Part3 Database Analysis and Design Techniques Chapter 04- Overview of Database Planning, Design and...

Part3 Database Analysis and Design TechniquesChapter 04- Overview of Database Planning, Design and Administration

Lu Wei

College of Software and Microelectronics

Northwestern Polytechnical University

Database Systems

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Outline

• Overview of the Information Systems Lifecycle• The Database Systems Lifecycle• The main stages of the Database Systems Lifec

ycle• The benefits of Computer-Aided Software Engin

eering (CASE) tools• Data Administration and Database Administratio

n• Fact-finding Techniques

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Outline





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Overview of the Information Systems Lifecycle

• Software has now surpassed hardware as the key to the success of many computerbased systems.

• Although the term ‘software crisis’ was first used in the late 1960s, the crisis is still with us.

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• OASIG reached the following conclusions about software projects (1996.)– 80%-90% do not meet their performance goals– About 80% are devilered late and budge– Around 40% fail or are abandoned– Under 40% fully address training and skills requireme

nts– Less than 25% properly integrate enterprise and tech

nology objectives– Just 10%-20% meet all their success criteria.

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• Major reasons for failure of software projects– Lack of a complete requirements specification– Lack of an appropriate development methodology– Poor decomposition of design into manageable comp

onents

• As a solution to these problems, a structured approach to the development of software was proposed called the information systems lifecycle or software development lifecycle (SDLC).

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• Information system– The resource that enable the collection, management,

control, and dissemination of information throughout an organization.

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• Typically, the stages in the lifecycle of an information system include:– Planning– Requirements collection and analysis– Design– Prototyping – Implementation– Testing– Conversion – Operational maintenance

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• The database is a fundamental component of an information system.

• The lifecycle of an organization’s information system is inherently linked to the lifecycle of the database system that supports it.

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Outline





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The Database Systems Lifecycle

• Database systems are typically large and complex software systems.

• As with any other software system before it is implemented and deployed, a database system needs to be carefully designed so that it can meet its intended use fully and correctly.

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Outline





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The main stages of the Database Systems Lifecycle

• Database Planning• System Definition• Requirements Collection and Analysis• Database Design• DBMS Selection• Application Design• Prototyping• Implementation

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The main stages of the Database Systems Lifecycle

• Data Conversion and Loading• Testing• Operational Maintenance

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Database Planning

• Database Planning– The management activities that allow the stages of th

e database application to be realized as efficiently and effectively as possible.

• Database planning must be integrated with the overall IS strategy of the organization.

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Database Planning

• There are three mian issues involved– Identification of enterprise plans and goals with subse

quent determination of information systems needs;– Evaluation of current information systems to determin

e existing strengths and weaknesses;– Appraisal of IT opportunities that might yield competiti

ve advantage.

• The most important objective of database plan is to clearly define the mission statement and mission objectives.

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Database Planning

• Database planning should also include the development of relative standards.– How data will be collected– How the format should be specified– What documentation will be needed– How design and implementation should proceed– …

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System Definition

• System definition– Describes the scope and boundaries of the database

application and the major user views.

• User view– Defines what is required of a database application fro

m the perspective of a particular job role(such as Manager or Supervisor) or enterprise application area(such as marketing, personnel, or stock control).

• Identifying user views is an important aspect of developing a database application.

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System Definition

• A user view defines what is required of a database application in terms of the data to be held and the transactions to be performed on the data.

• A database application may have one or more user views. A user view may be distinct to overlap with other views.

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Requirements Collection and Analysis

• Requirements collection and analysis– The process of collecting and analyzing information a

bout the part of the organization that is to be supported by the database application, and using this information to identify the user’s requirements of the new system.

• There are many techniques for gathering this information, called fact-finding techniques.

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• Information is gathered for each major user view including:– A description of the data used or generated;– The details of how data is to be used or generated;– Any additional requirements for the new database app

lication

• Requirements are described in documents refer to as requirements specifications.

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• The information collected at this stage may be poorly structured and include some informal requests, which must be converted into a more structured statement of requirements.

• Requirements specification techniques– Structured Analysis and Design (SAD)– Data Flow Diagrams (DFD)– Hierarchical Input Process Output (HIPO) charts– CASE tools

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• Identifiying the required functionality for a database application is a critical activity.– Inadequate or incomplete functionality will..– Excessive functionality can also be problematic

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• Another important activity associated with this stage is deciding how to deal with the situation where there is more than one user view for database application.– The centralized approach– The view integration approach– A combination of both approach

• Anyway identifying the user’s requirements is a difficult thing because…

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Database Design

• Database Design– The process of creating a design for a database that

will suport the enterprise’s operations and objectives.

• Approaches to Database design– Bottom-up– Top-down– Inside-out– Mixed strategy

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Database Design

• Data Modeling– Assist in the understanding of the meaning (semantic

s) of the data.– Facilitate communication about the information requir

ements.

• Building a data model requires answering questions about entities, relationships, and attributes.

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Database Design

• Phases of Database Design– Conceptual database design– Logical database design– Physical database design

• Database design is an iterative process, which has a starting point and an almost endless procession of refinements.

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Database Design

• Conceptual database design– The process of constructing a model of the informatio

n used in an enterprise, independent of all physical considerations.

– It is entirely independent of implementation details such as the target DBMS software, application programs, programming languages, hardware platform, or any other physical considerations.

– It is a source of information for the next phase, namely logical database design.

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Database Design

• Logical database design– The process of constructing a model of the informatio

n used in an enterprise based on a special data model, but independent of a particular DBMS and other physical consideration.

– A logical data model is derived knowing the underlying data model of the target DBMS.

– It is a source of information for the next phase, namely physical database design.

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Database Design

• Physical database design– The process of producing a description of the implem

entation of the database on secondary storage. It describes the base relations, file organizations, and indexes used to achieve efficient access to the data, and any associated integrity constraints and security measures.

– It is tailored to a specific DBMS system.

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DBMS Selection

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Application Design

• Application Design– The design of the user interface and the application pr

ograms that use and process the database.

• Transaction – An action, or series of actions, carried out by a single

user or application program which accesses or changes the content of the database.

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Application Design

• Transaction Design– 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 transaction– Update transaction– Mixed transaction

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Application Design

• User Interface Design– Meaningful title– Comprehensible instructions– Logical grouping and sequencing of fields– Visually appealing layout of the form/report– Familiar field labels– Error correction, error messages– Color, space, convenient cursor movement– …

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Prototyping

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Implementation

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Data Conversion and Loading

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Testing

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Operational Maintenance

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Outline





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The benefits of CASE tools

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Outline





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Data Administration and Database Administration

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Outline





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Fact-finding Techniques

• Fact-finding– The formal process of using techniques such as interv

iews and questionnaires to collect facts about systems, requirements, and preferences.

• When are Fact-Finding Techniques Used?– Database planning– System definition– Requirements collection and analysis

•

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数据库应用程序生存期阶段

收集的数据生成的文档

数据库规划数据库项目的目标和任务数据库应用程序的任务陈述和任务目标

系统定义描述主要用户视图定义数据库应用程序的分为和边界；定义要支持的用户视图

需求收集和分析用户视图和系统需求用户和系统需求说明书

数据库设计验证逻辑数据库设计的用户反映；目标 DBMS提供的功能；

概念/逻辑数据库设计；物理数据库设计

应用程序设计用户对界面设计的反映应用程序设计

DBMS选择目标 DBMS提供的功能 DBMS的评估和推荐

建立原型用户对系统原型的反响改进的用户需求和系统需求说明书

实现目标系统提供的功能

数据转换和加载当前数据的格式；目标 DBMS

的数据导入性能

测试测试结果采用的测试策略；测试结果分析

运行维护性能测试结果；用户和系统需求的增加和变化

用户手册；性能分析；改变的用户需求和系统说明书

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Fact-finding Techniques

• Fact-Finding Techniques– Examining documentation– Interviewing– Observing the enterprise in operation– Research– Questionnaires (问卷调查 )

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Summary

• In this chapter you should have learned:– The Database Systems Lifecycle– The main stages of the Database Systems Lifecycle

Part3 Database Analysis and Design Techniques Chapter 04- Overview of Database Planning, Design and...

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