The Maintenance of Software Products

The Maintenance of Software Products
An Introduction

Prof. David Bernstein
James Madison University

Computer Science Department

bernstdh@jmu.edu

Types of Maintenance (ISO/IEC 14764)

Corrective:
- Modifications that correct defects found in the production environment
Adaptive:
- Modifications that keep the product usable in a changed/changing production environment (e.g., migration to another platform)
Perfective:
- Modifications that satisfy additional functional requirements (e.g., new features) or non-functional requirements (e.g., improve performance)
Preventive:
- Modifications that correct faults discovered in the development environment before they give rise to failures/symptoms in the production environment

Frequency

Agile Processes:
- Tend to deploy more frequently so maintenance activities tend to occur more frequently
Heavyweight Processes:
- Tend to deploy Less frequently so maintenance is less frequent but no less significant

The Results of Several Surveys

Why Maintenance is Expensive

Endemic Reasons:
- Successful products are in the field for decades so huge costs are bound to accrue
Other Reasons:
- As a product is modified its structure deteriorates

Maintenance Tradeoffs

Related to Availability:
- Maintenance improves a product but may make it unavailable
Related to Quality:
- There are often "elegant" solutions and "quick and dirty" solutions

Who Is Involved?

There Are Options:
- The original development team
- A maintenance team
More Tradeoffs:
- The development team understand the product but may not understand the operational environment
- Maintenance teams and development teams may have (or think they have) different statuses

Metrics for Corrective Maintenance

Backlog (\(B\)):
- \(C\) denotes the number of problems closed during an interval of time (e.g., a month)
- \(A\) denotes the number of problem "arrivals" during an interval of time (e.g., a month)
- \(B = \frac{C}{A} \cdot 100\)
Response Time (Mean Time to Repair):
- The mean (or median) amount of time between the arrival of a problem and its correction

Tools for Corrective Maintenance (i.e., Bug/Issue Tracking)

Purpose:
- Provide a clear, centralized overview of corrective maintenance requests
- Calculate performance metrics
Some Open Source Examples:
- Apache Bloodhound
- Bugzilla
- Zentrack