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Unformatted text preview: Software Engineering CS 3601 Prof. Shaw 1 Why are you taking this course? Alternatively, why are we teaching this course? Do you need a course in software engineering? How is writing the code for a 2302 project different from software engineering (or is it)? What do you think we will be focusing on in this class? Why worry about SW Engineering? Quality issues: History of SW failures from http://www.wired.com/software/coolapps/news/2005/11/69355 Many more incidents... 3 Software is expensive to maintain Maintenance activities consume 7090% of the total lifecycle cost of software, summing to over $70 billion per year We want to "get it right" the first time But as we'll see this is nontrivial 4 Why is it so hard? Lots of "parts". Many more than mechanical devices Dishwasher 128 parts Car 14,000 parts Space shuttle 2.5 million parts Red Hat Linux 7.1 30 million source lines of code (SLOC) Mac Office 30 million SLOC Using 70 programmers = 428,000 SLOC / programmer But those are big... what about "normal size programs"? Average programmer SLOC (Source lines of code) / day = 100 5 days/week * 52 weeks/year = 26,000 SLOC / year 15 programmer team = 390,000 SLOC / year 5 Why is it so hard? (continued) We're a young field But giant As of 2004, the U. S. Bureau of Labor Statistics counts 760,840 software Unanticipated growth ENIAC/ MARKI in 1946 FORTRAN 1957 engineers holding jobs in the U.S.; for comparison, in the U.S. there are some 1.4 million practitioners employed in all other engineering disciplines combined. http://en.wikipedia.org/wiki/Software_engineering Still more art than science Everything we do is "new". (We don't build the exact same house 30 times.) Need to have more reproducible results Need to have more measurements
6 Why do projects fail so often? Why do projects fail? List from: http://www.spectrum.ieee.org/sep05/1685 Unrealistic or unarticulated project goals Inaccurate estimates of needed resources Badly defined system requirements Question: Poor reporting of the project's status Unmanaged risks Poor communication among customers, developers, and users Use of immature technology How many of these are caused by Inability to handle the project's complexity technical incompetence in your developers? Sloppy development practices A.0 Poor project management B.5 Stakeholder politics C.8 D.All of them Commercial pressures
7 How do we fix it? Need to have more reproducible results Standard processes / procedures to produce good outcomes Design patterns Object oriented programming (reuse) More measurements of both the software and the process More testing at all stages of development By creating a better understanding of the process we use to create software, we'll create better software faster. "Software engineering is the application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software." - IEEE Standard Glossary of Software Engineering Terminology
8 Software Engineering: A Practitioner's Approach, 7/e Chapter 1 Software and Software Engineering
copyright 1996, 2001, 2005 R.S. Pressman & Associates, Inc. For University Use Only May be reproduced ONLY for student use at the university level when used in conjunction with Software Engineering: A Practitioner's Approach. Any other reproduction or use is expressly prohibited. 9 What is Software?
Software is Instructions computer programs Data Structures that enable the programs to adequately manipulate information Documentation the describes the use and operation of the programs
10 Why is software different than hardware? Or manufacturing? software is engineered software doesn't wear out most software is still custom built software is complex 11 Wear vs. Deterioration
i ce s d al r n r a e f i ue r t d et sd ef cs ae u o i e f e t F ilue a r rt ae c ag hne a t ac r e cu l uv id a e c r e e liz d uv T e im 12 There are many types of applications system software OS, file management, networking, drivers, etc... application software data processing, point of sale, other business functions... engineering/scientific software CAD, stress analysis, orbital mechanics embedded software microwave oven keypad, automobile control, cell phone software, etc... productline software word processing, inventory control, etc... WebApps (Web applications) many different things today AI software robotics, data mining, expert systems 13 Legacy Software
Why must it change? software must be adapted to meet the needs of new computing environments or technology. software must be enhanced to implement new business requirements. software must be extended to make it interoperable with other more modern systems or databases. software must be rearchitected to make it viable within a network environment. environment 14 Software A.True or B.False?
1. 2. 3. 4. 5. If we get behind schedule we can add more programmers to catch up A general statement of objectives is sufficient to begin writing programs we can fill in the details later Project requirements change, but change can be easily accommodated because software is flexible Once we write the program and get it working our job is done Software engineering will make us create unnecessary documentation and will invariably slow us down 15 Software Myths
Affect managers, customers (and other nontechnical stakeholders) and practitioners Are believable because they often have elements of truth, but ... Invariably lead to bad decisions, therefore ... Insist on reality as you navigate your way through software engineering One of the goals in this class is to learn you how to determine what reality is!
16 Fixing the problem
Software engineering! Software engineering is really just a set of ideas and tools to use (when it makes sense) to give you a higher likelihood of success on a software project. Will your project fail if you don't use any software engineering techniques? No.... but you have a better chance at success if you do.
17 A Generic Framework Communication Planning Heavy collaboration with the customer, other stakeholders and encompasses requirements gathering and related activities Establish a plan for the work. Technical task to be conducted, risks, needed resources, work products to be created, and a schedule Creation of models to allow the customer and the developer to better understand the requirements and design that will achieve those requirements Combines code generation and testing required to uncover errors in the code The software (as a complete entity or partially complete increment) is delivered to the customer who evaluates it and provides feedback. Modeling Construction Deployment 18 Framework Activities Communication Planning Modeling Construction Analysis of requirements Design Code generation Testing Deployment What are some artifacts (work tasks, work products, milestones & deliverables, QA checkpoints) of each activity? What tools may help support them? 19 Umbrella Activities Software project management Formal technical reviews Software quality assurance Software configuration management Work product preparation and production Reusability management Measurement Risk management 20 A Layered Technology
tools methods process model a "quality" focus
Tools: anything that helps support the method Methods: what you do during each activity Model: a way to organize basic activities
21 The Process Model: Adaptability The framework activities will always be applied on every project ... BUT The tasks (and degree of rigor) for each activity will vary based on: the type of project characteristics of the project common sense judgment; concurrence of the project team 22 Question Pick any one of the project types below and tell me which process activity would be emphasized or deemphasized and why
Framework Activities Communication Planning Modeling Project Types: 1.Space Shuttle control system 2.Webbased calendar 3.Embedded controller in your refrigerator 4.Automatic "daily fortune" textmessenger Construction Analysis of requirements Design Code generation Testing
23 Deployment How to solve any problem Polya 1945 Understand the problem Plan a solution Carry out the plan Examine the result for accuracy Do these agree with our basic framework? communication, planning, modeling, construction deployment? 24 How do we improve our performance? We want to "provide guidance for developing or improving processes that meet the business goals of an organization" Capability Maturity Model Integration (CMMI) is a process improvement approach that helps organizations improve their performance 25 CMMI defines characteristics shown to achieve good results. The CMMI defines each process area in terms of "specific goals" and the "specific practices" required to achieve these goals. Specific goals establish the characteristics that must exist if the activities implied by a process area are to be effective. Specific practices refine a goal into a set of processrelated activities. The CMMI PP - project planning REQM - Requirements Mgmt MA - Measurement and Analysis CM - Configuration Mgmt PPQA - Process and Product QA 26 The CMMI 27 Process Assessment Does your process adhere to the qualities described in XYZ. The process should be assessed to ensure that it meets a set of basic process criteria that have been shown to be essential for successful software engineering. Many different assessment options are available: SCAMPI assessed for CMMI standards compliance SPICE assessed for ISO/IEC15504 compliance ISO 9001:2000 assessed for ISO 9001 compliance Process Assessment is often used to "certify" a company as compliant ("Company X is ISO9001 certified "or "Company Y is CMM level 4")
28 Assessment and Improvement
Software Process identifies modifications to is examined by identifies capabilities and risk of Software Process Assessment Software Process Improvement leads to motivates leads to Capability Determination Best use of assessment though is to improve your process! (Not just "get the certification")
29 The Waterfall Model Do all process steps in the following order (this is generally thought of as the most basic model)
Com m unic a t ion proje c t init ia t ion re quire m e nt ga t he ring Planning estimating scheduling tracking Mode ling
analysis design Const r uc t ion
code t est De ploy m e nt de liv e ry s upport f e e dba c k 1998, the Standish Group analyzed 23,000 projects to determine failure factors. The top reasons for project failure, according to the report, were associated with waterfall practices.
- http://www2.umassd.edu/SWPI/xp/articles/r6047.pdf 30 Different families of models
Prescriptive Prescriptive Models 1970->Present -Waterfall (1970) -Evolutionary (1975) -Incremental (1975) -Spiral (1988) -RAD (1991) Agile Agile Models 2001->Present - eXtreme Programming (1999) - SCRUM (1990s) - DSDM (1997) - Crystal (2001) All dates are approximate based on publications 31 Different families of models
Prescriptive Goal: Higher Quality Software Philosophy:
Bring order to chaos Provide repeatability/consistency Provide ability to control Provide ability to coordinate teams Agile Goal: Higher Quality Software Philosophy:
Individuals and interaction over process and tools Working software over large documentation Customer collaboration over contract negotiation Responding to change over following a plan Which is probably better for large teams? A. Prescriptive B. Agile C. Same Which is probably better for a web application? Which is probably better for Mars rover control system? Which is produces better software?
32 Project Team decisions due next Wednesday/Thursday (depending on section) Post to blackboard a document containing your team name, and the names and emails of the members of your team 45 students per team Everyone turn in your team interview sheets (handed out Sept 1/2) in class. If I didn't get an email from your team, I will use these sheets for the rest of you to assign teams for you. I will then set up accounts for teams on XPdev; you will be emailed information 33 Homework Pressman Ch 1 exercises: 5, 8, 10 Due next Tuesday (1/25) 34 ...
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This note was uploaded on 06/22/2011 for the course COMP 3002 taught by Professor Staff during the Spring '10 term at Kennesaw.
- Spring '10
- Software engineering