Query JSON with XPath

[arenas-guerrero-julian]

Last time I checked I could not find an implementation of JSONPath in python that was comprehensive and actively maintained. However, for XPath there are a couple of very good implementations.

The jsonpath library currently used by Morph-KGC has limitations and some bugs (e.g., #132). I though of internally converting JSON to XML (e.g., using json2xml) and using XPath to query JSON.

Some advantages:

• The XPath implementations available in python are good.
• XPath is standardized, JSONPath is not.
• XPath provides way more functions than JSONPath.
• This remains compliant w.r.t. RML (JSONPath is the default reference formulation for JSON, but RML does not enforce this language for JSON).

Some disadvantages:

• Conversion to XML may add some overhead in materialization.
• Mapping developers are used to using JSONPath for JSON.

@dgarijo @ocorcho @anaigmo what do you think? Do you see any other drawback? I am not that familiar with hierarchical data. A possible solution in the middle is to allow both for JSON, JSONPath and XPath, and add a configuration option to select which one to use.

[dgarijo]

As a user, I don't mind waiting a little more.
I do mind, however, if I wrap up my mappings in YARRRML and I don't get them to work with morph-KGC. My suggestion is to add whatever that makes my workflow easier, i.e., I need to be able to test my mappings in YARRRML without going to RML.

[arenas-guerrero-julian]

Translating YARRRML to RML and then executing Morph-KGC should work fine. However, you could not test your mappings in matey and then use the generated RML mapping with Morph-KGC.

This idea could wait for the moment in which Morph-KGC natively supports YARRRML so that Matey is not necessary for and testing the mappings can be done directly in Morph-KGC.

[dgarijo]

Then I would suggest waiting until having YARRRML support. At least I would not test new XPath configurations directly in RML, it's too cumbersome :(

[arenas-guerrero-julian]

As far as I could read here @marklogic follows this strategy querying JSON with XPath. I still need to read this better. Because we are suportting YARRRML in the short term I think there would be no problem with this @dgarijo.

[arenas-guerrero-julian]

JSON-to-XML.

[arenas-guerrero-julian]

Another possibility is to try this library besok/jsonpath-rust#29