Serving Metadata¶

The OData service generates two types of documents with metadata about the Denodo databases:

1. The “Service Document”: lists all the entities offered by the data service. It is available at the root URI of the service, specifying the database name where we are going to get information: /denodo-odata.svc/<database name>.

   Below, there is an example where the accessible collections of the movies database are actor, address, city, country, film and film_actor.

   http://localhost:9090/denodo-odata4-service/denodo-odata.svc/movies

   {
     "@odata.context": "/denodo-odata.svc/movies/$metadata",
     "value": [
       {
         "name": "actor",
         "url": "actor"
       },
       {
         "name": "address",
         "url": "address"
       },
       {
         "name": "city",
         "url": "city"
       },
       {
         "name": "country",
         "url": "country"
       },
       {
         "name": "film",
         "url": "film"
       },
       {
         "name": "film_actor",
         "url": "film_actor"
       }
     ]
   }
   

2. The “Service Metadata Document” (also called Entity Data Model (EDM): XML representation of the data model exposed by the service. It is available at .../$metadata.

   For example:

   http://localhost:9090/denodo-odata4-service/denodo-odata.svc/movies/$metadata

   Example of an entity country that has a relationship with zero or more city elements:

      <EntityType Name="country">
         <Key>
             <PropertyRef Name="country_id"/>
         </Key>
         <Property Name="country_id" Type="Edm.Int16"
                   Nullable="false"/>
         <Property Name="country" Type="Edm.String"
                   MaxLength="50"/>
         <Property Name="last_update" Type="Edm.DateTimeOffset"
                   Precision="19"/>
         <NavigationProperty Name="cities"
                      Type="Collection(com.denodo.odata4.city)"
                      Partner="country">
             <ReferentialConstraint Property="country_id"
                      ReferencedProperty="country_id"/>
         </NavigationProperty>
      </EntityType>
   

The service maps these OData structures to Virtual DataPort concepts like this: