OGC Web APIs as data sources to DotWebStack Orchestrate

Scope

DotWebStack Orchestrate is an open-source engine for model-driven orchestration.

This module adds support for OGC Web APIs implementing OGC API Features as a data source in DotWebStack Orchestrate.

Requirements

The current implementation depends on certain characteristics that the OGC Web API must support to be a valid backend to orchestrate:

• The API must support the OGC API Features "Core" conformance class.
• The API must support the OGC API Features "GeoJSON" conformance class, i.e., support GeoJSON as a feature encoding.
• The API must support the OGC API Features "Coordinate Reference Systems by Reference" conformance class, i.e., coordinate reference systems in addition to WGS84 longitude/latitude. The API must support the coordinate reference system http://www.opengis.net/def/crs/EPSG/0/28992. This is a temporary requirement that will be removed again.
• The name of the object type in the source model must be the collectionId path parameter of the collection in the OGC Web API.
• The source model must be defined with a single attribute per object type that has identifier: true.
• This attribute must be the featureId path parameter of the feature in the OGC Web API.
• For an ObjectTypeRef property in the source model, the value of property in the GeoJSON encoding must be the identifier if the referenced feature.
  • This implementation supports properties that are declared in the schema with x-ogc-role: reference. In that case, the option supportsRelProfiles has to be set to true in the source configuration.
• All feature properties that may be used to filter a collection must be declared as a queryable.
• The name of each queryable must be the same as the path of the property in the DotWebStack Orchestrate source model.
• The API must support the OGC API Features "Features Filter" conformance class and the OGC Common Query Language "CQL2 Text" conformance class

Hints

• If the API supports the OGC Common Query Language "Advanced Comparison Operators" conformance class, the IN operator will be used for batch loading. Otherwise a logical OR expression will be used.
• If the API supports the OGC API Features "Queryables as Query Parameters" conformance class, the query parameters for the queryables will be used to filter on property values, otherwise the filter parameter will be used.

Configuration

To declare an OGC Web API as a source, add the source to orchestrate/gateway/sources in the application configuration (application.yml). The type must be ogcapi.

Options:

Option	Default	xxx
url	-	REQUIRED The URL of the landing page of the OGC Web API.
limit	10	TEMPORARY The page size for collection and batch requests. This is a stopgap until DotWebStack Orchestrate supports paging.
supportsPropertySelection	false	TEMPORARY Set to true, if the API supports the properties query parameter on feature queries. The value is a list of properties to return. This is a stopgap until a conformance class URI for this capability is available in the conformance declaration of the API.
supportsRelProfiles	false	TEMPORARY Set to true, if the API supports the profile query parameter on feature queries with a value rel-as-key. This is a stopgap until a conformance class URI for this capability is available in the conformance declaration of the API.

Example:

orchestrate:
  gateway:
    sources:
      bag:
        type: ogcapi
        options:
          url: https://wau.ldproxy.net/bag
          limit: 100
          supportsPropertySelection: true
          supportsRelProfiles: true

Status

This is a work in progress.