Thank you Mike! It worked and explanation is very clear.
Can dfdl:discriminator be used as an attribute of a xs:element or only as a
xs:annotation?
> On Jun 18, 2020, at 4:11 PM, Beckerle, Mike <mbecke...@tresys.com> wrote:
>
> To use a pattern to discriminate a choice, you would use a dfdl:discriminator
> statement with testKind='pattern' on each branch of the choice. That
> assertion is using a regex to look at the data stream, and fails if the data
> stream at the current position doesn't start with a non-zero-length match of
> the pattern.
>
> E.g., something like:
>
> <xs:choice>
> <xs:sequence>
> <xs:annotation><xs:appinfo ...>
> <!-- Must begin with from 1 to 10 'a' characters -->
> <dfdl:discriminator testKind="pattern">a{1,10}</dfdl:discriminator>
> </xs:appinfo></xs:annotation>
> ... rest of 'a's branch...
> </xs:sequence>
> <xs:sequence>
> <xs:annotation><xs:appinfo ...>
> <!-- Must begin with from 1 to 10 'b' characters -->
> <dfdl:discriminator testKind="pattern">b{1,10}</dfdl:discriminator>
> </xs:appinfo></xs:annotation>
> ... rest of 'b's branch...
> </xs:sequence>
> ... other branches ...
> </xs:choice>
>
> Did that address your need?
>
> One detail is that the matching of the discriminator pattern isn't consuming
> any data. When the branch is selected and parsing starts, you are still
> looking at the start of the data, not after the pattern matched. An element
> has to absorb these characters and then go on to parse the remainder of the
> branch. Sometimes that's easy, sometimes a slightly different idea makes more
> sense:
>
> <xs:choice>
> <xs:sequence>
> <!--
> element that matches the pattern. If there is no match this will be
> zero-length string
> -->
> <xs:element name="aaBranchTag" type="xs:string"
> dfdl:lengthKind="pattern" dfdl:lengthPattern="a{1,10}"/>
> <xs:annotation><xs:appinfo ...>
> <!--
> if the match contains 1 or more characters, this is the right
> branch
> -->
> <dfdl:discriminator>{ fn:string-length(./aaBranchTag) gt 0
> }</dfdl:discriminator>
> </xs:appinfo></xs:annotation>
> ... rest of 'a's branch...starting from after the run of 'a's.
> </xs:sequence>
> .... other branches work similarly ....
> </xs:choice>
>
>
>
>
>
> From: Patrick Grandjean <p.r.grandj...@gmail.com
> <mailto:p.r.grandj...@gmail.com>>
> Sent: Thursday, June 18, 2020 3:28 PM
> To: users@daffodil.apache.org <mailto:users@daffodil.apache.org>
> <users@daffodil.apache.org <mailto:users@daffodil.apache.org>>
> Subject: dfdl:choiceDispatchKey
>
> Hi!
>
> I recently started using dfdl:choiceDispatchKey. According to the
> documentation, it only accepts DFDL expressions. Is it possible to use DFDL
> regular expressions instead? Or is there an alternative that would accept
> regexes?
>
> Patrick.
