The image below is a graphical representation of a business process in BPEL. The boxes and circles along the right are services, the lines running to those services are invocations, and the boxes in the middle are steps in the BPEL process (assign, invoke, copy etc.)
Spaghetti BPEL, welcome to hell!!!
An alternative is to use rules to manage your business process. A purely rules based approach would use a rule set as a content based router and every decision point becomes an evaluation of your business routing rules. In addition, rules can manage service invocation by making the service invocation the consequence of firing into another rule set. Coupled with a BRMS like Guvnor the rules based process orchestration of services becomes accessible by business users in a managed environment. Coupled with a workflow or integration engine like Drools-Flow or Apache Camel the rules based business process management will allow for the management of complex long running business processes without some of the complexity and development overhead introduced by BPEL. The rules manage the decision points and the workflow engine helps manage the progression through your business process. The rules based approach won’t provide everything that you get with BPEL. For example state management, persistence, and ease of integration with WSDL are all advantages that BPEL provides that you wouldn’t get for free with a rules driven approach. In the end a rules based approach to business process orchestration should provide simplicity, modularity, and ease of development. As an architect it is worth considering a rules driven approach to business process management.