Annotation Values: Booleans

[ChristianGruen]

Functions annotations in XQuery have become a popular feature to attach vendor-specific information (for unit testing, locking, RESTXQ, etc.) to functions.

Annotation values are limited to literals, though. It would often be helpful to supply boolean values, but we don’t have literals for that in the language.

I suggest enhancing the existing grammar…

Annotation  ::=  "%" EQName ("(" Literal ("," Literal)* ")")?

…and allowing the strings false() and true() as values:

Annotation  ::=  "%" EQName ("(" AnnotationValue ("," AnnotationValue)* ")")?
AnnotationValue  :=  Literal | "false()" | "true()"

The suggestion is upward compatible if we should decide later on that we want to allow arbitrary expressions for annotation values.

[michaelhkay]

There's a minor problem with this if the default function namespace isn't "fn". I propose tackling that simply by saying that within the Annotation, the default function namespace IS "fn", regardless what it might be outside.

[ChristianGruen]

There's a minor problem with this if the default function namespace isn't "fn". I propose tackling that simply by saying that within the Annotation, the default function namespace IS "fn", regardless what it might be outside.

Good point. +1.

I wasn't sure if we should also allow fn:true() and fn:false(). I eventually omitted those in order to minimize hard-coded string handling.