Small Worlds and Structural Stability in largescale software

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Small Worlds and Structural Stability in
large-scale software
Alex Iskold, President/CEO Information
Laboratory, Inc www.thesmallworlds.com www.inform
ationlaboratory.com
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Software as a complex system

• Modern software is a complex web of components
  and dependencies.
•  

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All systems start simple

• but quickly grow and soon become difficult to
  manage, understand and modify.
•  

Business Requirements
Unstable Unreliable Unpredictable
Business Requirements
Re-write
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Typical System Life-Span

•  

Cost
Complexity
Stability
Re-write
Time
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Simple example 
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More is different
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Does this sound familiar?

• 800 a.m.
•  
• Manager
• John, I dont see the reports in the usual
  directory, what is going on?
• Programmer
• I am not so sure
• Manager
• Didnt we put new release into production last
  night?
• Programmer
• Yes, well, we did put in new code for database
  access, but I dont see how it can be related to
  the report generation module.
• Let me investigate

• 1100 a.m.
•  
• Manager
• John, did you figure it out?
• Programmer
• Yes, we just found the problem.
• I could not believe when I saw it. Apparently
  there was a dependency between the code change
  and some old piece of business logic, which then
  impacted two other module, which are used by the
  report generation code and so it broke

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If you hear developers say

• I am not so sure about what happened
• We did not anticipate the impact of this
  change
• I did not realize that this dependency was even
  there
• This will take me long time to figure out

Unpredictable
Unreliable
Uncertain
Unstable

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Small Worlds

• Navigate
• Analyze
• Find Problems
• Make changes

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Navigate your software

• See all dependencies
• Local/Global Views
• Make quick snapshots
• Explore relationships
• Zoom in on details
• Use intelligent filtering
• See dependency matrix
• UML/Small World LF

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Analyze your software

• Compute stability
• See Report
• Study Charts
• Look at Statistics
• Circular dependencies
• Heavy Components
• Breakables/Butterflies
• Group Analysis

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Change your software

• What is the best way to change a component?
• What is the impact of the change?
• What needs to be retested?
• What has changed since last release?
• What problematic code was recently added?

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Key benefits of Small Worlds

• Facilitates more stable corporate software
• Reduces the cost of Software Development
• Allows to choose Vendor with better solution
• Reduces Learning Curve for new team members
• Simplifies the Knowledge Transfer process
• Helps maintenance and system improvement
• Seamlessly integrates into development process
• Reveals a lot without extra effort/time

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Unreliable
Predictable
Understanding the issues of structural
complexity in the modern systems is necessary
for successful software risk and complexity
management.
Unstable
Certain
Uncertain
Stable
Unpredictable
Reliable