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")("@context")

works as expected, but

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

and

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

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

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

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