preserve data type

[elf-pavlik]

just noticed it and will post way of reproducing in hour or two ;)

[mcollina]

Cool! :) Let me know!

[elf-pavlik]

sorry for this cryptic issue! we notticed it together with Markus Lanthaler during our short meeting in Graz yesterday and I didn't want to use too much time for writing proper bug report...

var levelgraph = require('levelgraph');                                                                                                                                                 
var lgJSONLD = require('levelgraph-jsonld');                                                                                                                                                                                                                                                 
var db = lgJSONLD(levelgraph('test'));                                                                          

var graz = {                                                                                                     
  "@context": {                                                                                                  
    "@vocab": "http://schema.org/"                                                                               
  },                                                                                                             
  "@id": "http://dbpedia.org/resource/Graz",
  "@type": "City",                                                         
  "name": "Graz",                                                                                                
  "geo": {                                                                                                       
    "latitude": 47.0708101,                                                                                      
    "longitude": 15.4382918                                                                                      
  }                                                                                                              
};                                                                                                               

db.jsonld.put(graz, function() {                                                                                 
  db.jsonld.get(graz["@id"], { "@context": graz["@context"] }, function(err, doc) {                              
    console.log(doc);                                                                                            
  });                                                                                                            
});

running it prints

{ '@context': { '@vocab': 'http://schema.org/' },
  '@id': 'http://dbpedia.org/resource/Graz',
  '@type': 'City',
  geo: 
   { '@id': '_:f26890d0-5e5f-11e3-b04e-e3cb44466f3c',
     latitude: '4.70708101E1',
     longitude: '1.54382918E1' },
  name: 'Graz' 

as you see latitude and longitude turned into strings

[mcollina]

this is fun! :)
Part of the problem is here: https://github.com/mcollina/levelgraph-jsonld/blob/master/index.js#L37-L48, as only s p o are copied, and not any type information of the triple.
Then, that information is not taken into account in here: https://github.com/mcollina/levelgraph-jsonld/blob/master/index.js#L144.

Would you like to propose a fix?

[elf-pavlik]

i'll try to chew on it but in next days hitchhiking might take some of my time :(

i understand that we only need to preserve type of object since subject and predicate always stay IRIs. at first sight i didn't notice exact place where numbers get converted into strings!

maybe we could use Tripple Properties for that? https://github.com/mcollina/levelgraph#triple-properties something in lines: "objectType": "xsd:double"...

BTW this one looks relevant: http://json-ld.org/spec/latest/json-ld-api/#data-round-tripping

and another one: http://json-ld.org/spec/latest/json-ld/#dfn-value-type
as well as section directly after it: http://json-ld.org/spec/latest/json-ld/#type-coercion

[elf-pavlik]

we also need to make sure that we can use it together with N3/Turtle extension ... will need to check how it happens over there!

[mcollina]

maybe we could use Tripple Properties for that? https://github.com/mcollina/levelgraph#triple-properties something in lines: "objectType": "xsd:double"...

Exactly, that was my idea, check what N3.js is doing and be consistent, so that the modules are interoperable. :)

[elf-pavlik]

var lg = require('levelgraph');                                                                                  
var lgN3 = require('levelgraph-n3');                                                                                                                                              
var db = lgN3(lg('test'));                                                                                       

var turtle = "@prefix c: <http://example.org/cartoons#>.\n" +                                                    
             "@prefix xsd: <http://www.w3.org/2001/XMLSchema#>.\n" +                                             
             "c:Tom a c:Cat.\n" +                                                                                
             "c:Jerry a c:Mouse;\n" +                                                                            
             "        c:smarterThan c:Tom;\n" +                                                                  
             "        c:place \"fantasy\";\n" +                                                                  
             "        c:iq \"200\"^^xsd:integer.";

db.n3.put(turtle, function() {                                                                                   
  db.get({ predicate: 'http://example.org/cartoons#iq' }, function(err, triples) {                               
    console.log(triples);                                                                                        
  });                                                                                                            
});

prints out

[ { subject: 'http://example.org/cartoons#Jerry',
    predicate: 'http://example.org/cartoons#iq',
    object: '"200"^^<http://www.w3.org/2001/XMLSchema#integer>',
    context: 'n3/contexts#default' } ]

and it makes sense to just store object type within the object itself 😄

i'll play with https://github.com/mcollina/levelgraph-jsonld/blob/master/index.js#L37-L48 and make sure that for object we add datatype to value in triples returned by jsonld.toRDF()

i hope to find some time tomorrow and just fix it... starting with writing proper tests!

[mcollina]

👍
If you feel it will grow too much for a single file, split it across multiple ones in the lib/ folder.

[elf-pavlik]

@mcollina please don't merge yet! i just wanted to share initial experiment and refactor both tests and implementation ... i need to go through jsonld.js since most of that logic exists already over there and i would prefer to reuse it instead of duplicating.

[elf-pavlik]

oops! i thought i can rebase and attach new pull request to this issue... looks like now i will need to create new PR!

[mcollina]

what's the state on this?
You can reopen this PR if you want to.

[elf-pavlik]

looks like i can't re-open this one and will need to create another one... need to stay careful in a future not to convert issues into pull-request!

end of this week and early next week i plan some time to re-implement it in new way also addressing #4