Meeting minutes
DICOM
eric: If you use a sentinal or a bnode, either approach would not work well for OWL.
… If you use a sentinal w a string type instead of xsd:datetime (for example) then OWL would be okay, but you would lose the datetime datatype.
jim: Now when we transform RDF lists we just change the property names from the rdf: namespace to soemthng else.
dbooth: RDF list ladders are the wrong way to do arrays. They should have indexes.
eric: SPARQL 1.2 might add mechanisms to get indexes from RDF lists.
jim: Are they doing anything to make property paths more powerful?
eric: IDK
erich: I don't want to break reasoning.
dbooth: FHIR RDF R5 already breaks OWL reasoning, but we have a workaround to convert data to be owl friendly.
detlef: Most of the time I need all of the values of the array, with the ordering.
eric: Some toolkits give a way to return an RDF list as an array.
erich: I access individual list elements in SPARQL.
… Implemented parts of geo SPARQL.
… Using polygons for filtering in SPARQL.
… Data is too much for a single triplestore. Using Apache Arrow with Jena.
… Federated SPARQL query, bring together data from different layers.
… Code is public: BeakGraph
erich: Named graphs are mapped to Arrow chunks.
… Hilbert pyramid
… Client side I pull reduced ersolution ploygons.
… DICOM 2.2 brigns pathology into it, but no mechanisms for spatial indexing
… Can't do performant viewing without indexing.
eric: You're using geosparql?
erich: Yes. I'm generating geosparql to represent the polygon in text form. Then BeakGraph is what the system actually uses.
eric: But you're not using sparql to pick a diagnoal through a cube?
erich: IDK
eric: When you use extension fns in sparql, you can take advantage of your engine donig someting optimal. I don't think you'd be using std sparql to look at diagnoal slices without using extension functions.
erich: You can do simple cube queries, but after that you'll need extensions.
eric: I wouldn't have to be stored as an RDF list.
https://
erich: IDK how often these nulls show up.
eric: I like bnode with a sentinal type.
… Bare sentinals (without bnode standoff) make sparql more complex.
detlef: Usually it's just an empty string if its null.
… But HL7 has dozens of null flavors, but I dont' think they're in DICOM.
dbooth: What if we had a bnode, with attached null type, that sounds easiest for sparql. Then it would need conversion to work for OWL.
ACTION: Eric to add option 10 for representing null as bnode with type that indicates null flavor.
ADJOURNED