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1 System Engineering based on Chapter 6 - Software Engineering: A Practitioner’s Approach, 6/e System Engineering based on Chapter 6 - Software Engineering:

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Presentation on theme: "1 System Engineering based on Chapter 6 - Software Engineering: A Practitioner’s Approach, 6/e System Engineering based on Chapter 6 - Software Engineering:"— Presentation transcript:

1 1 System Engineering based on Chapter 6 - Software Engineering: A Practitioner’s Approach, 6/e System Engineering based on Chapter 6 - Software Engineering: A Practitioner’s Approach, 6/e copyright © 1996, 2001, 2005 R.S. Pressman & Associates, Inc. For University Use Only May be reproduced ONLY for student use at the university level when used in conjunction with Software Engineering: A Practitioner's Approach. Any other reproduction or use is expressly prohibited.

2 2 Waterfall model 1 [aka Royce1970] Systems Engineering Software Req. Analysis Project Planning Design Implementation Testing/Verification Release Operation/Maintenance

3 3 System Engineering Elements of a computer-based system Elements of a computer-based system Software Software Hardware Hardware People People Database Database Documentation Documentation Procedures Procedures Systems Systems A hierarchy of macro-elements A hierarchy of macro-elements

4 4 Business Process (Re-)Engineering  to identify how information systems can best meet the strategic goals of an enterprise, using an integrated set of procedures, methods, and tools, given a set of business rules and constraints.  focuses first on the enterprise and then on the business area  creates enterprise models, data models and process models (processes/services and interrelationships of processes and data)  creates a framework for better information management, distribution, and control

5 5 System Architectures Three different architectures must be analyzed and designed within the context of business objectives and goals: Three different architectures must be analyzed and designed within the context of business objectives and goals: data architecture provides a framework for the information needs of a business or business function (e.g., incident location, patient status, ambulance location, drivers’ lunch hours and break, hospital locations, etc.) data architecture provides a framework for the information needs of a business or business function (e.g., incident location, patient status, ambulance location, drivers’ lunch hours and break, hospital locations, etc.) application architecture encompasses those elements of a system that transform objects within the data architecture for some business purpose application architecture encompasses those elements of a system that transform objects within the data architecture for some business purpose (e.g., determine ambulance availability, determine hospital availability, etc.) technology infrastructure provides the foundation for the data and application architectures (e.g., communication lines, computer platforms, etc.) technology infrastructure provides the foundation for the data and application architectures (e.g., communication lines, computer platforms, etc.)

6 6 System Modeling with UML Deployment diagrams Deployment diagrams Each 3-D box depicts a hardware element that is part of the physical architecture of the system Each 3-D box depicts a hardware element that is part of the physical architecture of the system Activity diagrams Activity diagrams Represent procedural aspects of a system element Represent procedural aspects of a system element Class diagrams Class diagrams Represent system level elements in terms of the data that describe the element and the operations that manipulate the data Represent system level elements in terms of the data that describe the element and the operations that manipulate the data

7 7 Skip – Self Reading Possibly One Lecture on UML

8 8 Conveyor Line Sorting System (CLSS) CLSS must be developed such that boxes moving along a conveyor line will be identified and sorted into one of six bins at the end of the line. The boxes will pass by a sorting station where they will be identified. Based on an identification number printed on the side of the box and a bar code, the boxes will be shunted into the appropriate bins. Boxes pass in random order and are evenly spaced. The line is moving slowly. A desk-top computer located at the sorting station executes all CLSS software, interacts with the bar-code reader to read part numbers on each box, interacts with the conveyor line monitoring equipment to acquire conveyor line speed, stores all part numbers sorted, interacts with a sorting station operator to produce a variety of reports and diagnostics, sends control signals to the shunting hardware to sort the boxes, and communicates with a central factory automation system.

9 9 Deployment Diagram

10 10 Activity Diagram

11 11 Class Diagram

12 12 Requirements Engineering based on Chapter 7 - Software Engineering: A Practitioner’s Approach, 6/e Requirements Engineering based on Chapter 7 - Software Engineering: A Practitioner’s Approach, 6/e copyright © 1996, 2001, 2005 R.S. Pressman & Associates, Inc. For University Use Only May be reproduced ONLY for student use at the university level when used in conjunction with Software Engineering: A Practitioner's Approach. Any other reproduction or use is expressly prohibited.

13 13 Requirements Engineering Process: A Basic Framework [Loucopolos] Many variations and extensions  3 fundamental activities: understand, (formally) describe, attain an agreement on, the problem User Problem Domain ElicitationSpecificationValidation Elicitation: determine what ’ s really needed, why needed, whom to talk to Elicitation: determine what ’ s really needed, why needed, whom to talk to Specification: produce a (formal) RS model: translate "vague" into "concrete", etc. make various decisions on what & how Specification: produce a (formal) RS model: translate "vague" into "concrete", etc. make various decisions on what & how Validation: assure that the RS model satisfies the users ’ needs Validation: assure that the RS model satisfies the users ’ needs Domain knowledge User reqs User feedback Req. models Val. result knowledge For more knowledge (domain experts, laws, standards, policies, documents, etc.)

14 14 Requirements Engineering Elicitation - Inception—ask a set of questions that establish … Elicitation - Inception—ask a set of questions that establish … (basic) understanding of the problem (basic) understanding of the problem the people who want a solution the people who want a solution the nature of the solution that is desired, and the nature of the solution that is desired, and the effectiveness of preliminary communication and collaboration between the customer and the developer the effectiveness of preliminary communication and collaboration between the customer and the developer Specification — can be any one (or more) of the following: Specification — can be any one (or more) of the following: A written document A written document A set of models - A formal mathematical? A set of models - A formal mathematical? A collection of user scenarios (use-cases) A collection of user scenarios (use-cases) A prototype A prototype Validation — a review mechanism that looks for Validation — a review mechanism that looks for errors in content or interpretation errors in content or interpretation areas where clarification may be required areas where clarification may be required missing information missing information inconsistencies (a major problem when large products or systems are engineered) inconsistencies (a major problem when large products or systems are engineered) conflicting or unrealistic (unachievable) requirements. conflicting or unrealistic (unachievable) requirements.

15 15 Eliciting Requirements - Inception Identify (key) stakeholders Identify (key) stakeholders These are the people who will be involved in the negotiation These are the people who will be involved in the negotiation “who else do you think I should talk to?” “who else do you think I should talk to?” Recognize multiple points of view Recognize multiple points of view Work toward collaboration Work toward collaboration The first questions The first questions Who is behind the request for this work? Who is behind the request for this work? Who will use the solution? Who will use the solution? What will be the (economic) benefit of a successful solution What will be the (economic) benefit of a successful solution Is there another source for the solution that you need? Is there another source for the solution that you need?

16 16 Eliciting Requirements meetings are conducted and attended by both software engineers and customers meetings are conducted and attended by both software engineers and customers rules for preparation and participation are established rules for preparation and participation are established an agenda is suggested an agenda is suggested a "facilitator" (can be a customer, a developer, or an outsider) controls the meeting a "facilitator" (can be a customer, a developer, or an outsider) controls the meeting a "definition mechanism" (can be work sheets, flip charts, or wall stickers or an electronic bulletin board, chat room or virtual forum) is used a "definition mechanism" (can be work sheets, flip charts, or wall stickers or an electronic bulletin board, chat room or virtual forum) is used the goal is the goal is to identify the problem to identify the problem propose elements of the solution propose elements of the solution negotiate different approaches, and negotiate different approaches, and specify a preliminary set of solution requirements specify a preliminary set of solution requirements

17 17 Elicitation Work Products a statement of need, scope, and feasibility. a statement of need, scope, and feasibility. a list of customers, users, and other stakeholders who participated in requirements elicitation a list of customers, users, and other stakeholders who participated in requirements elicitation a description of the system’s technical environment (cf. enterprise model in system engineering). a description of the system’s technical environment (cf. enterprise model in system engineering). a list of requirements (preferably organized by function) and the domain constraints that apply to each. a list of requirements (preferably organized by function) and the domain constraints that apply to each. a set of usage scenarios that provide insight into the use of the system or product under different operating conditions. a set of usage scenarios that provide insight into the use of the system or product under different operating conditions. any prototypesdeveloped to better define requirements any prototypes developed to better define requirements.

18 18 Building the Analysis Model Elements of the analysis model Elements of the analysis model Scenario-based elements Scenario-based elements Functional—processing narratives for software functions Functional—processing narratives for software functions Use-case—descriptions of the interaction between an “actor” and the system Use-case—descriptions of the interaction between an “actor” and the system Class-based elements Class-based elements Implied by scenarios Implied by scenarios Behavioral elements Behavioral elements State diagram State diagram Flow-oriented elements Flow-oriented elements Data flow diagram Data flow diagram

19 19 Skip – Self Reading Possibly One Lecture on UML

20 20Use-Cases A collection of user scenarios that describe the thread of usage of a system A collection of user scenarios that describe the thread of usage of a system Each scenario is described from the point-of-view of an “actor”—a person or device that interacts with the software in some way Each scenario is described from the point-of-view of an “actor”—a person or device that interacts with the software in some way Each scenario answers the following questions: Each scenario answers the following questions: Who is the primary actor, the secondary actor (s)? Who is the primary actor, the secondary actor (s)? What are the actor’s goals? What are the actor’s goals? What preconditions should exist before the story begins? What preconditions should exist before the story begins? What main tasks or functions are performed by the actor? What main tasks or functions are performed by the actor? What extensions might be considered as the story is described? What extensions might be considered as the story is described? What variations in the actor’s interaction are possible? What variations in the actor’s interaction are possible? What system information will the actor acquire, produce, or change? What system information will the actor acquire, produce, or change? Will the actor have to inform the system about changes in the external environment? Will the actor have to inform the system about changes in the external environment? What information does the actor desire from the system? What information does the actor desire from the system? Does the actor wish to be informed about unexpected changes? Does the actor wish to be informed about unexpected changes?

21 21 Use-Case Diagram

22 22 Class Diagram From the SafeHome system …

23 23 State Diagram

24 24 Validating Requirements Is each requirement consistent with the overall objective for the system/product? Is each requirement consistent with the overall objective for the system/product? Have all requirements been specified at the proper level of abstraction? That is, do some requirements provide a level of technical detail that is inappropriate at this stage? Have all requirements been specified at the proper level of abstraction? That is, do some requirements provide a level of technical detail that is inappropriate at this stage? Is the requirement really necessary or does it represent an add-on feature that may not be essential to the objective of the system? Is the requirement really necessary or does it represent an add-on feature that may not be essential to the objective of the system? Is each requirement bounded and unambiguous? Is each requirement bounded and unambiguous? Does each requirement have attribution? That is, is a source (generally, a specific individual) noted for each requirement? Does each requirement have attribution? That is, is a source (generally, a specific individual) noted for each requirement? Do any requirements conflict with other requirements? Do any requirements conflict with other requirements? Is each requirement achievable in the technical environment that will house the system or product? Is each requirement achievable in the technical environment that will house the system or product? Is each requirement testable, once implemented? Is each requirement testable, once implemented? Does the requirements model properly reflect the information, function and behavior of the system to be built. Does the requirements model properly reflect the information, function and behavior of the system to be built.


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