2. L5-S1 Software StabilitySJSU – CmpE © M.E. Fayad 2000-2005 Software Architectures Dr. M.E. Fayad, Professor Computer Engineering Department, Room #283I College of Engineering San José State University One Washington Square San José, CA 95192-0180 http://www.engr.sjsu.edu/~fayad

3. L5-S2Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad 2 Lesson 5: Software Stability

4. L5-S3Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad Lesson Objectives 3 Overview of Previous Lecture Understand the following: – Enduring Business Theme – Business Objects – Industrial Objects – Framework Layering

5. L5-S4Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad Roadmap 4 oScare - General State of Panic o Identify the Killers (Problems) oCatch the killers (Solutions)

6. L5-S5Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad The Current State of Software - I 5 Current software projects are engineered for the “here and now.” Changes in the support structure or the software market require massive reengineering projects. This reengineering costs ridiculous amounts of money.

7. L5-S6Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad The Current State of Software - II 6 Software has short life span. Often wrong software application is implemented Sometimes cancelled before completion maintenance cost over 80% of the development lifecycle

8. L5-S7Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad Sample Problem - The Loan 7 January 1998 –I gave a loan of $1000 to one of my students. –He promised to return the money by May 1998. April 1998 –Received an e-mail asking for an extension until August 1998 March 2002 –I have not received the money

9. L5-S8Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad Where Is The Problem? 8 After giving this problem to the students in a software engineering class, I received the following responses. –There is no problem. –Take him to court. –Kick his $@%#&! –Ignore it. What do you think?

10. L5-S9Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad A Traditional Model 9 LenderLoan Borrower OwesBorrowed Lent Do you think this model is an accurate representation of the problem?

11. L5-S10Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad Roadmap 10 oScare - General State of Panic o Identify the Killers (Problems) oCatch the killers (Solutions)

12. L5-S11Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad Problems 11 Wrong Analysis Industrial Objects Not stable architecture Missing the most enduring concepts

13. L5-S12Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad Roadmap 12 oScare - General State of Panic oIdentify the Killers (Problems) oCatch the killers (Solutions)

14. L5-S13Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad Open Discussion 13 Problem Domain Friendship Health Employment Family Other Relationships Borrower Schedule Lender Loan Education Expenses Finance Needs

15. L5-S14Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad EBT-Based Model - The Loan Problem 14 … Friendship {Enduring} Friend {Business} BorrowerLender Finance {Enduring} Loan {Business} Solvency {Enduring} Need {Enduring} Expenses {Business} Employment {Business} Health {Business} Education {Business} Family {Business}

16. L5-S15Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad Kitchens are systems that we are all familiar with. What makes a kitchen a kitchen? Traditionally, people think of a certain set of objects when they think of a kitchen: –Stove –Sink –Refrigerator –Dishwasher –etc... 15 Sample Problem II - The Kitchen

17. L5-S16Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad The result is a model like this: 16 The Kitchen - A Traditional Model Kitchen CabinetCounterApplianceSink RefrigeratorDishwasherRangePantry CooktopOvenFreezer

18. L5-S17Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad This model has inherent flaws, however. The model can be thought of as a “tree” of aggregations and generalizations. Many of the roots of the subtrees can change drastically, causing this model to break. For example, imagine replacing the appliance node with a Star Trek food replicator... 17 The Kitchen - A Traditional Model Kitchen CabinetCounterApplianceSink RefrigeratorDishwasherRangePantry CooktopOvenFreezer

19. L5-S18Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad To correct this model, one must concentrate on those aspects that do not change over time. Enduring Business Themes are those concepts that remain constant for a given problem. Business Objects are those support objects that remain externally stable. Objects that may be replaced as times change are Industrial Objects. 18 The Kitchen - Correcting The Model

20. L5-S19Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad What does a kitchen need? What do people do in a kitchen? What is a kitchen for? 19 The Kitchen - Correcting The Model Cooking Cuisine Livability Storage Cleanliness Convenience Spaciousness

21. L5-S20Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad 20 The Kitchen - A Stable Model CabinetPantry RefrigeratorFreezer Food Storage & Preservation {Enduring} Microwave Range Cooking {Enduring} CooktopOven Cuisine {Enduring} Recipe {Business} Food Livability {Enduring} Cleanliness {Enduring} Convenience {Enduring} Light {Business} CounterShelf SinkDishwasherWindowElectric Light Kitchen

22. L5-S21Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad Identifying Enduring Business Themes & Business Objects - Identification Criteria 21 Stability Adaptability Essentiality Explicitness Intuition Tangibility Commonality to the Domain

23. L5-S22Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad 22 Identification Criteria

24. L5-S23Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad 23 Identification Criteria

25. L5-S24Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad 24 Identification Criteria

26. L5-S25Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad 25 Identification Criteria

27. L5-S26Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad 26 Identification Criteria

28. L5-S27Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad 27 Identification Criteria

29. L5-S28Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad 28 Identification Criteria

30. L5-S29Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad Identification Heuristics - Enduring 29 Enduring Business Themes and Business Objects must be enduring. Watch out - Long field histories will not necessarily translate to true endurance.

31. L5-S30Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad Identification Heuristics - Industrial Object Identification 30 Is the object present in a “classical” model? Can the object be replaced? Is the object a representation of a concrete item?

32. L5-S31Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad Identification Heuristics - Top-Down Identification 31 Break off conceptual pieces of the problem. Recursively break these concepts down. Stop when a layer of industrial objects is reached.

33. L5-S32Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad Identification Heuristics - Bottom-Up Identification 32 Start with a “classical” model. Group the industrial objects under a conceptual “heading.” Continue this grouping until further grouping is impractical or nonsensical.

34. L5-S33Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad Identification Heuristics - There Is No Silver Bullet 33 EBT’s are conceptual themes… Usually Business objects are more concrete objects… Usually There are always exceptions to any rule.

35. L5-S34Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad 34 HealthCare Example: PID

36. L5-S35Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad Explain the following statements: 1. Objects should be intelligent agents 2. Mechanism rich and policy free 3. A valuable object works and plays well with others 4. Analysis model should not be too elaborate or too formal Explain how to build an analysis model Explain how do you make the analysis model more adaptable 35 Discussion Questions

37. L5-S36Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad Define: Criteria for Enterprise Frameworks Let’s discuss of how to build Enterprise Frameworks T/F: EBTs are testing patterns. BOs are stable design patterns. EBTs + BOs = Framework. 36 Questions for the Next Lecture

38. L5-S37Software Stability © M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad Task 1: Stable Analysis Patterns Task 2: Stable Design Patterns Task 3: Design Sessions for SSM (Discuss) 37 Tasks for Next Lecture