RDF-STaX: update metadata

Issue: RiverBench/RiverBench#55

metadata.ttl

@@ -7,6 +7,7 @@
 @prefix rbt: <https://w3id.org/riverbench/schema/theme#> .
 @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
 @prefix spdx: <http://spdx.org/rdf/terms#> .
+@prefix stax: <https://w3id.org/stax/ontology#> .
 @prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
 
 # This file contains the manually written metadata for the dataset.
@@ -49,8 +50,15 @@
     # Technical metadata
     rb:usesOntology <http://knoesis.wright.edu/ssw/ont/sensor-observation.owl> ;
     rb:hasStreamElementCount 5893763 ;
-    # One of: rb:triples, rb:quads, rb:graphs
-    rb:hasStreamElementType rb:triples ;
+    stax:hasStreamTypeUsage [
+        a stax:RdfStreamTypeUsage ;
+        rdfs:comment "The dataset can be viewed as a stream of graphs."@en ;
+        stax:hasStreamType stax:graphStream
+    ] , [
+        a stax:RdfStreamTypeUsage ;
+        rdfs:comment "The dataset can be viewed as a flattened stream of triples."@en ;
+        stax:hasStreamType stax:flatTripleStream
+    ] ;
     rb:hasStreamElementSplit [
         a rb:TopicStreamElementSplit, rb:TimeStreamElementSplit ;
         rdfs:comment "Each stream element corresponds to information from one weather station at a given time OR to a weather station-independent piece of information (e.g., time annotation)."@en