Important information from an existing system.

The reverse engineering process extracts elements and Software re-engineering is a combination of two consecutive processes i.e., software reverse engineering and software forward engineering as shown in the Figure. Reengineering tries to regenerate the abstract view of the system after which the forward engineering activities realize the system into new form. Reengineering involves implementing various techniques in analyzing and redesigning an existing system from the extracted information by the reverse engineering process. Reengineering can also be defined as “any activity that: improves one’s understanding of software, or prepares or improves the software itself, usually for increased maintainability, reusability, or evolvability”. Re-engineering is defined as “the examination and alteration of a subject system to reconstitute it in a new form and the subsequent implementation of the new form”.

Delivery: The modified system is released to the customer in this phase.

Acceptance testing: This type of testing involves the customers or the end users to use the system and point out errors, if any, which would be reported to the maintenance team, in order to make further changes.

Regression or system testing: After the modifications are made to the existing system, tests are conducted on the new system to ensure that the new system is free of any errors and also to monitor whether the new system has met its new specifications.

Implementation: This phase includes activities involving coding, implementation, testing, integration of modified code, analysis of risks etc.

The input to this phase is the result of the analysis phase and also the details of the existing system which includes the appropriate documentation. Boehm proposed COCOMO (Constructive Cost Estimation Model) in 1981.COCOMO is one of the most generally used software estimation models in the world.

Design: The changes or the modifications that have to be made to the existing system are designed in this phase.

Also analyzed in this phase are the alternative solutions, if any, for modifying the system in an efficient way, keeping the cost and other impacts in mind.

Analysis: The overall maintenance plan is sketched out which includes the design, implementation and test of the system to be modified.

It is the model that allows one to estimate the cost, effort and schedule when planning a new software development activity. The phase also includes decisions on whether to accept or reject the request sent from the customer. COCOMO II Model 4 COCOMO-II is the revised version of the original Cocomo (Constructive Cost Model) and is developed at University of Southern California.

Problem or modification identification: In this phase, the customer or the user sends in the request for change (also known as modification request – MR).

Cocomo model types