Metadata Document

The Metadata Document describes, in EDMX CSDL, the schema of all the data you can retrieve from the OData Form Service in question. This is essentially the XForms form schema translated into the OData format. EDMX/CSDL defines schemas in terms of objects, their properties, and relationships to other objects.

If you are writing a tool to analyze your own data, whose schema you already know and understand, there is very little reason to touch this endpoint. You can likely skip ahead to the data documents themselves and work directly with the simple JSON output returned by those endpoints. This endpoint is more useful for authors of tools which seek to generically work with arbitrary data whose schemas they cannot know in advance.

In general, the way we model the XForms schema in OData terms is to represent groups as ComplexTypes, and repeats as EntityTypes. In the world of OData, the primary difference between these two types is that Entity Types require Primary Keys, while Complex Types do not. This fits well with the way XForms surveys tend to be structured.

Most other types map to String. The exceptions are numbers, which map either to Int64 or Decimal as appropriate, datetime fields which are always DateTimeOffset, date fields which become Date, and geography points which will appear as GeographyPoint, GeographyLineString, or GeographyPolygon given a geopoint, geotrace, or geoshape.

We also advertise the relationships between tables (the point at which a repeat connects the parent data to the repeated subtable) using the NavigationProperty. This should allow clients to present the data in an interconnected way, without the user having to specify how the tables connect to each other.

This implementation of the OData standard includes a set of Annotations describing the supported features of the service in the form of the Capabilities Vocabulary. In general, however, you can assume that the server supports the Minimal Conformance level and nothing beyond.

While the latest 4.01 OData specification adds a new JSON EDMX CSDL format, most servers and clients do not yet support that format, and so for this release of ODK Central only the older XML EDMX CSDL format is available.