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Database System Development Lifecycle

Connolly BookChapter 10-11

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Objectives

• Learn some Fact-Finding techniques• DSDL (Database System Development Lifecycle)

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Fact Finding

• What is Fact Finding? A formal process of collecting facts about system, requirements, and preferences by using techniques such as interviews and questionnaires.

• When we do fact finding?We start finding facts in the early stages of the lifecycle including

database planning, system definition, and requirement collection and analysis.

Facts Finding Techniques

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Fact Findings Techniques

• How many fact-finding techniques we have?– Examining documentation – Interviewing – Observing the enterprise in operation– Research– Questionnaires

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Examining Documents

• Examining documentation is useful for– To gain some insights as to how the need for a database arose– To provide information on the part of enterprise associated with the

problem– To gain some understanding of the system

• Q: What problems may occur in examining documents?

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Interviewing

• Most useful technique for– Finding out facts– Clarifying facts– Generating enthusiasm– Getting user involvement– Identify requirements– Gathering ideas and opinions

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Making an Interview

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Observation the enterprise in operation

• Most effective techniques for understanding a system

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Research

• Useful for researching the application and problems

Advantages Disadvantages

Can save time if solution already exists Requires access to appropriate sources of information

Can see how others solve similar problems or met similar requirements

May not help if poor documentation

Can be up to date with current development

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Questionnaire

• Useful to get information from a large number of people (responses).

Advantages Disadvantages

Convenience for people to complete and return

Number of respondents may be low

Inexpensive way to get information from many people

It may be returned incomplete

Provide confidentiality for the real facts Misinterpreted questions my occur

Quickly tabulated and analyzed Cannot observe and analyze body language

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Database System Development Lifecycle

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Information System Lifecycle

• What is Information System?• What are the computer-based Information system components?• What is the fundamental component of an information system?

• Information System is a system to manage all resources that enable the collection, management, control, and dissemination of information throughout an organization.

• computer-based Information system components include database, database software, application software, computer hardware, personnel using and developing the system

• The fundamental component of an information system is the database. Therefore, the lifecycle of information system in an organization is linked to the lifecycle of database system that supports it.

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Database System Development Lifecycle

• What are the stages of Database System Development Life Cycle?

– Database Planning is planning how the stages of the life cycle can be realized most efficiently and effectively

– System Definition is specifying the scope and boundaries of database system– Requirement collection and analysis is collection and analysis the requirements for

the new database system– Database design is conceptual, logical, and physical design of the database– DBMS selection is selecting a suitable DBMS for the database system– Application Design is designing the user interface and application programs that use

and process the database– Prototyping is building a working model of database system– Implementation is creating the physical database definition and the application

programs– Data conversion and loading is loading data from the old system to the new system

and converting any existing applications to run on the new database– Testing is database system is tested for errors and validated against the requirements

specified by the users– Operational Maintenance is the system is continuously monitored and maintained.

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DSDL Stages

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Database Planning

• What is database planning? Database planning is the management activities to manage stages of DSDL to be

realized as efficient and effective as possible. • What are three main issues in formulating IS strategy?

– Identification of enterprise plans and goals IS needs– Evaluation of current information system IS strength and weakness analysis– Appraisal of IT opportunities competitive advantages

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Database Planning

• What is the first step in Database Planning?– Mission statement

• What is mission statement?– Mission statement defines the major aim of database system.

• What is mission statement purpose? It helps to clarify– the purpose of the database system (What database we want to make)– provide a clearer path toward the efficiency and effective creation of required

database system (How to make it)

• Example format of mission statement:– The purpose of {Database System Name} is to {purpose 1 for business

units/clients/customers} and to {purpose 2 for the company}.

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Database Planning

• What is the second step of database planning?

• Each of Mission Objectives identifies a particular task that database system must support.

• Both Mission statement and objectives must be accompanied by– What works need to be done– What resources we work with– How much money/budget we need

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Example of Mission Objectives

• To maintain (enter, update and delete) data on branches• To maintain (enter, update and delete) data on staff• …• To perform searches on branches• To perform searches on staff• …• To track the status of property for rent• …• To report on branches• …

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Standards

• Development of standard is included in Database Planning.

• How to create standards in database planning?– How data will be collected– What format the data should be– What documentations needed– How design and implementation should proceed

• What a well-defined standard provides?– Staff training requirements– quality control measurement– Works are matched with staff skill and experiences.– Documentation of any legal and enterprise requirements– Restriction of some confidential information

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Making the mission statement

• Read Chapter 11.4.2 about Creating the mission statement & objectives p. 352-353

• Which techniques do we use to make mission statement?• Who makes the mission statement?• What typical questions are used?

• Continue Reading p.353-358 about making mission objectives

• Which techniques do we use to make mission objectives?• Who makes the mission objectives?• What typical questions are used?

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System Definition

• What are determined in the System Definition?– the scope and boundaries of database system– the major user views

• What includes in our system boundaries?– Current Users and Applications– Future Users and Applications

• The purpose of user view is to – make sure no major users are forgotten when developing the new

system requirements– simplify complex database system by breaking it down into some

manageable pieces of views

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User View

• User view defines what is required of a database application from perspective of:– a particular job role (such as Manager or Supervisor) or – enterprise application area (such as marketing, personnel, or stock

control).

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Multiple User Views

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Making the system definition

• Read Chapter 11.4.3 about System Definition p. 358-359

• Which techniques do we use to make system definition?• Who makes it?• What typical questions are used?• What reports we have to make?

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Requirements Collection and Analysis

• Information is gathered from user views including:– A description of data used or generated– How data is to be used or generated– Any additional requirements for new database system

• Information is analyzed in a document called requirement specialization to identify new requirements included in new database system.

• More professional report is called Requirements Specialization Techniques that includes:– Structured Analysis and Design (SAD)– Data Flow Diagrams (DFD)– Hierarchical Input Process Output (HIPO)– Computer Aided Software Engineering (CASE)– Unified Modeling Language (UML)

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Requirements Collection and Analysis• This stage is critical as if it is inadequate then it will annoy users that may

lead to rejection or underutilization of the system and If it is excessive then it can overcomplicate the system, making it difficult to implement, maintain, use or learn

• Three types of managing requirements:– Centralized approach: requirements for each user view is merged into

a set of requirements– View integration approach: requirements for each user view remain as

separate lists.– Combination of both approaches

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Centralized Approach

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View integration approach

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Data Models of User Views

• There are two data models that represent user views:– Local data model represents a single user views– Global data model represents all user requirements for a database.

• For a complex database design which approach is more suitable?– Combination of centralized and view integration approach.

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Making Requirements Collection and Analysis

• Read Chapter 11.4.4. about Requirements Collection and Analysis p. 359-367

• Which techniques do we use to make it?• Who makes it?• What typical questions are used?• What reports we have to make?

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Database Design

• DB design is the process of creating a design that will support the mission statement and mission objectives for the required database system.

• Three phases of DB design: conceptual, logical, and physical design.

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DBMS Selection

• What is DBMS Selection? It is the selection of appropriate DBMS to support the database system.

• Main steps of selecting DBMS:– Define terms of reference of study: objective and scope of the study– Shortlist two or three products: a preliminary list of DBMS products

for evaluation– Evaluate products: features evaluation and comparison– Recommend selection and produce report.

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DBMS Evaluation Features

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DBMS Evaluation Features

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DBMS Evaluation Features

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Application Design• The design of user interface and the application programs that use and process the database• Two aspects of application design: Transaction Design and User Interface Design

• Transaction design: an action /series of actions carried out by a single user or application program that access or changes the content of database

• Important characteristics of transactions:– data to be used by the transaction;– functional characteristics of the transaction;– output of the transaction;– importance to the users;– expected rate of usage.

• Three main types of transactions: retrieval, update, and mixed.

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User Interface Design

– Guideline form/report design: • Meaningful title• Comprehensible instructions• Logical grouping and sequencing of fields• Visually appealing layout of the form/report• Familiar field labels• Consistent user f color• Visible space and boundaries for data entry fields• Convenient cursor movement• Error correction for individual characters and entire fields• Error messages for unacceptable values• Optional fields marked clearly• Explanatory messages for fields• Completion signal

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Prototype/Model/Artefact

• Prototyping is building a working model of database system• Why we need to make a prototype?

– To examine the model to find which features work well and inadequate

– To suggest improvement or new features to database system– To evaluate feasibility of system design

• Prototype must be inexpensive and quick to build• How many strategies in making prototypes?

– Requirement Prototype: Using a prototype to determine the requirement, once the requirements are complete, the prototype will be discarded

– Evolutionary Prototype: Using a prototype to determine the requirement, once the requirements are complete, the prototype will be the working database system

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Implementation

• The physical realization of database and application designs• Database implementation is performed together with application

implementation.• The application is implemented by using 3rd or 4th generation languages• Which parts of database is involved?

– Database transactions using DML– Non procedural query languages– Security and Integrity Control using DDL, DBMS utilities, and OS controls

• Q: What may be difficult in the implementation stage?

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Data Conversion and Loading

• Transferring any existing data into the new database and converting any existing applications to run on the new database

• Only needed when the new Database system is replacing the old one.• Q: What we need to transfer data from the old Database system to the new database

system?

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Testing• The process of running the database system with the intent of finding errors• Testing Criteria (Sommerville, 2006):

– Learnability: how long it takes a user to become familiar with the system– Performance: how well the system runs users’ work practices– Robustness: how tolerant is the system of user errors– Recoverability: How good is the system to recover from user errors– Adaptability: How closely is the system tied to a single model of work

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Operational Maintenance

• Operational Maintenance is the process of monitoring and maintaining the database system following installation

• Activities: – Monitoring the performance of the system: database usage, locking

efficiency, query execution strategy– Maintenance and upgrading the database system: system tuning and

create adding indexes

• Q: When we drop the old system?

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CASE Tools

• Computer Aided Software Engineering supports– A data dictionary to store information about the database system’s data– Design tools to support data analysis– Tools to permit development of the corporate data model– Tools to enable the prototyping of applications

• Three categories of CASE:– Upper-CASE: from database planning to database design– Lower-CASE: from implementation to testing– Integrated-CASE: all stages of DSDL and functionality for both Lower and Upper CASE.

• Benefits:– Standards: help to enforce standard– Integration: data is linked to ensure all parts of the system are integrated– Support for standard method: simple to draw and maintain manually– Consistency: CASE check its integrity– Automation: automatically transform parts of design specification to executable codes

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Fact Finding

• What is Fact Finding? A formal process of collecting facts about system, requirements, and preferences by using techniques such as interviews and questionnaires.

• When we do fact finding?We start finding facts in the early stages of the lifecycle including

database planning, system definition, and requirement collection and analysis.

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What facts we collect?Stages of DSDL Examples of Data Captured Example of Documentation

Produced Database Planning Aim and objectives of database

projects Mission statement and objectives of database system

System Definition Description of major user views Definition of scope and boundary of database system

Requirement Collection and Analysis

User and System Requirements User and System Requirements specifications

Database Design Users’ responses to checking Conceptual/Logical DB design, functionality of targeted DBMS

Conceptual/Logical/physical DB design

Application Design Users’ responses to checking user interfaces

Application Design

DBMS Selection functionality of targeted DBMS DBMS Evaluation and recommendation

Prototyping Users’ responses to prototype Modified users’ requirements and system specification

Implementation functionality of targeted DBMS Data Conversion and loading Format of current data; data

import capability of targeted DBMS

Testing Test Result Testing strategies used, analysis of test results

Operation Maintenance Performance Testing Results; new of changing user and system requirements

User manual; analysis of performance results; modified user s’ requirements and system specifications

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Fact Findings Techniques

• How many fact-finding techniques we have?– Examining documentation – Interviewing – Observing the enterprise in operation– Research– Questionnaires

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Examining Documents

• Examining documentation is useful for– To gain some insights as to how the need for a database arose– To provide information on the part of enterprise associated with the

problem– To gain some understanding of the system

• Q: What problems may occur in examining documents?

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Interviewing

• Interviewing is the most useful technique for– Finding out facts– Clarifying facts– Generating enthusiasm– Getting user involvement– Identify requirements– Gathering ideas and opinions

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Observation the enterprise in operation

• Most effective techniques for understanding a system

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Research

• Useful for researching the application and problems

Advantages Disadvantages

Can save time if solution already exists Requires access to appropriate sources of information

Can see how others solve similar problems or met similar requirements

May not help if poor documentation

Can be up to date with current development

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Questionnaire

• Useful to get information from a large number of people (responses).

Advantages Disadvantages

Convenience for people to complete and return

Number of respondents may be low

Inexpensive way to get information from many people

It may be returned incomplete

Provide confidentiality for the real facts Misinterpreted questions my occur

Quickly tabulated and analyzed Cannot observe and analyze body language