W3C home > Mailing lists > Public > public-qt-comments@w3.org > July 2016

[Bug 29743] New: XPath 3.1 maps recursive descent

From: <bugzilla@jessica.w3.org>
Date: Wed, 20 Jul 2016 05:07:06 +0000
To: public-qt-comments@w3.org
Message-ID: <bug-29743-523@http.www.w3.org/Bugs/Public/>
https://www.w3.org/Bugs/Public/show_bug.cgi?id=29743

            Bug ID: 29743
           Summary: XPath 3.1 maps recursive descent
           Product: XPath / XQuery / XSLT
           Version: Working drafts
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: XPath 3.1
          Assignee: jonathan.robie@gmail.com
          Reporter: jorge.williams@rackspace.com
        QA Contact: public-qt-comments@w3.org
  Target Milestone: ---

We use JSONPath (http://goessner.net/articles/JsonPath/) along side of XPath,
when working with JSON data.  Now that XPath supports maps and JSON, I've
started evaluating  whether it may be worth consolidating around XPath
exclusively.  This would certainly make our lives easier especially as JSONPath
implementations vary wildly.

One feature that appears to be missing, but which is used quite often by our
lazy developers is recursive decent ( .. in JSONPath).

Notice the examples here: http://goessner.net/articles/JsonPath/  it's a bit of
a challenge to replicate them with XPath 3.1.

I've created a function in XQuery which I believe captures what JSONPath is
doing and it looks like this:

declare function r:d($m as item()) as item()* {
  let $funs := $m?*[. instance of map(*) or . instance of array(*)]
  let $mps := $funs[. instance of map(*)]
  return  ($mps, $funs ! r:d(.))
};

Given that I can replicate all of the examples :

| Description                        | JSONPath                | XPath 3.1     
                     |
|------------------------------------+-------------------------+-------------------------------------|
| All of the authors of a book       | $.store.book[*].author  |
$_?store?book?*?author              |
| All authors                        | $..author               | r:d($_)?author
                     |
| All things in the store            | $.store.*               | $_?store?*    
                     |
| The price of everything in a store | $.store..price          |
r:d($_?store)?price                 |
| The third book                     | $..book[ 2 ]            | r:d($_)?book?3
                     |
| The last book in order             | $..book[(@.length-1)]   |
r:d($_)?book?*[position() = last()] |
|                                    | $..book[-1:]            |               
                     |
| The first two books                | $..book[0,1]            |
r:d($_)?book?(1, 2)                 |
|                                    | $..book[:2]             |
r:d($_)?book?(1 to 2)               |
| Filter all books with isbn number  | $..book[?(@.isbn)]      |
r:d($_)?book?*[?isbn]               |
| Filtar all books cheaper than 10   | $..book[?(@.price< 10)] |
r:d($_)?book?*[?price < 10]         |
| All members of JSON structure      | $..*                    | r:d($_)       
                     |

Defining a function to do this doesn't seem right though. I must be missing
something...or there is a gap.

Thanks.

-- 
You are receiving this mail because:
You are the QA Contact for the bug.
Received on Wednesday, 20 July 2016 05:07:20 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 16:58:01 UTC