Overview of the COSMIC Method

 

COSMIC (ISO 19761) is a functional size measurement method which generalizes the measurement process to address management information systems issues, as well as real-time and hybrid software projects. It conforms to the ISO meta-standard on functional size measurement (ISO 14143-1) and uses only the FURs (Functional User Requirements) of the software project as inputs to the measurement process.

 

 

Figure 1: COSMIC phases

 

The COSMIC process is based on two phases, as shown in Figure 1:

·          The Mapping Phase in which a COSMIC model of the FURs suitable for the measurement phase is generated.

·          The Measurement Phase, where the measurement rules are applied to this FUR model to derive size on the basis of the ISO standard for COSMIC.

  

COSMIC takes into account that the software FURs can be decomposed into a set of functional processes, and that each of these functional processes is a unique set of sub-processes performing either a data movement or a data manipulation (Figure 2).

 

 

Figure 2: A generic software model for measuring functional size

 

The COSMIC software model distinguishes four types of data movement: entry, exit, read and write, as identified in the context model (Figure 3).  All data movements move data contained in exactly one data group.  Entries move data from the user across the boundary to the inside of the functional process; exits move data from inside the functional process across the boundary to the user; reads and writes move data from and to persistent storage. 

 

 

Figure 3: COSMIC movement types

 

In COSMIC, each data movement is assigned a single unit of measure of 1, which is, by convention, equal to 1 CFP (Cosmic Function Point). The total size of the software being measured corresponds, therefore, to the addition of all data movements recognized by the COSMIC method.  For the detailed measurement rules, see Abran, A., Descharnais, J-M., Oligny, S., St. Pierre, D., Symons, C.R. ‘COSMIC Measurement Manual v3, The COSMIC Implementation Guide for ISO/IEC 19761:2003’.  This is obtainable  free-of-charge from www.gelog.etsmtl.ca.

 

For a more detailed overview of the COSMIC method and how it compares with a typical ‘1st generation’ method, see ‘Advantages of the COSMIC Method’.