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Hylke van der Schaaf edited this page Apr 19, 2017 · 5 revisions

GET

  • All standard paths
  • Navigating to sub-properties of complex properties. e.g.: Thing(1)/properties/property1
  • property/$value
  • Collection/$ref
  • Configuration option to set
    • Absolute or relative Navigation links
    • Maximum and default values for $top
    • Default value for $count

POST, PUT, PATCH

  • All types of observation results: Numeric, String, Boolean, Object and Array. Json type is exactly retained (if you put 2.00 in, you get 2.00 back out)
  • In-line objects, nested as deep as you want
  • GeoJSON geospatial objects for Location and FeatureOfInterest. Other encodings are accepted but can not be used in filters

DELETE

  • Data integrity is maintained. Deleting a Thing will also delete the Datastreams and Observations of that Thing.

Supported queries:

  • $top
  • $skip
  • $count
  • $select As per OData:
    • $select on navigation properties adds the navigationLink to the item
    • $expand on navigation properties adds the content of the item
    • If you want both the navigation link and the content, use both $select and $expand
  • $expand - Including full nesting. Each expand can have all query parameters ($top, $skip, $count, $select, $expand, $orderby and $filter)
  • $orderby - Includes full function support of all functions listed under $filter
  • $filter - Full support.
    • Arbitrary deep searches. For instance, you can find all Things that have ever been in a certain location with:
      • .../v1.0/Things?$filter=st_within(HistoricalLocations/Location/location, geography'POLYGON((7.5 51.5, 7.5 53.5, 8.5 53.5, 8.5 51.5, 7.5 51.5))')
    • Unfortunately, SensorThingsAPI nor OData defines functions for interval logic like overlaps, starts, meets, etc.
      • When comparing time intervals (Datastream/phenomenonTime, Datastream/resultTime, Observation/validTime and (possibly) Observation/phenomenonTime) to time instants:
        • equal tests of the time instant is inside the interval (inclusive)
        • not equal tests of the time instant is outside the interval (exclusive)
        • gt, ge, lt, le work as expected
      • When comparing a time interval to a time interval
        • equals test if the start and end times are the same
        • gt and lt test whether the end of one is greater / less than the start of the other
        • ge and le give an error, since it is not clear what is expected in this case
      • Durations can be specified in a url as duration'PnYnMnDTnHnMnS'
      • Subtracting two times results in a duration
      • Adding / subtracting a duration to / from a datetime results in a datetime
      • Adding / subtracting a duration to / from a time interval results in a time interval
    • When filtering on Observations/result:
      • If the filter is numeric ($filter=result gt 3), string results are ignored
      • If the filter is string-based ($filter=result gt '3'), numbers are cast to strings.
      • If the filter is direct ($filter=result), only boolean results are used.
    • Filtering on complex (JSON) properties (Observations?$filter=parameters/depth gt 10)
      • Direct filtering on boolean fields: (Things?$filter=properties/prop2)

DataArray Extension Support

Both fetching observations and creating observations using the DataArray extension is supported.

MultiDatastream Extension Support

MultiDatastreams are like Datastreams, but the Observations for MultiDatastreams contain more than one result value. The MultiDatastream has links to multiple ObservedProperties (one for each value) and the unitOfMeasurement property is a list instead of a single value. The observationType is of type OM_ComplexObservation and the observation types of the different result values are stored in the multiObservationDataTypes field.

MQTT Support

  • create observations via MQTT publish
    • including inline entities
  • subscribe to entity inserts & changes
    • on entity sets (e.g. v1.0/Things)
      • with selected properties (e.g. v1.0/Things?$select=id,name)
    • on entities (e.g. v1.0/Things(1))
    • on properties (e.g. v1.0/Things(1)/name)

To Do:

  • Backends for different databases
  • Investigate which additional database indices are needed
  • Extensions:
    • Batch Requests

Conformance Test Compliance

OGC publishes a conformance test at GitHub. The goal of this implementation of the API is to be fully compliant with the test suite. This test suite is still a work in progress, so as the tests change, the implementation might no longer pass. At the same time, the test suite is only intended to be a minimum requirement for implementations. Therefore we have a fork of the test suite with additional tests, published here. Differences between the two versions:

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