topic2 databasearchitecture aug14
DESCRIPTION
APU CT014!3!2 DWDSTRANSCRIPT
CT014-3-2 Database and Web Database Systems Database Architecture Slide 2 (of 44)
Topic and Structure of Lesson
•Purpose of three-level database architecture.
•Contents of external, conceptual, and internal levels.
•Purpose of external/conceptual and conceptual/internal
mappings.
•Meaning of logical and physical data independence.
•Distinction between DDL and DML.
•A classification of data models.
CT014-3-2 Database and Web Database Systems Database Architecture Slide 3 (of 44)
•Typical functions and services a DBMS should provide.
•Software components of a DBMS.
•Meaning of client–server architecture and advantages of this
type of architecture for a DBMS.
•Function and importance of the system catalogue.
Topic and Structure of Lesson (2)
CT014-3-2 Database and Web Database Systems Database Architecture Slide 4 (of 44)
Learning Outcomes
At the end of this lesson, YOU should be able to:
•explain the purpose of three-level database architecture.•explain the meaning of client–server architecture and advantages of this type of architecture for a DBMS.•discuss the contents of external, conceptual, and internal levels.•discuss the purpose of external/conceptual and conceptual/internal mappings.•explain the meaning of logical and physical data independence.•discuss the function and importance of the system catalogue.
CT014-3-2 Database and Web Database Systems Database Architecture Slide 5 (of 44)
Key Terms you must be able to use
If you have mastered this topic, you should be able to use the following terms correctly in your assignments and exams:
• Data Independence• External View• Conceptual View• Physical View• Record Based Model
• Hierarchical Model• Network Model• Relational Model
• Object Based Model
CT014-3-2 Database and Web Database Systems Database Architecture
Objectives of Architecture
• All users should be able to access same data.
• A user’s view is immune to changes made in other views.
• Users should not need to know physical database storage details.
Slide 6 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Objectives of Architecture (2)
• DBA should be able to change database storage structures without affecting the users’ views.
Slide 7 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Objectives of Architecture (3)
• Internal structure of database should be unaffected by changes to physical aspects of storage.
• DBA should be able to change conceptual structure of database without affecting all users.
Slide 8 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
ANSI-SPARC Architecture
Slide 9 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
ANSI-SPARC Architecture (2)
• External Level– Users’ view of the database. – Describes that part of database that is relevant to
a particular user.
• Conceptual Level– Community view of the database. – Describes what data is stored in database and
relationships among the data.
Slide 10 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
ANSI-SPARC Architecture (3)
• Internal Level– Physical representation of the database on the
computer. – Describes how the data is stored in the database.
Slide 11 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
ANSI-SPARC Architecture (4)
Slide 12 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Data Independence
• Logical data independence– Refers to immunity of external schemas to
changes in conceptual schema– Conceptual schema changes (e.G.
Addition/removal of entities)– Should not require changes to external schema or
rewrites of application programs
Slide 13 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Data Independence (2)
• Physical data independence– Refers to immunity of conceptual schema to
changes in the internal schema– Internal schema changes (e.G. Using different file
organizations, storage structures/devices)– Should not require change to conceptual or external
schemas
Slide 14 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Data Independence (3)
Slide 15 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Database Languages
• Data Definition Language (DDL)– Allows the DBA or user to describe and name
entities, attributes, and relationships required for the application
– plus any associated integrity and security constraints
Slide 16 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Database Languages (2)
• Data manipulation language (DML)– Provides basic data manipulation operations on
data held in the database
• Procedural DML– Allows user to tell system exactly how to
manipulate data
• Non-procedural DML– Allows user to state what data is needed rather
than how it is to be retrieved
Slide 17 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Database Languages (3)
• Fourth generation language (4GL)– Query languages– Forms generators– Report generators– Graphics generators– Application generators
Slide 18 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Data Model
Integrated collection of concepts for describing data, relationships between data, and constraints on the data in an organization.
• Data model comprises:– A structural part;– A manipulative part;– Possibly a set of integrity rules.
Slide 19 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Data Model (2)
• Purpose– To represent data in an understandable way
• Categories of data models include:– Object-based– Record-based– Physical
Slide 20 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Data Model (3)
• Object-based data models– Entity-relationship– Semantic– Functional– Object-oriented
• Record-based data models– Relational data model– Network data model– Hierarchical data model
• Physical data models
Slide 21 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Conceptual Model
• Conceptual schema is the core of a system supporting all user views.
• Should be complete and accurate representation of an organization’s data requirements.
• Conceptual modelling is process of developing a model of information use that is independent of implementation details.
• Result is a conceptual data model.
Slide 22 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Functions of DBMS
• Data storage, retrieval, and update.
• A user-accessible catalogue.
• Transaction support.
• Concurrency control services.
• Recovery services.
Slide 23 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Functions of DBMS (2)
• Authorization services.
• Support for data communication.
• Integrity services.
• Services to promote data independence.
• Utility services.
Slide 24 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Components of DBMS
Slide 25 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Component of Database Manager
Slide 26 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Multi-user DBMS Architecture
• Teleprocessing
• File-server
• Client-server
Slide 27 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Teleprocessing Architecture
• Traditional architecture.
• Single mainframe with a number of terminals attached.
• Trend is now towards downsizing.
Slide 28 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Teleprocessing Architecture (2)
Slide 29 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
File Server Architecture
• File-server is connected to several workstations across a network.
• Database resides on file-server.
• DBMS and applications run on each workstation.
• Disadvantages include:– Significant network traffic.– Copy of DBMS on each workstation.– Concurrency, recovery and integrity control more complex.
Slide 30 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
File Server Architecture (2)
Slide 31 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Client Server Architecture
• Server holds the database and the DBMS.
• Client manages user interface and runs applications.
• Advantages include:– Wider access to existing databases;– Increased performance;– Possible reduction in hardware costs;– Reduction in communication costs;– Increased consistency.
Slide 32 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Client Server Architecture (2)
Slide 33 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Client Server Architecture (3)
Slide 34 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Catalogue Manager
• Repository of information (metadata) describing the data in the database.
• Typically stores:– Names of authorized users;– Names of data items in the database;– Constraints on each data item;– Data items accessible by a user and the type of access.
• Used by modules such as authorization control and integrity checker.
Slide 37 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Information Resource Dictionary System (IRDS)
• Response to an attempt to standardize data dictionary interfaces.
• Objectives:– Extensibility of data;– Integrity of data;– Controlled access to data.
Slide 38 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
IRDS Interface Services
Slide 39 (of 44)
CT014-3-2 Database and Web Database Systems Database Architecture
Quick Review Questions
Slide 40 (of 44)
• What is metadata?
• List any FIVE functions in a DBMS.
• List and explain any five major components of a database manager.
•List and explain three types of multi user database system architectures.
CT014-3-2 Database and Web Database Systems Database Architecture
Follow Up Assignment
Slide 41 (of 44)
•We learnt only the concepts of database architecture. Conduct further research on the architecture of client server database architectures.
CT014-3-2 Database and Web Database Systems Database Architecture
Summary
Slide 42 (of 44)
• ANSI-SPARC Database Architecture
•DBMS Functions
•DBMS Components
•Multi User DBMS Architecture
CT014-3-2 Database and Web Database Systems Database Architecture
Question and Answer Session
Slide 43 (of 44)
Q & A