Process Preconditions and Effects

In order to tie a bunch of processes together (compose) we also need to know their preconditions for execution and any side-effects they might have.
So, OWL-S also has precondition and effect (yes, like AI planner operators. 1970's AI research might yet find an application :-).

ExpressCongoBuy service has two preconditions: you must have an account and credit:

<process:AtomicProcess rdf:ID="ExpressCongoBuy">
  <process:hasInput>
    <process:Input rdf:ID="ExpressCongoBuyBookISBN">
      <process:parameterType rdf:resource="&xsd;#string"/>
    </process:Input>
        </process:hasInput>
        <process:hasInput>
   <process:Input rdf:ID="CongoBuySignInInfo">
      <process:parameterType rdf:resource="#SignInData"/>
    </process:Input>
  </process:hasInput>
  <process:hasPrecondition rdf:resource="#AcctExists"/>
  <process:hasPrecondition rdf:resource="#CreditExists"/>
  <process:hasEffect>
    <process:ConditionalEffect rdf:ID="CongoOrderShippedEffect">
      <process:ceCondition rdf:resource="#BookInStock"/>
      <process:ceEffect rdf:resource="#OrderShippedEffect"/>
    </process:ConditionalEffect>
  </process:hasEffect>  

  <process:hasOutput> 
    <process:ConditionalOutput rdf:ID="CongoOrderShippedOutput">
      <process:coCondition rdf:resource="#BookInStock"/> 
      <process:parameterType rdf:resource="#OrderShippedOutput"/>
    </process:ConditionalOutput>
  </process:hasOutput>
  
  <process:hasOutput> 
    <process:ConditionalOutput rdf:ID="CongoOutOfStockOutput">
      <process:coCondition rdf:resource="#BookOutOfStock"/>
      <process:parameterType rdf:resource="#BookOutOfStockOutput"/>
    </process:ConditionalOutput>
  </process:hasOutput>
  
</process:AtomicProcess>

It has the effect of shipping the order, the the output tells if the book was in stock or not.