Hệ thống UML

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Requirementsrelated errors are the most numerous, persistent, expensive, dangerous...

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Requirements Engineering From System Goals to UML Models to Software Specifications www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons 1
What is requirements engineering ? Set of activities producing the requirements on a softwareintensive system  – elicitation, evaluation, specification, analysis, evolution management – system objectives, functionalities, target qualities, constraints, assumptions Requirements quality assurance is a key concern for software quality assurance  www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons 2
Requirements engineering (RE), roughly ... Identify & analyze problems with an existing system  (systemas-is), Identify & evaluate objectives, opportunities, options for new system (system  tobe), Identify & define functionalities of, constraints on, responsibilities in system  tobe, Specify & organize all of these in a requirements document to be maintained  throughout system evolution System = software + environment (people, devices, other software) www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons 3
Example: transportation between airport terminals Problem (systemasis):  – passengers frequently missing flight connections among different terminals; slow & inconvenient transportation – number of passengers regularly increasing Objectives, options (systemtobe):  – support highfrequency trains between terminals – with or without train drivers ? Functionalities, constraints:  – softwarebased control of train accelerations, doors opening etc. to achieve prompt and safe transportation RE deliverable: requirements document for systemtobe  www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons 4
Requirements in the software lifecycle Getting the Requirements engineering right system Software design Getting the software Software implementation right Software evolution www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons 5
Why requirements engineering ? RE is critical  – Major cause of software failure Requirementsrelated errors are the most numerous, persistent, expensive, dangerous – Severe consequences: cost overruns, delivery delays, dissatisfaction, degradations, accidents, ... – RE has multiple impact: legal, social, economical, technical – Certification issues RE is hard  www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons 6
What makes RE hard ? Broad scope  – multiple system versions: asis, tobe, tobenext – hybrid environment: human organizations, policies, regulations devices, physical laws Multiple concerns  – functional, quality, development concerns Multiple abstraction levels  – strategic objectives, operational details www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons 7
What makes RE hard ? (2) Multiple stakeholders  – with different background – with different interests and conflicting viewpoints Multiple intertwined tasks during iterative  elicitationevaluationspecificationconsolidation – conflict management – risk management – evaluation of alternatives, prioritization – quality assurance – change anticipation www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons 8
Modelbased RE Model:  – abstract representation of system (asis or tobe) – highlights, specifies, interrelates key system features Multiview model:  – different system facets for requirements completeness www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons 9
Why models for RE ? Focus on key aspects (abstraction from multiple details)  Provides structure for RE activities  – target for what must be elicited, evaluated, specified, consolidated, modified – interface among RE activities: produce/consume model items Facilitates analysis  – support for early detection and fix of errors Support for understanding, explanation to stakeholders  Basis for making decisions  – multiple options made explicit Basis for generating the requirements document  www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons 10
Learning RE: objectives Get a sound, precise understanding of concepts, principles, processes, and  products involved in RE Master stateofthe art techniques for requirements elicitation, evaluation,  specification, analysis, evolution Be able to construct, analyze and exploit highquality models for RE in a  systematic way Gain practical experience in applying techniques in concrete, realistic situations  www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons 11
Book support Requirements Engineering: From System Goals to UML Models to Software Specifications Axel van Lamsweerde Wiley, Jan. 2009 www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons 12
Some features, risks & challenges of RE ... unsuccessful unrealizable project Achieve goal Maintain goal model multilanguage multiple specs stakeholders www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons 13
Approach taken in the book Concentrates on solid, replicable RE techniques  – far beyond highlevel principles & guidelines Emphasizes model construction (beyond mere use of diagrammatic notations)  – procedures, heuristic rules, tactics, modeling patterns, bad smells – UML compliance wherever possible Based on case studies in a variety of domains  www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons 14
The book has three parts Part 1: Fundamentals of RE  Part 2: Building models for RE  Part 3: Analyzing and exploiting RE models  www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons 15
Part 1: Fundamentals of Requirements Engineering Setting the scene: basic concepts & principles  Domain understanding & requirements elicitation  Requirements evaluation  – Conflict management, risk analysis, evaluating alternative options, requirements prioritization Requirements specification and documentation  – Structured natural language, use of diagrammatic notations, formal specification Requirements quality assurance  – Inspections & reviews, requirements database queries, specification animation, formal verification Requirements evolution  – Change anticipation, traceability management, change control Goalorientation in RE  www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons 16
Part 2: Building system models for RE Modeling system objectives with goal diagrams  Risk analysis on goal models  Modeling conceptual objects with class diagrams  Modeling system agents and responsibilities  Modeling system operations  Modeling system behaviors: scenarios and state machines  Integrating multiple system views  A goaloriented model building method in action  www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons 17
Part 3 Reasoning about system models Semiformal reasoning for model analysis & exploitation  – Querybased analysis of the model database – Analysis of conflicts, obstacles, and security threats – Qualitative & quantitative reasoning about alternatives – Modeldriven generation of the requirements document – From goaloriented requirements to software architecture Formal specification of system models  – A realtime temporal logic for specifying model annotations – Specifying goals, domain properties, and operationalizations Formal reasoning for specification construction & analysis  – Checking goal refinements; deriving operationalizations – Generating obstacles and antigoals; analyzing conflicts – Synthesizing behavior models www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons 18
Additional resources http://www.wileyeurope.com/college/van lamsweerde Course slides  More case studies & examples  Requirements document generated from model built in Chap. 15  Instructor’s protocol for obtaining solutions to exercises  Book figures  http://www.objectiver.com Objectiver tool for building & playing with models  – Free limited access for educational use www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons 19