Post on 20-Dec-2015
SJSU – CmpE © M.E. Fayad 2000-2005 L5-S1 Software Stability
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
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S2 Software Stability
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Lesson 5:Software Stability
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S3 Software Stability
Lesson Objectives
Objectives
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Overview of Previous Lecture Understand the following:
– Enduring Business Theme
– Business Objects
– Industrial Objects
– Framework Layering
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S4 Software Stability
Roadmap
4
Scare - General State of Panic
Identify the Killers (Problems)
Catch the killers (Solutions)
Objectives
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S5 Software Stability
The Current State of Software - I
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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.
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S6 Software Stability
The Current State of Software - II
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Software has short life span. Often wrong software application is
implemented Sometimes cancelled before completion maintenance cost over 80% of the
development lifecycle
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S7 Software Stability
Sample Problem - The Loan
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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
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S8 Software Stability
Where Is The Problem?
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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?
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S9 Software Stability
A Traditional Model
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Lender Loan
Borrower
Owes Borrowed
Lent
Do you think this model is an accurate representation of the problem?
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S10 Software Stability
Roadmap
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Scare - General State of Panic
Identify the Killers (Problems)
Catch the killers (Solutions)
Objectives
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S11 Software Stability
Problems
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Wrong Analysis
Industrial Objects
Not stable architecture
Missing the most enduring concepts
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S12 Software Stability
Roadmap
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Scare - General State of Panic
Identify the Killers (Problems)
Catch the killers (Solutions)
Objectives
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S13 Software Stability
Open Discussion
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Problem DomainFriendship
Health
EmploymentFamily
Other Relationships
Borrower
Schedule
Lender
Loan
Education
Expenses
Finance
Needs
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S14 Software Stability
EBT-Based Model - The Loan Problem
14…
Friendship{Enduring}
Friend{Business}
Borrower Lender
Finance{Enduring}
Loan{Business}
Solvency{Enduring}
Need{Enduring}
Expenses{Business}
Employment{Business}
Health{Business}
Education{Business}
Family{Business}
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S15 Software Stability
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...
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Sample Problem II - The Kitchen
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S16 Software Stability
The result is a model like this:
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The Kitchen - A Traditional Model
Kitchen
Cabinet Counter Appliance Sink
Refrigerator Dishwasher RangePantry
Cooktop OvenFreezer
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S17 Software Stability
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
Cabinet Counter Appliance Sink
Refrigerator Dishwasher RangePantry
Cooktop OvenFreezer
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S18 Software Stability
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.
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The Kitchen - Correcting The Model
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S19 Software Stability
What does a kitchen need? What do people do in a kitchen? What is a kitchen for?
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The Kitchen - Correcting The Model
Cooking
Cuisine
Livability
Storage
Cleanliness
Convenience
Spaciousness
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S20 Software Stability
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The Kitchen - A Stable Model
Cabinet Pantry
Refrigerator Freezer
Food Storage &
Preservation{Enduring}
Microwave
Range
Cooking{Enduring}
Cooktop Oven
Cuisine{Enduring}
Recipe{Business}
Food
Livability{Enduring}
Cleanliness{Enduring}
Convenience{Enduring}
Light{Business}
Counter Shelf
Sink DishwasherWindow Electric Light
Kitchen
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S21 Software Stability
Identifying Enduring Business Themes & Business Objects - Identification
Criteria
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Stability Adaptability Essentiality Explicitness Intuition Tangibility Commonality to the Domain
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S22 Software Stability
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EnduringBusinessThemes
BusinessObjects
IndustrialObjects
Intuition Intuition Intuition andReading
Reading Only
Identification Criteria
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S23 Software Stability
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EnduringBusinessThemes
BusinessObjects
IndustrialObjects
Intuition Intuition Intuition andReading
Reading Only
Stability OverTime
Stable Over Time Externally Stable Unstable
Identification Criteria
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S24 Software Stability
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EnduringBusinessThemes
BusinessObjects
IndustrialObjects
Intuition Intuition Intuition andReading
Reading Only
Stability OverTime
Stable Over Time Externally Stable Unstable
Adaptability AdaptableWithout Change
AdaptableThrough InternalChange
Not Adaptable
Identification Criteria
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S25 Software Stability
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EnduringBusinessThemes
BusinessObjects
IndustrialObjects
Intuition Intuition Intuition andReading
Reading Only
Stability OverTime
Stable Over Time Externally Stable Unstable
Adaptability AdaptableWithout Change
AdaptableThrough InternalChange
Not Adaptable
Essentiality Essential Essential Replaceable
Identification Criteria
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S26 Software Stability
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EnduringBusinessThemes
BusinessObjects
IndustrialObjects
Intuition Intuition Intuition andReading
Reading Only
Stability OverTime
Stable Over Time Externally Stable Unstable
Adaptability AdaptableWithout Change
AdaptableThrough InternalChange
Not Adaptable
Essentiality Essential Essential Replaceable
Commonalityto the Domain
Core Core Peripheral
Identification Criteria
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S27 Software Stability
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EnduringBusinessThemes
BusinessObjects
IndustrialObjects
Intuition Intuition Intuition andReading
Reading Only
Stability OverTime
Stable Over Time Externally Stable Unstable
Adaptability AdaptableWithout Change
AdaptableThrough InternalChange
Not Adaptable
Essentiality Essential Essential Replaceable
Commonalityto the Domain
Core Core Peripheral
Tangibility Conceptual Semi-tangible Tangible
Identification Criteria
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S28 Software Stability
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Enduring Business Themes
Business Objects
Industrial Objects
Intuition Intuition Intuition and Reading
Reading Only
Stability Over Time
Stable Over Time Externally Stable Unstable
Adaptability Adaptable Without Change
Adaptable Through Internal Change
Not Adaptable
Essentiality Essential Essential Replaceable
Commonality to the Domain
Core Core Peripheral
Tangibility Conceptual Semi-tangible Tangible
Explicitness Implicit Sometimes Explicit
Explicit
Identification Criteria
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S29 Software Stability
Identification Heuristics - Enduring
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Enduring Business Themes and Business Objects must be enduring.
Watch out - Long field histories will not necessarily translate to true endurance.
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S30 Software Stability
Identification Heuristics - Industrial Object Identification
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Is the object present in a “classical” model?
Can the object be replaced?
Is the object a representation of a concrete item?
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S31 Software Stability
Identification Heuristics - Top-Down Identification
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Break off conceptual pieces of the problem.
Recursively break these concepts down.
Stop when a layer of industrial objects is reached.
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S32 Software Stability
Identification Heuristics - Bottom-Up Identification
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Start with a “classical” model.
Group the industrial objects under a conceptual “heading.”
Continue this grouping until further grouping is impractical or nonsensical.
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S33 Software Stability
Identification Heuristics - There Is No Silver Bullet
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EBT’s are conceptual themes… Usually
Business objects are more concrete objects… Usually
There are always exceptions to any rule.
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S34 Software Stability
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Security_Manager (I O)
CheckPassword( )
Trait_Gatekeeper (I O)
CheckTraits( )
1 Identity (enduring)1Security (enduring) 11
*1 *1
IDSession (B O)
DomainName : type = string
FindCandidates( )AddPerson( )DeletePerson( )GetPersonProfile( )
11IDManager (B O) 1
PersonIdentifier (B O)
Search( )Search( )
1
1
*PersonProfile (I O)
uniqueID : type = longvalCandidateListGenerator (I O) *1
DataManager (B O)11 11
1
*
PersonTraits (I O)*1
HealthCare Example: PID
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S35 Software Stability
• 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
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Discussion Questions
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S36 Software Stability
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.
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Questions for the Next Lecture
© M.E. Fayad 2000-2005 SJSU – CmpE M.E. Fayad L5-S37 Software Stability
Task 1: Stable Analysis Patterns
Task 2: Stable Design Patterns
Task 3: Design Sessions for SSM (Discuss)
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Tasks for Next Lecture