Concept
Semantic Data and EWS
The EWS metadata makes it possible to add semantic information to the EWS items, provided that the EBO object that is exposed by EWS is semantically described.
For more information, see EcoStruxure Web Services .
Metadata with semantic information is implemented for GetContainerItems and GetItems and the metadata is included in the response when the EWS input attribute “metadata” is set to “true”.
The metadata describes the connection between the EWS item in the request and the nodes/items in the semantic database. This description includes the Brick-type information (“semantic information”) of the connected node, for example “Air Temperature Sensor”.
The semantic database is exposed as an EWS container called “Ontology Graph” that makes it possible to navigate in the semantic database with EWS. Ontology Graph is exposed directly under the server container item.
The connected EBO properties and objects are represented by “address nodes” in the semantic database (namespace nspg). If you know how to construct SPARQL queries to a semantic database, you can retrieve these addresses and use them as EWS Id in the following EWS methods:
GetHistoryItem
Subscribe
GetItems
GetValues
SetValues
ForceValues
UnforceValues
EWS can expose the semantic database nodes if this feature is enabled.
Nodes in the semantic database are modeled as EWS container items.
With GetContainerItem you can get relations between the semantic database nodes.
With GetContainerItem you can get relations between the semantic database nodes and the EBO objects (EWS Items: Container, Value, Alarm, History).
With GetContainerItem you can get relations between the EBO objects (EWS Items: Container) and the semantic database nodes.
With GetItems you can get the relations between the EBO objects (EWS Items: Value, Alarm, History) and the semantic database nodes.
Semantic Overview
Enabling Semantics for EWS
EcoStruxure Web Services