Legacy systems & Ethics & Closing

Question 1

What 4 reasons exist for software change?

Answer 1

• Functionality (Add a new feature)
• Maintenance (Fixing a bug)
• Improving design
• Optimization (of performance and usage)

Question 2

What is legacy code?

Answer 2

In the industry, legacy code is often used as a slang term for difficult-to-change code
that we don’t understand. […] To me, legacy code is simply code without tests.

Question 3

What is the legacy code change algorithm’s steps?

Answer 3

1. Identify change points
2. Find test points
3. Break dependencies
4. Write tests
5. Make changes and refactor

Question 4

What means exist to address the challenges of legacy code?

Answer 4

Wrapping
* Surround legacy data, programs, systems, or interfaces with new interfaces
-Disadvantages: Need for legacy maintenance and thus competence maintenance i.e. wrapping = existing technologies maintenance plus one more
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Migration
* Maintain: functionality, process, and operational & business environment. I.e. keep many years of requirement elicitation.
- Challenges: High complexity, Requires solid understanding of LIS functionality, operation, and interactions
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Redevelopment
* Develop the system from scratch in modern technology, tools, architecture, and hardware
- Risk of failure too great, Requirement elicitation challenging, unable to extract from LIS, hard to identify from scratch

Question 5

What is LIS?

Answer 5

A LIS (legacy information systems) can be defined as “any information system that significantly resists modification and evolution.” In fact, if a software system can be maintained within an acceptable budget it is usually not considered a LIS.

Question 6

What migration methods exist?

Answer 6

• Chicken little strategy
  Lets LIS and target systems interoperate during migration using a mediating module, generally known as a “gateway”.
  11 step plan for cutting over from the LIS to the target system. Each step is incremental
• Butterfly methodology