulation and structural consideration of documents, their representation in the application, storage on the storage medium requires the use of a database, and therefore its design with development.
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