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" <[email protected]>
To: [email protected]
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 <[email protected]> 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 <[email protected]> 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" <[email protected]>
To: [email protected]
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 <[email protected]> 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 <[email protected]>
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
