For most changes that you make, you need only run the incremental build, as the changes will be detected automatically and only the dependent output files will be updated. However, some changes are not detected and you may need to run a full build for your changes to take effect. In particular, if you change a setting in the curam-config.xml configuration file that affects the build process (typically by affecting the appearance of the pages in a way that is applied at build-time), then you will need to perform a full build manually, as the changes will not be detected automatically.
Dependency checking will identify changes to server interfaces used by UIM pages. Server interfaces are defined in the application's UML model and more information can be found in Server Interface Reference. Only changes to interface properties, not their underlying domain types, are recognized in an incremental build. For example, changing a code-table name will not be detected by dependency checking and a clean build will be required.