Cosmos and Function Point Analysis

The COSMOS application does not help with function counting, per se -- a knowledgeable user still has to correctly identify EIs, EOs, EQs, ILFs, and EIFs of low, average, and high complexity. COSMOS will calculate a function point count (i.e., applies complexity weights and the value adjustment factor) from the user's "raw" function counts and 14 general system characteristic settings.

COSMOS does, however, facilitate the use of function point analysis as a project sizing technique for input into other tools. For example, in addition to COSMOS' native estimation capabilities, one could use a function point model from COSMOS to produce a SLOC estimate for input into other models that use SLOC as an input, such as REVIC, the U.S. Air Force's implementation of COCOMO.

One can estimate effort by simply multiplying an adjusted function point count by the productivity rate (FP/month) to get an estimate — if the productivity rate is known and where function point counting measures the kind of work performed [i.e. user-defined functionality is added, removed, changed, or converted]. However, COCOMO- and Rayleigh-based models deal with relevant factors that are not directly expressed in function point analysis, and allow the exploration of the degree of effort increase associated with schedule compression.

Function Point Formulae Unadjusted Function Point Count

UFPC = (3 x LEI) + (4 x AEI) + (6 x HEI) + (4 x LEO) + (5 x AEO) + (7 x HEO) + (7 x LILF) + (10 x AILF) + (15 x HILF) + (5 x LEIF) + (7 x AEIF) + (10 x HEIF) + (3 x LEQ) + (4 x AEQ) + (6 x HEQ)

where:

UFPC = Unadjusted function point count

LEI = Number of low external inputs

AEI = Number of average external inputs

HEI = Number of high external inputs

LEO = Number of low external outputs

AEO = Number of average external outputs

HEO = Number of high external outputs

LILF = Number of low internal logical files

AILF = Number of average internal logical files

HILF = Number of high internal logical files

LEIF = Number of low external interface files

AEIF = Number of average external interface files

HEIF = Number of high external interface files

LEQ = Number of low external inquiries

AEQ = Number of average external inquiries

HEQ = Number of high external inquiries

Total Degree of Influence

The Total Degree of Influence(TDI) is the sum of selected complexity ratings for 14 project complexity traits where the ratings are as follows:

	None	0
	Insignificant	1
	Moderate	2
	Average	3
	Significant	4
	Strong	5

Value Adjustment Factor

The Value Adjustment Factor (VAF) is used to convert unadjusted function points into adjusted function points. The VAF is computed from the Total Degree of Influence(TDI) as follows:

where:

VAF =	Value Adjustment Factor
TDI =	Total Degree of Influence