Yes, could be a bug. But that aspect of daffodil is quite well tested so
I'm surprised at this.
Can you send your Document element declaration showing the 3 children row,
initialWord and foo ?
If the schema is confidential you can send me an encrypted email to my Owl
email address.
On Thu, Jan 4, 2024 at 8:45 AM Roger L Costello <coste...@mitre.org> wrote:
> Hi Mike,
>
>
>
> - Normally that message would also tell you what the possibilities for
> children of Document are (assuming there are some children of Document). Do
> you also get that in the error message? I think it should be telling you
> your choices are {}row
>
>
>
> Yes, that’s correct. The error messsage told me my choices are {}row and
> {}initial_word
>
>
>
> - Is foo a local element declaration with no namespace (meaning
> schema's elementFormDefault='unqualified')?
>
>
>
> Correct.
>
>
>
> - Assuming we figure out why it can't find your foo element decl, you
> are on the right track with the if (fn:exists(... stuff.
>
>
>
> Great. Then there is a bug in Daffodil, rigfht?
>
>
>
> /Roger
>
>
>
> *From:* Mike Beckerle <mbecke...@apache.org>
> *Sent:* Thursday, January 4, 2024 8:27 AM
> *To:* users@daffodil.apache.org
> *Subject:* [EXT] Re: How to count the number of child elements of the
> root element?
>
>
>
> There could be a bug, but we don't have enough here to reproduce it. That
> error message: No element corresponding to step {}foo, means that to
> Daffodil, the path /Document/foo doesn't make sense because Daffodil cannot
> find the element
>
> ZjQcmQRYFpfptBannerStart
>
> annerEnd
>
> There could be a bug, but we don't have enough here to reproduce it.
>
>
>
> That error message: No element corresponding to step {}foo, means that to
> Daffodil, the path /Document/foo doesn't make sense because Daffodil cannot
> find the element declaration for foo as a child element declaration of the
> element declaration for Document. The "{}" would contain a namespace URI
> if the foo element it was seeking was in a namespace. It is seeking a
> no-namespace child element decl for foo.
>
>
>
> Normally that message would also tell you what the possibilities for
> children of Document are (assuming there are some children of Document). Do
> you also get that in the error message? I think it should be telling you
> your choices are {}row and perhaps others.
>
>
>
> Is foo a local element declaration with no namespace (meaning schema's
> elementFormDefault='unqualified')?
>
>
>
> Assuming we figure out why it can't find your foo element decl, you are on
> the right track with the if (fn:exists(... stuff.
>
>
>
> In DFDL expressions, you can't just issue an expression as a query and get
> back "empty node set" to indicate that the expression wasn't meaningful.
> The expression must (a) be type-correct vis a vis the schema (b) cannot ask
> for counts, values, null-ness, etc. of things that are non-existing. This
> allows us to detect most errors at schema compilation time, not run time.
> It also allows the run-time to be very efficient with almost no runtime
> checking required.
>
>
>
> On Thu, Jan 4, 2024 at 7:09 AM Roger L Costello <coste...@mitre.org>
> wrote:
>
> Suppose in the future there will be a foo element. So, I first test for
> the existence of foo:
>
>
>
> {
>
> if (fn:exists(/Document/foo)) then
> fn:count(/Document/row)+fn:count(/Document/foo)+1
>
> else fn:count(/Document/row)+1
>
> }
>
>
>
> Daffodil gives the same error message: No element corresponding to step
> {}foo found.
>
>
>
> Eek! That seems like a bug in Daffodil. Or a bug in the DFDL
> specification. Or both. Yes?
>
>
>
> /Roger
>
>
>
> *From:* Roger L Costello <coste...@mitre.org>
> *Sent:* Thursday, January 4, 2024 6:49 AM
> *To:* users@daffodil.apache.org
> *Subject:* Re: How to count the number of child elements of the root
> element?
>
>
>
> Mike said:
>
>
>
> - { fn:count(/Document/row) + 1 } should give the value you want.
>
>
>
> Question: Suppose I call fn:count on a non-existent foo element:
>
>
>
> {fn:count(/Document/row)+fn:count(/Document/foo)+1}
>
>
>
> I would expect fn:count(/Document/foo) to return 0 since there are no foo
> elements. But it doesn’t. Daffodil generates an error. Why is that?
>
>
>
> /Roger
>
>
>
> *From:* Mike Beckerle <mbecke...@apache.org>
> *Sent:* Tuesday, January 2, 2024 8:32 AM
> *To:* users@daffodil.apache.org
> *Subject:* [EXT] Re: How to count the number of child elements of the
> root element?
>
>
>
> DFDL's count function does not operate on any "node set", but on specific
> named array elements only. In your case, the array is the row element, so {
> fn: count(/Document/row) + 1 } should give the value you want. On Wed, Dec
> 27,
>
> DFDL's count function does not operate on any "node set", but on specific
> named array elements only.
>
>
>
> In your case, the array is the row element, so { fn:count(/Document/row) +
> 1 } should give the value you want.
>
>
>
> On Wed, Dec 27, 2023 at 8:44 AM Roger L Costello <coste...@mitre.org>
> wrote:
>
> Hi Folks,
>
>
>
> My input file has a field containing the number of “words” in the file,
> where the “words” are the child elements of the root element. Here’s the
> XML that parsing produces:
>
>
>
> <Document>
> <initial_word>
> <message_length>3</message_length>
> </initial_word>
> <row>...</row>
> <row>...</row>
> </Document>
>
>
>
> The message_length is the initial_word + number of <row> elements, i.e., 1
> + 2 = 3
>
>
>
> I would like to hide message_length because it provides no meaningful
> information in the XML (after all, if you want to know the message length
> simply count the child elements of <Document>).
>
>
>
> To hide message_length, I will need a hidden group in my DFDL schema:
>
>
>
> <xs:group name="hidden-MESSAGE_LENGTH ">
> <xs:sequence>
> <xs:element name="hidden" type="unsignedint3"
> dfdl:outputValueCalc="{????}"/>
> </xs:sequence>
> </xs:group>
>
>
>
> The challenge that I am having is what XPath to use in
> dfdl:outputValueCalc. Initially, I used this:
>
>
>
> dfdl:outputValueCalc="{fn:count(/Document/*)}
>
>
>
> Daffodil complained: *Wildcard * is not supported.*
>
>
>
> Then I tried this:
>
>
>
> dfdl:outputValueCalc="{fn:count(../following-sibling::row)+1}
>
>
>
> Daffodil complained: *following-sibling axis is not supported.*
>
>
>
> Eek!
>
>
>
> I don’t know what else to try. Any suggestions?
>
>
>
> /Roger
>
>
>
>
