Hi Tim,

"Funky" made me chuckle too!

I tested your code with the closest thing at hand - a local build of branch of Wolfgang Meier's eXist repo with support for the arrow operator (https://github.com/wolfgangmm/exist/tree/feature/arrowop) - and your code worked fine there. So my hunch is that there's a bug in BaseX or some syntax error I'm not seeing in your code. For the record, here's the code I'm running:

-- xquery version "3.1";

json-doc("http://lae.princeton.edu/catalog/0bp35.jsonld%22)(%22@context") => json-doc()("@context") --

To check the results I actually use `=> serialize(<serialization-parameters xmlns="http://www.w3.org/2010/xslt-xquery-serialization"><method>json</method><indent>yes</indent></serialization-parameters>)` on the results since eXist doesn't support adaptive serialization.

I hope this is helpful.

Joe

On Sat, Jan 9, 2016 at 6:20 PM, Tim Thompson timathom@gmail.com wrote:

Thanks, Joe! I guess I'd glossed over the "funky" example ;-) Regarding the arrow operator, I was wondering whether something like this was possible:

json-doc(" http://lae.princeton.edu/catalog/0bp35.jsonld%22)(%22@context") => json-doc()("@context")

which throws an error: [XPST0003] Unexpected end of query: '("@context")'.

Tim

On Sat, Jan 9, 2016 at 3:53 PM, Joe Wicentowski joewiz@gmail.com wrote:

...

Hi Tim,

For your first question, I think your example falls into what the spec calls "funky looking" keys. See the 3rd bullet point example under http://www.w3.org/TR/xquery-31/#id-lookup:

...

funky / <looking @string") is equivalent to .("$funky / <looking @string"), an appropriate lookup for a map with rather odd conventions for keys.

In other words, I think you're stuck with the ("@context") approach.

As to your second question, it looks like what you're proposing should work - but am I reading you as saying you get an error with your proposed approach? If so, what's the error?

Joe

Sent from my iPad

---

From: Tim Thompson timathom@gmail.com Sent: Saturday, January 9, 2016 3:11 PM Subject: [basex-talk] Lookups and arrows To: BaseX basex-talk@mailman.uni-konstanz.de

Hello,

I'm testing some XQuery 3.1 features against a JSON-LD[1] document and had a few questions. In the JSON-LD format, the "@" symbol has special semantics in key names, but seems to cause problems with the 3.1 lookup operator.

For example:

json-doc(" http://lae.princeton.edu/catalog/0bp35.jsonld%22)(%22@context")

works as expected, but

json-doc(" http://lae.princeton.edu/catalog/0bp35.jsonld%22)?@context

throws an error: [XPST0003] No specifier after lookup operator: '@'.

Also, when using the "=>" operator, should it be possible to perform a lookup on the last expression in a chain, if that expression returns a map?

For example:

json-doc(" http://lae.princeton.edu/catalog/0bp35.jsonld%22)(%22@context") evaluates to " http://iiif.io/api/presentation/2/context.json"

and

json-doc(" http://lae.princeton.edu/catalog/0bp35.jsonld%22)(%22@context") => json-doc()

returns another map object. So, how would one achieve this:

json-doc(json-doc(" http://lae.princeton.edu/catalog/0bp35.jsonld%22)(%22@context%22))(%22@conte...")

using the arrow operator?

Thanks, Tim

[1] http://www.w3.org/TR/json-ld/

-- Tim A. Thompson Metadata Librarian (Spanish/Portuguese Specialty) Princeton University Library

Thanks very much for this info, Christian! I'll pass your observations on to the eXist team.

Joe

On Sun, Jan 10, 2016 at 3:50 AM, Christian Grün christian.gruen@gmail.com wrote:

Hi Tim, hi Joe,

The query works if you use parentheses around the arrow operands:

(json-doc("http://lae.princeton.edu/catalog/0bp35.jsonld%22)(%22@context") => json-doc())("@context")

This is in compliance with the XQuery 3.1 spec [1].

Out of interest, I spent some time and looked up the W3 bug tracker history, and I spotted a change in the precedence of the arrow operator [2]. Maybe this change is not reflected in eXist?

Hope this helps, Christian

[1] http://www.w3.org/TR/xquery-31/#doc-xquery31-ArrowExpr [2] https://www.w3.org/Bugs/Public/show_bug.cgi?id=27537

...

I tested your code with the closest thing at hand - a local build of branch of Wolfgang Meier's eXist repo with support for the arrow operator (https://github.com/wolfgangmm/exist/tree/feature/arrowop) - and your code worked fine there. So my hunch is that there's a bug in BaseX or some syntax error I'm not seeing in your code. For the record, here's the code I'm running:

-- xquery version "3.1";

json-doc("http://lae.princeton.edu/catalog/0bp35.jsonld%22)(%22@context") => json-doc()("@context") --

To check the results I actually use `=> serialize(<serialization-parameters xmlns="http://www.w3.org/2010/xslt-xquery-serialization"><method>json</method><indent>yes</indent></serialization-parameters>)` on the results since eXist doesn't support adaptive serialization.

I hope this is helpful.

Joe

On Sat, Jan 9, 2016 at 6:20 PM, Tim Thompson timathom@gmail.com wrote:

...

Thanks, Joe! I guess I'd glossed over the "funky" example ;-) Regarding the arrow operator, I was wondering whether something like this was possible:

json-doc(" http://lae.princeton.edu/catalog/0bp35.jsonld%22)(%22@context") => json-doc()("@context")

which throws an error: [XPST0003] Unexpected end of query: '("@context")'.

Tim

On Sat, Jan 9, 2016 at 3:53 PM, Joe Wicentowski joewiz@gmail.com wrote:

...

Hi Tim,

For your first question, I think your example falls into what the spec calls "funky looking" keys. See the 3rd bullet point example under http://www.w3.org/TR/xquery-31/#id-lookup:

...

funky / <looking @string") is equivalent to .("$funky / <looking @string"), an appropriate lookup for a map with rather odd conventions for keys.

In other words, I think you're stuck with the ("@context") approach.

As to your second question, it looks like what you're proposing should work - but am I reading you as saying you get an error with your proposed approach? If so, what's the error?

Joe

Sent from my iPad

---

From: Tim Thompson timathom@gmail.com Sent: Saturday, January 9, 2016 3:11 PM Subject: [basex-talk] Lookups and arrows To: BaseX basex-talk@mailman.uni-konstanz.de

Hello,

I'm testing some XQuery 3.1 features against a JSON-LD[1] document and had a few questions. In the JSON-LD format, the "@" symbol has special semantics in key names, but seems to cause problems with the 3.1 lookup operator.

For example:

json-doc(" http://lae.princeton.edu/catalog/0bp35.jsonld%22)(%22@context")

works as expected, but

json-doc(" http://lae.princeton.edu/catalog/0bp35.jsonld%22)?@context

throws an error: [XPST0003] No specifier after lookup operator: '@'.

Also, when using the "=>" operator, should it be possible to perform a lookup on the last expression in a chain, if that expression returns a map?

For example:

json-doc(" http://lae.princeton.edu/catalog/0bp35.jsonld%22)(%22@context") evaluates to " http://iiif.io/api/presentation/2/context.json"

and

json-doc(" http://lae.princeton.edu/catalog/0bp35.jsonld%22)(%22@context") => json-doc()

returns another map object. So, how would one achieve this:

json-doc(json-doc(" http://lae.princeton.edu/catalog/0bp35.jsonld%22)(%22@context%22))(%22@conte...")

using the arrow operator?

Thanks, Tim

[1] http://www.w3.org/TR/json-ld/

-- Tim A. Thompson Metadata Librarian (Spanish/Portuguese Specialty) Princeton University Library