JSONPath as a search query language

[farshidtz]

We propose the use of JSONPath as one of the query languages in the discovery spec. However, we can't propose that as a normatice recommendation since the specification of JSONPath is not yet a standard.

We now have several issues addressing this very same problem:

• Reach out to JSONPath community #56
• Capture requirements for JSONPath #100
• Review IETF JSON Path draft #129
• JSONPath response data model #156
• Create Basic Query entry point #231

The goal of this issue is solely to monitor the progress of JSONPath standardization.

IETF datatracker: https://datatracker.ietf.org/doc/html/draft-ietf-jsonpath-base
Feature matrix of most existing implementations: https://cburgmer.github.io/json-path-comparison/#filter_expression_with_regular_expression

[mmccool]

Has been resolved (we have to make it informative at best, which has been done) so I think we can close this issue.

[mmccool]

Discussion in 22.8:

• if aim for Discovery 1.1 that allows for compatibility, can at most make this an optional feature
• Probably a good idea for our next release to be backward-compatible to maximize adoption
• could make it a "SHOULD" assertion, though... and if testing works out, mandatory in 2.0 (although of course we can discuss later after implementation experience)

[mmccool]

Issue #129 closed, should carry forward items discussed there as appropriate here. Removing "Consolidation" label.

[JKRhb]

FYI: JSONPath has just been released as RFC 9353 :) So for Discovery 2.0, we can use it as a normative reference.

[benfrancis]

@JKRhb: I can't tell from skim-reading this RFC whether it includes a standardised operator/filter/selector/some other mechanism for filtering objects in an array by the presence of a string in an array inside the object.

In #387 this is needed for searching a directory for Thing Descriptions which have a particular value in their @type array.

e.g.

• $[?(@['@type'].indexOf('iot:TemperatureSensor') != -1)] in Goessner JSONPath, or:
• $[?('iot:TemperatureSensor' in @['@type'])] in Jayway

Can anyone figure out if there is now a standardised way to do this? Perhaps via some kind of nested match expression? Or are there implementations which support this latest RFC that we can experiment with?

[JKRhb]

I only skimmed through the document myself so far, but at first glance, it seems to me as if you can use the filter selector for that. If I am not mistaken, with the RFC's syntax, the filter would then look something like this:

$[?(@['@type'] == 'iot:TemperatureSensor')]

Edit:

After some testing with one of the sandboxes, it seems as if the query should actually look like this (if I understood the examples you gave correctly):

$['@type'][?@ == 'iot:TemperatureSensor']

[JKRhb]

According to this blog post, there are also at least these two online sandboxes available:

• https://json-everything.net/json-path/
• https://serdejsonpath.live/