Function Point Modeler allows you to define a software structure to meet your needs. Your project might consist of several application systems with different platform or language or of one application system with several sub systems (different platform or language). You want to estimate each application system or sub system separately.
Your initial estimate might be made on the basis of a application system. Your second estimate might made on the basis of several application system system which will consist of several subsystems, etc. You can use Function Point Modeler to define the sub estimation of each subsystem. Function Point Modeler permits you to continue this process until you arrive at the level of detail that suits your needs.
You can use Function Point Modeler to define the sub estimation of each subsystem and to quantify each subsystem separately by using COCOMO cost factor. You can also use Function Point Modeler to define some factors for whole project by using COCOMO scale factor. Your project might contain two application systems, one of them is system A based on the J2EE and other is system B based SAP . You have to estimate your project as a whole. You can define the COCOMO cost factor in the CocomoBase estimation for whole project. You might create two CocomoSub estimation for the system A and system B.
You'll define sub estimations, assign COCOMO cost factor values of each sub estimation, etc. The sum of the CocomoSub estimations is the total project estimation.