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Quiz 1. 2. 3. What activities are part of a software development process? What Quiz 1. 2. 3. What activities are part of a software development process? What are the phases of the waterfall software development process model ? What are the advantages of using an evolutionary development process model? Computer Science Software Engineering Slide 1

Today l l l Quiz Announcements Questions on Assignment 1? Group Names and Team Today l l l Quiz Announcements Questions on Assignment 1? Group Names and Team Leads Library System Software processes … cont’d Computer Science Software Engineering Slide 2

Group Names/Team Leads Paul Simmerlink Stephen Herbert Daniel Coming Ogechi Ugwulebo James King Jigna Group Names/Team Leads 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 Richard. D. Van. Horn 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 3

Library System l l l Need a book tracking system for a library Check-in, Library System l l l Need a book tracking system for a library Check-in, check-out, reshelve Procedural view • l What happens to books in a library? ) Object-oriented View • Computer Science Identify ideas, things : objects that make up system Software Engineering Slide 4

OO System conceptualization l l Unambiguous notation: Unified Modeling Language (UML) Object behavior • OO System conceptualization l l Unambiguous notation: Unified Modeling Language (UML) Object behavior • • Application specific Inheritance Aggregation/containment … Computer Science Software Engineering Slide 5

Application specific relationships l l Library System Consider Book and Patron • • • Application specific relationships l l Library System Consider Book and Patron • • • l Checks-out, returns, requests Changes state of book and patron objects in system Messages are being passed between book and patron objects One object uses the other • • Computer Science Patron’s list of checked out books Method in patron object that checks all books to see which have been checked out by patron Software Engineering Slide 6

Inheritance l Library has things other than books l Many kinds of patrons Computer Inheritance l Library has things other than books l Many kinds of patrons Computer Science Software Engineering Slide 7

Aggregation/Composition l l Address class Patron object contain address object means that there is Aggregation/Composition l l Address class Patron object contain address object means that there is an aggregation/composition relationship between the patron class and the address class Patron is an aggregation of its attributes This is a relation between CLASSES, not attributes Computer Science Software Engineering Slide 8

UML l Dependency • l Association • l Aggregation + application specific Generalization • UML l Dependency • l Association • l Aggregation + application specific Generalization • l One class affects the semantics of another Half of inheritance Realization • Computer Science One class provides a service for another class Software Engineering Slide 9

Modeling l l l A representation of the system that aids in analysis and Modeling l l l A representation of the system that aids in analysis and communication Gets more detailed with time Reviewable/improvable before significant effort spent in implementation Computer Science Software Engineering Slide 10

Good Models l Cohesive • l Loosely coupled • l Minimal connectivity to other Good Models l Cohesive • l Loosely coupled • l Minimal connectivity to other modules/objects Encapsulated • l Functionality must be well defined, easily expressible Data hiding (Do not give client access to stack ADT’s inner array) Reusable Computer Science Software Engineering Slide 11

Effective Teams l l Use the completion of deliverables as objectives when creating agendas Effective Teams l l Use the completion of deliverables as objectives when creating agendas for your team meetings Do not end a team meeting unless each member has a clear idea of what he or she should accomplish Focus Assign tasks as equitably as possible Computer Science Software Engineering Slide 12

Today’s Dilbert Computer Science Software Engineering Slide 13 Today’s Dilbert Computer Science Software Engineering Slide 13

Software Processes l Coherent sets of activities for specifying, designing, implementing and testing software Software Processes l Coherent sets of activities for specifying, designing, implementing and testing software systems Computer Science Software Engineering Slide 14

Objectives l l l To introduce software process models To describe a number of Objectives l l l 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 15

Topics covered l l l l Software process models Process iteration Software specification Software Topics covered l l l l Software process models Process iteration Software specification Software design and implementation Software validation Software evolution Automated process support Computer Science Software Engineering Slide 16

The software process l A structured set of activities required to develop a software The software process l A structured set of activities required to develop a software system • • l 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 17

Generic software process models l The waterfall model • l Evolutionary development • l Generic software process models l The waterfall model • l Evolutionary development • l Specification and development are interleaved Formal systems development • l Separate and distinct phases of specification and development A mathematical system model is formally transformed to an implementation Reuse-based development • Computer Science The system is assembled from existing components Software Engineering Slide 18

Waterfall model Computer Science Software Engineering Slide 19 Waterfall model Computer Science Software Engineering Slide 19

Waterfall model phases l l l Requirements analysis and definition System and software design Waterfall model phases l l l 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 20

Waterfall model problems l l l Inflexible partitioning of the project into distinct stages Waterfall model problems l l l 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 21

Evolutionary development l Exploratory development • l Objective is to work with customers and Evolutionary development l Exploratory development • l 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 • Computer Science Objective is to understand the system requirements. Should start with poorly understood requirements Software Engineering Slide 22

Evolutionary development Computer Science Software Engineering Slide 23 Evolutionary development Computer Science Software Engineering Slide 23

Evolutionary development l Problems • • • l Lack of process visibility Systems are Evolutionary development l Problems • • • l Lack of process visibility Systems are often poorly structured Special skills (e. g. in languages for rapid prototyping) may be required Applicability • • • 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 24

Formal systems development l l l Based on the transformation of a mathematical specification Formal systems development l l l 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 25

Formal systems development Computer Science Software Engineering Slide 26 Formal systems development Computer Science Software Engineering Slide 26

Formal transformations Computer Science Software Engineering Slide 27 Formal transformations Computer Science Software Engineering Slide 27

Formal systems development l Problems • • l Need for specialised skills and training Formal systems development l Problems • • l 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 • 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 28

Reuse-oriented development l l Based on systematic reuse where systems are integrated from existing Reuse-oriented development l l Based on systematic reuse where systems are integrated from existing components or COTS (Commercial-off-the-shelf) systems Process stages • • l 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 29

Reuse-oriented development Computer Science Software Engineering Slide 30 Reuse-oriented development Computer Science Software Engineering Slide 30

Process iteration l l l System requirements ALWAYS evolve in the course of a Process iteration l l l 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 • • Incremental development Spiral development Computer Science Software Engineering Slide 31

Incremental development l l l Rather than deliver the system as a single delivery, Incremental development l l l 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 32

Incremental development Computer Science Software Engineering Slide 33 Incremental development Computer Science Software Engineering Slide 33

Incremental development advantages l l Customer value can be delivered with each increment so Incremental development advantages l l 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 34

Extreme programming l l New approach to development based on the development and delivery Extreme programming l l 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 Slide 35

Spiral development l l Process is represented as a spiral rather than as a Spiral development l l 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 36

Spiral model of the software process Computer Science Software Engineering Slide 37 Spiral model of the software process Computer Science Software Engineering Slide 37

Spiral model sectors l Objective setting • l Risk assessment and reduction • l Spiral model sectors l Objective setting • l Risk assessment and reduction • l Risks are assessed and activities put in place to reduce the key risks Development and validation • l Specific objectives for the phase are identified A development model for the system is chosen which can be any of the generic models Planning • Computer Science The project is reviewed and the next phase of the spiral is planned Software Engineering Slide 38

Software specification l l The process of establishing what services are required and the Software specification l l The process of establishing what services are required and the constraints on the system’s operation and development Requirements engineering process • • Computer Science Feasibility study Requirements elicitation and analysis Requirements specification Requirements validation Software Engineering Slide 39

The requirements engineering process Computer Science Software Engineering Slide 40 The requirements engineering process Computer Science Software Engineering Slide 40

Software design and implementation l l The process of converting the system specification into Software design and implementation l l The process of converting the system specification into an executable system Software design • l Implementation • l 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 41

Design process activities l l l Architectural design Abstract specification Interface design Component design Design process activities l l l Architectural design Abstract specification Interface design Component design Data structure design Algorithm design Computer Science Software Engineering Slide 42

The software design process Computer Science Software Engineering Slide 43 The software design process Computer Science Software Engineering Slide 43

Design methods l l l Systematic approaches to developing a software design The design Design methods l l l Systematic approaches to developing a software design The design is usually documented as a set of graphical models Possible models • • Computer Science Data-flow model Entity-relation-attribute model Structural model Object models Software Engineering Slide 44

Programming and debugging l l l Translating a design into a program and removing Programming and debugging l l l 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 45

The debugging process Computer Science Software Engineering Slide 46 The debugging process Computer Science Software Engineering Slide 46

Software validation l l l Verification and validation is intended to show that a Software validation l l l 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 47

The testing process Computer Science Software Engineering Slide 48 The testing process Computer Science Software Engineering Slide 48

Testing stages l Unit testing • l Modules are integrated into sub-systems and tested. Testing stages l Unit testing • l Modules are integrated into sub-systems and tested. The focus here should be on interface testing System testing • l Related collections of dependent components are tested Sub-system testing • l Individual components are tested Testing of the system as a whole. Testing of emergent properties Acceptance testing • Computer Science Testing with customer data to check that it is acceptable Software Engineering Slide 49

Testing phases Computer Science Software Engineering Slide 50 Testing phases Computer Science Software Engineering Slide 50

Software evolution l l l Software is inherently flexible and can change. As requirements Software evolution l l l 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 51

System evolution Computer Science Software Engineering Slide 52 System evolution Computer Science Software Engineering Slide 52

Automated process support (CASE) l l Computer-aided software engineering (CASE) is software to support Automated process support (CASE) l l Computer-aided software engineering (CASE) is software to support software development and evolution processes Activity automation • • • 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 53

Case technology l Case technology has led to significant improvements in the software process Case technology l Case technology has led to significant improvements in the software process though not the order of magnitude improvements that were once predicted • • 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 54

CASE classification l l Classification helps us understand the different types of CASE tools CASE classification l l Classification helps us understand the different types of CASE tools and their support for process activities Functional perspective • l Process perspective • l Tools are classified according to their specific function Tools are classified according to process activities that are supported Integration perspective • Computer Science Tools are classified according to their organisation into integrated units Software Engineering Slide 55

Functional tool classification Computer Science Software Engineering Slide 56 Functional tool classification Computer Science Software Engineering Slide 56

Activity-based classification Activity-based classification

CASE integration l Tools • l Workbenches • l Support individual process tasks such CASE integration l Tools • l Workbenches • l 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 • Computer Science Support all or a substantial part of an entire software process. Normally include several integrated workbenches Software Engineering Slide 58

Tools, workbenches, environments Computer Science Software Engineering Slide 59 Tools, workbenches, environments Computer Science Software Engineering Slide 59

Key points l l Software processes are the activities involved in producing and evolving Key points l l 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 60

Key points l l l Requirements engineering is the process of developing a software Key points l l l 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 61