CS 3610 Software Engineering Spring 2009 Dr Hisham

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. Chapter 3 Prescriptive Process Models Discussion of the Software Process models: Prescriptive Process Models

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. Software Process Models (1) Prescriptive process models evolved over the years to bring some order to the software development (structure, order, consistency)… But, the software industry is fast changing! A prescriptive process model is a strategy/paradigm that prescribes a set of process elements (activities, actions, work tasks, product, QA, CM) and a workflow. Different software projects require different process models! Why? - nature of the application - complexity - methods and tools - required control - expected quality - outcomes/products

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. Software Process Models (2) Key phases of a software process model:

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. The Waterfall Model (1) Known as classic life cycle or sequential model. Communication Planning Development Modeling Deployment

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. The Waterfall Model (2) Life cycle phases: 1. Communication (Requirements Analysis): Good understanding of the system (databases, performance, interface/user, functions). Document: SRS - What the system will do. 2. Planning: Developing project development plan (estimation, scheduling, tracking, and risk management). Document: SDP – The project development plan.

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. The Waterfall Model (3) 3. Modeling (Design): Translating requirement specifications of a software systems that can be assessed for against requirements. Design elements: data structures, software architecture, interfaces, implementation (algorithmic) details. Document: SDD - How the system will work. 4. Coding: Translation design into code (programming task). Document: generated code (modules, procedures, packages, classes, etc. . )

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. The Waterfall Model (4) 5. Testing: Process of finding unknown errors and defects using a test plan that consist of test cases. Testing begins before coding starts! Test cases are traceable to requirements Testing begins in the small Unit testing Integration testing System testing Acceptance testing Document: Test Plan and Test Cases

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. The Waterfall Model (5) 5. Deployment (Support): Delivery, support, and feedback. Application of previous phases when making a change to deployed system (new requirements, environment changes, interface/user changes, etc…). Potential Problems: - Incomplete requirements - Long waiting for a working version (client perspective) - Critical path - blocking states and waiting time - Projects do not follow sequential flow! Too many changes BUT, the model defines essential activities for software development. . .

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. The Incremental Model (1) It is an iterative linear process that produces functional increments (usable modules) of the system. increment 1 analysis design increment 2 code analysis test design increment 3 analysis delivery of Core 1 st increment Product code design Additional delivery of 2 nd increment Features test code test calendar time delivery of 3 rd increment

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. The Incremental Model (2) - It is an evolutionary model. - First increment is the core product (focus on the essential requirements of the system) - Plans for future increments (additional requirements) must be developed. Advantages: - Increments are functional products (unlike prototyping) - Staffing is not an issue, adjusted as needed - Facilitates managing technical and other risks Any disadvantages?

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. The RAD Model (1) - Incremental process that uses component-based development for business applications, and emphasizes short life cycle. - Ideally, each business function is completed in 2 to 3 months. team #3 team #2 b u s i n e s s m o d e l i n g team #1 b u s i n e s s m o d e li n g Business Modeling d a t a m o d e l i n g p r o c e s s m o d e l i n g d a t a m o d e li n g Data Modeling a p pl i c a ti o n g e n e r a t i o n t e s ti n g & t u r n o v e r p r o c e s s m o d e li n g Process modeling a p p li c a ti o n g e n e r a ti o n t e s ti n g & t u r n o v e r Application generation Testing and turnover 60 - 90 days

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. The RAD Model (2) RAD phases: (Applied to modeling and development phases) 1. Business modeling - identify business functions, processes, and what/how/who generates information. 2. Data modeling - redefine business information to data objects, and define object attributes and relationships among objects. 3. Process modeling - describe how processes manipulate (add, delete, retrieve, update) data objects to implement business functions. 4. Application generation - automated tools (4 th generation techniques) are used to create the application by using component reuse.

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. The RAD Model (3) 5. Testing - mainly component integration and system testing since components are already tested. Challenges: - Requires sufficient human resources Require careful planning for multiple teams Requires commitment (developer and customer) Limited to specific systems (with modularity nature) (business applications) - Inappropriate when technical risks are high (technology and interoperability)

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. The Prototyping Model (1) - Evolutionary model - iterative - Incomplete requirements? Go prototyping! - The prototype shows software aspects visible to the user. Listen to customer Quick Plan Design/Build /Revise mock-up Customer test-drives mock-up

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. The Prototyping Model (2) The purpose: - to satisfy customer needs - to understand system requirements What to do with the prototype? - throw it away or reuse it? Must decide before you build it. Potential problems: - Pressure to extend the prototype to a working system! - The “less-than-ideal choice” becomes part of the system! Prototyping keeps everyone happy! Only if the customer agrees to its purpose and what you will do with it. . .

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. The Spiral Model (1) An evolutionary iterative process (with controlled step-wise waterfall) that produces incremental releases of the system (not necessarily functional increments!) Planning Risk Analysis Customer Communication SRS Engineering Prototype Customer Evaluation Construction & Release Complete System Working Version

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. The Spiral Model (2) - Each release goes through task regions, each task region defines a set of work tasks relevant to the project type and size. - It is appropriate for large-scale evolving software projects. - It facilitates prototyping (in early passes) to reduce risks! - Allows constant risk assessment in all region - Each pass thought the planning region, the project plan, schedule, and cost are adjusted accordingly. Drawback: - Less popular than sequential and prototype models - Does not appeal to the customer! - Require considerable risk assessment expertise

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. The Concurrent Process Model An evolutionary iterative concurrent process where all process activities are concurrent, but at different states. - Appropriate for system engineering (different engineering teams) - Similar to RAD model, but at the system level! - Uses events and states to represent process activities. - Defines a “network” of activities with changing states (via events) See figure 3. 6, page 57 - States of modeling activity.

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. The Unified Process (1) - A “use-case driven, architecture-centric, iterative and incremental” software process. - It integrates different component-based development models into one scenario-based unified model. - It emphasizes customer communications through use-cases. - It is a framework for OO development with UML modeling. - Developed by James Rumbaugh, Grady Booch, and Ivar Jacobson in early 1990 s, by combing the best of their individual OOA and OOD methods.

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. Unified Process (2) Phase: Elab o rat io n Inc ept io n Planning Communication inception Deployment Release soft ware increment p r o d uct io n Modeling Construction co nst r uct io n t ransit io n

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. Unified Process (3)

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. Unified Process (4) See Figure 3. 8, page 67: UP Work Products.

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. Other Process Models (1) Component-Based Development model: A specialized model that Integrates OO technology to the engineering and construction activities of the spiral model. Used when reuse of COTS components is the main objective. This model aims to improve software development. (70% saving in time, 84% saving in cost, 26. 2 productive index (the norm is 16. 9) (see page 60)

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. Other Process Models (2) Formal Methods (Cleanroom SE): The application of formal mathematical specifications to develop safety-critical software applications. The emphasis is on defect-free software using formal methods during analysis and design. Issues: cost is high, training is extensive, communication with customer is difficult. Aspect-Oriented Model: New “immature” process model that focus on modeling aspects as customer concerns that cut cross multiple system functions, features, and information. (self-reading)

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. Suggested Problems Try to work problems 2, 3, 4, 5, 6, 7, 8, 10, 11, 14, and 15 from Chapter 3, page 69. No submission is required for practice assignments. Work it for yourself!

CS 3610: Software Engineering – Spring 2009 Dr. Hisham Haddad – CSIS Dept. Last Slide End of chapter 3