Evaluation of JSON-LD for OSLC Usage

Status of this Document: Informational purposes only

Purpose of this page is to determine if the standardization work for defining a JSON format for RDF would be acceptable for OSLC needs. There a number of factors to consider which will be outlined below.

Samples

oslc_cm:ChangeRequest as OSLC JSON

{
  "prefixes" : {
    "dcterms" : "http://purl.org/dc/terms/",
    "oslc"     : "http://open-services.net/ns/core#",
    "oslc_cm" : "http://open-services.net/ns/cm#",
    "ex"       : "http://example.com/bugtracker"
  },
  "rdf:about"           : "http://example.com/bugs/2314",
  "rdf:type" : [{
    "rdf:resource" : "http://open-services.net/ns/cm#ChangeRequest"
  }],
  "dcterms:identifier"  : "00002314",
  "oslc:shortTitle"     : "Bug 2314",
  "dcterms:title"       : "Invalid installation instructions",
  "oslc:instanceShape" : {
    "rdf:resource" : "http://example.com/shapes/defect"
  },
  "dcterms:description" : "Invalid installation instructions indicating invalid patches to be applied.",
  "dcterms:creator" : [{
    "rdf:resource" : "http://myserver/mycmapp/users/joe"
  }],
  "dcterms:contributor" : [{
    "rdf:resource" : "http://myserver/mycmapp/users/bob"
  }],
  "dcterms:modified" : "2008-09-16T08:42:11.265Z",
  "dcterms:created" : "2008-07-04T11:00:00.000Z",
  "oslc_cm:status" : "InProgress",
  "oslc_cm:tracksRequirement" : [{
    "rdf:resource" : "http://myserver/reqtool/req/34ef31af",
    "dcterms:title" : "Link label for local req"
  },
  { "rdf:resource" : "http://remoteserver/reqrepo/project1/req456",
    "dcterms:title" : "Req456: Link label for remote requirement"
  }],
  "ex:priority" : "Medium",
  "ex:severity" : "Normal"
}

oslc_cm:ChangeRequest as OSLC JSON + JSON-LD

{
  "@context" : {
    "dcterms" : "http://purl.org/dc/terms/",
    "oslc"     : "http://open-services.net/ns/core#",
    "oslc_cm" : "http://open-services.net/ns/cm#",
    "ex"       : "http://example.com/bugtracker"
  },
 "@id"       : "http://example.com/bugs/2314",
 "@type"   : "http://open-services.net/ns/cm#ChangeRequest",
  "prefixes" : {
    "dcterms" : "http://purl.org/dc/terms/",
    "oslc"     : "http://open-services.net/ns/core#",
    "oslc_cm" : "http://open-services.net/ns/cm#",
    "ex"       : "http://example.com/bugtracker"
  },
  "rdf:about"           : "http://example.com/bugs/2314",
  "rdf:type" : [{
    "rdf:resource" : "http://open-services.net/ns/cm#ChangeRequest"
  }],
  "dcterms:identifier"  : "00002314",
  "oslc:shortTitle"     : "Bug 2314",
  "dcterms:title"       : "Invalid installation instructions",
  "oslc:instanceShape" : {
    "rdf:resource" : "http://example.com/shapes/defect"
  },
  "dcterms:description" : "Invalid installation instructions indicating invalid patches to be applied.",
  "dcterms:creator" : [{
    "rdf:resource" : "http://myserver/mycmapp/users/joe"
  }],
  "dcterms:contributor" : [{
    "rdf:resource" : "http://myserver/mycmapp/users/bob"
  }],
  "dcterms:modified" : "2008-09-16T08:42:11.265Z",
  "dcterms:created" : "2008-07-04T11:00:00.000Z",
  "oslc_cm:status" : "InProgress",
  "oslc_cm:tracksRequirement" : [{
    "rdf:resource" : "http://myserver/reqtool/req/34ef31af",
    "dcterms:title" : "Link label for local req"
  },
  { "rdf:resource" : "http://remoteserver/reqrepo/project1/req456",
    "dcterms:title" : "Req456: Link label for remote requirement"
  }],
  "ex:priority" : "Medium",
  "ex:severity" : "Normal"
}

Issues

1. What happens when a server returns any variant of JSON-LD it wants: compact, expanded, compact IRI
2. Why is @type not defined to be same semantics as rdf:type ? see type defn It also appears to overload the definition of value type and resource type using @type, a problem?
3. Appears that @type object doesn't support multi-values, i.e. doesn't allow for multi-typed resources.
4. TODO: determine if how "link labels" will be represented and/or round tripped (likewise for other concepts such as bnodes)
5. Still have the problem knowing objects vs. arrays ahead of time to ease consumers?
6. Recommend this as 3.0 JSON format and how to migrate (or content negotiation)

Issues have been sent to the public-rdf-comments@w3.org maillist

References

• OSLC Core JSON Guidelines
• OSLCCoreSpecJSONExamples
• JSON-LD Syntax 1.0 - July 12, 2012 draft
• JSON-LD API - July 12, 2012 draft