Technical Writing - Software Engineering Life Cycle Review

Transcription

1 CS212: HARD SKILLS Announcements Overview motivation solitary programming engineering and software engineering software life cycle development models modularity documentation quality, legality, 1. Motivation 1.1 Last Time people work with people! need soft skills - project management - leadership - group dynamics - pair programming 1.2 This Time people work on stuff! hard skills - solitary programming reminder - beyond programming: engineering - software engineering - business and legal issues 1.3 Goals now: work in teams to write code later: work in teams on projects ultimately: satisfying career! Solitary Programming 2.1 The Gist Problem Process Solution? 2.2 Programming As Writing brainstorming research outline draft polish Iterate brainstorming planning (nouns, verbs) algorithm code program 2.3 Iteration and Development stepwise refinement: - baby steps - breaking problem into more manageable pieces development process: - top-down - bottom-up 2.4 Stubbing stubbing - classes - methods - documentation/specification examples: class BinExpr implements AST { } class UnExpr implements AST { } public class Program implements AST { public Program(Tokenizer t, String sourcename) throws Exception { } public String generatecode() { return ""; } public String tostring() { return ""; } } // public class BC: { // Start program (compile Bali into sam) // Set source (Bali) and output file (sam): // Create AST and store in progtree: // Generate sam code and store in progcode: // Print target to output file (sam): // Print actual parse tree: // Close file streams: // } 3 4

2 3. Engineering 3.1 What is Engineering? ABET: 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. 3.2 History of Engineering historical: - military engineering - civil(ian) engineering: John Smeaton (1700s) - first woman civil engineer: Nora Stanton Blatch, Cornell, Class of 1905! engineering in the US - started at US Military Academy - specialization and drift from military caused more branching 4. Software Engineering 4.1 What is Software Engineering? From The application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software; that is, the application of engineering to software. Original definition (1969, first conference on SE): The establishment and use of sound engineering methods and principles to obtain reliable software that works on real machines. see also Documentation/history_html Brief History Robert L. Glass from his book In the Beginning: Recollections of Software Pioneers The Pioneering Era ( ) - punch cards! - introduction of high(er)-level languages The Stabilizing Era ( ) - notion of structured programming - software becomes valuable The Micro Era (1980-Present) - computers for everybody! - GUIs 4.3 Engineering VS Software Engineering some controversy! - states attach legality to engineer - see davis.pdf primary differences: - E: ability to build from prefab components SE: redesigns from scratch - E: tolerances SE: lacks them - E: metrics (measuring systems, as in physical units) SE: yes? no? what do you think? 7 8

3 4.4 Virtual Engineering a DIS invention game design, but more general: - application and extension of engineering principles and design for a virtual environment - the virtual engineer not only designs entities, but defines the principles to which the entities must adhere 4.5 Classic References The Art of Computer Programming, D. E. Knuth Introduction to Algorithms, T. H. Cormen, et al The C Programming Language, Kernighan and Ritchie 4.6 Organizations Software Life Cycle 5.1 The Gist birth growth rebirth eventual death: Develop Use Modify Obsolete? Phases - Analysis - Design - Implementation - Testing description of phases below order of phases? next section Analysis the what : specifications for software four steps: - define user - define needs - define requirements - define methods 5.3 Design the how : plans on how to develop the specs no actual programming yet mostly planning lots of charts and diagrams 5.4 Implementation the stuff : actual coding interim steps: - pseudocode - flowcharts, data flow diagrams choice of language(s) 5.5 Testing the check : does the software meet the specs? two general approaches: - black box: tester knows nothing of program - white box: tester knows everything about program 11 12

4 6. Development Models 6.1 Waterfall Model most classic development flows in one direction: analysis testing Analysis Design Implementation Testing should you use? - advantage: phases finish in synch - disadvantage: finding problem 6.2 Incremental Model break process into many steps each step provides more detail for example, complete entire program as stubs then begin to fill them in essentially, waterfall repeated many times 6.3 Extreme Programming popular new methodology snippets of approach: - frequent small releases - testing up front: unit testing JUnit: - pair programming many more details check out CASE computer aided software engineering software to help build software Modularity 7.1 Modules small portion of code/plan modularity overriding philosophy: - stepwise refinement - structured program - unit testing approach - top-down/bottom-up design - classes! 7.2 Tools want to represent module connections structure chart for procedural flow class diagram for OOP UML: unified modeling language - flow - design Coupling want modules to be independent forms of coupling: - control: transfer control, as with procedures - data: sharing data - more OOP: mostly control coupling because of encapsulation horrors of global data 7.4 Cohesion how closely processes are related; degree of relatedness of internal parts want this to be high why? - philosophy: each function has unique purpose - example: UNIX tools forms: - logical cohesion (weaker): related activities collected together - functional cohesion (stronger): all parts of module geared for same task OOP: objects usually logically cohesive, but methods can be functionally cohesive 15 16

5 8. Documentation 8.1 Engineers and Writing do engineers need to write? reports, presentations papers, books 8.2 Technical Writing actually, it s own field must interact with writers in design team 8.3 Comments preconditions, postconditions Javadoc 8.4 User Manuals/On-line Help short, active sentences simple language KISS 9. Legal Issues 9.1 Ownership and Copyright who owns software that you write? copyright, fair use, Liability engineering and law: - liability insurance - professional engineering license software liability? peer review? Free? peer review issue possibly handled by rethinking privacy ware : - shareware - freeware free software : - freedom to share - open source initiative: Open source promotes software reliability and quality by supporting independent peer review and rapid evolution of source code. 9.4 Quality Standards interesting facts (1996, IEEE study): - for 25 million lines of code, 90% of all defects attributed to modules that had 13% of the code - 95% of serious design defects from 2.5% of code documented horrors: : Risks Forum: Certification and Licensing software engineering as engineering profession? 19 20