Components Based Design and Development. Unit 2: Software Engineering Quick Overview

Transcription

1 Components Based Design and Development Computer Engineering Studies Universidad Carlos III de Madrid Unit 2: Software Engineering Quick Overview Juan Llorens Högskolan på Åland Finland / Universidad Carlos III de Madrid - Spain Juan.llorens@uc3m.es 1

2 Engineering... Software Engineering the profession in which a knowledge of the mathematical and natural sciences gained by study, experience and practice is applied with judgment to develop ways to utilize, economically, the materials and forces of nature for the benefit of mankind. (Accreditation Board for Engineering and Technology, 1996). Particularities of software engineering The product (software) A lot of development, little engineering discipline Frequent changes in the product It is not seen as necessary by the so called software engineers From Gonzalo Genova 2

3 Software Engineering The economies of ALL developed nations are dependent on software. More and more systems are software controlled Software engineering is concerned with theories, methods and tools for professional software development. Expenditure on software represents a significant fraction of GNP in all developed countries. Ian Sommerville Software Engineering, 7th edition. Chapter 1 3

4 The systems engineering process Requirements definition System decommissioning System design System evolution Sub-system development System installation System integration Ian Sommerville Software Engineering, 7th edition. Chapter 2 4

5 Inter-disciplinary involvement Software engineering Electronic engineering Mechanical engineering Structural engineering ATC systems engineering User interface design Civil engineering Electrical engineering Architecture Ian Sommerville Software Engineering, 7th edition. Chapter 2 5

6 What is a software process? Objectives, needs, ideas problems, failures,.. How is a software project done? Software application Not a Software system 6

7 What is a software process? A set of activities whose goal is the development or evolution of software. Generic activities in all software processes are: Specification - what the system should do and its development constraints Development - production of the software system Validation - checking that the software is what the customer wants Evolution - changing the software in response to changing demands. Ian Sommerville Software Engineering, 7th edition. Chapter 1 7

8 What is a software process model? A simplified representation of a software process, presented from a specific perspective. Examples of process perspectives are Workflow perspective - sequence of activities; Data-flow perspective - information flow; Role/action perspective - who does what. Generic process models Waterfall; Iterative development; Component-based software engineering. Ian Sommerville Software Engineering, 7th edition. Chapter 1 8

9 Usual workflow Activities Req. analysis design implementation tests Not so Usual workflow Activities Vocabulary Id. Project Mgmt Estimation Debriefing Sw For Reuse Risk Mgmt. Project Plan. Indexing 9

10 Types of Software Processes : the waterfall process Need analysis of requirements A single iteration design implementation is an idealization never realized in this pure form tests Final product 10

11 Iterative process [spiral] Requirements analysis design N iterations need final product N versions of the product, documentation... tests implementation 11

12 Iterative and incremental process Enables the evolution in parallel of several workflows, and by that the work in parallel of several teams of people the different versions of the documents produced in each iteration are not necessarily compatible between them: organize well the documentation iteration 1 iteration 2 iteration 3 analysis (version 1) analysis (version 2) design (version 1) analysis (version 3) design (version 2) implementation (version 1) 12

13 UP: Phases, iterations and workflows Phases of the life cycle Workflows Inception Elaboration Construction Transition requirements analysis an iteration in the phase of Elaboration design implementation tests Preliminary iteration(s) Iter. #1 Iter. #2 Iter. #n Iter. #n+1 Iter. #n+2 Iter. #m Iter. #m+1 iterations 13

14 New Project My Favorite workflow structure for Development Voc Software for Reuse CM WG PMgnt Req Cap Risk Sw for reuse Plan-Est Req Ana Arc. Des Traceability D Des Document Mngmnt. Dev Find + Reuse Software with Reuse Tes Db Ix New Solution 14

15 My Favorite dataflow structure for Development Voc PMgnt Req Cap Risk Ontology Document Templates Text based Requirements Text Based Risks Spreadsheets Documents Documents Plan-Est Documents Documents Code Req Ana Arc. Des D Des Gantt Diagrams Architectural Models Dev Acknowledged Reports Requirements Models Tes Db Software Models Ix Reports Documents 15

16 Other frameworks and nomenclatures Terminology of UP requirements analysis design implementation tests Classical terminology requirements analysis design implementation integration tests Eric Braude, Software Engineering. An Object-Oriented Perspective, John Wiley & Sons, 2001, p

17 How to perform an Iterative Software Process divide a project in mini-projects, easier to manage and complete each mini-project is an iteration each iteration contains all the elements of a normal project: planning analysis and design construction integration and tests generate a version of the product (internal or external) each iteration generates a baseline that includes a partially completed version of the final system, and all the associated documentation the successive iterations build on top of each other until the final system is finished the difference between two baselines is known as an increment 17

18 What are software engineering methods? Structured approaches to software development which include system models, notations, rules, design advice and process guidance. Model descriptions Descriptions of graphical models which should be produced; Rules Constraints applied to system models; Recommendations Advice on good design practice; Process guidance What activities to follow. Based on Ian Sommerville Software Engineering, 7th edition. Chapter 1 18

19 What are the costs of software engineering? Roughly 60% of costs are development costs, 40% are testing costs. For custom software, evolution costs often exceed development costs. Costs vary depending on the type of system being developed and the requirements of system attributes such as performance and system reliability. Distribution of costs depends on the development model that is used. Ian Sommerville Software Engineering, 7th edition. Chapter 1 19

20 Software costs Software costs often dominate computer system costs. The costs of software on a PC are often greater than the hardware cost. Software costs more to maintain than it does to develop. For systems with a long life, maintenance costs may be several times development costs. Software engineering is concerned with cost-effective software development. Ian Sommerville Software Engineering, 7th edition. Chapter 1 20

21 Activity cost distribution 0 Waterfall model Specification Design Development Integration and testing Iterative development Specification Iterative development System testing Component-based software engineering Specification Development Integration and testing 0 Development and evolution costs for long-lifetime systems System development System evolution Ian Sommerville Software Engineering, 7th edition. Chapter 1 21

22 Product development costs Ian Sommerville Software Engineering, 7th edition. Chapter 1 22

23 The maturity of the Software Engineering discipline (swing) 1. Real need: what the customer really wanted. 2. Client side: what the client was able to describe as his/her clear need. 3. Sale process: what the software manufacturer promised the client. 4. Requirements: the final understanding of what the customer described as requirements. 5. Analysis: how was planned that the system should finally work at the client side. 6. Design: how the system should perform the analysed functionality. 7. Coding: what the programmer finally produced. 8. On-site installation: what was really installed in the client site. 9. Test: what the responsibles saw in the system. 23