Database Fundamentals PDF

1 Types of Databases and Database Applications: Numeric and Textual Databases Multimedia Databases Geographic Information Systems (GIS) Data Warehouses Real-time and Active Databases Database: A collection of related data. Data: Kno...

1 Types of Databases and Database Applications: Numeric and Textual Databases Multimedia Databases Geographic Information Systems (GIS) Data Warehouses Real-time and Active Databases Database: A collection of related data. Data: Known facts that can be recorded and have an implicit meaning. Mini-world: Some part of the real world about which data is stored in a database. Database Management System (DBMS): A software package/ system to facilitate the creation and maintenance of a computerized database. Database System: The DBMS software together with the data itself. the applications are also included. Typical DBMS Functionality - Define a database: in terms of data types, structures, Constraints - Construct or Load the Database on a secondary storage medium - Manipulating the database: querying, generating reports, insertions, deletions and modifications to its content - Concurrent Processing and Sharing by a set of users and programs yet, keeping all data valid and consistent - other features: Protection or Security measures to prevent unauthorized access, “Active” processing to take internal actions on data Presentation and Visualization of data. DataBase.ch1 2 Main Characteristics of the Database Approach 1- Self-describing nature of a database system: A DBMS catalog stores the description of the database. The description is called meta- data. This allows the DBMS software to work with different databases. 2- Insulation between programs and data: Called program-data independence. Allows changing data storage structures and operations without having to change the DBMS access programs. 3- Data Abstraction: A data model is used to hide storage details and present the users with a conceptual view of the database. 4- Support of multiple views of the data: Each user may see a different view of the database, which describes only the data of interest to that user. 5- Sharing of data and multiuser transaction processing: allowing a set of concurrent users to retrieve and to update the database. Concurrency control within the DBMS guarantees that each transaction is correctly executed or completely aborted. OLTP (Online Transaction Processing): is a major part of database applications. DataBase.ch1 3 Database Users 1- Actors on the Scene: who actually use and control the content. 2- Workers Behind the Scene: who enable the database to be developed and the DBMS software to be designed and implemented. Actors on the scene: Database administrators: responsible for authorizing access to the database, for co-ordinating and monitoring its use, acquiring software, and hardware resources, controlling its use and monitoring efficiency of operations. Database Designers: responsible to define the content, the structure, the constraints, and functions or transactions against the database. They must communicate with the end- users and understand their needs. End-users: they use the data for queries, reports and some of them actually update the database content. DataBase.ch1 4 Categories of End-users Casual: access database occasionally when needed Naïve or Parametric: they make up a large section of the end-user population. They use previously well-defined functions in the form of “canned transactions” against the database. Sophisticated: these include business analysts, scientists, engineers, others thoroughly familiar with the system capabilities. Many use tools in the form of software packages that work closely with the stored database. Stand-alone: mostly maintain personal databases using ready-to-use packaged applications. Advantages of Using the Database Approach ⚫ Controlling redundancy in data storage and in development and maintenance efforts. ⚫ Sharing of data among multiple users. ⚫ Restricting unauthorized access to data. ⚫ Providing persistent storage for program Objects. ⚫ Providing Storage Structures for efficient Query Processing. ⚫ Providing backup and recovery services. ⚫ Providing multiple interfaces to different classes of users. ⚫ Representing complex relationships among data. ⚫ Enforcing integrity constraints on the database. ⚫ Drawing Inferences and Actions using rules. DataBase.ch1 5 Additional Implications of Using the Database Approach ⚫ Potential for enforcing standards: this is very crucial for the success of database applications in large organizations Standards refer to data item names, display formats, screens, report structures, meta-data, etc. ⚫ Reduced application development time: incremental time to add each new application is reduced. ⚫ Flexibility to change data structures: database structure may evolve as new requirements are defined. ⚫ Availability of up-to-date information very important for on-line transaction systems such as airline, hotel, car reservations. ⚫ Economies of scale: by consolidating data and applications across departments wasteful overlap of resources and personnel can be avoided. DataBase.ch1 6 When not to use a DBMS ⚫ Main inhibitors (costs) of using a DBMS: High initial investment and possible need for additional hardware. Overhead for providing generality, security, concurrency control, recovery, and integrity functions. ⚫ When a DBMS may be unnecessary: If the database and applications are simple, well defined, and not expected to change. If there are stringent real-time requirements that may not be met because of DBMS overhead. If access to data by multiple users is not required. ⚫ When no DBMS may suffice: If the database system is not able to handle the complexity of data because of modeling limitations If the database users need special operations not supported by the DBMS. DataBase.ch1