Database Management Systems 2

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Information about Database Management Systems 2

Published on January 27, 2014

Author: NickkishaFarrell



Part 2 in the DBMS Series. Focusing on the Database Development Lifecyle

Database Management Systems The Database DevelopmentLife Cycle By Nickkisha Farrell, BSc IT, Dip Ed January 2014

IN THIS PRESENTATION Information Systems and The SDLC Database Development The Database Life Cycle Conceptual, Logical and Physical Data Models Summary 2

INFORMATION SYSTEMS • Allows for data collection, storage, and retrieval • Facilitates the transformation of data into information and the management of data and information Hardware & Software Databases Information Systems Services Networking 3

Systems Development • Process of creating and maintaining an IS/software. • The development process is divided into a series of phases. • The collection of phases is known as the development lifecycle. • The software product moves through this life cycle until it is finally retired from use. • Ideally, each phase in the life cycle can be checked for correctness before moving on to the next phase • The waterfall model is a popular model of development 4

SYSTEMS DEVELOPMENT LIFECYCLE (SDLC) • Establishing Requirements • consultation with, and agreement among, stakeholders as to what they want of a system, expressed as a statement of requirements. • Feasibility Study is conducted • Should the existing system be: Continued? | Modified? | Replaced? • System Cost estimated Planning Analysis Detailed System Design Implementation Maintenance 5

SYSTEMS DEVELOPMENT LIFECYCLE (SDLC) • Analysis starts by considering the statement of requirements and finishes by producing a system specification. The specification is a formal representation of what a system should do, expressed in terms that are independent of how it may be realized User Requirements Existing System Evaluation Logical System Design Planning Analysis Detailed System Design Implementation Maintenance 6

SYSTEMS DEVELOPMENT LIFECYCLE (SDLC) •Detailed Specifications •Screen, menu, report layouts •Conversion from old to new • Design begins with a system specification and produces design documents, and provides a detailed description of how a system should be constructed. Planning Analysis Detailed System Design Implementation Maintenance 7

SYSTEMS DEVELOPMENT LIFECYCLE (SDLC) • Implementation is the construction of a computer system according to a given design document and taking account of the environment in which the system will be operating. Planning Analysis • Testing compares the implemented system against the design documents and requirements specification and produces an acceptance report or, more usually, a list of errors and bugs that require a review of the analysis, design and implementation processes to correct  Usually the task that leads to the waterfall model iterating through the life cycle). Coding Testing Debugging Installation Detailed System Design Implementation 8 Maintenance

SYSTEMS DEVELOPMENT LIFECYCLE (SDLC) • Involves dealing with changes in the requirements, or the implementation environment, bug fixing or porting of the system to new environments (for example migrating a system from a standalone PC to a networked environment). Evaluation Maintenance System Errors Business Changes Enhancements Planning Analysis Detailed System Design Implementation 9 Maintenance

GETTING DATABASE DESIGN RIGHT • Uncontrolled ad hoc creation of tables by end users may lead to an unmanageable and unusable database environment. • Resulting in the inclusion of multiple copies of potentially inconsistent data. • Thus when creating databases there is a need for a methodical approach to development 10

DESIRABLE PROPERTIES OF A DATABASE Completeness Integrity Flexibility Efficiency Usability (ease of use) Ensures that users can access the data they want. Note that this includesad hoc queries, which would not be explicitly given as part of a statement of data requirements. Ensures that data is both consistent (no contradictory data) and correct (no invalid data), and ensures that users trust the database. Ensures that a database can evolve (without requiring excessive effort) to satisfy changing user requirements. Ensures that users do not have unduly long response times when accessing data. Ensures that data can be accessed and manipulated in ways which match user requirements. 11

DATABASE DEVELOPMENT • Not just a matter of creating tables that seem to match the way you see data on forms or reports. • Requires a detailed understanding of the meaning of the data and their relationships to ensure that a database has the right properties. • Thus data analysis, which is concerned with representing the meaning of data as a conceptual data model, must be performed. 12

DATABASE DEVELOPMENT • Process of database design and development • Database Design • Complete, normalized, non-redundant and fully integrated conceptual, logical, and physical database models • Database Implementation • Database storage structure, loading data, and data management 13

STAGES OF THE DATABASE LIFECYLE Gathering Requirements Database Analysis Database Maintenance Database Testing and Evaluation Database Design Database Implementation 14

STAGES OF THE DATABASE LIFECYLE • The database designer/s interview the customers (database users) • Obtains and documents the data and functional requirements. • The result: document including the detail requirements provided by the users • Document contains data they want to store along with an agreement as to the meaning and interpretation of the data elements. • To make sure that it is easily understood, it should not be overly formal or highly encoded. Gathering Requirements Database Analysis Database Maintenance Database Testing and Evaluation • The requirements should not describe how the data is to be processed, but rather what the data items are, what attributes they have, what constraints apply and the relationships that hold between the data items. Database Design Database Implementation 15

STAGES OF THE DATABASE LIFECYLE Data analysis begins with the statement of data requirements and then produces a conceptual data model. Gathering Requirements Database Maintenance - aim is to obtain a detailed description of the data that will suit user requirements. - these include properties such as the possible range of values that can be permitted for attributes such as, in the School Database example; the Student course code, course title and credit points. Database Analysis Database Design Database Testing and Evaluation A conceptual data model is concerned with the meaning and structure of data, but not with the details affecting how they are implemented. Analysis focuses on ‘What is required?’ not ‘How is it achieved? Database Implementation 16

STAGES OF THE DATABASE LIFECYLE • The database design phase is divided into three steps: - conceptual database design - logical database design - physical database design Gathering Requirements Database Maintenance Database Analysis Database Design Database Testing and Evaluation Conceptual Design Phase - the model of the data to be used is independent of all physical considerations is to be constructed. The model is based on the requirements specification of the system. Database Implementation 17

STAGES OF THE DATABASE LIFECYLE • Logical Design Phase - the model of the data to be used is constructed, while based on a specific data model, it remains independent of a particular database management system. • e.g. relational data model. • Physical Design Phase - the description of the implementation of the database on secondary storage is created. The base relations, indexes, integrity constraints, security, etc. are defined using the SQL language. Gathering Requirements Database Maintenance Database Analysis Database Design Database Testing and Evaluation Database Implementation 18

DATABASE DESIGN Feature Conceptual Logical Entity Names ✓ ✓ Entity Relationships ✓ Physical ✓ Attributes ✓ Primary Keys ✓ ✓ Foreign Keys ✓ ✓ Table Names ✓ Column Names ✓ Column Data Types ✓ • There are three levels of data modeling  Conceptual  Logical  Physical 19

DATABASE DESIGN Conceptual Logical Physical 20

STAGES OF THE DATABASE LIFECYLE • Realising the design  Install the selected DBMS  Create the databases  Populating the database Gathering Requirements Database Maintenance Database Analysis Database Design Database Testing and Evaluation • Supporting users and user processes • Supporting data management strategies Database Implementation 21

STAGES OF THE DATABASE LIFECYLE The aim of testing is to uncover errors in the design and implementation of the database. Testing is usually Database Maintenance considered to involve two main tasks – validation and verification. Validation answers the question: has the right database been developed to meet the requirements? Verification answers the question: has the database design been implemented correctly? Gathering Requirements Database Analysis Database Testing and Evaluation Database Design Database Implementation 22

STAGES OF THE DATABASE LIFECYLE • Operational maintenance Gathering Requirements • Performance of the database is monitored. Database • If it falls below some acceptable standard, re-organisation Maintenance of the database, takes place to ensure that performance is maintained at an acceptable level. • Porting and implementation maintenance Database Testing and Evaluation • The DBMS, user processes, underlying computer system Database or some other aspect undergoes changes that require the Implementation database implementation to be revised. • Requirements change - original requirement specification changes. • Typically involves a ‘mini life cycle’ related to the development of changes to meet the new requirements. Database Analysis Database Design 23

SUMMARY • Database Development requires careful planning and organization. • The DBLC is an instance of the popular SDLC, in this presentation particularly the waterfall model. • Each stage of development is directly dependent on the previous. • Stages of development may sometimes iterate. 24

REFERENCES • Gillenson, Mark L.,2012, Fundamentals of Database Management Systems / Mark L. Gillenson.—2nd ed., John Wiley and sons inc • • r-13-database-application-development-process/ 25

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