= Day 1:  SADI Web Services = 

We are beginning to publish a set of best practices for service providers by codifying the lessons we've learned in the last year of service-building.

For example, say we have a service '[http://sadiframework.org/services/getKEGGParalogsByGene getKEGGParalogsByGene]', which will provide the KEGG ID of the paralogs of any input KEGG gene id. Click on the link to see the full service description - '''note that you do not have to generate this document yourself'''''''!!  It is auto-generated for you by the SADI codebase!!

The input class is '''http://purl.oclc.org/SADI/LSRN/KEGG_Record'''  and is defined by a third-party ontology - simply "any KEGG Record":

{{{
<a:inputParameter>
  <a:parameter rdf:about="illuminae.comgetKEGGParalogsByGeneddd">
    <a:hasParameterNameText>
       input
    </a:hasParameterNameText>
    <a:objectType rdf:resource="http://purl.oclc.org/SADI/LSRN/KEGG_Record"/>
  </a:parameter>
</a:inputParameter>
}}}


The output class is specific to our service (since our service is creating a new 'kind' of data, based on the input class) and is defined in '''http://sadiframework.org/ontologies/service_objects.owl#getKEGGParalogsByGene_Output''':

{{{
<a:outputParameter>
  <a:parameter rdf:about="illuminae.comgetKEGGParalogsByGeneeee">
     <a:hasParameterNameText>
        output
     </a:hasParameterNameText>
     <a:objectType rdf:resource="http://sadiframework.org/ontologies/service_objects.owl#getKEGGParalogsByGene_Output"/>
  </a:parameter>
</a:outputParameter>
}}}

Let's have a look at the OWL ontology that defines our output class.  I have "pruned" the service_objects.owl ontology to show only the relevant parts for this discussion... :

{{{

<rdf:RDF 
 xml:base="http://sadiframework.org/ontologies/service_objects.owl#" 
 xmlns:service="http://sadiframework.org/ontologies/service_objects.owl#" 
 xmlns:owl="http://www.w3.org/2002/07/owl#" 
 xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" 
 xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" 
 xmlns="http://sadiframework.org/ontologies/service_objects.owl#">

<!-- Ontology Information -->
<owl:Ontology rdf:about="">
  <owl:imports>
    <owl:Ontology rdf:about="http://sadiframework.org/ontologies/service_objects.owl#"/>
  </owl:imports>
  <owl:imports>
    <owl:Ontology rdf:about="http://purl.oclc.org/SADI/LSRN"/>
  </owl:imports>
</owl:Ontology>

<owl:SymmetricProperty rdf:about="http://sadiframework.org/ontologies/service_objects.owl#isParalogOf"/>

<owl:Class rdf:about="http://sadiframework.org/ontologies/service_objects.owl#getKEGGParalogsByGene_Output">
   <rdfs:subClassOf rdf:resource="http://purl.oclc.org/SADI/LSRN/KEGG_Record"/>
   <rdfs:subClassOf>
      <owl:Restriction>
          <owl:onProperty rdf:resource="http://sadiframework.org/ontologies/service_objects.owl#isParalogOf"/>
          <owl:someValuesFrom rdf:resource="http://purl.oclc.org/SADI/LSRN/KEGG_Record"/>
      </owl:Restriction>
   </rdfs:subClassOf>
</owl:Class>

</rdf:RDF>
}}}

The important things to note are:

 1. we are explicitly importing any ontology we refer to

 2. our output class is a subclass of the input class (in this case, a KEGG_Record)

 3. our output class includes a restriction indicating that the service returns KEGG_Records related to the input by the 'isParalogOf' predicate (i.e.: KEGG_Records that are paralogs of the input KEGG_Record).  The owl:valuesFrom property on the restriction allows us to do reasoning about how to chain services together.  It is important that we put this restriction here instead of in the owl definition of the predicate itself, since it allows us to constrain OUR use of the predicate, without constraining its range for anyone else!

 4.  the "isParalogOf" property is symmetric, meaning that of X is a paralog of Y, then Y is also a paralog of X.  Note also that, in this case, I am defining the isParalogOf property in my service ontology; however '''THIS IS NOT ALWAYS NECESSARY''' - if you produce data that represents a relationship that has been adequately defined by someone else, then you are free to use that third-party's predicate and you don't need to define it yourself!  Re-use re-use re-use!!  That's what the Semantic Web is all about!


The SADI Taverna plugin has been updated to use the information in these restrictions for service discovery.