Transcript CS425/CS625     List of classes for the banking system Groups for projects Software development process Assignment 1 • • • • Computer Science Due Sept 11, 2001 Individual AND group portions Requirements for.

CS425/CS625
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List of classes for the banking system
Groups for projects
Software development process
Assignment 1
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Computer Science
Due Sept 11, 2001
Individual AND group portions
Requirements for Galaxy Sleuth – Questions (group)
Informal scenarios – group and individual
Software Engineering
Slide 1
Groups
Paul Simmerlink
Stephen Herbert
Daniel Coming
Ogechi Ugwulebo
James King
Jigna J. Bhatt
Brett Harrison
Jonathan Ward
Michael Vidal
Howard C. Wu
Don Miller
James Frye
David Brewer
Olja Mihic
Casey Mees
Maggie Lu
Reid Webber
Taisuke Nagayama
Jeff Payne
Matasaka Sako
Casey J. Powell
Shana Rheault
RichardD.VanHorn
Rodel Mangoba
Steve Luong
Jason Dodd
Beifang Yi
Dorothy P. Cheung
William Nelson
Will Woolsey
Andrew Rodgers
James Cohen, Judy Rowley, Stan Sexton, Rajashekhar Yakkali,
Kazuhito Mori
Computer Science
Software Engineering
Slide 2
Engineering and Administration
Computer Science
Software Engineering
Slide 3
Informal Scenarios
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Help understand the problem
Come up with questions on requirements
Help constrain architecture
Computer Science
Software Engineering
Slide 4
Informal Scenarios - Guidelines
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Large number of small informal scenarios – short
scenarios
An informal scenario should address one coherent aspect
of the system (logon, make a move, …)
Should specify concrete values
Address some errors
Implementation details must not be in informal scenario
Each informal scenario should have the form:
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Computer Science
System state at start
Informal scenario
Next informal scenario in sequence
Software Engineering
Slide 5
Sample: User makes a move
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Current system state: The system state consists of each
player at his or her starting location on the game board.
The 3 players in the game, Andrea, Max, and Emma have
each been dealt six cards (evidence). Value of cards is
irrelevant to this scenario
Informal Scenario: Andrea has the next move. She spins
the spinner which lands on the number 5. Andrea has the
white playing piece. She moves this piece one space to
the left, one space toward the top, two spaces to the right,
and finally, one space to the top. Because of the final
position of the game piece, Andrea has not additional
option and her turn ends.
Next scenario: The player to the left of Andrea goes next,
Max goes next
Computer Science
Software Engineering
Slide 6
Software Processes
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Coherent sets of activities for
specifying, designing, implementing
and testing software systems
Computer Science
Software Engineering
Slide 7
Objectives
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To introduce software process models
To describe a number of different process models
and when they may be used
To describe process models for requirements
engineering, software development, testing and
evolution
Computer Science
Software Engineering
Slide 8
Topics covered
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Software process models
Process iteration
Software specification
Software design and implementation
Software validation
Software evolution
Automated process support
Computer Science
Software Engineering
Slide 9
The software process
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A structured set of activities required to develop a
software system
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Specification
Design
Validation
Evolution
A software process model is an abstract
representation of a process. It presents a
description of a process from some particular
perspective
Computer Science
Software Engineering
Slide 10
Generic software process models
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The waterfall model
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Evolutionary development
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Specification and development are interleaved
Formal systems development
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Separate and distinct phases of specification and development
A mathematical system model is formally transformed to an
implementation
Reuse-based development
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Computer Science
The system is assembled from existing components
Software Engineering
Slide 11
Waterfall model
Requirements
definition
System and
software design
Implementation
and unit testing
Integr ation and
system testing
Operation and
maintenance
Computer Science
Software Engineering
Slide 12
Waterfall model phases
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Requirements analysis and definition
System and software design
Implementation and unit testing
Integration and system testing
Operation and maintenance
The drawback of the waterfall model is the
difficulty of accommodating change after the
process is underway
Computer Science
Software Engineering
Slide 13
Waterfall model problems
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Inflexible partitioning of the project into distinct
stages
This makes it difficult to respond to changing
customer requirements
Therefore, this model is only appropriate when
the requirements are well-understood
Computer Science
Software Engineering
Slide 14
Evolutionary development
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Exploratory development
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Objective is to work with customers and to evolve a final
system from an initial outline specification. Should start with
well-understood requirements
Throw-away prototyping
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Computer Science
Objective is to understand the system requirements. Should start
with poorly understood requirements
Software Engineering
Slide 15
Evolutionary development
Concurr ent
activities
Outline
description
Computer Science
Specification
Initial
version
Development
Intermediate
versions
Validation
Final
version
Software Engineering
Slide 16
Evolutionary development
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Problems
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Lack of process visibility
Systems are often poorly structured
Special skills (e.g. in languages for rapid prototyping) may be
required
Applicability
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Computer Science
For small or medium-size interactive systems
For parts of large systems (e.g. the user interface)
For short-lifetime systems
Software Engineering
Slide 17
Formal systems development
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Based on the transformation of a mathematical
specification through different representations to
an executable program
Transformations are ‘correctness-preserving’ so it
is straightforward to show that the program
conforms to its specification
Embodied in the ‘Cleanroom’ approach to
software development
Computer Science
Software Engineering
Slide 18
Formal systems development
Requirements
definition
Computer Science
Formal
specification
Software Engineering
Integration and
system testing
Formal
transformation
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Formal transformations
Formal transformations
T1
Formal
specification
T2
R1
P1
T3
R2
P2
T4
P3
P4
Proofs of transformation correctness
Computer Science
Software Engineering
Executable
program
R3
Slide 20
Formal systems development
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Problems
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Need for specialised skills and training to apply the technique
Difficult to formally specify some aspects of the system such as
the user interface
Applicability
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Computer Science
Critical systems especially those where a safety or security case
must be made before the system is put into operation
Software Engineering
Slide 21
Reuse-oriented development
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Based on systematic reuse where systems are
integrated from existing components or COTS
(Commercial-off-the-shelf) systems
Process stages
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Component analysis
Requirements modification
System design with reuse
Development and integration
This approach is becoming more important but
still limited experience with it
Computer Science
Software Engineering
Slide 22
Reuse-oriented development
Requirements
specification
Component
analysis
Requirements
modification
System design
with reuse
Development
and integration
Computer Science
Software Engineering
Slide 23
System
validation
Process iteration
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System requirements ALWAYS evolve in the
course of a project so process iteration where
earlier stages are reworked is always part of the
process for large systems
Iteration can be applied to any of the generic
process models
Two (related) approaches
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Incremental development
Spiral development
Computer Science
Software Engineering
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Incremental development
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Rather than deliver the system as a single
delivery, the development and delivery is broken
down into increments with each increment
delivering part of the required functionality
User requirements are prioritised and the highest
priority requirements are included in early
increments
Once the development of an increment is started,
the requirements are frozen though requirements
for later increments can continue to evolve
Computer Science
Software Engineering
Slide 25
Incremental development
Define outline
requirements
Develop system
increment
Assign requirements
to increments
Valida te
increment
Design system
architecture
Integrate
increment
Valida te
system
Final
system
System incomplete
Computer Science
Software Engineering
Slide 26
Incremental development advantages
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Customer value can be delivered with each
increment so system functionality is available
earlier
Early increments act as a prototype to help elicit
requirements for later increments
Lower risk of overall project failure
The highest priority system services tend to
receive the most testing
Computer Science
Software Engineering
Slide 27
Extreme programming
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New approach to development based on the
development and delivery of very small
increments of functionality
Relies on constant code improvement, user
involvement in the development team and
pairwise programming
Computer Science
Software Engineering
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Spiral development
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Process is represented as a spiral rather than as a
sequence of activities with backtracking
Each loop in the spiral represents a phase in the
process.
No fixed phases such as specification or design loops in the spiral are chosen depending on what
is required
Risks are explicitly assessed and resolved
throughout the process
Computer Science
Software Engineering
Slide 29
Spiral model of the software process
Determine objectives
alternatives and
constraints
Risk
analysis
Evaluate alternatives
identify, resolve risks
Risk
analysis
Risk
analysis
REVIEW
Requirements plan
Life-cycle plan
Development
plan
Plan next phase
Computer Science
Integration
and test plan
Prototype 3
Prototype 2
Risk
a nayl sis Prototype 1
Operational
protoype
Simulations, models, benchmarks
Concept of
Operation
S/W
requirements
Requirement
validation
Product
design
Detailed
design
Code
Unit test
Design
V&V
Integr ation
test
Acceptance
test
Develop, verify
Service
next-level product
Software Engineering
Slide 30
Spiral model sectors
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Objective setting
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Risk assessment and reduction
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Risks are assessed and activities put in place to reduce the key
risks
Development and validation
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Specific objectives for the phase are identified
A development model for the system is chosen which can be
any of the generic models
Planning
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Computer Science
The project is reviewed and the next phase of the spiral is
planned
Software Engineering
Slide 31
Software specification
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The process of establishing what services are
required and the constraints on the system’s
operation and development
Requirements engineering process
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Computer Science
Feasibility study
Requirements elicitation and analysis
Requirements specification
Requirements validation
Software Engineering
Slide 32
The requirements engineering process
Feasibility
study
Requirements
elicitation and
analysis
Requir ements
specification
Feasibility
report
Requirements
validation
System
models
User and system
requirements
Requirements
document
Computer Science
Software Engineering
Slide 33
Software design and implementation
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The process of converting the system
specification into an executable system
Software design
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Implementation
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Design a software structure that realises the specification
Translate this structure into an executable program
The activities of design and implementation are
closely related and may be inter-leaved
Computer Science
Software Engineering
Slide 34
Design process activities
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Architectural design
Abstract specification
Interface design
Component design
Data structure design
Algorithm design
Computer Science
Software Engineering
Slide 35
The software design process
Re quire me nts
spec if ication
Design a cti
vitie s
Arc hitec tura l
design
Abstra ct
spec if ication
Inte rf ac e
design
Com ponent
design
Data
structure
design
Algor ithm
design
System
a rc hitec ture
Softwa re
spec if ication
Inte rf ac e
spec if ica
tion
Com ponent
spec if ication
Data
structure
spec if ication
Algor ithm
spec if ica
tion
Design pr
oducts
Computer Science
Software Engineering
Slide 36
Design methods
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Systematic approaches to developing a software
design
The design is usually documented as a set of
graphical models
Possible models
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Computer Science
Data-flow model
Entity-relation-attribute model
Structural model
Object models
Software Engineering
Slide 37
Programming and debugging
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Translating a design into a program and removing
errors from that program
Programming is a personal activity - there is no
generic programming process
Programmers carry out some program testing to
discover faults in the program and remove these
faults in the debugging process
Computer Science
Software Engineering
Slide 38
The debugging process
Locate
error
Computer Science
Design
error repair
Software Engineering
Repair
error
Re-test
program
Slide 39
Software validation
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Verification and validation is intended to show
that a system conforms to its specification and
meets the requirements of the system customer
Involves checking and review processes and
system testing
System testing involves executing the system
with test cases that are derived from the
specification of the real data to be processed by
the system
Computer Science
Software Engineering
Slide 40
The testing process
Unit
testing
Module
testing
Sub-system
testing
System
testing
Acceptance
testing
Component
testing
Computer Science
Integration testing
Software Engineering
User
testing
Slide 41
Testing stages
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Unit testing
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Module testing
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Modules are integrated into sub-systems and tested. The focus here
should be on interface testing
System testing
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Related collections of dependent components are tested
Sub-system testing
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Individual components are tested
Testing of the system as a whole. Testing of emergent properties
Acceptance testing
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Computer Science
Testing with customer data to check that it is acceptable
Software Engineering
Slide 42
Testing phases
Requir ements
specification
System
specification
System
integration
test plan
Acceptance
test plan
Service
Computer Science
System
design
Acceptance
test
Detailed
design
Sub-system
integration
test plan
System
integration test
Software Engineering
Module and
unit code
and tess
Sub-system
integration test
Slide 43
Software evolution
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Software is inherently flexible and can change.
As requirements change through changing
business circumstances, the software that
supports the business must also evolve and
change
Although there has been a demarcation between
development and evolution (maintenance) this is
increasingly irrelevant as fewer and fewer
systems are completely new
Computer Science
Software Engineering
Slide 44
System evolution
Define system
requirements
Assess existing
systems
Modify
systems
Propose system
changes
Existing
systems
Computer Science
New
system
Software Engineering
Slide 45
Automated process support (CASE)
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Computer-aided software engineering (CASE) is
software to support software development and
evolution processes
Activity automation
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Computer Science
Graphical editors for system model development
Data dictionary to manage design entities
Graphical UI builder for user interface construction
Debuggers to support program fault finding
Automated translators to generate new versions of a program
Software Engineering
Slide 46
Case technology
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Case technology has led to significant
improvements in the software process though not
the order of magnitude improvements that were
once predicted
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Computer Science
Software engineering requires creative thought - this is not
readily automatable
Software engineering is a team activity and, for large projects,
much time is spent in team interactions. CASE technology does
not really support these
Software Engineering
Slide 47
CASE classification
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Classification helps us understand the different types of
CASE tools and their support for process activities
Functional perspective
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Process perspective
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Tools are classified according to their specific function
Tools are classified according to process activities that are supported
Integration perspective
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Computer Science
Tools are classified according to their organisation into integrated units
Software Engineering
Slide 48
Functional tool classification
Tool type
Planning tools
Editing tools
Change ma nagement tools
Configuration management tools
Prototyping tools
Method-support tools
Language-processing tools
Program analysis tools
Testing tools
Debugging tools
Documentation tools
Re-engineering tools
Computer Science
Examples
PERT tools, estimation tools,
spreadsheets
Text editors, diagram editors, word
processors
Requirements traceability tools, change
control systems
Version management systems , system
building tools
Very high-level languages,
user interface generators
Design editors, data dictionaries, code
generators
Compilers, interpreters
Cross reference generators, static
analysers, dynamic analysers
Test data generators, file comp arators
Interactive debugging systems
Page layout programs , ima ge editors
Cross-reference systems , program restructuring systems
Software Engineering
Slide 49
Reengineering tools
Testing tools
Debugging tools
Program analysis tools
Language-processing
tools
Method support tools
Prototyping tools
Configuration
management tools
Change management tools
Documentation tools
Editing tools
Planning tools
Specification
Design
Activity-based classification
Implementation
Verification
and
Validation
CASE integration
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Tools
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Workbenches
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Support individual process tasks such as design consistency
checking, text editing, etc.
Support a process phase such as specification or design,
Normally include a number of integrated tools
Environments
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Computer Science
Support all or a substantial part of an entire software process.
Normally include several integrated workbenches
Software Engineering
Slide 51
Tools, workbenches, environments
CASE
technology
Tools
Editors
Compilers
Workbenches
File
comparators
Analysis and
design
Multi-method
workbenches
Computer Science
Integrated
environments
Programming
Single-method
workbenches
Software Engineering
Environments
Process-centred
environments
Testing
General-purpose
workbenches
Language-specific
workbenches
Slide 52
Key points
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Software processes are the activities involved in
producing and evolving a software system. They
are represented in a software process model
General activities are specification, design and
implementation, validation and evolution
Generic process models describe the organisation
of software processes
Iterative process models describe the software
process as a cycle of activities
Computer Science
Software Engineering
Slide 53
Key points
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Requirements engineering is the process of developing a
software specification
Design and implementation processes transform the
specification to an executable program
Validation involves checking that the system meets to its
specification and user needs
Evolution is concerned with modifying the system after it
is in use
CASE technology supports software process activities
Computer Science
Software Engineering
Slide 54