Mod2 by jianghongl


									CSEB233 Fundamentals of
  Software Engineering
 Module 2: Software Processes

                            Badariah Solemon 2010
• To describe types of process flows.
• To explain software process patterns.
• To identify several process
  assessment and improvements
• To analyze prescriptive and
  specialized software process models.
• To select a process model for
  software development project.
• To determine task set for software
  process activities.
                            Badariah Solemon 2010
  A Generic Process Model
• A software process:
    a collection of work activities, actions,
     tasks, which are performed when
     software is to be created.
• A process model or framework
    is where these activities, actions, and
     tasks reside, and that defines their
     relationship with the process and with
     one another.
    Also known as an abstract
     representation of a software process.

                                    Badariah Solemon 2010
    A Generic Process Model (cnt’d)
•   The technical work
    hierarchy – activities
    encompassing actions,
    populated by tasks.
•   Each action is defined by
    a set of task that defines:
     1. the actual work to be
     2. the work products to
        be produced,
     3. the quality assurance
        filters to be applied,
     4. The milestones that will
        be used to indicate the
        project and product

                                   Badariah Solemon 2010
  Process Activities:
  Framework and Umbrella
• Framework activities :
   o generic activities that are applicable to all
     software projects, regardless of their size or
   o Include communication; planning; modeling,
     construction; and deployment.
• Umbrella activities:
   o complementary activities applied throughout a
     software project and help manage and control
     progress, quality, change, and risk.
   o Include project tracking and control; risk
     management; software quality assurance
     (SQA); technical reviews; configuration
     management (CM); etc.
                                      Badariah Solemon 2010
  Process Flow
• Describes how the framework activities
  and the actions and tasks that occur within
  each activity are organized with respect to
  sequence and time.
• The flows:
   1. Linear – execute the framework activities in
   2. Iterative – repeats one or more of the
      activities before proceeding to the next.
   3. Evolutionary – execute the activities in a
      ‗circular‘ manner.
   4. Parallel – executes one or more activities
      simultaneously with other activities.

                                       Badariah Solemon 2010
Process Flow

     Badariah Solemon 2010
  Process Patterns
• It would be useful if proven solution to the problems,
  encountered as project team moves through a
  software process, were readily available , which can
  be reused in another project.
• In more general terms, a process pattern provides
  you with a template [Amb98]—a consistent method
  for describing problem solutions within the context of
  the software process.
• A process pattern
    •   describes a process-related problem that is
        encountered during software engineering work,
    •   identifies the environment in which the problem has
        been encountered, and
    •   suggests one or more proven solutions to the
                                             Badariah Solemon 2010
                  Process Assessment and
•   Approaches:
     1. Standard CMMI Assessment Method for Process
        Improvement (SCAMPI) :
         •   Is used to identify strengths, weaknesses, and ratings relative to SEI CMMI
             appraisal reference model, which is applicable to internal process
             improvement and external capability determination.
     2. CMM-Based Appraisal for Internal Process Improvement (CBA
         •   provides a diagnostic technique for assessing the relative maturity of a
             software organization; uses the SEI CMM as the basis for the assessment
             [Dun01]. However, CMM has been retired by SEI since the introduction of
             CMMI group of standards.
     3. SPICE (ISO/IEC15504):
         •   standard that defines a set of requirements for software process
             assessment. The intent of the standard is to assist organizations in
             developing an objective evaluation of the efficacy of any defined software
             process. [ISO08]
     4. ISO 9001:2000 for Software:
         •   a generic standard that applies to any organization that wants to improve the
             overall quality of the products, systems, or services that it provides.
             Therefore, the standard is directly applicable to software organizations and
             companies. [Ant06]
                                                                 Badariah Solemon 2010
Prescriptive Process Models
• Promote an orderly, structured approach
  to SE
• That leads to a few questions …
   • If prescriptive process models strive for
     structure and order, are they inappropriate for
     a software world that thrives on change?
   • Yet, if we reject traditional process models
     (and the order they imply) and replace them
     with something less structured, do we make it
     impossible to achieve coordination and
     coherence in software work?

                                     Badariah Solemon 2010
  Prescriptive Process Models
• Waterfall Model – represents elements of a linear
  process flow
   • V
• Incremental Model – combines elements of linear
  and parallel process flows
• Evolutionary Model – follows the evolutionary
  process flow that combines elements of linear and
  iterative process flows
   • Prototyping
   • Spiral
• Concurrent Model – combines elements of
  iterative and parallel process flows

                                         Badariah Solemon 2010
                                           The Waterfall Model
• Represents a linear process flow from communication
  through deployment.
    Communicat ion
    project init iat ion     Planning
    requirement gat hering    estimating   Modeling
                                            analysis   Const ruct ion
                                            design                       Deployment
                                                         t est            delivery
                                                                          f eedback

*  Also known as the classic SDLC
* The original Waterfall model proposed by Winston Royce in 1970 made
  provision for feedback loops, but many organizations apply this model as
  if it were strictly linear.
                                                                  Badariah Solemon 2010
The V-Model
           A variation in the
            representation of the
            Waterfall model.
           Illustartes how V&V
            actions are
            associated with
            earlier SE action.
           In reality, there is no
            difference between
            the Waterfall model
            and the V-model.

                  Badariah Solemon 2010
                                        The Waterfall Model: An
Characteristics                 Strengths                         Weaknesses                            Applicability
   It suggests a systematic,      Simple and easy to use/explain    Real projects rarely follow the      When requirements are
    sequential approach to          to customers.                      linear flow that the model            well understood and
    SE, staring from                                                   proposes. Although iteration is       unlikely to change radically
                                   The staged development cycle
    requirements                                                       indirectly allowed, changes are       during system
                                    enforces discipline: every
    specification going                                                costly, involve significant           development (e.g.: in a
                                    phase has a defined start and
    through planning,                                                  rework and can cause confusion        well-defined enhancement
                                    end point, and progress can be
    modeling, construction,                                            to project team and involve.          to an existing system).
                                    conclusively identified
    testing, deployment and
                                    (through the use of               The model requires the               When software
    support of the
                                    milestones)                        customer to state all                 development technologies
    completed system.
                                                                       requirements explicitly, which is     and tools are well known.
   Each major activity is                                             often very difficult to achieve.
                                                                                                            The work tasks in the
    marked by milestones
                                                                      The working software will not         project are to proceed to
    and deliverables
                                                                       available until late in the           completion in a linear
    (artifacts i.e.
                                                                       project, which can be disastrous      manner.
                                                                       for late discovery of major
                                                                      Leads to “blocking states” in
                                                                       which some project team
                                                                       members must wait for others
                                                                       to complete dependent tasks.

                                                                                                         Badariah Solemon 2010
                                                 The Incremental Model

                                                                                                                                            increment # n
                                                                                                                                                       Co m m u n i c a t i o n
                                                                                                                                                                                  Pla nning
                                                                                                                                                                                              M odeling
                                                                                                                                                                                                analy s is   Co n s t ru c t i o n
                                                                                                                                                                                                des ign
                                                                                                                                                                                                                c ode                De p l o y m e n t
                                                                                                                                                                                                                t es t                 d e l i v e ry
                                                                                                                                                                                                                                       fe e dba c k

                                                                                                                                                                                                                                     deliv ery of
                                                                                                                                                                                                                                     nt h increment
                                                       increment # 2

                                                           Co m m u n i c a t i o n
                                                                                       Pla nning
                                                                                                           M odeling
                                                                                                            analy s is   Co n s t ru c t i o n
                                                                                                            des ign         c ode                De p l o y m e n t
                                                                                                                            t es t                 d e l i v e ry
                                                                                                                                                   fe e dba c k
                                                                                                                                                                             deliv ery of
increment # 1                                                                                                                                                                2nd increment

  Co m m u n i c a t i o n
                             Pla nning
                                         M odeling
                                          analy s is      Co n s t ru c t i o n
                                          des ign            c ode                    De p l o y m e n t
                                                             t es t                     d e l i v e ry       deliv ery of
                                                                                        fe e dba c k
                                                                                                             1st increment

                                                                                                  project calendar t ime

                                                                                                                                                                                                          Badariah Solemon 2010
                               The Incremental
                                 Model (cnt’d)
 Rather than deliver the software product 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.

                                               Badariah Solemon 2010
                 The Incremental Model:
                            An Analysis

Ask the students to analyze this process model and to
discuss their findings in class.

                                              Badariah Solemon 2010
The Evolutionary Model:
                    Q u i ck p l an
 Com m unicat ion      plan
                                  Mo d e l i n g
                                    Q u i ck d e si g n
                                Quick design

  De live r y
  delivery &
  & Fe e dback            Const r uct ion
  feedback                Construction
                          of prototype
                          pr ot ot ype

                                                          Badariah Solemon 2010
                 The Evolutionary Model:
                      Prototyping (cnt’d)
 Using this process model, a prototype (an early
  approximation of a final software product) is built, tested,
  and then reworked as necessary until an acceptable
  prototype is finally achieved from which the complete
  software product can now be developed.
 Although it can be implemented as a stand-alone process
  model, it is more commonly used as part of other process
 The main purpose of the model is to help better
  understand what it is to built when requirements are fuzzy.

                                                    Badariah Solemon 2010
                 The Prototyping Model:
                             An Analysis

Ask the students to analyze this process model and to
discuss their findings in class.

                                              Badariah Solemon 2010
          The Evolutionary Model:
                           risk analysis



        delivery                           code
        feedback                           test

                                                      Badariah Solemon 2010
                The Evolutionary Model:
                            Spiral (cnt’d)
 A process model that combines the iterative nature of
  prototyping with the systematic aspects of waterfall
 The spiral model can be thought of as a repeating
  waterfall model that emphasizes risk assessment and
  that is executed in an incremental fashion.
 Each loop/pass through the spiral model consists of
  risk assessment and other framework activities from
  communication through deployment.

                                              Badariah Solemon 2010
                            The Spiral Model:
                                  An Analysis

Ask the students to analyze this process model and to
discuss their findings in class.

                                              Badariah Solemon 2010
The Concurrent Process Model

       Modeling act ivit y

                                                               represents the state
                                        Under                  of a software engineering
                                                               activity or task

               Await ing

                                                        Under review




                                                                                           Badariah Solemon 2010
                  The Concurrent Process
                           Model (cnt’d)
 A process model that combines the iterative and
  parallel elements of any of the prescriptive process
 In this process model, all SE activities (framework or
  umbrella activities) exist concurrently but reside in
  different states.

                                                Badariah Solemon 2010
            The Concurrent Model: An

Ask the students to analyze this process model and to
discuss their findings in class.

                                              Badariah Solemon 2010
Specialised Process Models
• Component based software development (CBSD)
   •   the process to apply when reuse is a development
• Formal methods
   •   emphasizes the mathematical specification of
       requirements, which can demonstrate software
       correctness but are not widely used.
• Aspect-oriented software development (AOSD)
   •   provides a process and methodological approach
       for defining, specifying, designing, and constructing
• Unified Process
   •   a ―use-case driven, architecture-centric, iterative
       and incremental‖ software process closely aligned
       with the Unified Modeling Language (UML)
                                          Badariah Solemon 2010
Specialised Process Models (cnt’d)
 • Agile Process
    •   An iterative approach to requirements specification,
        construction and deployment, which support rapid
        changes to requirements.
 • Personal Process Model
    •   Emphasizes the need to record and analyze errors each
        individual practitioner made, so that he/she can develop a
        strategy to eliminate them.
 • Team Process Model
    •   Build self-directed teams that plan and track their work,
        establish goals, and own their processes and plans.
        These can be pure software teams or integrated product
        teams (IPT) of three to about 20 engineers.
    •   Show managers how to coach and motivate their teams
        and how to help them sustain peak performance.

                                               Badariah Solemon 2010
Agile Development
• Combines a philosophy and a set of
  development guidelines.
• The philosophy encourages:
    customer satisfaction and early incremental delivery
     of software;
    small, highly motivated project teams;
    informal methods;
    minimal SE work products; and
    overall development simplicity.
• The development guidelines:
    stress delivery over analysis and design, and
    active and continuous communication between
     developers and customers

                                         Badariah Solemon 2010
The Agile Manifesto
1. Value individuals and interactions over process and
2. Prefer to invest time in producing working
   software rather than in producing comprehensive
3. Focus on customer collaboration rather than
   contract negotiation
4. Concentrate on responding to change rather than
   on creating a plan and then following it
• Why?
   • The modern business environment is fast-paced and
     ever-changing. This process model has been
     demonstrated to deliver successful systems quickly.

                                         Badariah Solemon 2010
                              The Agile Principles
1.   Our highest priority is to satisfy the customer through early and
     continuous delivery of valuable software.
2.   Welcome changing requirements, even late in development. Agile
     processes harness change for the customer's competitive
3.   Deliver working software frequently, from a couple of weeks to a
     couple of months, with a preference to the shorter timescale.
4.   Business people and developers must work together daily
     throughout the project.
5.   Build projects around motivated individuals. Give them the
     environment and support they need, and trust them to get the job
6.   The most efficient and effective method of conveying information
     to and within a development team is face–to–face conversation.

                                                        Badariah Solemon 2010
             The Agile Principles (cnt’d)

7. Working software is the primary measure of progress.
8. Agile processes promote sustainable development. The
    sponsors, developers, and users should be able to maintain a
    constant pace indefinitely.
9. Continuous attention to technical excellence and good
    design enhances agility.
10. Simplicity – the art of maximizing the amount of work not
    done – is essential.
11. The best architectures, requirements, and designs emerge
    from self–organizing teams.
12. At regular intervals, the team reflects on how to become
    more effective, then tunes and adjusts its behavior
                                                   Badariah Solemon 2010
Agile: Human Factors
• the process molds to the needs of the people
  and team, not the other way around
• key traits must exist among the people on an
  agile team and the team itself:
    Competence.
    Common focus.
    Collaboration.
    Decision-making ability.
    Fuzzy problem-solving ability.
    Mutual trust and respect.
    Self-organization.

                                   Badariah Solemon 2010
The Agile Process Models
• Also known as approaches to agile software
  engineering, which include:
   •   Extreme Programming (XP)
   •   Industrial XP
   •   Scrum
   •   Adaptive Software Development (ASD)
   •   Dynamic Systems Development Method (DSM)
   •   Crystal
   •   Feature Driven Development (FDD)
   •   Lean Software Development (LSD)
   •   Agile Modeling (AM)
   •   Agile Unified Process (AUP)
                                   Badariah Solemon 2010
 The Extreme Programming
• The most widely used approach to agile SE.
                                                                          spike solut ions
                                                     simple design
                                                                            prot ot ypes
                                                       CRC cards
        user st ories
           accept ance t est crit eria
        it erat ion plan

                                                        refact oring


    sof t ware increment                             unit t est
        project velocit y comput ed                  cont inuous int egrat ion

                                      accept ance t est ing

                                                                                    Badariah Solemon 2010
                              The XP: Activities

XP Planning
• Begins with the creation of “user stories”
• Agile team assesses each story and assigns a cost
• Stories are grouped to for a deliverable increment
• A commitment is made on delivery date
• After the first increment “project velocity” is used to
   help define subsequent delivery dates for other

                                                Badariah Solemon 2010
                    The XP: Activities (cnt’d)

XP Design
•   Follows the KISS principle
•   Encourage the use of CRC cards (see Chapter 8)
•   For difficult design problems, suggests the creation of “spike
    solutions”—a design prototype
•   Encourages “refactoring”—an iterative refinement of the internal
    program design
XP Coding
•   Recommends the construction of a unit test for a store before
    coding commences
•   Encourages “pair programming”
XP Testing
•   All unit tests are executed daily
•   “Acceptance tests” are defined by the customer and executed to
    assess customer visible functionality              Badariah Solemon 2010
            The Extreme Programming
                     (XP): An Analysis

Ask the students to analyze this process model and to
discuss their findings in class.

                                              Badariah Solemon 2010
 Selecting a Process Model
• Analyze the sidebars in pages 45 and 47.
• What are the lesson-learned from these

                                   Badariah Solemon 2010
   Selecting a Process Model
• Factors to consider:
   1. The characteristics of the problems to be solved.
       •   Such as complexity of the problem, etc
       •   E.g.: simple with clear, stable requirements, complex with
           changing, unstable requirements, etc.
   2. The characteristics of the project
       •   Such as the customers who have requested the product and the
           people who will do the work, etc.
       •   E.g.: Uncertain requirements, breakthrough technology
   3. The characteristics of the product.
       •   Such as quality attributes or metric of the product, product
           domain, etc
   4. The project environment in which the software
      team works
       • Such as political, cultural, language ,etc.

                                                        Badariah Solemon 2010
                                     Key Questions in
                                 Determining Task Set

• Different projects requires different task sets. The tasks
  should be selected based on problems and project
• Q: What actions are appropriate for a framework activity,
    the nature of the problem to be solved;
    the characteristics of the people doing the work; and
    the stakeholders of the project?
• Q: What work tasks (task set) that these actions should
  encompasses of?
                                                             Badariah Solemon 2010

• Nature of the problems and project :
    A small software project requested by one person (at a remote
     location) with simple, straightforward requirements.
• Actions:
    Communication action: develop requirements
• Task set:
      Make contact with stakeholder via telephone.
      Discuss requirements and take notes.
      Organize notes into a brief written statement of requirements.
      E-mail to stakeholder for review and approval.
                                                            Badariah Solemon 2010
   Process Management Tools
• Also known as process modeling tools or
  process technology.
• Allows a team to define and manage the
  elements of a process model (activities, actions,
  task, work products, milestones, and QA
• Such tools also provide detailed guidance on the
  content of each process element.
• The tools may also provide standard project
  management tasks such as estimating,
  scheduling, tracking and control.
• Example:
   • Igrafx Process Tools (
                                      Badariah Solemon 2010
                                Selecting a Process
                                Model: an Exercise
• The project:
     Assume that you are in charge of a project to create a
  portal for the Shah Alam district of Selangor state. This
  portal would include a homepage with links to a wide range
  of discounted travel packages to major destinations in
  Selangor, links to certain featured places like golf
  courses, shopping complexes and places to eat, links to the
  detailed map of Selangor, and links to news and events
  listing. It also includes a bulletin board and chat room
  feature where tourists (international and local tourists)
  can exchange information. The portal should also provide
  Automated Teller Machine (ATM) locator, timezone converter,
  and currency converter.
• Select a software process model that you would recommend
                                               Badariah Why is
  to be implemented in the above mentioned project. Solemon 2010
• There are four types of process flows – linear,
  iterative, evolutionary, and parallel.
• Software process patterns may suggest one or more
  proven solutions to the problem from other projects,
  which can be reused in another project.
• There are several process assessment and
  improvements frameworks that can be exercised by
• The analyses of prescriptive and specialized software
  process models would help you select the most
  appropriate process model for a software
  development project, which can be proceeded with
  the identification of task set for the project.

                                         Badariah Solemon 2010
 References and credit
Contents in the slides are adapted from the
book and the slides that accompanied the
book by R.S. Pressman, Software Engineering:
A Practitioner‘s Approach, 7th. Edition, McGraw
Hill, 2009.

                                  Badariah Solemon 2010

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