Semantic Web for Workflow

Why an ontology for workflow? "The purpose is clear and simple - workflow orchestration at any level requires both the Pull and Push model...the Push model happens when a workflow has to report to its superior workflow - a natural strategy in many current solutions - this is easy when both the workflows are implemented using the same platform. Things get botchy when they are implemented differently - and thats where the ontology comes in. Now this person also asked my why an ontology and not a simple xml - and my answer was the requirements forced me to. One of the requirements was to ask a given instance to show me all 'user entry form' kind of activities which were completed recently. Now if you look at the last sentence carefully you see I use the clause 'kind of' - a good ontology fit !."