In most organizations, software maintenance activities are often more than meets the eye. There are at least three types of maintenance activities:

• Corrective (about 20%)— Removing defects in the product deliverables (software, manuals, training, etc.)

• Adaptive (about 20%)— Accommodating changing environments (platform changes, rules and regulation changes such as tax rates, and laws governing official data reporting)

• Perfective (about 60%)— Adding capabilities or changing features as requested by users

The sum of these types of maintenance activities constitutes about two-thirds of the total costs for an average software product during its lifetime. Because perfection at initial release is unlikely for most software products, some corrective maintenance can be expected to occur in any operations phase of a product's full life cycle. This should be factored into the operations budget for the sustaining organization. The adaptive and perfective types, however, could probably be treated as a separate development project to prepare a major release of the software product. These are the types of maintenance that result from changing environments and increased problem knowledge during the course of the original software product development project. Some of the life cycle models discussed next include these operations and maintenance activities in their descriptions, and some do not.

Another thing to note about the activity arrangements for a WBS in the models is that, even though some models are depicted as circular, they must be "straightened" for representation in a project WBS. Their circular, looping, iterative nature comes from doing certain activities repeatedly. For instance, the spiral model can be thought of as a straight line if it is "uncoiled" and flattened. The project planner must use judgment and experience to decide how many loops through the spiral to plan for.

Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

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