Introduction to Software Process CEN 5016 Software Engineering

Introduction to Software Process CEN 5016 Software Engineering © Dr. David A. Workman School of EE and Computer Science January 9, 2007 (c) Dr. David A. Workman

Software Engineering DEFINITION [Barry Boehm’ 76]. The practical application of scientific knowledge in the design and construction of computer programs and the associated documentation required to develop, operate, and maintain them. – – – Practical Applications Scientific Knowledge Design and Construction Computer Programs and Documentation Develop, operate, and maintain DEFINITION [IEEE 1993] 1. The application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software; that is, the application of engineering to software. 2. The study of approaches relevant to 1. January 9, 2007 (c) Dr. David A. Workman 2

Computer Science DEFINITION Computer Science is concerned with the scientific study and description of algorithms, programs, the devices that interpret them, and the phenomena surrounding their creation and usage. Software Engineering focuses on the application of this scientific knowledge to achieve stated technical, economic, and social goals. [Peter Freeman’ 80] January 9, 2007 (c) Dr. David A. Workman 3

Life Cycle vs. Development Cycle Software Development Cycle “Grave” “Cradle” Code & Unit Testing Systems Engineering Component Integration and System Test Software Requirements Elicitation Software Requirements Elaboration Delivery Installation & Training Software Specification and Project Planning January 9, 2007 Obsolescence and De-Commission Software Design Need and Concept Formation (c) Dr. David A. Workman Operation and Maintenance 4

Summary of the Software Lifecycle Definition The complete history of a software system from concept formation through decommission broken down into the following “maturation” phases: – Conception – System Requirements elicitation and definition Systems Engineering – System Architecture Development – Software Requirements elicitation and definition – Software Requirements elaboration and specification – Software Project Planning – Design • • – Implementation • • – Construction Subsystem testing System testing (acceptance testing) Operation & Maintenance • • • – Coding Unit Testing Integration • • – Architectural Design Detailed Design Corrective : removing bugs ( 17. 5% ) Enhancement: improving exiting capability = perfective ( 60. 5%) + adaptive ( 18% ) Reengineering (includes adaptive and perfective maintenance) Retirement January 9, 2007 (c) Dr. David A. Workman 5

Development Cycle Costs Requirements = 6% Integration = 24% Unit Testing = 21% Specification = 15% Design = 19% Coding = 15% (Schach - Classical and Object-Oriented Software Engineering) January 9, 2007 (c) Dr. David A. Workman 6

Process Models • Definition Process models are “algorithms for developing software. ” Software process is the execution of a process model. Data = development artifacts; Processors = people; Algorithms = methods + tools • Water Fall Model (Winston Royce ’ 70) – First formal software development method (1950 -70). – Each development phase was completed before the next could begin. – Documents produced as the output of one phase become inputs to the next phase. – Did not allow for changing requirements. Frequently, the user was not happy with the delivered system. Phases: • • • System Engineering Software Requirements Analysis Software Design (Architectural & Detailed) Code and Unit Testing Integration Installation & Maintenance January 9, 2007 (c) Dr. David A. Workman 7

Water Fall Model Features & Contributions – – – Author: Winston Royce 1970 First formal software development method (1950 -70). Encouraged specification of what the system is supposed to do before building it. Encouraged planning and management monitoring and control. Each development phase was completed before the next could begin. Documents produced as the output of one phase become inputs to the next phase. These documents provided a basis for verification and validation. – Did not allow for changing requirements. Frequently, the user was not happy with the delivered system. System Requirements rework Code & Unit Test Software Requirements Architectural Design rework January 9, 2007 rework Detailed Design (c) Dr. David A. Workman Integration & Test Installation & Maintenance rework 8

Water Fall Model 1. System Requirements: The system concept is defined, customer and client requirements are captured, hardware and software components defined and mapped. 2. Software Requirements: a formal (complete, precise, consistent, and unambiguous) description of “what” each software component must do is prepared by the developer and reviewed by the customer (software specification document); a software project plan is produced at the end of this phase. 3. Design phase: The specification is elaborated in two steps that define “how” the product will work: Architectural Design breaks down the whole system into component parts (modules) and the interactions between them (interfaces); Detailed Design involves elaborating the design of individual components by specifying data structures and algorithms. 4. Code & Unit: Software module designs are translated to code and then unit tested. 5. Integration & Test: Software modules are integrated into larger functional aggregates (subsystems) and tested in the operational environment. The final step tests the complete system (acceptance testing or validation – customer agrees that the system meets the specification). 6. Installation & Maintenance: The completed system is installed in the operational environment and maintained (error correction and enhancement) for the remainder of the system lifetime. January 9, 2007 (c) Dr. David A. Workman 9

Water Fall Model Errors Detected Errors Introduced Requirements Specification Design Code Unit Test Integration & Test System Acceptance Tests Ref: The Impact of Prototyping on Software System Engineering, by Hassan Gomaa, George Mason University, IEEE System and Software Requirements Engineering, 1990. January 9, 2007 (c) Dr. David A. Workman 10

Prototyping • Prototyping The rapid and (relatively) inexpensive development of an operating model of the desired system (or a subset) developed only for the purpose of defining or elaborating requirements, and/or resolving unknown performance issues before a full commitment of resources is made to produce the final system. • Benefits – Water Fall models limit the amount of iteration among phases – a key feature of prototyping is iterating rapidly through early phases of development. – Water Fall models tend to produce a working system very late in the development cycle – thus major problems may go undetected until the system is almost complete. Prototyping focuses on identifying major technical problems as early as possible. – System requirements cannot be properly validated without a working version – prototyping focuses on understanding and elaborating requirements through demonstration. Ref: The Impact of Prototyping on Software System Engineering, by Hassan Gomaa, George Mason University, IEEE System and Software Requirements Engineering, 1990. January 9, 2007 (c) Dr. David A. Workman 11

Prototyping Requirements for a Prototype 1. It must be an actual working system with which one can experiment and from which lessons can be learned to revise the requirements specification. 2. It must be comparatively cheap to develop – approximately 10% of the total estimated cost of the complete system. 3. Must be developed quickly so that it may be evaluated early in the development cycle; it should be used to collect early feedback from system users. Phases of Development 1. Preliminary analysis and specification of user requirements. (understand user's problem) 2. Design and implementation of a prototype. (emphasize user interface, small development team, development language, use prototyping development tools) 3. Exercise the prototype. (preliminary user training, user feedback) 4. Iterative refinement of the prototype. 5. Refinement of the requirements specification. See Notes 6. Design and implementation of the production system. January 9, 2007 (c) Dr. David A. Workman 12

Prototyping • Throwaway Prototypes are constructed as part of the problem understanding or analysis activity. Their purpose is to gain a deeper understanding of the problem and its feasible solutions. It is a learning device never intended for use - it is “thrown away” after it has served its purpose. – Because the prototype will be discarded, the time and effort spent on satisfying nonfunctional requirements and formal documentation can almost be eliminated. This reduces development time. – This approach should focus on understanding of requirements from the user's perspective and to obtain early user feedback. • Evolutionary Prototypes are constructed to satisfy a subset of the system requirements - as refinements are made or layers of functionality are added, they “evolve” into the final system. – Because each increment or prototype version is to be of production quality, nonfunctional requirements must be considered and some formal documentation must be part of the prototyping process. – The incremental nature of evolutionary prototyping ensures that a useful version of the system is produced earlier that water fall methods. See Notes January 9, 2007 (c) Dr. David A. Workman 13

Reengineering Process Model Establish Baseline Legacy System Legacy Test Procedures, Test Data & Results Legacy Baseline Reuse & Modify Legacy Units Legacy Requirements Proposed New Capability New Requirements Extract Requirements Modified Requirements Analysis Reuse Libraries January 9, 2007 Extract Design Legacy Design Re-test Procedures Test Changes Design Changes Identifiy off-the-shelf Units For reuse Without modification Modify & Enhance Design Identified Legacy Units for Reuse & Modification New Design Produce New Test Plan (c) Dr. David A. Workman Re-Test Legacy Units Tested Legacy Units Integration test Procedures New Unit test Procedures Construct & Test new Units Set of Test-ready Legacy Units Integrate & Test All Units Tested new Units Target System Off-the-shelf Units ready for Integration 14

Spiral Model A cyclic approach to software development marked by four basic stages that are repeated on each cycle until the target system is delivered. A risk-driven meta model. Developed by Barry Boehm, “A Spiral Model of Software Development and Enhancement”, IEEE Computer, Vol 21, No 5, May 1988. Stage 1: Identify objectives, alternative solutions, and constraints for the part of the system currently under consideration. Stage 2: Evaluate alternatives and identify associated risks using prototyping and simulation. Stage 3: Develop and verify the next system increment. Stage 4: Review outcome of earlier stages and plan the next cycle. January 9, 2007 (c) Dr. David A. Workman 15

Spiral Model See Notes 2: Evaluate alternatives and their risks 1: Determine objectives, alternative solutions, & constraints. risk analysis prototyping Acceptance & Installation Design Planning Implementation Review Test 4: Review outcome and Plan next cycle. January 9, 2007 (c) Dr. David A. Workman 3: Develop, verify next system increment. 16

Measurement and Control Nominal Process Flow or Execution See Notes Process Quality Assessment and Control Product Quality Assessment and Control (Project Mangement) Process Change Directives Progress & Quality Assessment Data Effort and Size Metrics Product Specifications Development Activity or Procedure Raw Products Quality Metrics Quality Review Product Change Metrics Repository Quality Products (and specification for next Activity) Directives January 9, 2007 (c) Dr. David A. Workman 17

Unified Software Process Software Phases & Artifacts January 9, 2007 (c) Dr. David A. Workman

Overview of USP Requirements Elicitation (Definition) Use Case Model Requirements Elaboaration (OO-Analysis) Analysis Model The process of defining and modeling the Problem Space Object-Oriented Design & Deployment Models January 9, 2007 Problem Statement & User Needs The process of defining and modeling the Solution Space Object-Oriented Implementation (Programming) (c) Dr. David A. Workman Mapping design to Implementation Space Code in an OOPL (Ada 95) (C++)(Java) Component Model 19

Overview of USP Birth Death Inception Itera- Iteration • Elaboration Iteration Construction Iteration … Iteration Transition … Itera- Iteration Inception (focus on “Feasibility”) Develop a vision of the end product and prepare a business case. Answers the questions: • What is the system boundary? Begin to identify interfaces with systems outside the boundary. • What is the system going to do? What are the major classes of users? (Develop Initial Use Case Model )( Identify and describe only a small % of use cases ) • What is a possible system architecture? ( Identify most critical subsystems ) • What is the project plan? What will the system cost? ( Identify critical risks ) (Develop a Project Management Plan) • Demonstrate feasibility by building a prototype. • • • Elaboration Construction Transition January 9, 2007 (c) Dr. David A. Workman 20

Overview of USP Birth Death Inception Itera- Iteration Elaboration Iteration Arch. Design • • Iteration Construction Iteration … Iteration Transition … Itera- Iteration Detailed Design Inception Elaboration ( focus on “Do-Ability” )(Architecture + high-fidelity cost est. ) – Develop detailed use cases (80% of use cases). – Develop a stable architectural view of the system using the Analysis Model, Design Model, Implementation Model, and Deployment Model. – Create a baseline system specification (SRS). – Produce the Software Development Plan (SDP) which describes the next phase. • • Construction Transition January 9, 2007 (c) Dr. David A. Workman 21

Overview of USP Birth Inception Itera- Iteration • • • Death Elaboration Iteration Construction Iteration … Iteration Transition … Itera- Iteration Inception Elaboration Construction (focus on building an operational capability) Build the system (usually in increments defined by releases ). Each release encapsulates defined use cases. Releases are ordered by priority determined by customer needs and project risks. • Transition (focus on producing a formal release ) Product (release) enters beta testing and then distribution. This phase involves manufacturing, training, and providing customer support infrastructure. Transition ends with maintenance: corrective, adaptive, perfective. January 9, 2007 (c) Dr. David A. Workman 22

Overview of USP USDP Models Use Case Model verified by test 2 OK specified by realized by implemented by Implementation Model January 9, 2007 test 1 OK Test Model distributed by Analysis Model Design Model (c) Dr. David A. Workman Deployment Model 23

Overview of USP Core Work Flows Inception Elaboration Construction Transition Elicitation Analysis Design Implementation Test Distribution of Core Activities Across Phases January 9, 2007 (c) Dr. David A. Workman 24

Use Case Modeling © Dr. David A. Workman School of EE and Computer Science University of Central Florida September 18, 2002 January 9, 2007 (c) Dr. David A. Workman

Requirements Capture • Input Client approaches Developer with a problem and or product concept. This may be expressed verbally or in the form of a document (Statement of Work (SOW)) (Request for Proposal (RFP)) • Activities Developer interacts with Client and Users to elicit product requirements. This involves face-to-face meetings and possibly the exchange of technical documents. The Developer must determine as completely and precisely as possible the following information: – cost and time constraints – target system platform and operational environment – user groups – functional capabilities – non-functional constraints: quality and performance – Client and User's needs (as opposed to "wants") • Outputs A complete understanding of the problem the Client and Users need to have solved. Client should be in agreement with the Developer’s assessment of the problem. This shared view of the system is captured in the form of a UML Use Case Model. January 9, 2007 (c) Dr. David A. Workman 26

Use Case Model • Definitions 1 A Use Case is a sequence of actions that the system performs to offer some results of value to a User. – Use cases drive the whole development process. “They offer a systematic and intuitive means of capturing functional requirements from the user’s perspective. ” – A system has many types of users. Each type of user is define by an actor. Actors may be people or external systems. Actors interact with the product via one or more Use Cases. An actor role is defined by a particular set of use cases performed by that actor to accomplish a particular goal or objective. – “All actors and uses cases make up a Use Case Model. ” – A good collection of use cases is central to understanding what your users want. Use Cases also present a good vehicle for project planning, because they control iterative development, … it gives regular feedback to users about where the software is going. – Use cases provide the basis of communication between the client and the developers in planning the project. 1 The Unified Software Development Process, by Rumbaugh, Jacobson, and Booch, Addison-Wesley, 1999, 0 -201 -57169 -2. January 9, 2007 (c) Dr. David A. Workman 27

Use Case Model • Definition 2 (Fowler) A Use Case captures a typical interaction between a user and a computer system. – A use captures some user-visible function. – A use case may be small or large. – A use case achieves a discrete objective for the user. In its simplest usage, you capture a use case by talking to typical users and discussing the various things they might want to do with the system. Take each discrete task or action they want to do, give it a name, and write up a short description. During the Elaboration phase, this is all you need to do to get started. 2 UML Distilled, by Scott & Fowler January 9, 2007 (c) Dr. David A. Workman 28

Use Case Model Outline • Title (System Name, Author Name, Assignment, Course, Pub. Date) – – TOC List of Figures (optional for small documents) 1. System Summary – – – Overview of System Purpose and Context Business Case ( business need and how this system will address this need ) System Operation • • – Use Case Diagram Supporting Narrative (explains diagram: operational flow, actor roles ) System Interfaces ( External Interfaces with Actors ) 2. Use Case Specifications 1. Purpose ( function from user’s perspective ) • • 2. 3. 4. 5. 6. Collaboration diagram (flow of interactions between actors and interface objects ) Narrative summary of use case purpose or function Precondition (system states & triggering events ) Flow of Events (nominal flow of interaction events between actor and interface objects) Alternative Paths (error processing flows; special case flows ) Post Condition (system states & completion events ) Special Requirements (non-functional : performance and quality ) 3. Requirements Traceability 4. Glossary January 9, 2007 (c) Dr. David A. Workman 29

Requirements Elicitation Work Flow System Analyst System Architect Use Case Specialist Structure Use Case Model Find Actors & Use Cases Prioritize Use Cases Detail Use Cases Prototype User Interface Designer January 9, 2007 (c) Dr. David A. Workman 30

Requirements Elaboration • Purpose "To achieve a more precise understanding of requirements and to achieve a description of requirements that is easy to maintain and that helps give structure to the whole system including the architecture. " • Inputs – – – • Outputs from Requirements Elicitation ( Use Case Model ). Technical documents or expertise relevant to problem domain, in general, and to the Client's problem, in particular. Legacy System (optional) Activities Refine requirements by eliminating inconsistencies and ambiguities. Formalize requirements by preparing a System/Software Requirements Specification. Develop an initial Software Development Plan. • Outputs – System/Software Requirements Specification (SRS) • • • – UML Use Case Model and Scenarios UML Class Model UML Collaboration Model UML Sequence Diagrams Problem Glossary Other info. Software Development Plan (SDP) January 9, 2007 (c) Dr. David A. Workman 31

Software Requirements Specification (SRS)1 1 • Title • TOC 1. Introduction 1. 1 1. 2 1. 3 1. 4 1. 5 IEEE Std 830 -1998 Purpose Scope Definitions, Acronyms, and Abbreviations References Overview 2. Overall Description 2. 1 2. 2 2. 3 2. 4 2. 5 Product Perspective Product Functions User Characteristics Constraints Assumptions and Dependencies 3. 0 Specific Requirements … next slide January 9, 2007 (c) Dr. David A. Workman 32

Software Requirements Specification (SRS) 3. 0 Specific Requirements 3. 1 External Interfaces 3. 2 Functions 3. 3 Performance Requirements 3. 4 Logical Database Requirements 3. 5 Design Constraints 3. 6 Software System Quality Attributes 3. 7 Object Oriented Models 3. 7. 1 Analysis Class Model 3. 7. 2 Analysis Collaboration Model 3. 8 Additional Comments • Index • Appendices January 9, 2007 (c) Dr. David A. Workman 33

Software Development Plan (SDP)2 • Front Matter (Title, Toc, Lof, Lot) 1. Overview 2 IEEE Std 1058 -1998 1. 1 Project Summary 1. 2 Evolution of Plan 2. 3. 4. 5. References Definitions Project Organization Managerial Process Plans 5. 1 5. 2 5. 3 5. 4 5. 5 Start-up Plan Work Plan Control Plan Risk Management Plan Closeout Plan 6. Technical Process Plan 7. Supporting Plans January 9, 2007 (c) Dr. David A. Workman 34

Requirements Elicitation vs Elaboration (USP) January 9, 2007 (c) Dr. David A. Workman 35

Design (USP) • Purpose The system is shaped to accommodate all functional and non-functional requirements. It contributes to a sound and stable architecture and creates a blueprint for the implementation model. – Acquire an in-depth understanding of non-functional requirements and constraints related to: programming languages, component reuse, operating systems, distribution topology, network and database technologies, user-interface technology, etc. – Define and harden the boundaries between subsystems. • Artifacts – Design Model An object model that describes the physical realization of use cases by focusing on how functional and non-functional requirements, together with other constraints related to the implementation environment, impact the system architecture and structure. • Design classes • Use-case realizations (design) • Detailed Interfaces January 9, 2007 (c) Dr. David A. Workman 36

Design (USP) • Artifacts – Architecture Description A view of the design model focusing on the following architecturally significant artifacts: • Subsystems, interfaces, and their dependencies • Key classes that trace to key analysis and active classes • Key use case realizations that are functionally critical and need to be developed early in the lifecycle. Ones that have coverage across subsystems are particularly important. – Deployment Model An object model that describes the physical distribution of the system in terms of how functionality is distributed among computational nodes. An essential input to the activities in design and implementation. It is a manifestation of the mapping between software architecture and system architecture. • Nodes that denote computational resources • Node processes and corresponding functional allocation • Node relationships and their types (internet, shared memory, ATM link, etc. ) • Network topology(ies) January 9, 2007 (c) Dr. David A. Workman 37

Analysis vs Design (USP) January 9, 2007 (c) Dr. David A. Workman 38

Implementation (USP) • Purpose To translate the design into machine-readable and executable form. Specifically to: – Plan system integrations required in each implementation increment or iteration – Distribute the system by mapping executable components to nodes in the deployment model. – Implement design classes and subsystems found in the Design Model. – Unit test the components, and integrate them by compiling and linking them together into one or more executables, before they are sent to integration and system tests. • Artifacts – Implementation Model • Components: <executable>, <file>, <library>, <Dbtable>, <document> • Interfaces • Implementation subsystems – – Components Implementation Subsystems Interfaces Build Plan January 9, 2007 (c) Dr. David A. Workman 39

Integration & Test (USP) • Purpose To verify the result of each build and to validate the complete system via acceptance tests. – Plan tests required in each iteration, including integration and system tests. Integration tests are required after each build, while system tests are done as part of client acceptance and system delivery. – Design and implement test plans by creating test cases. Test cases specify what to test and define procedures and programs for conducting test exercises. – Perform various test cases to capture and verify test results. Defects are formally captured, tracked and removed before delivery. January 9, 2007 (c) Dr. David A. Workman 40

Integration & Test (USP) • Artifacts – Test Plan Describes testing strategies, resources, and schedule for each build and for the system. – Test Model • Test Case • Test Component • Test Procedure – Test Cases Designed to verify certain requirements and use cases, or use case scenarios. Demonstrates that pre- and post-conditions of use cases are satisfied. Predicts or describes expected component output and behavior. – Test Components The implementation artifacts to be tested. – Test Procedures Specifies how to perform one or several test cases. Test programs (or "harnesses")(or "benches") and shell scripts may have to be executed as part of a test procedure. – Test Evaluations Capture results of test cases; declares whether or not test case was successful; generates defect or anomaly reports for tracking. – Defect or Anomaly Reports January 9, 2007 (c) Dr. David A. Workman 41

IEEE Std (829) for Software Testing • Test Plan To prescribe the scope, approach, resources, and schedule of testing activities. To identify items to be tested, the features to be tested, the testing tasks to be performed, the personnel responsible for each task, and the risks associated with the plan. • • Test Design Spec Test Case Spec Test Procedure Spec Test Item Transmittal Report Test Log Test Incident Report Test Summary Report January 9, 2007 (c) Dr. David A. Workman 42