Why are the build.properties and runtime-conf.xml properties separate?
build.properties is where you define generator properties, while the runtime-conf.xml file is where you define runtime-environment properties. Typically these files will contain some duplicate information — in particular, the database connection information will probably be the same (but it doesn’t have to be). The runtime properties file is turned into a multi-dimensional PHP assoc array by a Phing task. The Phing task also adds class mapping information for the Propel autoload mechanism. When you initialize Propel you pass the path to the converted file (by default the converted file is placed in the build/conf directory).
