Software development processes

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Software development processes

• People
• Products
• Processes Life-cycle models
• Traceability

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Software development
People
Processes
Products
3
The players

• Senior managers define business issues
• Technical managers Plan, motivate, organize,
  control developers
• Developers (Practitioners) Engineer product
• Customer Specifies requirements
• End users Use the product

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Three engineering vice presidents

• I guess if you had to pick one thing out that is
  most important in our environment. Id say its
  not the tools that we use, its the people
• The most important ingredient that was
  successful on the project was having smart
  people....very little else matters in my opinion
• The only rule I have in management is to ensure
  I have good people - real good people - and that
  I grow good people

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What are companies looking for?

• Problem solving skills
• Being able to work in all phases
• Soft skills
• communication
• teamwork
• motivation to be productive
• project management
• Technical skills
• OO technology
• Databases
• Conceptual design

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Software development processes

• People
• Products
• Processes Life-cycle models
• Traceability

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Which product or lifecycle model?

• There exist many lifecycle models that differ in
• number / type of the resulting physical products
  (documents)
• number / type / coordination of the steps of
  development

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Product reference model

• Overlap of product models between different
  life-cycle modelsa logical model of software
  products is the base of a reference model for
  software development

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V - model for documentation of large software
products
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Problem description

• Which problems exist for the customer?
• Which of those shall be solved by the software
  system?
• Problems in problem descriptions
• Not precise - Incomplete
• Ambiguous - Superficial
• Redundant - Not on target

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System requirements

• Based on problem description .... and
  communication with customer
• What functional and non-functional
  characteristics are expected from the software
  system?
• What Black box description
• User requirements describes system requirements
  from the users perspective
• Developer requirements describes system
  requirements from the developers perspective
  (contract!)

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System design

• Describes the structure of the system that
  fulfills given developer requirements
• components
• component interfaces
• component requirements
• How White box description
• Component requirements describes component
  interfaces

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Components design

• Describes the structure of a component that
  fulfills given component requirements
• data structure
• algorithms
• How (Very detailed)

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Components code

• How can a component be realized on a concrete
  execution engine (e.g. Java) ?
• Source code

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Validation of results
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Software products (7)

• X is developed inDeveloped by activities that
  are essential to build the x-code ( construction
  plan for executable x)

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Software products (8)

• X is verified againstVerified by activities
  that are essential to prove the consistence of
  x-code and the related x-requirements

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Software products (9)

• X is integrated inIntegrated by activities
  that are essential to create an executable
  component from the x-code (compiling, binding,
  loading, debugging)

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Software products (10)

• X is validated againstValidated by activities
  that are essential to convince oneself or others
  that the executable component does not contain
  any inconsistencies with the x-requirements

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V - model for documentation of large software
products
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Software development processes

• People
• Products
• Processes Life-cycle models
• Traceability

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Processes are everywhere

• Process connected series of actionsseries
  of operations deliberately undertaken
• A S Hornby Oxford Advanced Learners
  Dictionary of Current English, Oxford University
  Press
• Work processes
• Production processes
• Development processes
• Social processes

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Software engineering layers
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Generic View

• Definition phase What
• Requirements analysis
• Project planning
• Development phase How
• Software design
• Coding
• Testing
• Maintenance

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Umbrella activities

• Software project tracking and control
• Formal technical reviews
• Software quality assurance
• Software configuration management
• Document preparation and production
• Managing software reuse
• Risk management

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Common misconceptions about the software process

• We must start with firm requirements
• The problems are technical
• We need better people
• Software management is different

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The phases of a problem solving loop
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Process model

• Describe development strategy encompassing
• process
• methods
• tools
• Bring order into chaotic activity
• Assist in controlling and coordination of SE
  projects

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The linear sequential model (Waterfall model)
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Linear sequential model (2)

• Systems engineering Software is part of a larger
  system
• Software requirements analysis
• information domain, function, behavior,
  performance, interfacing
• Design
• Code generation (ev. Automatic)
• Testing

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Problems with the linear sequential model

• Real projects rarely follow a sequential flow
• Stating all requirements at the beginning of a
  project is difficult
• Customer must have patience
• Applicable for projects that are well understood

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The prototyping paradigm
build / revise mock-up
listen to customer
customer test-drives mock-up
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Prototyping model (2)

• Only general objectives available
• Being unsure about
• efficiency of an algorithm
• human-computer interaction
• Often used for identifying requirements
• Throw-away prototype (Risk?)
• Fast decisions are not always good decisions!
• Often Code generators, report generators etc.
• fast enough?

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Evolutionary software process models

• Software evolves over time
• Straight path to an end product is unrealistic
• Tight market deadlines
• Deliver limited version
• Core product requirements well understood
• Need for extensions foreseeable

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The incremental model
Increment 1
Increment 2
.
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Incremental model

• Combines elements of the linear model and
  prototyping
• Produces deliverable increments
• First increment often core product
• Focuses on operational product (not throw-away
  prototype)
• Used when not enough resources are available to
  deliver the complete product in time
• Increments help to manage technical risks (e.g.
  currently unavailable hardware)

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Spiral model
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Spiral model (2)

• Customer communication Establish effective
  communication
• Planning Define resources, timelines etc.
• Risk analysis Assess technical and management
  risks
• Construction release construct, test, install,
  provide user support
• Customer evaluation obtain feedback

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Spiral model (3)

• Couples iterative nature of prototyping with
  controlled and systematic aspect of the linear
  sequential model
• Early iterations may be paper models or
  prototypes
• Can be used throughout the life of the product
• Reduces risk if properly applied

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The component assembly model
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Component assembly model (2)

• Object technologies provide technical basis
• Software reuse reliability, cost reduction
• Problems
• Finding components
• Are components reusable?
• Adaptation

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The concurrent development model
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Concurrent development model

• Tasks have states and are carried out in parallel
• Process support system (assignment) supports this
  model
• Assignment is developed following this model

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The formal methods model

• Specify, develop, verify a system by applying a
  rigorous mathematical foundation
• Discovers ambiguity, incompleteness,
  inconsistency by mathematical analysis
• Problems
• Time consuming and expensive
• Education insufficient
• No basis for communication with customer

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Process technology tools allow ...

• to analyze current processes
• to organize work tasks
• to control and monitor progress
• to generate To-Do lists

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Software development processes

• People
• Products
• Processes Life-cycle models
• Traceability

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Changes Happen

• Software is not stable over time
• Correction defect correction
• Adaptation Environment changes
• Enhancement New requirements
• Prevention Overcome deteriorating software
• Software and related documents have to be kept up
  to date

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What is Impact Analysis?

• Software change impact analysis estimates what
  will be affected in software and related
  documentation if a proposed changed is made
  Bohner/Arnold Software Change Impact Analysis,
  Preface, IEEE Computer Society Press, 1996

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Traceability

• Traditionally Impacts are determined by people
  using their heads
• Now Repositories store interdependent software
  artifacts
• Relationships between artifacts are often
  implicit
• Impact analysis makes relationships explicit

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Traceability illustration

• vertical between abstraction levels
• horizontal on abstraction levels

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Examples of impact analysis techniques

• cross-referenced listings to determine parts that
  reference a variable of procedure
• program slicing to determine the subset of a
  program that can affect the value of a variable
• browsing of (hyper linked) files
• using traceability matrixes
• configuration management systems to find and
  track changes
• consulting design and specification documents to
  determine the scope of a change

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Traceability matrix
Req 1 Req 2 Design 1 Design 2 Design 3 Code
1 Code 2 Code 3 Test 1 Test 2
Req 1 1 1 1 Req 2 1 Design 1 1 1 Design
2 1 1 Design 3 Code 1 1 Code
2 Code 3 1 Test 1 Test 2 1