Database System Development Lifecycle

The management activities that allow the stages of database system development lifecycle to be realized as efficiently and effectively as possible.

·       Database planning

·       System definition

·       Requirements collection and analysis

·       Database design

·       DBMS selection (optional)

·       Application design

·       Prototyping (optional)

·       Implementation

·       Data conversion and loading

·       Testing

·       Operational maintenance

Database Planning – Mission Statement:-

An important first step in database planning is to clearly define the mission statement for the database system.

Ø  Mission statement for the database project defines major aims of database application.

Ø  Those driving database project normally define the mission statement.

Ø  Mission statement helps clarify purpose of the database project and provides clearer path towards the efficient and effective creation of required database system.

Ø  Once mission statement is defined, mission objectives are defined.

Ø  Each objective should identify a particular task that the database must support.

Ø  May be accompanied by some additional information that specifies the work to be done, the resources with which to do it, and the money to pay for it all.

·       Database planning should also include development of standards that govern:

• how data will be collected,
• how the format should be specified,
• what necessary documentation will be needed,
• How design and implementation should proceed.

System Definition:-

Describes the scope and boundaries of database system and the major user views.

Ø  User view defines what is required of a database system from perspective of:

• a particular job role (such as Manager or Supervisor) or

• Enterprise application area (such as marketing, personnel, or stock control).

Ø  Database application may have one or more user views.

Ø  Identifying user views helps ensure that no major users of the database are forgotten when developing requirements for new system.

Ø  User views also help in development of complex database system allowing requirements to be broken down into manageable pieces.

Requirements Collection and Analysis:-

               The process of collecting and analyzing information about the part of organization that is to be supported by the database system, and using this information to identify users’ requirements of new system.

Ø  Information is gathered for each major user view including:

• a description of data used or generated; 

• details of how data is to be used/generated;

• Any additional requirements for new database system.

Ø  Information is analyzed to identify requirements to be included in new database system. Described in the requirements specification.

Ø  Another important activity is deciding how to manage the requirements for a database system with multiple user views.

Ø  Three main approaches:

• centralized approach;

• view integration approach;

• combination of both approaches.

Database Design:-

               The Process of creating a design for a database that will support the enterprise’s mission statement and mission objectives for the required database system.

Three phases of database design:

Ø  Conceptual database design

Ø  Logical database design

Ø  Physical database design.

Conceptual Database Design:-

        The Process of constructing a model of the data used in an enterprise, independent of all physical considerations.

• Data model is built using the information in  users’ requirements specification.
• Conceptual data model is source of information for logical design phase.

Logical Database Design:-

       The Process of constructing a model of the data used in an enterprise based on a specific data model (e.g. relational), but independent of a particular DBMS and other physical considerations.

• Conceptual data model is refined and mapped on to a logical data model.

Physical Database Design:-

         The Process of producing a description of the database implementation on secondary storage;

• It describes base relations, file organizations, and indexes used to achieve efficient access to data. Also describes any associated integrity constraints and security measures.
• Therefore, physical design is tailored to a specific DBMS system.

DBMS Selection:-

Ø  The Selection of an appropriate DBMS to support the database system.

Ø  Undertaken at any time prior to logical design provided sufficient information is available regarding system requirements.

Ø  Main steps to selecting a DBMS:

• Define Terms of Reference of study;
• Shortlist two or three products;
• Evaluate products;
• Recommend selection and produce report.

 Application Design:-

Ø  The Design of user interface and the application programs that use and process the database.

Ø  Database design and application design are parallel activities.

Ø  Includes two important activities:

• transaction design;
• user interface design.

 Prototyping:-

·         Ø  Building a working model of a database system.

·         Ø  Purpose

o   to identify features of a system that work well, or are inadequate;

o   to suggest improvements or even new features;

o   to clarify the users’ requirements;

o   to evaluate feasibility of a particular system design.

Implementation:-

·        Ø The Physical realization of the database and application designs.

o   Use DDL to create database schemas and empty database files.

o   Use DDL to create any specified user views.

o   Use 3GL or 4GL to create the application programs. This will include the database transactions implemented using the DML, possibly embedded in a host programming language.

 Data Conversion and Loading:-

·       Ø  Transferring any existing data into new database and converting any existing applications to run on new database.

·       Ø  Only required when new database system is replacing an old system.

o   DBMS normally has utility that loads existing files into new database.

·       Ø  May be possible to convert and use application programs from old system for use by new system.

Testing:-

·       Ø  The process of running the database system with intent of finding errors.

·       Ø  Use carefully planned test strategies and realistic data.

·       Ø  Testing cannot show absence of faults; it can show only that software faults are present.

·       Ø  Demonstrates that database and application programs appear to be working according to requirements.

·       Ø  Should also test usability of system.

·       Ø  Evaluation conducted against a usability specification.

·       Ø  Examples of criteria include:

• Learnability;
• Performance;
• Robustness;
• Recoverability;
• Adaptability.

Operational Maintenance:-

·       Ø  The Process of monitoring and maintaining database system following installation.

·       Ø  Monitoring performance of system.

o   If performance falls, may require tuning or reorganization of the database.

·       Ø  Maintaining and upgrading database application (when required).

Ø Incorporating new requirements into database application.

Stage	Main Activities
Database planning	Planning how the stage of lifecycle can be realized most efficiently and effectively.
System definition	Specifying the scope and boundaries of the database system, including the major user views, its users, and application areas.
Requirements collection and analysis	Collection and analysis of the requirements for the new database system.
Database design	Conceptual, logical and physical design of the database.
DBMS Selection (optional)	Selection a suitable DBMS for the database system .
Application design	Designing the user interface and application programs that use and process the database.
Prototyping(optional)	Building a working model of the database system, which allows the designers or users to visualize and evaluate how the final system will look and function.
Implementation	Creating a physical database definitions and the application programs.
Data conversion and loading	Loading data from the old system to the new system and, where possible, converting any existing applications to run on the new database.
Testing	Database system is testing for errors and validated against the requirements specified by the users.
Operational maintenance	Database system is fully implemented. The system is continuously monitored and maintained. When necessary new requirements are incorporated into the database system through the preceding stages of the lifecycle.