Modeling software maintenance requests: a case study

Software maintenance costs often total twice the original development cost in the lifetime of application software. Modeling the changes of software maintenance activities might improve software maintenance planning. Current studies model software activities only covering a portion of software lifetimes. This study investigates the changes of maintenance requests during the lifetime of large application software. It discusses the modeling of different software maintenance requests such as: user support, repair and enhancement. We found four distinct stages. User support reaches its peak in the first stage, repair inundates in the second stage. In the third stage, enhancement is the dominant factor. The frequencies of all three different maintenance requests are small in the last stage, when the IS department is looking for new software to replace the existing one