Final spiralmodel97
- 1. General Idea of Iterative Models- Spiral Model CS 641 13 September 2001 Presented by Matt Heusser & Tabrez Sait
- 3. Waterfall Model – Revisited • Disadvantages of Waterfall Model – 1. Real projects are rarely so straightforward and sequential – 2. It is generally not possible to completely define (and freeze) all the requirements at the start of the project – 3. Problem is discovered in testing? – 4. Freight-Train Effect, or Late, or Over-Budget
- 4. What is “Wicked Problem” • Problems we can’t really understand until we’ve developed a solution. • “That is not what I want ... but now I know what I do want!”
- 5. The Mythical Man MonthDr. Frederick Brooks • In software projects, what will take one person ten months can not be solved by ten people in one month. • Throwing people onto a late project will just make it later • Because of Wicked Problems, “Plan to the throw one away”
- 6. Rapid Prototyping • Put together a team of “Smart Guys” from multiple disciplines • Develop the GUI on Paper • Code the GUI in a fast language (Make it look like it’s working) <=Requirements=> • • Show it to the USERS (A Picture is worth a 1,000 words) Get Feedback **<=Prototype=>** <=Design=> <=Code=> <=Test=> <=Deploy=>
- 7. Case Study- RAD Grand Community Calendar Project – Project Manager, Developer, Community Members write user requirements – Coder writes sample HTML – Shows the web page; heads bob, some changes to navigation – DBA, Coder, Project Manager determine the architecture (Design) – Coding & Review – Shifting Requirements priced project out-ofbudget
- 8. Problems With Prototyping • No “Current” Documents • Functional Spec is Prototype + Feedback • Prototype is not “baseline” functionality • Same problems with Functional Spec as waterfall!
- 9. Prototyping Part II: The Rigged Demo • Re-Visit and improve the prototype to serve as a “baseline” Listen To Customer • Turns prototype into a “rigged demo” • Show that to the customer Customer Test Drives Mockup Build/Revise Mockup
- 10. At the Demo Dialogue • Customer:“This looks great, and it looks like you’re about done. When can we have it?” • Developer: “Uh, it’s only a prototype – we plan to throw it away and start over.” • Customer: “No – this is exactly what we need, and we need it now! We’ll take 50 prototypes!” – – The Sales Guy begins to see $$ signs. Under Rigged Demo scenarios, there is either a lot of wasted effort, or prototypes that were never intended to ship end up shoved into production.
- 11. Case Studies Multi-Stage Prototyping • Telecommunication – The prototype made the sale! – Was pushed into production – From user requirements to “Ship”ing in 4 month – Errors, Bugs, High Turn-Over – Had to support bug fixes plus “incremental” change • Visual Product Explorer – Prototype created for internal consumption – Feedback Cycle – Modified for trade demo – Next step: How do we write the spec? – Product is the spec; shove it into production!
- 12. Iterative Models What’s an Iteration? • • Iterative Design: Code as much as you can questions surface, then start over. Every model we’ll talk about below is a variation on the Iterative Model.
- 13. Spiral Model Determine objectives, alternatives, constraints Evaluate alternatives, identify and resolve risks Plan next phases Develop verify next level product
- 14. Risk Assessment • Spiral Model – risk driven rather than document driven • The "risk" inherent in an activity is a measure of the uncertainty of the outcome of that activity • High-risk activities cause schedule and cost overruns • Risk is related to the amount and quality of available information. The less information, the higher the risk • What happened with Denver Airport Luggage System?
- 15. Spiral Model Strength and Weaknesses • Strengths – – – – – Introduces risk management Prototyping controls costs Evolutionary development Release builds for beta testing Marketing advantage • Weaknesses – – – – – Lack of risk management experience Lack of milestones Management is dubious of spiral process Change in Management Prototype Vs Production
- 16. Win Win Spiral Model • Win-Win Spiral Process Model is a model of a process based on Theory W, which is a management theory and approach "based on making winners of all of the system's key stakeholders as a necessary and sufficient condition for project success."
- 17. WinWin Spiral Model ••Identify Nextproduct & process definitions ••Validate commitment holders process Identify Stake holders win conditions Evaluate Product of Process and Reconcile Level Stake Define next level & product Alternatives Review, Win conditions
- 18. Win Win Spiral Cont • Identifying the system's stakeholders and their win conditions and • reconciling win conditions through negotiation to arrive at a mutually satisfactory set of objectives, constraints, and alternatives for the next level. • Evaluate Product and Process Alternatives. Resolve Risks • Define next level of product and process including partitions • Validate Product and Process Definitions • Review, commitment
- 19. WinWin SpiralAnchor Points • Life Cycle Objective(LCO) – What should the system accomplish? • Life Cycle Architecture(LCA) – What is the structure of the system? • Initial Operational Capability(IOC) – The first released version
- 21. Key Elements of IOC Milestone • Software preparation – Including both operational and support software with appropriate commentary and documentation – data preparation or conversion – the necessary licenses and rights • Site preparation – including facilities, equipment, supplies and vendor support • User, Operator and Maintenance preparation – including selection – team building – training
- 22. Win Win Spiral - Case Study • Extending USC Integrated Library System to access multimedia – Flexibility and Discipline let the projects teams adapt to challenges while staying on schedule – Use of risk management helped team focus on CSF for their projects – One cycle for each milestone – Communication and trust between stakeholders, shared vision – Don’t finish negotiations before prototyping – Client acceptance
- 23. Another Extreme CleanRoom Methodologies • From Hardware Cleanrooms • An incremental process that encourages continuous improvement; • Technical reviews that prevent defects and significantly reduce costs • Design and coding practices that make it easy to adapt as requirements change • • • Testing techniques that focus on measuring quality; Solution-oriented teams that encourage cooperation, reduce the dependence on "gurus," and promote flexibility Documentation structures that reveal the big picture and help team members maintain intellectual control.
- 24. Clean Room Continued • REAL Peer Review Mathematical proof of correctness (Challenges associated with it?) • Functional Specifications as Box Diagrams (State, Black, Clear)
- 25. Yet Another Extreme: Hacking • Hacking: – Code ‘n Fix – More Common than you thought • Makes Sense for: – – – – Low-Risk, Small Project We know exactly what we want (not “Wicked”) Use once, then throw away Bugs can be tolerated/fixed • Problem: – “Why not just re-use Hack X here with change Y …” – Hack Code is hard to maintain, but appealing from a management perspective. • Case Study: – I’m guessing … just about every project you ever did as an undergraduate.
- 26. Summary Summary • Waterfall – good for budgeting, but doesn’t analyze risk or have a good way to manage errors found later in the process. • Iterative – Models attempt to solve this by coding “as far as possible”, gathering feedback, and coding again.. – Prototyping “Plan to throw one away”, then re-build it “right.” – Incremental (“Staged”) Delivery Builds the software by a series of waterfalls
- 27. Summary • Spiral: – Addresses Risk at every stage & let the stakeholders determine the outcome. • Win/Win – Seeks ways to provide customer feedback through anchor points, manages risk for management, and provides win conditions for developers. • Cleanroom / Hacking – Are alternative models that work for large projects that must work right the first time, and small projects with little risk.
- 28. Resources • Generally Interesting Theories for REAL-WORLD Development: • Wicked Problems/State of Coding: – http://www.unidata.ucar.edu/staff/caron/collab/wicked.html – http://www.chc-3.com/pub/beautifulsoftware.htm • Mythical Man Month – (http://www.amazon.com/exec/obidos/ASIN/0201835959/ref=bxgy_ sr_text_a/002-7413073-4868053) • Code Complete – (http://www.amazon.com/exec/obidos/ASIN/1556154844/ref=bxgy_ sr_text_a/002-7413073-4868053) • Joel Spolsky on Real-World Software Development – http://www.joelonsoftware.com • Software Engineering, A Practitioner’s Approach – http://www.mhhe.com/engcs/compsci/pressman/
- 29. Resources (2) • Spiral Model – Using the WinWin Spiral Model: A case study, Boehm Barry, July 1998, Computer • Spiral Development workshop – www.sei.cmu.edu/cbs/spiral2000/february2000/BoehmSR.html • Anchoring the Software Process, Boehm Barry – http://www.csis.gvsu.edu/~ferguson/classes/cs641/papers/ASP.pdf • Denver Airport Project – http://www.time.com/time/magazine/archive/1994/940516/940516.tr ansportation.html • Cleanroom Model – http://www.cleansoft.com/cleansoft_mgrguide.html – http://www.sei.cmu.edu/pub/documents/96.reports/pdf/tr022.96.pdf • Hacking – http://www.plethora.net/~seebs/faqs/hacker.html
- 30. Homework • Objective Question – One major difference between the Waterfall and iterative models is that the iterative models address risk. How do they do that? • Subjective Question – Which of these models is the best for the Customer? The Seller? Why?