面向对象系统分析与设计 Object-Oriented Systems Analysis and Design...

面向对象系统分析与设计

Object-Oriented Systems Analysis and Design

河北农业大学信息科学与技术学院滕桂法教授

主要内容

1 、系统分析与设计概论2 、面向对象概念与术语3 、面向对象分析与设计4 、面向对象编程5 、 UML 面向对象设计基础6 、 UML 面向对象开发

第一章系统分析与设计概论(System Analysis and Design)

Chapter Objectives(You should be able to)1. Define a system, information system, and

automated information system.2. Define the basic components and the basic

characteristics of an automated information system.

3. Define system analysis and design and discuss why it is a difficult human endeavor.

4. Describe the skills and activities of a system analyst.

系统分析与设计概论(System Analysis and Design)

5. Describe a general model of the analysis, design, and implementation process.

6. Discuss systems analysis and design as a career.

7. Discuss what a system analyst does.

8. Discuss systems analysis and design projects and where they come from.

9. Discuss the need for creating information systems requirements specifications.


10. Define and describe the information systems life cycle.

11. Define and describe the information system development life cycle.

12. Discuss the principles used to guide system analysis and design.


1. Development Process

◆ Systems planning

◆ Systems analysis

◆ System design

◆ Systems implementation

◆ Systems evolution


2. Concept of System Analysis and Design

◆ What is a system?

A system is a set of interrelated components, working together for a common purpose. There are two types of systems: natural and fabricated.


System Model with Six Components:

systemsystem

boundaryboundary

controlscontrols

processingprocessing

inputsinputs

feedbackfeedback outputsoutputs


◆ What is an information system?

An information system is a type of fabricated system that is used by one or more persons to help accomplish a task or assignment.


◆ What is an information system?

datadata peoplepeople

proceduresprocedures


◆ What is an automated information system?

A automated information system is an information system that incorporates the use of computer hardware and software as part of the system.


◆ What is an automated information system?

datadata peoplepeople

softwaresoftware proceduresprocedures

hardwarehardware


◆ What are the basic characteristics of an information system?

The basic characteristics that exist within an information system are data, functions, and behavior, as illustrated in the following figure.

DataData FunctionsFunctions

BehaviorBehavior


◆ What are the basic characteristics of an information system?

Data: input, stored, or output

Function: business activity performed

Behavior: the observable effects of a request


◆ What is systems analysis and design?

System analysis and design is about developing software, but it is more about developing a complete automated information system, which includes hardware, software, people, procedures, and data. These five components exist in virtually all automated information systems, although the amount of each will vary with respect to the specific system being developed. All of these components must be considered and addressed during system analysis and design.


◆ Actors of systems analysis and design?

System Analyst;

System Engineer;

Programmer;

Architect;

系统分析与设计过

程


◆ What makes systems analysis and design such a difficult human endeavor?

Seven reasons:

1. Analysis problems, at their inception, have ill-defined boundaries and structure(users are not certain of what they want), and have a sufficient degree of uncertainty about the nature of the solution.



2. The solutions systems analysts come up with to solve the problems are artificial, and since they are designed by humans with different backgrounds, experiences, biases, and so on, there exists an endless variety of potential solutions. That means that there is no single correct solution to a problem. Many needs and Many solutions.



3. Analysis problems are dynamic. No business is standing still. Change!

4. The solutions to analysis problems require interdisciplinary knowledge and skills, hence, the need for a team approach to IS development. Emphasis on the partnership concept between the user community and the IS developers.



5. The knowledge base of the systems analysis is continually evolving. As the apprentice systems analyst progresses through the junior, associate, and senior systems analyst ranks over time, he or she continues to learn more about business problem domains as well as improving his or her analytical skills and software development tool and technique skills.



6. The process of analysis is primarily a cognitive activity in that we are asked to (1) put structure to an abstract problem domain, (2) process diverse information from a variety of users, and (3) develop a logical and consistent specification that will lead to the creation of a successful information system.

7. The People! Study human and org. behavior.

Stakeholders: Players in the Systems Development Team

• A stakeholder is any person who has an interest in an existing or new information system. Stakeholders can be technical or nontechnical workers.

• For information systems, the stakeholders can be classified as ( six groups of information workers):– System owners– System users– Systems analysts– System designers– System builders– IT vendors and consultants

Information versus Knowledge Workers

Information workers are those workers whose jobs involve the creation, collection, processing, distribution, and use of information.

(In USA they are so called)

Knowledge workers are a subset of information workers whose responsibilities are based on a specialized body of knowledge.

(College educated; Depending on information and ability to properly use and react to information)

System Owners

System owners are the information system’s sponsors and chief advocates. They are usually responsible for funding the project to develop, operate, and maintain the information system.

System Users

System users are the people who use or are affected by the information system on a regular basis—capturing, validating, entering, responding to, storing, and exchanging data and information. A common synonym is client. Types include:– Internal users

• Clerical and service workers• Technical and professional staff• Supervisors, middle managers, and executive managers• Remote and mobile users (internal but disconnected)

– External users (customer and other system users)

System Designers and System Builders

System designers translate system users’ business requirements and constraints into technical solutions. They design the computer files, databases, inputs, outputs, screens, networks, and programs that will meet the system users’ requirements.

System builders construct the information system components based on the design specifications from the system designers. In many cases, the system designer and builder for a component are one and the same.

Systems Analysts

A systems analyst studies the problems and needs of an organization to determine how people, data, processes, communications, and information technology can best accomplish improvements for the business. When information technology is used, the analyst is responsible for:

– The efficient capture of data from its business source, – The flow of that data to the computer, – The processing and storage of that data by the computer, and

– The flow of useful and timely information back to the business and its people.

Variations on the Systems Analysts Title

• A business analyst is a systems analyst that specializes in business problem analysis and technology-independent requirements analysis.

• A programmer/analyst (or analyst/programmer) includes the responsibilities of both the computer programmer and the systems analyst.

• Other synonyms for systems analyst include:– Systems consultant– Systems architect– Systems engineer– Information engineer– Systems integrator

Problem-Solving Scenarios

• True problem situations, either real or anticipated, th

at require corrective action

• Opportunities to improve a situation despite the abse

nce of complaints

• Directives to change a situation regardless of whethe

r anyone has complained about the current situation

General Problem-Solving Approach

1. Identify the problem.

2. Analyze and understand the problem.

3. Identify solution requirements or expectations.

4. Identify alternative solutions and decide a course of action.

5. Design and implement the “best” solution.

6. Evaluate the results. If the problem is not solved, return to

step 1 or 2 as appropriate.

Where Systems Analysts Work• In traditional businesses

– Working in traditional information services organizations(permanent project teams)

– Working in contemporary information services organizations(dynamic project teams)

• In outsourcing businesses– Contracted to traditional businesses

• In consulting businesses– Contracted to traditional businesses

• In application software businesses– Building software products for traditional businesses

Traditional IS Services Organization

Contemporary IS Services Organization

Business Trends and Drivers

• Total quality management (TQM)

• Continuous process improvement (CPI)

• Globalization of the economy

• Information technology problems and opportunities

– Year 2000 problem (Y2K)

– Euro currency directive

– Enterprise resource planning (ERP)

– Electronic commerce (EC or E-commerce)

Total Quality Management

• Total quality management (TQM) is a comprehensive approach to facilitating quality improvements and management within a business.

• Information systems quality standards:– ISO 9001, Quality systems – Model for quality assurance i

n design/development, production, installation, and servicing.

– Capability Maturity Model (CMM) is a framework to assess the maturity level of an organization’s information systems development and management processes and products. It consists of five levels of maturity as measured by a set of guidelines called the key process areas.

The CMM Process Management Model

The Capability Maturity Model (CMM) is a framework to assess the maturity level of an organization’s information system development and management processes and products. It consists of five levels of maturity as measured by a set of guidelines called the key process areas.

– Level 1—Initial: System development projects follow no prescribed process.

– Level 2—Repeatable: Project management processes and practices are established to track project costs, schedules, and functionality.

– Level 3—Defined: A standard system development process (sometimes called a “methodology”) is purchased or developed, and integrated throughout the information systems/services unit of the organization.

– Level 4—Managed: Measurable goals for quality and productivity are established.

– Level 5—Optimizing: The standardized system development process is continuously monitored and improved based on measures and data analysis established in Level 4.

The CMM Process Management Model

Level5

OPTIMIZED

Level4

MANAGED

Level3

DEFINED

Level2

REPEATABLE

RISK

COMPETITIVENESS

Level1

INITIAL

Business Process Redesign

Business process redesign (BPR) is the study,

analysis, and redesign of fundamental business

processes to reduce costs and/or improve value

added to the business.

– Usually complemented by continuous process i

mprovement

Continuous Process Improvement

Continuous process improvement (CPI) is the continuous monitoring of business processes to effect small but measurable improvements to cost reduction and value added.

– Essentially the opposite of business process redesign; however,

– CPI can and frequently does complement BPR.

Legacy Systems

Legacy systems are older information system applications that have become crucial to the day-to-day operation of a business and that may use technologies considered old or outdated by current standards.

– Can be adversely affected by technology and economic forces:

• Year 2000• Euro

– Can be replaced by alternative solutions:• ERP• E-Commerce

Enterprise Resource Planning

An Enterprise resource planning (ERP) software product is a fully integrated information system that spans most basic business functions required by a major corporation. An ERP product is built around a common database shared these business functions. Examples of ERP software vendors include.

– Baan

– J. D. Edwards

– Oracle

– Peoplesoft

– SAP

Electronic Commerce

Electronic commerce (e-commerce or EC) involves conducting both internal and external business over the Internet, intranets, and extranets.

– Electronic commerce includes the buying and selling of goods and services, the transfer of funds, and the simplification of day-to-day business processes – all through digital communications.

– Three basic types of electronic commerce applications include:• Marketing

• Business-to-consumer (B2C)

• Business-to-business (B2B)

The Systems Analyst as a Facilitator

Skills Required by Systems Analysts

• Working knowledge of information technology

• Computer programming experience and expertise

• General business knowledge

• Problem-solving skills

• Interpersonal communication skills

• Interpersonal relations skills

• Flexibility and adaptability

• Character and ethics

• Systems analysis and design skills

The Ten Commandments of Computer Ethics1. Thou shalt not use a computer to harm other people. 2. Thou shalt not interfere with other people's computer work. 3. Thou shalt not snoop around in other people's computer files. 4. Thou shalt not use a computer to steal.5. Thou shalt not use a computer to bear false witness. 6. Thou shalt not copy or use proprietary software for which you ha

ve not paid. 7. Thou shalt not use other people's computer resources without au

thorization or proper compensation. 8. Thou shalt not appropriate other people's intellectual output. 9. Thou shalt think about the social consequences of the program y

ou are writing or the system you are designing. 10. Thou shalt always use a computer in ways that insure consider

ation and respect for your fellow human

Computer Ethics

Source: Computer Ethics Institute

Source: Computer Ethics Institute

Information System Building Blocks

Information System Building Blocks• What are information systems, and who are the stakeholders in the information syste

ms game?• Describe the difference between data and information.• Define the product called an information system, and describe the role of information t

echnology in information systems.• Differentiate between front- and back-office information systems.• Describe five classes of information system applications (transaction processing, ma

nagement information, decision support, expert, and office automation systems) and how they interoperate.

• Describe the role of information systems architecture in system development.• Name six groups of stakeholders in information system development.• Name three focuses for information systems.• Describe four perspectives of the DATA focus for an information system.• Describe four perspectives of the PROCESS focus for an information system.• Describe four perspectives of the INTERFACE focus for an information system.

• Describe the role of a computer network as it relates to DATA, PROCESSES, and INTERFACES.

Building Blocks of An Information System

Data and Information

Data are raw facts about the organization and its business transactions. Most data items have little meaning and use by themselves.

Information is data that has been refined and organized by processing and purposeful intelligence. The latter, purposeful intelligence, is crucial to the definition—People provide the purpose and the intelligence that produces true information.

Information Systems & Technology

An information system (IS) is an arrangement of people, data, processes, communications, and information technology that interact to support and improve day-to-day operations in a business as well as support the problem-solving and decision making needs of management and users.

Information technology is a contemporary term that describes the combination of computer technology (hardware and software) with telecommunications technology (data, image, and voice networks).

Front- and Back-Office Information Systems

• Front-office information systems support business functions that reach out to customers (or constituents).– Marketing– Sales– Customer management

• Back-office information systems support internal business operations and interact with suppliers (of materials, equipment, supplies, and services). – Human resources– Financial management– Manufacturing– Inventory control

A Federation of Information Systems

Classes of Information Systems

• Transaction processing systems

• Management information systems

• Decision support systems

• Expert systems

• Office automation systems

Transaction Processing

Transaction processing systems are information system applications that capture and process data about business transactions.

– Includes data maintenance, which provides for custodial updates to stored data.

– Business process redesign (BPR) is the study, analysis, and redesign of fundamental business (transaction) processes to reduce costs and/or improve value added to the business.

Management Information Systems

A management information system (MIS) is an information system application that provides for management-oriented reporting. These reports are usually generated on a predetermined schedule and appear in a prearranged format.

Decision Support Systems

A decision support system (DSS) is an information system application that provides its users with decision-oriented information whenever a decision-making situation arises. When applied to executive managers, these systems are sometimes called executive information systems (EIS).

– A data warehouse is a read-only, informational database that is populated with detailed, summary, and exception data and information generated by other transaction and management information systems. The data warehouse can then be accessed by end-users and managers with DSS tools that generate a virtually limitless variety of information in support of unstructured decisions.

Expert Systems

An expert system is a programmed decision-making information system that captures and reproduces the knowledge and expertise of an expert problem solver or decision maker and then simulates the “thinking” or “actions” of that expert.

– Expert systems are implemented with artificial intelligence technology that captures, stores, and provides access to the reasoning of the experts.

Office Automation Systems

Office automation (OA) systems support the wide range of business office activities that provide for improved work flow and communications between workers, regardless of whether or not those workers are located in the same office.

– Personal information systems are those designed to meet the needs of a single user. They are designed to boost an individual’s productivity.

– Work group information systems are those designed to meet the needs of a work group. They are designed to boost the group’s productivity.

Information Systems Applications

Information Systems Architecture

Information systems architecture provides a unifying framework into which various people with different perspectives can organize and view the fundamental building blocks of information systems.

Perspectives or Stakeholders• System owners pay for the system to be built and maintained.• System users use the system to perform or support the work to

be completed.• System designers design the system to meet the users’ require

ments.• System builders construct, test, and deliver the system into ope

ration.• Systems analysts facilitate the development of information syst

ems and computer applications by bridging the communications gap that exists between nontechnical system owners and users and technical system designers and builders.

• IT vendors and consultants sell hardware, software, and services to businesses for incorporation into their information systems.

Focuses for Information Systems

• Data—the raw material used to create useful information.

• Processes—the activities (including management) that carry out the mission of the business.

• Interfaces—how the system interfaces with its users and other information systems.

The DATA Focus

The DATA Focus• System owners’ perspective

– Business knowledge is the insight that is gained from timely, accurate, and relevant information. (Recall that information is a product of raw data.)

• System users’ perspective– Data requirements are a representation of users’ data in terms o

f entities, attributes, relationships, and rules. Data requirements should be expressed in a format that is independent of the technology that can or will be used to store the data.

• System designers’ perspective– Database schema

• System builders’ perspective– Database management system

The PROCESS Focus

The PROCESS Focus

• System owners’ perspective– Business functions are ongoing activities that su

pport the business. Functions can be decomposed into other subfunctions and eventually into processes that do specific tasks.

– A cross-functional information system supports relevant business processes from several business functions without regard to traditional organizational boundaries such as divisions, departments, centers, and offices. Continued ...

The PROCESS Focus (continued)

• System users’ perspectives– Business processes are activities that respond to busines

s events. Business processes are the “work” performed by the system.

– Process requirements are a representation of the users’ business processes in terms of activities, data flows, or work flow.

– A policy is a set of rules that govern a business process.– A procedure is a step-by-step set of instructions and logic

for accomplishing a business process.

Continued ...

The PROCESS Focus (continued)

• System designers’ perspectives– An application schema is a model that communicates how sel

ected business processes are, or will be, implemented using the software and hardware.

– Software specifications represent the technical design of business processes to be automated or supported by computer programs to be written by system builders.

• System builders’ perspectives– Application programs are language-based, machine-readable

representations of what a software process is supposed to do, or how a software process is supposed to accomplish its task.

– Prototyping is a technique for quickly building a functioning, but incomplete model of the information system using rapid application development tools.

The INTERFACE Focus

The INTERFACE Focus

• System owners’ perspective• System users’ perspectives

– Interface requirements are a representation of the users’ inputs and outputs.

• System designers’ perspective– User dialogues describe how the user moves from windo

w-to-window, interacting with the application programs to perform useful work.

• System builders’ perspective– Middleware is a layer of utility software that sits in between

application software and systems software to transparently integrate differing technologies so that they can interoperate.

The Role of the Network in IS

A COMMUNICATIONS Focus in IS

面向对象系统分析与设计 Object-Oriented Systems Analysis and Design...

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