01__Introduction _to_Database_konsep dasar.pdf
- 1. 1 01 Introduction to Database CII1J3 Database Modelling
- 2. 2 Learning Outcomes Students can explain the concepts of data, data model and the advantages of database approach
- 3. 3 Topics Basic Concepts and Definitions Traditional Database Processing Database Approach Advantages, costs, and risks of database approach
- 5. 5 DEFINITION • Database • An organized collection of logically related data. • Data • Facts concerning objects and events that could be recorded and stored on computer media • Stored representations of objects and events that have meaning and importance in the user’s environment. • Information • Data that have been processed in such a way as to increase the knowledge of the person who uses the data.
- 6. 6 Examples • List of facts • Data in context Useful information to some users, such as the course instructor and the registrar’s office. Figure 1. Data in context Data
- 7. 7 Examples (2) • Summarized Data Data presented as graphical information. This information could be used as a basis for deciding whether to add new courses or to hire new faculty members. Figure 2. Summarized Data
- 8. 8 • Databases today may contain either data or information (or both). • For example, a database may contain an image of the class roster document shown in Figure 1. • Also, data are often pre-processed and stored in summarized form in databases that are used for decision support. • Throughout this course we use the term database without distinguishing its contents as data or information.
- 9. 9 Metadata • Metadata • Data that describe the properties or characteristics of end-user data and the context of those data.
- 11. 11 Traditional File Processing Systems • When computer-based data processing was first available, there were no databases • To be useful for business applications, computers had to store, manipulate, and retrieve large files of data. • Computer file processing systems were developed for this purpose.
- 12. 12 Disadvantages of File Processing Systems (1) • Program-data dependence, • File descriptions are stored within each database application program that accesses a given file. Figure 3. Example of File Processing Systems
- 13. 13 Disadvantages of File Processing Systems (2) • Duplication of data • Because applications are often developed independently in file processing systems, unplanned duplicate data files are the rule rather than the exception. • Limited Data Sharing • With the traditional file processing approach, each application has its own private files, and users have little opportunity to share data outside their own applications.
- 14. 14 Disadvantages of File Processing Systems (3) • Lengthy development times • With traditional file processing systems, each new application requires that the developer essentially start from scratch by designing new file formats and descriptions and then writing the file access logic for each new program. • Excessive program maintenance • The preceding factors all combined to create a heavy program maintenance load in organizations that relied on traditional file processing systems.
- 16. 16 Data Models • Data models is graphical systems used to capture the nature and relationships among data. • Entity is a person, a place, an object, an event, or a concept in the user environment about which the organization wishes to maintain data. • The data you are interested in capturing about the entity (e.g., Customer Name) is called an attribute. • Data are recorded for many customers. Each customer’s information is referred to as an instance of CUSTOMER. • A well-structured database establishes the relationships between entities that exist in organizational data so that desired information can be retrieved.
- 17. 17 Example of Data Model Figure 4. Segment of an enterprise data model Figure 5. Segment of a project data model
- 18. 18 Relational Database • Relational database is a database that represents data as a collection of tables in which all data relationships are represented by common values in related tables. • Relational databases establish the relationships between entities by means of common fields included in a file, called a relation
- 20. 20 Database Management System (DBMS) • A database management system (DBMS) is a software system that enables the use of a database approach. • The primary purpose of a DBMS is to provide a systematic method of creating, updating, storing, and retrieving the data stored in a database. • It enables end users and application programmers to share data, and it enables data to be shared among multiple applications rather than propagated and stored in new files for every new application (Mullins, 2002). • A DBMS also provides facilities for controlling data access, enforcing data integrity, managing concurrency control, and restoring a database.
- 21. 21 Advantages of the Database Approach
- 22. 22 Program-Data Independence • The separation of data descriptions (metadata) from the application programs that use the data is called data independence. • With the database approach, data descriptions are stored in a central location called the repository. • This property of database systems allows an organization’s data to change and evolve (within limits) without changing the application programs that process the data.
- 23. 23 Planned Data Redundancy • Good database design attempts to integrate previously separate (and redundant) data files into a single, logical structure. • Ideally, each primary fact is recorded in only one place in the database.
- 24. 24 Improved Data Consistency • By eliminating or controlling data redundancy, we greatly reduce the opportunities for inconsistency. • For example, if a customer’s address is stored only once, when the customer’s address changes, recording the new address is greatly simplified because the address is stored in a single place. • Finally, we avoid the wasted storage space that results from redundant data storage.
- 25. 25 Improved Data Sharing • A database is designed as a shared corporate resource. • Authorized internal and external users are granted permission to use the database, and each user (or group of users) is provided one or more user views into the database to facilitate this use. • A user view is a logical description of some portion of the database that is required by a user to perform some task. • For example, an employee working in human resources will need access to confidential employee data; a customer needs access to the product catalog available on Web site. • The views for the human resources employee and the customer are drawn from completely different areas of one unified database.
- 26. 26 Enforcement of Standards • When the database approach is implemented with full management support, the database administration function should be granted single-point authority and responsibility for establishing and enforcing data standards. • These standards will include naming conventions, data quality standards, and uniform procedures for accessing, updating, and protecting data.
- 27. 27 Improved Data Quality • Database designers can specify integrity constraints that are enforced by the DBMS. • A constraint is a rule that cannot be violated by database users. • For example, if a customer places an order, the constraint that ensures that the customer and the order remain associated is called a “relational integrity constraint,” and it prevents an order from being entered without specifying who placed the order.
- 28. 28 More Advantages • Increased productivity of application development. A major advantage of the database approach is that it greatly reduces the cost and time for developing new business applications. • Improved data accessibility and responsiveness. With a relational database, end users without programming experience can often retrieve and display data, even when they cross traditional departmental boundaries. • Reduced program maintenance. In a database environment, data are more independent of the application programs that use them. Within limits, we can change either the data or the application programs that use the data without necessitating a change in the other factor. • Improved decision support. Some databases are designed expressly for decision support applications.
- 29. 29 Costs and Risks of the Database Approach
- 30. 30 Costs and Risks of the Database Approach (1) • New, specialized personnel. Frequently, organizations that adopt the database approach need to hire or train individuals to design and implement databases, provide database administration services, and manage a staff of new people. • Installation and management cost and complexity. A multiuser database management system is a large and complex suite of software that has a high initial cost, requires a staff of trained personnel to install and operate, and has substantial annual maintenance and support costs.
- 31. 31 Costs and Risks of the Database Approach (2) • Conversion costs. The cost of converting older systems to modern database technology—measured in terms of dollars, time, and organizational commitment—may often seem prohibitive to an organization. • Need for explicit backup and recovery. A shared corporate database must be accurate and available at all times. This requires that comprehensive procedures be developed and used for providing backup copies of data and for restoring a database when damage occurs.
- 32. 32 Costs and Risks of the Database Approach (3) • Organizational conflict. A shared database requires a consensus on data definitions and ownership, as well as responsibilities for accurate data maintenance. Experience has shown that conflicts on data definitions, data formats and coding, rights to update shared data, and associated issues are frequent and often difficult to resolve.
- 33. 33 Reference Hoffer, Jeffrey A., et.al., "Modern Database Management", Twelfth Edition, Pearson, 2016. Chapter 1
- 34. 34 Questions