Systems development life cycle (SDLC)
* The traditional methodology used to develop, maintain, and replace information systems. * The SDLC is a complete set of steps that a team of information systems professionals, including database designers and programmers, follow in an organization to specify, develop, maintain, and replace information systems.
Conceptual schema a detailed, technology- independent specification of the overall structure of organizational data. Logical schema the representation of a database for a particular data management technology. Physical schema Specifications for how data from a logical schema are stored in a computer’s secondary memory by a database management system. Prototyping An iterative process of systems development in which requirements are converted to a working system that is continually revised through close work between analysts and users.
Three-Schema Architecture for Database Development
1. External schema this is the view (or views) of managers and other employees who are the database users. 2. Conceptual schema this schema combines the different external views into a single, coherent, and comprehensive definition of the enterprise’s data. 3. Internal schema, an internal schema today really consists of two separate schemas: a logical schema and a physical schema. The logical schema is the representation of data for a type of data management technology. The physical schema describes how data are to be represented and stored in secondary storage using a particular DBMS.
A systems or database development team can include one or more of the following:
• Business analysts these individuals work with both management and users to analyze the business situation and develop detailed system and program specifications for projects. • Systems analysts these individuals may perform business analyst activities but also specify computer systems requirements and typically have a stronger systems development background than business analysts. • Database analysts and data modelers these individuals concentrate on deter- mining the requirements and design for the database component of the information system. • Users provide assessments of their information needs and monitor that the developed system meets their needs. • Programmers These individuals design and write computer programs that have commands to maintain and access data in the database embedded in them. • Database architects these individuals establish standards for data in business units, striving to attain optimum data location, currency, and quality. • Data administrators These individuals have responsibility for existing and future databases and ensure consistency and integrity across databases, and as experts on database technology, provide consulting and training to other project team members. • Project managers Project managers oversee assigned projects, including team composition, analysis, design, implementation, and support of projects. • Other technical experts Other individuals are needed in areas such as networking, operating systems, testing, data warehousing, and documentation.
Over the past two decades there has been enormous growth in the number and importance of database applications. Databases are used to store, manipulate, and retrieve data in every type of organization. In the highly competitive environment of the 2000s, there is every indication that database technology will assume even greater user’s environment. Information is data that have been processed in such a way that the knowledge of the person who uses the data increases. Both data and information may be stored in a database. Metadata are data that describe the properties or characteristics of end-user data and the context of that data. A database management system (DBMS) is a soft- ware system that is used to create, maintain, and provide controlled access to user databases. ADBMS stores meta- data in a repository,...
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