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, DAML-S also has precondition and effect (yes, like AI planner operators. 1970's AI research might yet find an application :-).

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

<rdf:Property rdf:ID="congoBuyAcctExistsPrecondition">
  <rdfs:subPropertyOf rdf:resource="&process;#precondition"/>
  <rdfs:domain rdf:resource="#CongoBuy"/>
  <rdfs:range rdf:resource="#AcctExists"/>
</rdf:Property>

<rdf:Property rdf:ID="congoBuyCreditExistsPrecondition">
  <rdfs:subPropertyOf rdf:resource="&process;#precondition"/>
  <rdfs:domain rdf:resource="#CongoBuy"/>
  <rdfs:range rdf:resource="#CreditExists"/>
</rdf:Property>

CongoBuy has an effect of either shipping the order or failure:

<daml:Class rdf:ID="BuyEffectType">
  <daml:oneOf rdf:parseType="daml:collection">
    <BuyEffectType rdf:ID ="OrderShipped"/>
    <BuyEffectType rdf:ID ="Failure"/>
  </daml:oneOf>
</daml:Class>

<rdf:Property rdf:ID="congoBuyEffect">
  <rdfs:subPropertyOf rdf:resource="&process;#effect"/>
  <rdfs:domain rdf:resource="#CongoBuy"/>
  <rdfs:range rdf:resource="#BuyEffectType"/>
</rdf:Property>