1. A method for defining, reusing and visualizing subprocesses using Business Process Modeling Language (BPEL) activities and elements executed by one or more processors, where subprocesses are called by a parent process, where a subprocess is an encapsulated and reusable portion of process logic adapted to be called by another process, the method comprising: executing, by the parent process and by the one or more processors, a call activity identifying a subprocess to be called, with the call activity having one or more arguments employing a plurality of parameter mappings, with the parent process having a parent process root scope and a subscope including a context for executing the call activity, and with the call activity setting the subscope as a parent scope of a root scope of the subprocess, where a scope is a demarcated section or grouping of computer code and where the functionality, behavior, and semantics of the call activity are defined via a BPEL extension activity specified in a subprocess XML (Extended Markup Language) namespace incorporated in computer code of the parent process; activating, by the one or more processors, the subprocess, where an activated instance of a subprocess refers to an instance of a call activity within an instance of the parent process that calls the subprocess; analyzing, by the subprocess and one or more processors and with reference to parameter mapping employed by the call activity, at least one subprocess activity; determining, by the subprocess and one or more processors, variable references which are referenced in the at least one subprocess activity; locating, by the subprocess and one or more processors, any referenced variables in different scopes, starting with a most local subprocess scope containing a referenced variable and working up to the root scope of the parent process as needed until all referenced variable are found; and resolving, by the subprocess and one or more processors, located variables by mapping the located variables as specified by the subprocess or the by the one or more call activity arguments.