Service-Enabling Data Sources

here, we provide additional information related to the WCf data services example in order to make the example more concrete. figure a shows a graphical representation of the edM model for the relational database in figure 2, as displayed to a WCf data service developer, along with the declarative mapping details for the Order entity at the bottom. the navigation properties are displayed at the bottom of each entity type, and the connecting lines denote the property associations between the entity types that facilitate navigation.

Clients consuming WCf data services can retrieve metadata describing the underlying edM model by issuing a request to return a service’s entity types and their relationships, for example,

http://<service _ uri>/SalesDS. svc/$metadata

Metadata is returned in the Conceptual schema definition language (Csdl), an example of which is shown in figure B.

In terms of data service results in WCf, figure C shows the results returned for the example query in the section entitled “service-enabling data stores,” which requested a list of the open orders for Customer C43. the tuples retrieved by the underlying sQl query are subsequently transformed to the atompub result format used by odata services, as shown in the figure. note that the query result contains link elements that allow the client to form navigation requests to related entities.

figure A. An entity data model.

figure B. An oData service metadata document.

figure C. An oData service response document.