What is BPEL: workflow, BPM or integration? Is BPEL the all-encompassing language for modeling process logic?
A great deal of effort has been put into making BPEL a semantically-rich language for composing services into business processes (and exposing the latter as services). By combining XLANG and WSFL into BPEL, the language is capable of expressing fairly complex patterns of process logic. However, one of BPEL's design goals was to keep it simple and clean and avoid as much as possible adding language constructs that may hamper usability and general applicability.
For example, the BPEL process does not directly support abstractions for people, roles, work items or inboxes/queues, hence BPEL is not equivalent to workflow. Such capabilities can be added outside the scope of BPEL in a service-oriented fashion, e.g. by adding a specialized "task service" that manages people, roles, etc. BPEL is also not equivalent to BPM, since the language does not specify a data model for process reporting, analysis or monitoring/administration.
Finally, BPEL is not equivalent to integration, as the specification is protocol independent and does not include common integration facilities such as adapters, transformation, etc. As with workflow, such facilities can be easily provided in a service-oriented manner into a BPEL solution framework.