Hệ thống UML potx

www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons
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Requirements Engineering
From System Goals
to UML Models
to Software Specifications
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www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons
What is requirements engineering ?

Set of activities producing the requirements on a software-
intensive system
– elicitation, evaluation, specification, analysis,
evolution management
–
system objectives, functionalities, target qualities,
constraints, assumptions

Requirements quality assurance
Requirements quality assurance is a key concern for software
quality assurance
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www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons
Requirements engineering (RE), roughly

Identify & analyze problems with an existing system
(system-
as-is
as-is),

Identify & evaluate objectives, opportunities, options for

new system (system-
to-be
to-be),

Identify & define functionalities of, constraints on,
responsibilities in system-to-be,

Specify & organize all of these in a
requirements document
requirements document

to be maintained throughout system evolution
System = software + environment
(people, devices, other software)
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www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons
Example:
transportation between airport terminals

Problem (system-
as-is
as-is):
–
passengers frequently missing flight connections among
different terminals; slow & inconvenient transportation
–
number of passengers regularly increasing

Objectives, options (system-
to-be

to-be):
–
support high-frequency trains between terminals
– with

or
or

without train drivers ?

Functionalities, constraints:
–
software-based control of train accelerations, doors opening
etc. to achieve
prompt
and
safe
transportation

RE deliverable: requirements document

for system-to-be
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www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons
Requirements in the software lifecycle
Requirements engineering
Software design
Software implementation
Software evolution
Getting

the
right
right

system
system
Getting
the
software
software
right
right
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www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons
Why requirements engineering ?

RE is critical
– Major cause of software failure
Requirements-related 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
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www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons
What makes RE hard ?


Broad scope
– multiple system versions:
as-is
,
to-be, to-be-next
– hybrid environment:
human organizations, policies, regulations
devices, physical laws

Multiple concerns
– functional, quality, development concerns

Multiple abstraction levels
– strategic objectives, operational details
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www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons
What makes RE hard ? (2)

Multiple stakeholders
– with different background
– with different interests and conflicting viewpoints

Multiple intertwined tasks during iterative
elicitation-evaluation-specification-consolidation
– conflict management
– risk management
– evaluation of alternatives, prioritization
– quality assurance
– change anticipation

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www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons
Model-based RE

Model:
– abstract representation of system (
as-is
or
to-be
)
– highlights, specifies, inter-relates key system features

Multi-view
Multi-view model:
– different system facets for requirements completeness
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www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons
Why models for RE ?

Focus on
key aspects
key aspects (abstraction from multiple details)

Provides
structure
structure for RE activities
– target for what must be elicited, evaluated, specified,
consolidated, modified
– interface among RE activities: produce/consume model items


Facilitates
analysis
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
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www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons
Learning RE: objectives

Get a
sound
sound,
precise
precise understanding of concepts, principles,
processes, and products involved in RE

Master state-of-the art
techniques
techniques for requirements
elicitation, evaluation, specification, analysis, evolution

Be able to construct, analyze and exploit high-quality models
for RE in a
systematic

systematic way

Gain
practical
practical experience in applying techniques in concrete,
realistic situations
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www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons
Book support
Requirements Engineering:
From System Goals
to UML Models
to Software Specifications
Axel van Lamsweerde
Wiley,
Jan. 2009
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www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons
Some features, risks & challenges of RE
unsuccessful
project
unrealizable
Achieve
goal
Maintain

goal
multi-language
specs
multiple

stakeholders
model
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www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons

Concentrates on solid, replicable RE
techniques
techniques
– far beyond high-level principles & guidelines

Emphasizes model
construction
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
Approach taken in the book
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www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons
The book has three parts

Part 1: Fundamentals of RE

Part 2: Building models for RE

Part 3: Analyzing and exploiting RE models
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www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons
Part 1:
Fundamentals of Requirements Engineering

Setting the scene:
basic concepts
basic concepts & principles

Domain understanding & requirements
elicitation
elicitation

Requirements
evaluation
evaluation
–
Conflict management, risk analysis, evaluating alternative options,
requirements prioritization

Requirements
specification
specification and
documentation
documentation
–
Structured natural language, use of diagrammatic notations, formal
specification

Requirements
quality assurance

quality assurance
– Inspections & reviews, requirements database queries, specification
animation, formal verification

Requirements
evolution
evolution
–
Change anticipation, traceability management, change control

Goal-orientation
Goal-orientation in RE
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www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons
Part 2:
Building system models for RE

Modeling system
objectives
objectives with goal diagrams

Risk
Risk analysis on goal models

Modeling
conceptual objects
conceptual objects with class diagrams

Modeling system
agents

agents and responsibilities

Modeling system
operations
operations

Modeling system
behaviors
behaviors: scenarios and state machines

Integrating multiple system views

A goal-oriented
model building method
model building method in action
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www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons
Part 3
Reasoning about system models

Semi-formal reasoning for model analysis & exploitation
–
Query-based analysis of the model database
– Analysis of conflicts, obstacles, and security threats
–
Qualitative & quantitative reasoning about alternatives
–
Model-driven generation of the requirements document
– From goal-oriented requirements to software architecture


Formal specification of system models
– A real-time 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 anti-goals; analyzing conflicts
–
Synthesizing behavior models
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www.wileyeurope .com/college/van lamsweerde Requirements Engineering © 2009 John Wiley and Sons
Additional resources
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


Objectiver tool for building & playing with models
–
Free limited access for educational use