OLDM: Object Linked Data Mapper

OLDM has the same role as an ORM for SQL data, but for Linked Data instead. It turns triples into an object graph that you can just use in your javascript code.

It uses JSONTag to represent the meta data needed to support all features of linked data triples.

The parse() method returns either the full graph or the specific subject requested:

import oldmParser from '@muze-nl/oldm'
import JSONTag from '@muze-nl/jsontag'

const parser = new oldmParser({
	prefixes: {
		'ldp':    'http://www.w3.org/ns/ldp#',
	    'rdf':    'http://www.w3.org/1999/02/22-rdf-syntax-ns#',
	    'dct':    'http://purl.org/dc/terms/',
	    'stat':   'http://www.w3.org/ns/posix/stat#',
	    'turtle': 'http://www.w3.org/ns/iana/media-types/text/turtle#',
	    'schem':  'https://schema.org/',
	    'solid':  'http://www.w3.org/ns/solid/terms#',
	    'acl':    'http://www.w3.org/ns/auth/acl#',
	    'pims':   'http://www.w3.org/ns/pim/space#',
	    'vcard':  'http://www.w3.org/2006/vcard/ns#',
	    'foaf':   'http://xmlns.com/foaf/0.1/'
	}
})
const url = 'https://auke.solidcommunity.net/profile/card#me'
const response = await fetch(url)
if (!response.ok) {
	throw new Error(response.status+':'+response.statusText)
}
const text = await response.text()
const profile = parser.parse(text, url)

To get the full graph (an array of subjects) from the result, use the URL without a hash (#me here):

// ... copy the same code as above here
const url = 'https://auke.solidcommunity.net/profile/card'
const response = await fetch(url)
if (!response.ok) {
	throw new Error(response.status+':'+response.statusText)
}
const text = await response.text()
const data = parser.parse(text, url)
const profile = data.index.id.get(url+'#me')

In both cases the profile should look like this (JSON stringified):

{
        "vcard$bday":"1972-09-20",
        "vcard$fn":"Auke van Slooten",
        "vcard$hasEmail":[
            {
                "vcard$value":"mailto:auke@muze.nl"
            },
// etc...

Unlike JSON-LD, the profile doesn't contain meta information like '@id' or '@context'. The '@id' part is instead available through JSONTag.getAttribute(profile, 'id'). Or you can use JSONTag.stringify and get this result:

<object id="https://auke.solidcommunity.net/profile/card#me">{
    "vcard$bday":<date>"1972-09-20",
    "vcard$fn":"Auke van Slooten",
    "vcard$hasEmail":[
        <object id="https://auke.solidcommunity.net/profile/card#id1673612033018">{
            "vcard$value":"mailto:auke@muze.nl"
        },
// etc...

JSON-LD uses @context to translate json property names (keys) to linked data predicate URI's. OLDM instead doesn't translate predicate URI's at all, it just shortens them using the prefixes you define. So http://www.w3.org/2006/vcard/ns#bday becomes vcard$bday.

Subject and Object id's are never shortened. The graph.index.id is a map with the full subject and object id's as key.

Predicate URI's are shortened by using the prefixes you defined in the options for the OLDM parser. They appear as prefix$part properties in the objects. You can switch this to appear as prefix:part, by setting the separator option to ":" in the options for the parser. The reason the default is $ is so that you can access predicates (properties) without using the ["..."] syntax. So you can type object.vcard$bday instead of object["vcard:bday"].

XSD types in the source are translated to JSONTag types. So "1972-09-20"^^xsd:date is translated to <date>"1972-09-20". In javascript this value is a String() object. You can get the exact type by calling JSONTag.getType:

	const type = JSONTag.getType(profile.vcard$bday)
	// returns 'date'

The full list of currently supported types (and translations) is:

{
	xsd$dateTime: '<datetime>',
	xsd$time: '<time>',
	xsd$date: '<date>',
	xsd$duration: '<duration>',
	xsd$string: '<string>',
	xsd$float: '<float>',
	xsd$decimal: '<decimal>',
	xsd$double: '<float64>',
	xsd$anyURI: '<url>',
	xsd$integer: '<int>',
	xsd$int: '<int>',
	xsd$long: '<int64>',
	xsd$short: '<int16>',
	xsd$byte: '<int8>',
	xsd$nonNegativeInteger: '<uint>',
	xsd$unsignedLong: '<uint64>',
	xsd$unsignedInt: '<uint>',
	xsd$unsignedShort: '<uint16>',
	xsd$unsignedByte: '<uint8>',
	xsd$base64Binary: '<blob class="base64">'
}

You can read more about JSONTag here on github

Check out a running demo on glitch