 ## Constructive Cost Model

(COCOMO) A method for estimating the cost of a software package, proposed by Dr Barry Boehm.

The Basic COCOMO Model estimates the effort required to develop software in three modes of development (Organic Mode, Semidetached Mode, or Embedded Mode) using only DSIs as an input. The Basic model is good for quick estimates.

The Intermediate Model extends the Basic Model with an Effort Adjustment Factor (EAF) and different coefficients for the effort equation. The user supplies settings for cost drivers that determine the effort and duration of the software projects. It also allows DSI values and cost drivers to be chosen for individual components instead of for the system as a whole.

The Detailed COCOMO Model uses effort multipliers for each phase of the project and provides a three-level product hierarchy and has some other capabilities such as a procedure for adjusting the phase distribution of the development schedule.

["Software Engineering Economics", B. Boehm, Prentice-Hall, 1981].

Last updated: 1996-05-29

## constructive proof

A proof that something exists that provides an example or a method for actually constructing it.

For example, for any pair of finite real numbers n < 0 and p > 0, there exists a real number 0 < k < 1 such that

``` f(k) = (1-k)*n + k*p = 0.

```
A constructive proof would proceed by rearranging the above to derive an equation for k:

``` k = 1/(1-n/p)

```
From this and the constraints on n and p, we can show that 0 < k < 1.

A few mathematicians actually reject *all* non-constructive arguments as invalid; this means, for instance, that the law of the excluded middle (either P or not-P must hold, whatever P is) has to go; this makes proof by contradiction invalid. See intuitionistic logic.

Constructive proofs are popular in theoretical computer science, both because computer scientists are less given to abstraction than mathematicians and because intuitionistic logic turns out to be an appropriate theoretical treatment of the foundations of computer science.

Last updated: 2014-08-24

## constructive solid geometry

<graphics>

(CSG) A method used in solid modeling to describe the geometry of complex three-dimensional scenes by applying set operations (union, difference, intersection) to primitive shapes (cuboids, cylinders, prisms, pyramids, spheres and cones).