Chapter 1- Introduction.pdf

Chapter 1 Introduction: Databases and Database Users Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Outline ◼ Types of Databases and Database Applications ◼ Basic Definitions ◼ Typical DBMS Functionality ◼ Example of a Database (UNIVERSITY) ◼ Main Characteristics of the Databas...

Chapter 1 Introduction: Databases and Database Users Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Outline ◼ Types of Databases and Database Applications ◼ Basic Definitions ◼ Typical DBMS Functionality ◼ Example of a Database (UNIVERSITY) ◼ Main Characteristics of the Database Approach ◼ Database Users ◼ Advantages of Using the Database Approach ◼ When Not to Use Databases Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 2 Types of Databases and Database Applications ◼ Traditional Applications: ◼ Numeric and Textual Databases ◼ More Recent Applications: ◼ Multimedia Databases ◼ Geographic Information Systems (GIS) ◼ Data Warehouses ◼ Real-time and Active Databases ◼ Many other applications ◼ First part of book focuses on traditional applications ◼ A number of recent applications are described later in the book Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 3 Basic Definitions ◼ Database: ◼ A collection of related data. ◼ Data: ◼ Known facts that can be recorded and have an implicit meaning. ◼ Examples: phone number, name, address, etc. ◼ This collection of related data is called a database ◼ Mini-world: ◼ Some part of the real world about which data is stored in a database. For example, student grades and transcripts at a university. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 4 Basic Definitions ◼ 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. Sometimes, the applications are also included. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 5 Simplified database system environment Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 6 Typical DBMS Functionality ◼ Define a particular database in terms of its data types, structures, and constraints ◼ Construct or Load the initial database contents on a secondary storage medium ◼ Manipulating the database: ◼ Retrieval: Querying, generating reports ◼ Modification: Insertions, deletions and updates to its content ◼ Accessing the database through Web applications ◼ Processing and Sharing by a set of concurrent users and application programs – yet, keeping all data valid and consistent Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 7 Typical DBMS Functionality ◼ Other features: ◼ Protection or Security measures to prevent unauthorized access ◼ Presentation and Visualization of data ◼ Maintaining the database and associated programs over the lifetime of the database application ◼ Called database, software, and system maintenance Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 8 Example of a Database (with a Conceptual Data Model) ◼ Mini-world example: ◼ Part of a UNIVERSITY environment. ◼ Some mini-world entities: ◼ STUDENTs ◼ COURSEs ◼ SECTIONs (of COURSEs) ◼ (academic) DEPARTMENTs ◼ INSTRUCTORs Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 9 Example of a Database (with a Conceptual Data Model) ◼ Some mini-world relationships: ◼ SECTIONs are of specific COURSEs ◼ STUDENTs take SECTIONs ◼ COURSEs have prerequisite COURSEs ◼ INSTRUCTORs teach SECTIONs ◼ COURSEs are offered by DEPARTMENTs ◼ STUDENTs major in DEPARTMENTs ◼ Note: The above entities and relationships are typically expressed in a conceptual data model, such as the ENTITY-RELATIONSHIP data model Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 10 Example of a simple database Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 11 Main Characteristics of the Database Approach ◼ Self-describing nature of a database system: ◼ A DBMS catalog stores the description of a particular database (e.g. data structures, types, and constraints) ◼ The description is called meta-data. ◼ This allows the DBMS software to work with different database applications. ◼ Insulation between programs and data: ◼ Called program-data independence. ◼ Allows changing data structures and storage organization without having to change the DBMS access programs. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 12 Example of a simplified database catalog Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 13 Example of Storage Format Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 14 Main Characteristics of the Database Approach (continued) ◼ Data Abstraction: ◼ A data model is used to hide storage and implementation details and present the users with a conceptual view of the database. ◼ Program-data independence and program-operation independence are called data abstraction. ◼ 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. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 15 Example of Different Views Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 16 Main Characteristics of the Database Approach (continued) ◼ Sharing of data and multi-user transaction processing: ◼ Allowing a set of concurrent users to retrieve from and to update the database. ◼ Concurrency control within the DBMS guarantees that each transaction is correctly executed or aborted ◼ Recovery subsystem ensures each completed transaction has its effect permanently recorded in the database ◼ OLTP (Online Transaction Processing) is a major part of database applications. This allows hundreds of concurrent transactions to execute per second. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 17 Database Users ◼ Users may be divided into ◼ Actors on the Scene ◼ Those who actually use and control the database content ◼ Those who design, develop and maintain database applications ◼ Workers Behind the Scene ◼ Those who design and develop the DBMS software and related tools Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 18 Database Users ◼ Actors on the scene ◼ Database administrators: ◼ Responsible for authorizing access to the database for ◼ coordinating and monitoring its use, ◼ acquiring software and hardware resources, ◼ monitoring efficiency of operations. ◼ Database Designers: ◼ Responsible for ◼ defining the content, structure, constraints, and functions or transactions of the database. ◼ communicate with the end-users and understand their needs. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 19 Categories of End-users ◼ Actors on the scene (continued) ◼ End-users: ◼ They issue queries, reports and update content. ◼ End-users can be categorized into: ◼ Casual: access database occasionally when needed ◼ Example: high-level managers. ◼ 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. ◼ Examples: bank-tellers or reservation clerks who do this activity for an entire shift of operations. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 20 Categories of End-users (continued) ◼ 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. ◼ Examples: a tax program and an address book program. ◼ System Analysts and Application Programmers Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 21 Categories of End-users (continued) ◼ Workers behind the Scene ◼ DBMS system designers & implementers: ◼ Design & implement DBMS modules and interfaces. ◼ Tool developers: ◼ Design and implement tools that facilitate modeling, performance monitoring, etc. ◼ Operators and maintenance personnel: ◼ Responsible for running and maintaining hardware and software environment. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 22 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 ◼ In Object-oriented DBMSs ◼ Providing Storage Structures (e.g. indexes) for efficient Query Processing Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 23 Advantages of Using the Database Approach (continued) ◼ 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 from the stored data using deductive and active rules Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 24 Extending Database Capabilities ◼ New functionality is being added to DBMSs in the following areas: ◼ Scientific Applications ◼ XML (eXtensible Markup Language) ◼ Image Storage and Management ◼ Audio and Video Data Management ◼ Data Warehousing and Data Mining ◼ Spatial Data Management ◼ Time Series and Historical Data Management ◼ The above gives rise to new research and development in incorporating new data types, complex data structures, new operations and storage and indexing schemes in database systems. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 25 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. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 26 When not to use a DBMS ◼ 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. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 27 Summary ◼ Types of Databases and Database Applications ◼ Basic Definitions ◼ Typical DBMS Functionality ◼ Example of a Database (UNIVERSITY) ◼ Main Characteristics of the Database Approach ◼ Database Users ◼ Advantages of Using the Database Approach ◼ When Not to Use Databases Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 28