Add Datatypes To Instance Data

[VladimirAlexiev]

In CGMES instance data, all literals are string, but should be marked with the appropriate datatype.

• E.g. cim:ACDCConverter.baseS should be marked ^^xsd:float
• Otherwise sort won't work and range queries will be slower.
• This pertains to boolean, dateTme, float, gMonthDay, integer as string is the default datatype

This query counts props by XSD datatype:

PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>

select ?range (count(*) as ?c) {
   ?x rdfs:range ?range
    filter(strstarts(str(?range), str(xsd:)))
} group by ?range order by ?range

Here are the current results, but it should be rerun after fixes to ontology: see col "comment"	range	c	comment
xsd:boolean	218	Inflated because meta-data props are duplicated, and many are boolean
xsd:dateTime	5
xsd:decimal	1
xsd:float	310	Deflated because eg cim:ActivePower.value may be used by hundreds of "real" props
xsd:gMonthDay	2
xsd:integer	36
xsd:string	51

I have a tentative SPARQL Update, but need to revise it.

[griddigit-ci]

Need to discuss if we have concerns related to the file size. It will be very good if we have explicit datatypes in the instance data as this will not require post processing and mappings are parsing time to enable SHACL validation of datatypes. Is it common to assume the xsd:string so that we do not want to declare that one? How JSON-LD will deal with it? I think we can manage this with some sort of context so that we do not have repetitions in the serialisations.

[VladimirAlexiev]

@griddigit-ci @Sveino

• I don't think you should worry about file size because when files get big, they are zipped, and compression will reduce such datatypes to a few bits per literal.
• Curiously, integer and decimal take less space in Turtle than an equivalent string because the string needs quotes (1.23 is a decimal, whereas "1.23" is the corresponding string. But xsd:float always needs the datatype to be specified.
• xsd:string is default by spec, so "foo" and "foo"^^xsd:string mean the same. Whether a repo stores it internally without datatype or with that default datatype, it doesn't matter

About JSON-LD: #55