tep and that compatible documentation exists. allowing the consequences of changes to an item to be assessed. Both parts lists and 'where-used' lists are nominally maintained automatically be configuration management tools. 25.10 Software cost estimating 25.9.3 Configuration control A number of approaches have been taken to software cost estimat- ing, some fairly simple (Reifer, 1980) and some less so. The most Change control is the administrative mechanism for requesting, common are COCOMO (Boehm, 1981), SLIM (Putnam, 1979) and preparing, evaluating and authorising change proposals. Function Point Analysis (Albrecht, 1983). Change control applied both to delivered products and to products under development. Once a baseline has been drawn for a configu- ration item then all changes to that baseline should be controlled. 25.10.1 COCOMO The terms used in change control are not consistent across usage, but the following are representative: COCOMO stands for Constructive Cost Model, and comes in three flavours, basic, intermediate and detailed. 1. Change request. A request identified the effect required to be Basic COCOMO first requires the project to be classed as one of achieved by a change, the advantages of the change and the 'organic', 'semidetached', or 'embedded'. urgency of the change as seen by the initiator of the request. Change Proposal. Proposals are responses to change requests, 1. Organic projects tend to have small experienced teams produc- describing the way in which the change can be implemented ing a small product, using a stable environment. and estimating its cost and ramifications. 2. Semidetached projects have a mix of experience in their teams, 3. Change control board. This is the formal or information deci- and may be producing a larger sized product. sion making body which determines whether and then a change 3. Embedded projects work under tight constraints and require will be made. innovative solutions. 4. Change note. The note authorises the change, describes it, and says what other confi