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Posted to users@jena.apache.org by ajs6f <aj...@apache.org> on 2018/11/07 15:21:05 UTC
JSON-LD Was: Loosely converting JSON/XML to RDF
On the particular topic of JSON-LD 1.1, because it has some relevance to the Jena community, I'd like to note again that there are several different groups working out things we can call "1.1", in concert. There is the current Community Group [1] and there is the current Working Group [2].
The difference is that the CG (like all W3C Community Groups) uses a much simpler and less-burdensome process to develop its products. This makes it more flexible and speedy. On the other hand, the WG is slower, very careful, and goes though the whole W3C process [3] to create a recommendation (the highest level of certification that W3C provides to a specification). The WG is sceheduled to deliver its products by 15 June 2020.
You can track the work of either group easily, keeping in mind that implementators make independent choices about if and when to implement new features.
The reason I mention all this here is as preface to pointing out that both CG and WG have agreed to add "arrays of arrays" or "lists of lists" to 1.1 [4]. That doesn't refute Conal's basic point about not all JSON being usable for JSON-LD. There might very well be other places where that is still true. But (wearing my "member of the WG" hat) we hope we've gotten the vast majority of potential use cases.
It is worth repeating what others have mentioned in passing-- JSON-LD's primary use case is what used to be called "semantic lifting": adding semantic information to data that lacks it (JSON => JSON-LD). Of course, it's also meant to function as an RDF serialization, but if your first interest is moving from something that isn't JSON to RDF, you may very well find other tools to be more natural and helpful.
ajs6f
[1]https://www.w3.org/community/json-ld/ and https://json-ld.org
[2[] https://www.w3.org/2018/json-ld-wg/
[3] https://www.w3.org/2018/Process-20180201/
[4] https://www.w3.org/2018/json-ld-wg/Meetings/Minutes/2018/2018-08-03-json-ld#section4 . For an example, see https://w3c.github.io/json-ld-syntax/#ex-57-coordinates-expressed-in-geojson and above.
> On Nov 7, 2018, at 8:22 AM, Conal Tuohy <co...@gmail.com> wrote:
>
> Hi Laura
>
> If I recall correctly, not every JSON document can be parsed as JSON-LD
> merely by supplying a JSON-LD context. I think it is still the case that
> arrays of arrays are not valid in JSON-LD, so you may want to check your
> JSON data to ensure that it complies with that restriction.
>
> I think Martynas Jusevičius is absolutely right to say that different RDF
> syntaxes and RDF conversion techniques are better suited to different types
> of data sources. Personally, I like to use XSLT to convert both XML and
> JSON data to RDF/XML, because although XSLT generally allows use to use a
> simple templating style like SPARQL-Generate or CSVW, it also allows you to
> the flexibility to define more complex mapping operations where that's
> necessary (since XSLT is a Turing-complete programming language).
>
> Good luck with your conversions!
>
> Con
>
>
> On Wed, 7 Nov 2018 at 20:41, Laura Morales <la...@mail.com> wrote:
>
>> This made me thinking... if I can convert CSV, XML, and other formats to
>> JSON, and then use JSON-LD context and framing to change the data to my
>> linking, why do tools such as RML, YARRRML, and SPARQL-Generate exist at
>> all? Do they do anything at all that can't be done with JSON-LD?
>>
>>
>>
>>
>> Sent: Monday, November 05, 2018 at 9:10 AM
>> From: "Christopher Johnson" <ch...@gmail.com>
>> To: users@jena.apache.org
>> Subject: Re: Loosely converting JSON/XML to RDF
>> Another approach is to use JSON-LD. A JSON document can be "converted" to
>> RDF by adding a context and using the toRDF method[1] in one of the JSON-LD
>> libraries. Defining the context is similar to what is done with RML,
>> basically mapping data objects to structured vocabulary terms. If your XML
>> is sufficiently denormalized, you can also convert that to JSON and repeat
>> the same process as above.
>>
>> Christopher Johnson
>> Scientific Associate
>> Universitätsbibliothek Leipzig
>>
>> [1] https://json-ld.org/spec/latest/json-ld-api/#object-to-rdf-conversion
>>
>> On Mon, 5 Nov 2018 at 08:55, Alex To <to...@gmail.com> wrote:
>>
>>> We have web services returning XML and JSON in our environment. We use
>>>
>> https://github.com/RMLio/rmlmapper-java[https://github.com/RMLio/rmlmapper-java]
>> to map XML/JSON to RDF with
>>> satisfied results.
>>>
>>> Or course you need a valid URI for your XML or Json elements for e.g. in
>>> our XML, if we have <Student id="...">...</Student> then we use RML to
>> map
>>> it to
>>>
>>>
>> http://ourdomain.com/resources/students/[http://ourdomain.com/resources/students/]{id}
>> rdfs:type
>>> http://ourdomain.com/ont/Student[http://ourdomain.com/ont/Student]
>>>
>>> You can define your own URI generation scheme whatever works for you
>>>
>>> You can read more about RDF Mapping Language (RML) from W3C website.
>>>
>>> Regards
>>>
>>> On Mon, 5 Nov 2018 at 6:34 pm, Laura Morales <la...@mail.com> wrote:
>>>
>>>> I have a mixed set of datasets in XML, JSON, and RDF formats. I would
>>> like
>>>> to convert all the XML/JSON ones to RDF such that I can only use one
>>> query
>>>> language/library to access all the data, instead of having three
>>> different
>>>> ones. I'm also not interested in using any particular ontology or
>>>> vocabulary for the conversion, so anything will work as long as I can
>>> make
>>>> the conversion.
>>>> What would be an appropriate strategy for this? Since RDF requires
>>>> absolute IRIs, would it be a good idea for example to convert all
>>>> properties to
>> http://example.org/property-name-1[http://example.org/property-name-1],
>>>> http://example.org/property-name-2[http://example.org/property-name-2],
>> ...? And maybe use UUIDs for nodes?
>>>> Or is there a better way of doing this?
>>>>
>>>
>>
>
>
> --
> Conal Tuohy
> http://conaltuohy.com/
> @conal_tuohy
> +61-466-324297
Re: JSON-LD Was: Loosely converting JSON/XML to RDF
Posted by Paul Houle <on...@gmail.com>.
I did some projects last year where I converted XML to JSON in some
formulaic way (dependent on the kind of document you have) and then
stuffed the JSON into databases such as CouchDB or arangodb. At that
point I would sometimes pass the JSON data into RDF-world through
JSON/RDF or alternately put RDF-world data into JSON blobs in the
aforesaid databases.
There are many problems that could turn up in XML-to-JSON translation,
for instance dealing with the attribute-vs-element distinction,
maintaining ordering, namespaces, mixed content, etc. In practice I
find that most document collections have one or two problems like that
to deal with, but that they did not all come up at the same time so I
was always able to come up with a simple transformation that was
idiomatic.
Note also that the JSON model is an approximation of the data model
common in languages like Perl, Python, etc. With the right idioms
that data model is easy to work with in Java, C++, etc.
I imagine some kind of system that round trips these all as simply as
possible with a small amount of metadata and that might be the next
"JSON-LD" but this time it has to be marketed better.
------ Original Message ------
From: "ajs6f" <aj...@apache.org>
To: users@jena.apache.org
Sent: 11/7/2018 10:21:05 AM
Subject: JSON-LD Was: Loosely converting JSON/XML to RDF
>On the particular topic of JSON-LD 1.1, because it has some relevance
>to the Jena community, I'd like to note again that there are several
>different groups working out things we can call "1.1", in concert.
>There is the current Community Group [1] and there is the current
>Working Group [2].
>
>The difference is that the CG (like all W3C Community Groups) uses a
>much simpler and less-burdensome process to develop its products. This
>makes it more flexible and speedy. On the other hand, the WG is slower,
>very careful, and goes though the whole W3C process [3] to create a
>recommendation (the highest level of certification that W3C provides to
>a specification). The WG is sceheduled to deliver its products by 15
>June 2020.
>
>You can track the work of either group easily, keeping in mind that
>implementators make independent choices about if and when to implement
>new features.
>
>The reason I mention all this here is as preface to pointing out that
>both CG and WG have agreed to add "arrays of arrays" or "lists of
>lists" to 1.1 [4]. That doesn't refute Conal's basic point about not
>all JSON being usable for JSON-LD. There might very well be other
>places where that is still true. But (wearing my "member of the WG"
>hat) we hope we've gotten the vast majority of potential use cases.
>
>It is worth repeating what others have mentioned in passing-- JSON-LD's
>primary use case is what used to be called "semantic lifting": adding
>semantic information to data that lacks it (JSON => JSON-LD). Of
>course, it's also meant to function as an RDF serialization, but if
>your first interest is moving from something that isn't JSON to RDF,
>you may very well find other tools to be more natural and helpful.
>
>ajs6f
>
>
>[1]https://www.w3.org/community/json-ld/ and https://json-ld.org
>[2[] https://www.w3.org/2018/json-ld-wg/
>[3] https://www.w3.org/2018/Process-20180201/
>[4]
>https://www.w3.org/2018/json-ld-wg/Meetings/Minutes/2018/2018-08-03-json-ld#section4
>. For an example, see
>https://w3c.github.io/json-ld-syntax/#ex-57-coordinates-expressed-in-geojson
>and above.
>
>>On Nov 7, 2018, at 8:22 AM, Conal Tuohy <co...@gmail.com> wrote:
>>
>>Hi Laura
>>
>>If I recall correctly, not every JSON document can be parsed as
>>JSON-LD
>>merely by supplying a JSON-LD context. I think it is still the case
>>that
>>arrays of arrays are not valid in JSON-LD, so you may want to check
>>your
>>JSON data to ensure that it complies with that restriction.
>>
>>I think Martynas Jusevičius is absolutely right to say that different
>>RDF
>>syntaxes and RDF conversion techniques are better suited to different
>>types
>>of data sources. Personally, I like to use XSLT to convert both XML
>>and
>>JSON data to RDF/XML, because although XSLT generally allows use to
>>use a
>>simple templating style like SPARQL-Generate or CSVW, it also allows
>>you to
>>the flexibility to define more complex mapping operations where that's
>>necessary (since XSLT is a Turing-complete programming language).
>>
>>Good luck with your conversions!
>>
>>Con
>>
>>
>>On Wed, 7 Nov 2018 at 20:41, Laura Morales <la...@mail.com> wrote:
>>
>>>This made me thinking... if I can convert CSV, XML, and other formats
>>>to
>>>JSON, and then use JSON-LD context and framing to change the data to
>>>my
>>>linking, why do tools such as RML, YARRRML, and SPARQL-Generate exist
>>>at
>>>all? Do they do anything at all that can't be done with JSON-LD?
>>>
>>>
>>>
>>>
>>>Sent: Monday, November 05, 2018 at 9:10 AM
>>>From: "Christopher Johnson" <ch...@gmail.com>
>>>To: users@jena.apache.org
>>>Subject: Re: Loosely converting JSON/XML to RDF
>>>Another approach is to use JSON-LD. A JSON document can be
>>>"converted" to
>>>RDF by adding a context and using the toRDF method[1] in one of the
>>>JSON-LD
>>>libraries. Defining the context is similar to what is done with RML,
>>>basically mapping data objects to structured vocabulary terms. If
>>>your XML
>>>is sufficiently denormalized, you can also convert that to JSON and
>>>repeat
>>>the same process as above.
>>>
>>>Christopher Johnson
>>>Scientific Associate
>>>Universitätsbibliothek Leipzig
>>>
>>>[1]
>>>https://json-ld.org/spec/latest/json-ld-api/#object-to-rdf-conversion
>>>
>>>On Mon, 5 Nov 2018 at 08:55, Alex To <to...@gmail.com> wrote:
>>>
>>>>We have web services returning XML and JSON in our environment. We
>>>>use
>>>>
>>>https://github.com/RMLio/rmlmapper-java[https://github.com/RMLio/rmlmapper-java]
>>>to map XML/JSON to RDF with
>>>>satisfied results.
>>>>
>>>>Or course you need a valid URI for your XML or Json elements for
>>>>e.g. in
>>>>our XML, if we have <Student id="...">...</Student> then we use RML
>>>>to
>>>map
>>>>it to
>>>>
>>>>
>>>http://ourdomain.com/resources/students/[http://ourdomain.com/resources/students/]{id}
>>>rdfs:type
>>>>http://ourdomain.com/ont/Student[http://ourdomain.com/ont/Student]
>>>>
>>>>You can define your own URI generation scheme whatever works for you
>>>>
>>>>You can read more about RDF Mapping Language (RML) from W3C website.
>>>>
>>>>Regards
>>>>
>>>>On Mon, 5 Nov 2018 at 6:34 pm, Laura Morales <la...@mail.com>
>>>>wrote:
>>>>
>>>>>I have a mixed set of datasets in XML, JSON, and RDF formats. I
>>>>>would
>>>>like
>>>>>to convert all the XML/JSON ones to RDF such that I can only use
>>>>>one
>>>>query
>>>>>language/library to access all the data, instead of having three
>>>>different
>>>>>ones. I'm also not interested in using any particular ontology or
>>>>>vocabulary for the conversion, so anything will work as long as I
>>>>>can
>>>>make
>>>>>the conversion.
>>>>>What would be an appropriate strategy for this? Since RDF requires
>>>>>absolute IRIs, would it be a good idea for example to convert all
>>>>>properties to
>>>http://example.org/property-name-1[http://example.org/property-name-1],
>>>>>http://example.org/property-name-2[http://example.org/property-name-2],
>>>...? And maybe use UUIDs for nodes?
>>>>>Or is there a better way of doing this?
>>>>>
>>>>
>>>
>>
>>
>>--
>>Conal Tuohy
>>http://conaltuohy.com/
>>@conal_tuohy
>>+61-466-324297
>