Archive for the ‘PRELIM’ Category
Angeles University Foundation
Angeles City
COLLEGE OF COMPUTER STUDIES
Center of Excellence in I.T. Education
SAD310A-Systems Analysis and Design
Prelim Handouts#3
I. Use Case Modeling
– Originally introduced as a diagram for use in the object-oriented UML (Unified Modeling Language)
– is a type of behavioral diagram defined by and created from a Use-case analysis. Its purpose is to present a graphical overview of the functionality provided by a system in terms of actors, their goals (represented as use cases), and any dependencies between those use cases. (Source: Wikipedia)
II. Use Case Symbols
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Actors are similar to external entities; they exist outside the system.
– The term actor refers to a particular ROLE of a user of the system.
– For example, the actor may be an employee, but also may be a customer at the company store.
– It interacts with the system in a specific way.
– An actor may be a human, another system, or a device such as a keyboard or Web connection.
– Actors can initiate an instance of a use case. An actor may interact with one or more use cases; and a use case may involve one or more actors.
Actors may be divided into two groups. Primary actors supply data or receive information from the system. Supporting actors (or secondary actors) help to keep the system running or provide other services. These are the people who run the help desk, the analysts, programmers, and so on.
– Provides developers with a view of what the users want. It is free of technical and implementation details.
– It is a sequence of transactions in a system.
– The use case model is based on the interactions and relationships of individual use cases.
– The use case always describes three things: an actor that initiates an event; the event that triggers a use case; and a use case that performs the actions triggered by the event.
– Used to document a single transaction or event. An event is an input to the system that happens at a specific time and place and causes the system to do something.
– It is better to create fewer use cases rather than more. Often, queries and reports are not included. 20 use cases ( and no more than 40 or 50) are sufficient for a large system.
A use case is named with a VERB and a NOUN
Communicates – An actor is connected to a use case using a line with no arrowheads.
Includes – A use case contains a behavior that is common to more than one other use case. The arrow points to the common use case.
Extends – A different use case handles exceptions from the basic use case. The arrow points from the extended to the basic use case.
Generalizes – One UML “thing” is more general than another “thing”. The arrow points to the general “thing”.
Connecting Lines (or Relationships)
III. Developing Use Case Diagrams
When diagramming a use case, start by asking the users to list everything the system should do for them. This can be done by using interviews or through other facilitated team sessions. Write down who is involved with each use case, and the responsibilities or services the use case must provide to actors or other systems.
Use the following guidelines:
1. Review the business specifications and identify the actors involved.
2. Identify the high-level events and develop the primary use cases that describe those events and how the actors initiate them. Carefully examine the roles played by the actors to identify all possible primary use cases initiated by each actor.
3. Review each primary use case to determine the possible variations of flow through the use case. From this analysis, establish the alternative paths.
Note: If a context level data flow diagram has been created, it can be a starting point for creating a use case. The external entities are potential actors. Then examine the data flow to determine if it would initiate a use case or be produced by a use case.
IV. Examples of Use Case Diagrams
Understanding Organizational style & its impact on information systems
Key Points and Objectives
1. Organizations – complex systems composed of interrelated and interdependent subsystems.
2. Both System and subsystem boundaries and environments impact on information system analysis and design.
3. Systems are classified as either open, with free flowing information, or closed with restricted access to information.
4. A virtual organization has parts of the organization in different physical locations. They use computer networks and communications technology to work on projects. The advantages of a virtual organization are:
A. Reduced costs of physical facilities
B. More rapid response to customer needs
C. Flexibility for employees to care for children or aging parents
5. Enterprise Resource Planning (ERP) is an integrated organizational information system. The software helps the flow of information between the functional areas within the organization.
6. A Context-level Data Flow Diagram is an analysis tool for showing data used and information produced by a system. It provides an overview of the setting or environment the system exists within: which entities supply and receive data/information.
7. Entity-relationship diagrams (ERD) help the analyst understand the organizational system and the data stored by the organization.
8. There are three types of entities:
A. Fundamental entity, describing a person, place or thing
B. Associative entity (also called a gerund, junction, intersection or concatenated entity), joining two entities. It can only exist between two entities.
C. Attributive entity, to describe attributes and repeating groups.
9. Relationships may be shown with a zero or circle representing none, a vertical line representing one, or crow’s foot representing many and can be:
A. One to one
B. One to many
C. Many to many
10. A use case diagram reflects the view of the system from the perspective of a user outside of the system.
11. A use case model partitions the way the system works into behaviors, services, and responses that are significant to the users of the system.
12. A use case diagram has symbols for:
A. An actor – the role of a user of the system
B. A use case – representing a sequence of transactions in a system
13. There are two kinds of use cases.
A. Primary, the standard flow of events within a system that describe a standard system behavior.
B. Use case scenarios that describe variations of the primary use case.
14. There are four active behavioral relationships:
A. Communicates, is used to connect an actor to a use case.
B. Includes, describes the situation where a use case contains a behavior that is common to more than one use case.
C. Extends, describes the situation where one use case possesses the behavior that allows the new use case to handle a variation or exception.
D. Generalizes, implies that one thing is more typical than the other thing.
15. The steps required to create a use case model are:
A. Review the business specifications and identify the actors within the problem domain.
B. Identify the high-level events and develop the primary use cases that describe the events and how actors initiate them.
C. Review each primary use case to determine possible variations of flow through the use case.
D. Develop the use case documents for all primary use cases and all important use case scenarios.
16. Use case scenarios are text descriptions of the use case, and may contain the following:
A. The use case name.
B. The area of the business.
C. The actors.
D. A brief description of the use case.
E. The triggering event
F. The type of trigger, either external or temporal.
G. The steps performed for the use case.
H. Preconditions, what must have occurred before the use case can start to execute.
I. Postconditions or what has been accomplished by the use case.
J. Assumptions that have been made for the use case to execute.
K. Requirements met by the use case.
L. Any outstanding issues.
M. An optional priority.
N. An optional risk.
17. Use cases are helpful because they:
A. Effectively communicate systems requirements.
B. Allow people to tell stories.
C. Make sense to nontechnical people.
D. Do not depend on a special language.
E. Can describe functional requirements.
F. Can describe nonfunctional requirements.
G. Help analysts define boundaries.
H. Can be traceable, allowing analysts to identify links between use cases and other design and documentation tools.
18. The three levels of managerial control are:
A. Operations management
B. Middle management
C. Strategic management
19. Each of the three levels of management, different organization structure, leadership style, technological considerations, organization culture, and human interaction all carry implications for the analysis and design of information systems.
Answers to Review Questions (page 52)
1. What are the three groups of organizational fundamentals that carry implications for the development of information systems?
The three groups of organizational fundamentals include:
A. level of management
B. design of organizations
C. other factors–leadership style, technology, and organizational subcultures.
2. What is meant by saying that organizational subsystems are interrelated and interdependent?
Organizational subsystems are said to be interrelated and interdependent when a change in one subsystem affects other subsystems.
3. Define the term organizational boundary.
Organizational boundary – separates the system from its environment.
4. What are the two main purposes for feedback in organizations?
Two main purposes of feedback are: (a) system control and (b) formulating and revising organizational goals.
5. Define openness in an organizational environment.
Openness – refers to an organization with a relatively free flow of information within its boundaries.
6. Define closedness in an organizational environment.
Closedness – refers to an organization with relatively little flow of information within its boundaries.
7. What is the difference between a traditional organization and a virtual one?
A traditional organization is one that has a physical location, whereas a virtual organization has parts of the organization in different locations, connected electronically.
8. What are the potential benefits and a drawback of a virtual organization?
The benefits of a virtual organization are: reduced costs of physical facilities, a more rapid response to customer needs and flexibility for employees to care for children or aging parents. A drawback is that it is difficult to meet the social needs of virtual workers.
9. Give an example of how systems analysts could work with users as a virtual team.
The example provided in the text allows the analyst to see the software and hardware configuration of the user requesting help.
10. What is ERP, and what is its purpose?
ERP (Enterprise Resource Planning) is a system that is usually purchased from outside vendors and customized to fit the requirements of a particular company. Its purpose is to help the flow of information between the functional areas of an organization.
11. What problems do analysts often encounter when they try to implement an ERP package?
The problems that the analyst encounters when trying to implement an ERP package are the difficulty of trying to analyze a system currently in use and then fit an ERP model to the system. Another problem is that the business model does not always match the ERP functionality. The impact is delayed implementation, higher costs and the loss of user confidence.
12. What are the two symbols on a use case diagram and what do they represent?
A) Actor – the role of a user of the system
B) Use case – representing a sequence of transactions in a system.
13. What is a use case scenario?
A use case scenario is a text description of the flow of events in a use case. There may be alternate scenarios representing conditions that produce variations on the primary scenario.
14. What are the three main parts of a use case scenario?
A) The use case identifiers and initiators;
B) the steps performed;
C) the conditions, assumptions and questions.
15. What does a process represent on a context-level data flow diagram?
A process represents the entire system on a context-level data flow diagram.
16. What is an entity on a data flow diagram?
An entity on a data flow diagram represents an entity that supplies and receives information that is outside of the system.
17. What is meant by the term entity-relationship diagram?
An entity-relationship diagram is a graphical depiction of organizational system elements and the association among the elements.
18. What symbols are used to draw E-R diagrams?
The three symbols used for E-R diagrams are (1) rectangle-to show the entity, (2) diamond in a rectangle – to join two many-to-many entities, and (3) oval in a rectangle to represent an attribute, especially a repeating group.
19. List the types of E-R diagrams.
The following are types of E-R Diagrams:
A. one-to-one relationship
B. one-to-many relationship
C. many-to-one relationship
D. many-to-many relationship
20. How do an entity, an associative entity, and an attributive entity differ?
An entity represents a person, place or thing. An associative entity can only join two fundamental entities. An attributive entity is used to represent an attribute of an entity, often a repeating group, and cannot exist without being linked to a fundamental entity.
21. List the three broad, horizontal levels of management in organizations.
The three levels of management in organizations are (a) operations management, (b) middle management, and (c) strategic management.
Key Points and Objectives
1. Information is an organizational resource that must be managed as carefully as other resources.
2. Information systems fall into one of the following eight categories:
A. Transaction processing systems (TPS) process large volumes of data, routine business transactions.
B. Office automation systems (OAS) manipulate information and share it throughout the organization. Software, such as spreadsheets, word processing, e-mail and so on are routinely used in OAS.
C. Knowledge work systems (KWS) help professionals to develop new knowledge, often in teams.
D. Management information systems (MIS) are computerized information systems that support a broader range of business functions than do data processing systems.
E. Decision support systems (DSS) are information systems that help support decision makers in making semi-structured decisions.
F. Expert systems capture the expertise of a human expert or experts for solving particular organizational problems.
G. Group decision support systems (GDSS) and computer supported collaborative work systems (CSCWS) allow group members to interact and help facilitate group problem solving.
H. Executive support systems (EES) help senior management to make strategic decisions.
3. New technologies, such as ecommerce, Enterprise Resource Planning, wireless devices and open source software, are being integrated into traditional systems.
4. Ecommerce uses the Web to perform business activities. The benefits of using the Web are:
A. Increasing awareness of the availability of the service, product, industry, person or group
B. 24-hour access for users
C. Improving the usefulness and usability of interface design
D. Creating a global system
5. Enterprise Resource Planning (ERP) has the goal of integrating many different information systems within the corporation, using proprietary software.
6. Systems must be designed for wireless and handheld devices, including mobile commerce (mcommerce).
7. Open source software (OSS) provides both software and the program source code used to create the software. Many users and programmers may provide modifications to the programs. Open source software may be categorized into four types of communities:
A. Ad hoc
B. Standardized
C. Organized
D. Commercial
8. Open source communities differ from each other on six key dimensions:
A. General structure
B. Environment
C. Goals
D. Methods
E. User community
F. Licensing
9. Systems analysis and design is a systematic approach to identifying problems, opportunities, and objectives; analyzing the information flows in organizations; and designing computerized information systems to solve a problem.
10. User involvement throughout the systems project is a critical success factor.
11. Systems analysts act as outside consultants to businesses, as supporting experts within a business and as change agents.
12. Analysts are problem solvers and require communication skills.
13. It is important for analysts to be aware of their ethical framework as they work to build relationships with users and customers.
14. The systems development life cycle is a systematic approach to solving business problems.
15. The Human-computer interaction (HCI) is a human-centered approach that places an emphasis on human needs before the needs of an organizational or a system.
16. The human-computer interaction should be included into every phase of the systems development life cycle.
17. The systems development life cycle is divided into seven phases:
A. Identifying problems, opportunities and objectives
B. Determining human information requirements
C. Analyzing system needs
D. Designing the recommended system
E. Developing and documenting software
F. Testing and maintaining the system
G. Implementing and evaluating the system
18. Rapid Application Development (RAD) is an object-oriented approach to systems development.
19. System maintenance is removing undetected errors and enhancing existing software.
20. Systems are enhanced for the following reasons:
A. Adding additional features to the system.
B. Business and governmental requirements change over time.
C. Technology, hardware, and software are rapidly changing.
21. CASE tools are automated, microcomputer-based software packages for systems analysis and design.
22. Four reasons for using CASE tools are:
A. To increase analyst productivity.
B. Facilitate communication among analysts and users.
C. Providing continuity between life cycle phases.
D. To assess the impact of maintenance.
23. CASE tools may be divided into several categories, namely:
A. Upper CASE (also called front-end CASE) tools are used to perform analysis and design.
B. Lower CASE (also called back-end CASE) tools are used to generate computer language source code from CASE design. The advantage in generating source code are:
a. The time to develop new systems decreases.
b. The time to maintain generated code is less than to maintain traditional systems.
c. Computer programs may be generated in more than one language.
d. CASE design may be purchased from third-party vendors and tailored to organizational needs.
e. Generated code is free from program coding errors.
24. Structured analysis and design provides a systematic approach to developing systems and is cyclical in nature.
25. Object-oriented (O-O) analysis and design is used to build object-oriented programs. This includes not only data, but the instructions about operations that manipulate the data. The Unified Modeling Language (UML), a standardized object-oriented modeling language. Object-oriented methodologies focus on small, quick iterations of development.
26. The agile approach takes good software development practices and pushes them to extreme lengths. It is based on:
A. Values
B. Principles
C. Core practices
27. The four values of the agile approach are:
A. Communication
B. Simplicity
C. Feedback
D. Courage
28. Alternate methodologies (to the systems development life cycle) are available for analyzing systems. These include:
A. Prototyping
B. ETHICS
C. Project champions
D. Soft Systems Methodology
E. Multiview
Answers to Review Questions (page 23)
1. Compare treating information as a resource to treating humans as a resource.
Information fuels business and can be the critical factor in determining the success or failure of the business. Treating humans as a resource include physical or ergonomic factors, usability factors, aesthetic and enjoyable aspects, and behavioral aspects relating to the usefulness of the system. Treating humans as a resource means learning frustrations and feelings that humans have when working with a system.
2. List the difference between OAS and KWS.
An office automation system (OAS) is a set of familiar commercial software tools that allow data workers to manipulate data, rather than create it. General tools, such as word processing and spreadsheets, are used to manipulate the data. A knowledge work system (KWS) is used by professionals to create new knowledge.
3. Define what is meant by MIS.
Management information systems (MIS) includes transaction processing, decision analysis and produce output that is used in decision making.
4. How does MIS differ from DSS?
Both depend on a database as a source of data. However, DSS emphasizes the support of decision making in all phases and is more closely tailored to the person or group using them.
5. Define the term expert systems. How do expert systems differ from decision support systems?
An expert system captures and uses the knowledge of an expert for solving organizational problems. Expert systems select the best solutions to problems, whereas DSSs leave the ultimate judgment to the decision maker.
6. List the problems of group interaction that group decision support systems (GDSS) and computer-supported collaborative work systems (CSCWS) were designed to address.
The problems of group interaction that group decision support systems address are:
A. Lack of participation
B. Domination by group members
C. Group think decision making.
7. Which is the more general term, CSCWS or GDSS? Explain.
CSCW is a more general term, and may include software support called groupware for team collaboration.
8. Define the term mcommerce.
Mcommerce is mobile commerce, performing ecommerce using handheld wireless devices.
9. List the advantages of mounting applications on the Web.
The advantages of mounting applications on the World Wide Web are:
A. Increasing awareness of the availability of the service, product, industry, person or group.
B. The possibility of 24-hour access for users
C. Standardizing the design of the interface
D. Creating a global system without worry about time zones.
10. What is the overarching reason for designing ERP systems?
The overarching reason for designing ERP systems is the integration of many information systems existing on different managerial levels and within different functions.
11. Provide an example of an open source software project.
There are many open source software projects that are available. Students may be familiar with ones that are not mentioned. Mozilla Firefox, Apache, and Linux are mentioned in this chapter.
12. List the advantages of using systems analysis and design techniques in approaching computerized information systems for business.
System analysis and design techniques provide the analyst with a systematic procedure for analyzing data input, data flow, and information output; furthermore, the techniques can improve the functioning of business.
13. List three roles that the systems analyst is called upon to play. Provide a definition for each one.
The three roles of a system analyst are:
A. Consultant–hired from outside an organization to address information systems issues within that organization.
B. Supporting Expert–serves as a resource for those who are managing a systems project.
C. Change Agent–an analyst who serves as a catalyst for change, develops a plan for change, and works with others in facilitating that change.
14. What personal qualities are helpful to the systems analyst? List them.
Personal qualities helpful to systems analysts include:
A. Problem-solving abilities
B. Communication skills
C. Computer experience
D. Self-discipline and self-motivation
E. Project management capabilities
15. List and briefly define the seven phases of the systems development life cycle (SDLC).
The seven phases of the SDLC are:
A. Identifying problems, opportunities, and objectives–recognizing problems and opportunities confronting the business and determining business objectives.
B. Determining information requirements–understanding what information users need to perform their jobs.
C. Analyzing system needs–structured analysis of information needs and decision making.
D. Designing the recommended system–logical design of the information system.
E. Developing and documenting software–structured development of software and documentation.
F. Testing and maintaining the system–testing and revising the system.
G. Implementing and evaluating the system–training users and reviewing system.
16. What is rapid application development (RAD)?
Rapid application development (RAD) uses operational prototypes to construct a system.
17. List the four reasons for adopting CASE tools.
The four reasons for adopting CASE tools are:
A. Increasing analyst productivity.
B. Facilitating communication among analysts and users.
C. Providing continuity between life cycle phases.
D. Accurately assessing software maintenance changes.
18. Define what is meant by the agile approach?
The agile approach is based on values, principles and core practices. It values communication, simplicity, feedback and courage.
19. Define the terms object-oriented analysis and object-oriented design.
Object-oriented analysis and object-oriented design are techniques intended to facilitate the development of systems that must change rapidly in response to dynamic business environments.
20. What is UML?
UML is the Unified Modeling Language, a standardized object-oriented language used to break down a system into a use case model
Completion
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Decision makers are beginning to understand that (information) is not just a by‑product of conducting business, but a critical factor in determining the success or failure of a business. (p. 1) |
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(Transaction processing systems) are computerized information systems developed to process large amounts of data for routine business transactions such as payroll and inventory. (p. 2) |
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When groups of people need to work together to make decisions, a (group decision support system) may be used. (p. 4) |
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The (database) stores data and models that help the user interpret and use the data. (p. 3) |
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An (expert system), also called a knowledge‑based system, effectively captures and uses the knowledge of an expert for solving a particular problem experienced in an organization. (p. 4) |
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When analysts perform any activities in the systems development life cycle and are present in the business for an extended period of time, they are acting as (change agents). (p. 9) |
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The most prominent quality of an analyst is that of a (problem solver). (p. 9) |
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(Opportunities) are situations that the analyst believes can be improved through the use of information systems. (p. 11) |
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The (systems proposal) summarizes what has been found during the systems analysis phase, provides cost/benefit analyses of alternatives, and makes recommendations on what should be done. (p. 13) |
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The (program specifications packet) contains design information necessary for programmers to construct programs. (p. 13) |
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(Implementation) involves training users to use the system and planning for the smooth conversion of the old system to the new one. (p. 14) |
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One important justification for CASE tools is to increase analyst (productivity). (p. 16) |
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CASE tools are useful in (integrating) life‑cycle activities. (p. 17) |
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CASE tools help the analyst to increase productivity, (communicate) more effectively with users and integrate the system’s life cycle work. (p. 16) |
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(Lower CASE) tools generate computer code. (p. 18) |
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The (human computer interaction) is the layer of the computer that is between humans and the computer. (p. 10) |
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(Ecommerce) is mounting an application on the Web. (p. 5) |
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(Enterprise resource planning) is the integration of many information systems existing on different management levels and within different functions. (p. 5) |
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Wireless ecommerce is referred to as (mcommerce). (p. 6) |
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Software that is distributed free along with the program source code is called (open source software) (p. 6) |
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The (unified modeling language) is an industry standard for modeling object-oriented systems. (p. 20) |
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The (agile approach) is based on values, principles, and core practices. (p.20) |
Data Flow Diagrams
A structured analysis technique that employs a set of visual representations of the data that moves through the organization, the paths through which the data moves, and the processes that produce, use, and transform data.
Why Data Flow Diagrams?
• Can diagram the organization or the system
• Can diagram the current or proposed situation
• Can facilitate analysis or design
• Provides a good bridge from analysis to design
• Facilitates communication with the user at all stages
Types of DFDs
• Current – how data flows now
• Proposed – how we’d like it to flow
• Logical – the “essence” of a process
• Physical – the implementation of a process
• Partitioned physical – system architecture or high-level design
Levels of Detail
• Context level diagram – shows just the inputs and outputs of the system
• Level 0 diagram – decomposes the process into the major subprocesses and identifies what data flows between them
• Child diagrams – increasing levels of detail
• Primitive diagrams – lowest level of decomposition
Recommended Progression
• Current logical diagrams
– start with context level
– decompose as needed for understanding
• Proposed logical diagrams
– start at level where change takes place
– decompose as far as possible
• Current physical diagrams
– at level of change
• Proposed physical diagrams
– same levels as proposed logical
– lower levels become design
Context Level Diagram
• Just one process
• All sources and sinks that provide data to or receive data from the process
• Major data flows between the process and all sources/sinks
• No data stores
Course Registration: Context level Diagram
Level 0 Diagram
• Process is “exploded”
• Sources, sinks, and data flows repeated from context diagram
• Process broken down into subprocesses, numbered sequentially
• Lower-level data flows and data stores added
Source: http://userpages.umbc.edu/~cseaman/ifsm636/lect0913.ppt
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