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Posted to users@daffodil.apache.org by Mike Beckerle <mb...@apache.org> on 2024/01/02 13:32:06 UTC
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, 2023 at 8:44 AM Roger L Costello <co...@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
>
>
>
Re: How to count the number of child elements of the root element?
Posted by Mike Beckerle <mb...@apache.org>.
The simplest reason this is not allowed is because DFDL is a strongly typed
language, so all expressions must type check. Daffodil assumes verifying
that all paths match existing element declarations is an important check
that saves users from many errors that are otherwise very hard to debug
when left to runtime. This also enables compilation of expressions to a
very efficient runtime that doesn't have to check very much.
Pragmatically, consider "foo" in /Document/foo was not you anticipating a
future need, but was an accidental typo on some field name that should have
been "Foo" or "bar/foo" or some other variation. This is a very VERY common
kind of mistake. Just rename an element or nest it under another element,
or hoist it out from inside an element, where your element's name appears
in lots of expressions and suddenly all those expressions need updating
also. If we didn't check that path steps in expression match element decls,
then just renaming an element doesn't make any expressions illegal/errors,
it just makes them mean something different that is almost certainly not
what you want them to mean.
XPath doesn't do any of this checking because it's a query language
designed to work even (or primarily) when there is no schema, so no way of
knowing whether any given path step should or could exist. When there is no
schema enforcement, then all paths could theoretically exist so no paths
are illegal.
On Thu, Jan 4, 2024 at 10:19 AM Roger L Costello <co...@mitre.org> wrote:
> The scenario is this: in the future I may add a foo element:
>
>
>
> <xs:element name="Document">
> <xs:complexType>
> <xs:sequence>
> <xs:element ref="initial_word"/>
> <xs:element ref="row" maxOccurs="unbounded"/>
> <xs:element ref="foo"/>
> </xs:sequence>
> </xs:complexType>
> </xs:element>
>
>
>
> I want message_length to correctly count the number of child elements of
> Document now and in the future. So I test for the existence of the foo
> element. If there is no foo element, then I don’t attempt to count it:
>
>
>
> dfdl:outputValueCalc="{
> *if* (*fn:exists*(/*Document*/*foo*)) *then* *fn:count*(/
> *Document*/*row*)+*fn:count*(/*Document*/*foo*)+1
> *else* *fn:count*(/*Document*/*row*)+1
> }"
>
>
>
> You are saying that this is not allowed? Why?
>
>
>
> /Roger
>
> *From:* Mike Beckerle <mb...@apache.org>
> *Sent:* Thursday, January 4, 2024 10:08 AM
> *To:* users@daffodil.apache.org
> *Subject:* [EXT] Re: How to count the number of child elements of the
> root element?
>
>
>
> So there actually isn't a declaration for an element named foo here. DFDL
> will not allow the expression "/Document/foo" at all because it is
> meaningless. There is no declaration of an element named foo. That
> expression has no
>
>
>
> So there actually isn't a declaration for an element named foo here.
>
>
>
> DFDL will not allow the expression "/Document/foo" at all because it is
> meaningless. There is no declaration of an element named foo.
>
> That expression has no type but your expression requires it to be an array
> type.
>
>
>
>
>
> On Thu, Jan 4, 2024 at 9:22 AM Roger L Costello <co...@mitre.org>
> wrote:
>
> Hi Mike,
>
>
>
> I created a simple DFDL schema which shows the problem:
>
>
>
> <?xml version="1.0" encoding="UTF-8"?>
> <xs:schema xmlns:dfdl=http://www.ogf.org/dfdl/dfdl-1.0/ xmlns:f="function"
> xmlns:fn=http://www.w3.org/2005/xpath-functions xmlns:xs=
> http://www.w3.org/2001/XMLSchema>
> <xs:include schemaLocation="default-dfdl-properties/defaults.dfdl.xsd"
> />
> <xs:annotation>
> <xs:appinfo source=http://www.ogf.org/dfdl/>
> <dfdl:format ref="default-dfdl-properties"
> emptyValueDelimiterPolicy="none"/>
> </xs:appinfo>
> </xs:annotation>
> <xs:element name="Document">
> <xs:complexType>
> <xs:sequence>
> <xs:element ref="initial_word"/>
> <xs:element ref="row" maxOccurs="unbounded"/>
> </xs:sequence>
> </xs:complexType>
> </xs:element>
> <xs:element name="initial_word">
> <xs:complexType>
> <xs:sequence>
> <xs:sequence dfdl:hiddenGroupRef="hidden-message-length"/>
> <xs:element name="E1" type="xs:string"/>
> </xs:sequence>
> </xs:complexType>
> </xs:element>
> <xs:element name="row">
> <xs:complexType>
> <xs:sequence>
> <xs:element name="E2" type="xs:string"/>
> </xs:sequence>
> </xs:complexType>
> </xs:element>
> <xs:group name="hidden-message-length">
> <xs:sequence>
> <xs:element name="hidden" type="xs:integer"
> dfdl:outputValueCalc="{
> *if* (*fn:exists*(/*Document*/*foo*)) *then* *fn:count*(/
> *Document*/*row*)+*fn:count*(/*Document*/*foo*)+1
> *else* *fn:count*(/*Document*/*row*)+1
> }"
> />
> </xs:sequence>
> </xs:group>
> </xs:schema>
>
>
>
>
>
> *From:* Mike Beckerle <mb...@apache.org>
> *Sent:* Thursday, January 4, 2024 8:57 AM
> *To:* users@daffodil.apache.org
> *Subject:* [EXT] Re: How to count the number of child elements of the
> root element?
>
>
>
> 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
>
> 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 <co...@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 <mb...@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 <co...@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 <co...@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 <mb...@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 <co...@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
>
>
>
>
Re: How to count the number of child elements of the root element?
Posted by Roger L Costello <co...@mitre.org>.
The scenario is this: in the future I may add a foo element:
<xs:element name="Document">
<xs:complexType>
<xs:sequence>
<xs:element ref="initial_word"/>
<xs:element ref="row" maxOccurs="unbounded"/>
<xs:element ref="foo"/>
</xs:sequence>
</xs:complexType>
</xs:element>
I want message_length to correctly count the number of child elements of Document now and in the future. So I test for the existence of the foo element. If there is no foo element, then I don’t attempt to count it:
dfdl:outputValueCalc="{
if (fn:exists(/Document/foo)) then fn:count(/Document/row)+fn:count(/Document/foo)+1
else fn:count(/Document/row)+1
}"
You are saying that this is not allowed? Why?
/Roger
From: Mike Beckerle <mb...@apache.org>
Sent: Thursday, January 4, 2024 10:08 AM
To: users@daffodil.apache.org
Subject: [EXT] Re: How to count the number of child elements of the root element?
So there actually isn't a declaration for an element named foo here. DFDL will not allow the expression "/Document/foo" at all because it is meaningless. There is no declaration of an element named foo. That expression has no
So there actually isn't a declaration for an element named foo here.
DFDL will not allow the expression "/Document/foo" at all because it is meaningless. There is no declaration of an element named foo.
That expression has no type but your expression requires it to be an array type.
On Thu, Jan 4, 2024 at 9:22 AM Roger L Costello <co...@mitre.org>> wrote:
Hi Mike,
I created a simple DFDL schema which shows the problem:
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:dfdl=http://www.ogf.org/dfdl/dfdl-1.0/ xmlns:f="function" xmlns:fn=http://www.w3.org/2005/xpath-functions xmlns:xs=http://www.w3.org/2001/XMLSchema>
<xs:include schemaLocation="default-dfdl-properties/defaults.dfdl.xsd"/>
<xs:annotation>
<xs:appinfo source=http://www.ogf.org/dfdl/>
<dfdl:format ref="default-dfdl-properties" emptyValueDelimiterPolicy="none"/>
</xs:appinfo>
</xs:annotation>
<xs:element name="Document">
<xs:complexType>
<xs:sequence>
<xs:element ref="initial_word"/>
<xs:element ref="row" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="initial_word">
<xs:complexType>
<xs:sequence>
<xs:sequence dfdl:hiddenGroupRef="hidden-message-length"/>
<xs:element name="E1" type="xs:string"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="row">
<xs:complexType>
<xs:sequence>
<xs:element name="E2" type="xs:string"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:group name="hidden-message-length">
<xs:sequence>
<xs:element name="hidden" type="xs:integer"
dfdl:outputValueCalc="{
if (fn:exists(/Document/foo)) then fn:count(/Document/row)+fn:count(/Document/foo)+1
else fn:count(/Document/row)+1
}"
/>
</xs:sequence>
</xs:group>
</xs:schema>
From: Mike Beckerle <mb...@apache.org>>
Sent: Thursday, January 4, 2024 8:57 AM
To: users@daffodil.apache.org<ma...@daffodil.apache.org>
Subject: [EXT] Re: How to count the number of child elements of the root element?
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
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 <co...@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 <mb...@apache.org>>
Sent: Thursday, January 4, 2024 8:27 AM
To: users@daffodil.apache.org<ma...@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 <co...@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 <co...@mitre.org>>
Sent: Thursday, January 4, 2024 6:49 AM
To: users@daffodil.apache.org<ma...@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 <mb...@apache.org>>
Sent: Tuesday, January 2, 2024 8:32 AM
To: users@daffodil.apache.org<ma...@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 <co...@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
Re: How to count the number of child elements of the root element?
Posted by Mike Beckerle <mb...@apache.org>.
So there actually isn't a declaration for an element named foo here.
DFDL will not allow the expression "/Document/foo" at all because it is
meaningless. There is no declaration of an element named foo.
That expression has no type but your expression requires it to be an array
type.
On Thu, Jan 4, 2024 at 9:22 AM Roger L Costello <co...@mitre.org> wrote:
> Hi Mike,
>
>
>
> I created a simple DFDL schema which shows the problem:
>
>
>
> <?xml version="1.0" encoding="UTF-8"?>
> <xs:schema xmlns:dfdl=http://www.ogf.org/dfdl/dfdl-1.0/ xmlns:f="function"
> xmlns:fn=http://www.w3.org/2005/xpath-functions xmlns:xs=
> http://www.w3.org/2001/XMLSchema>
> <xs:include schemaLocation="default-dfdl-properties/defaults.dfdl.xsd"
> />
> <xs:annotation>
> <xs:appinfo source=http://www.ogf.org/dfdl/>
> <dfdl:format ref="default-dfdl-properties"
> emptyValueDelimiterPolicy="none"/>
> </xs:appinfo>
> </xs:annotation>
> <xs:element name="Document">
> <xs:complexType>
> <xs:sequence>
> <xs:element ref="initial_word"/>
> <xs:element ref="row" maxOccurs="unbounded"/>
> </xs:sequence>
> </xs:complexType>
> </xs:element>
> <xs:element name="initial_word">
> <xs:complexType>
> <xs:sequence>
> <xs:sequence dfdl:hiddenGroupRef="hidden-message-length"/>
> <xs:element name="E1" type="xs:string"/>
> </xs:sequence>
> </xs:complexType>
> </xs:element>
> <xs:element name="row">
> <xs:complexType>
> <xs:sequence>
> <xs:element name="E2" type="xs:string"/>
> </xs:sequence>
> </xs:complexType>
> </xs:element>
> <xs:group name="hidden-message-length">
> <xs:sequence>
> <xs:element name="hidden" type="xs:integer"
> dfdl:outputValueCalc="{
> *if* (*fn:exists*(/*Document*/*foo*)) *then* *fn:count*(/
> *Document*/*row*)+*fn:count*(/*Document*/*foo*)+1
> *else* *fn:count*(/*Document*/*row*)+1
> }"
> />
> </xs:sequence>
> </xs:group>
> </xs:schema>
>
>
>
>
>
> *From:* Mike Beckerle <mb...@apache.org>
> *Sent:* Thursday, January 4, 2024 8:57 AM
> *To:* users@daffodil.apache.org
> *Subject:* [EXT] Re: How to count the number of child elements of the
> root element?
>
>
>
> 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
>
> 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 <co...@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 <mb...@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 <co...@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 <co...@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 <mb...@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 <co...@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
>
>
>
>
Re: How to count the number of child elements of the root element?
Posted by Roger L Costello <co...@mitre.org>.
Hi Mike,
I created a simple DFDL schema which shows the problem:
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:dfdl=http://www.ogf.org/dfdl/dfdl-1.0/ xmlns:f="function" xmlns:fn=http://www.w3.org/2005/xpath-functions xmlns:xs=http://www.w3.org/2001/XMLSchema>
<xs:include schemaLocation="default-dfdl-properties/defaults.dfdl.xsd"/>
<xs:annotation>
<xs:appinfo source=http://www.ogf.org/dfdl/>
<dfdl:format ref="default-dfdl-properties" emptyValueDelimiterPolicy="none"/>
</xs:appinfo>
</xs:annotation>
<xs:element name="Document">
<xs:complexType>
<xs:sequence>
<xs:element ref="initial_word"/>
<xs:element ref="row" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="initial_word">
<xs:complexType>
<xs:sequence>
<xs:sequence dfdl:hiddenGroupRef="hidden-message-length"/>
<xs:element name="E1" type="xs:string"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="row">
<xs:complexType>
<xs:sequence>
<xs:element name="E2" type="xs:string"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:group name="hidden-message-length">
<xs:sequence>
<xs:element name="hidden" type="xs:integer"
dfdl:outputValueCalc="{
if (fn:exists(/Document/foo)) then fn:count(/Document/row)+fn:count(/Document/foo)+1
else fn:count(/Document/row)+1
}"
/>
</xs:sequence>
</xs:group>
</xs:schema>
From: Mike Beckerle <mb...@apache.org>
Sent: Thursday, January 4, 2024 8:57 AM
To: users@daffodil.apache.org
Subject: [EXT] Re: How to count the number of child elements of the root element?
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
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 <co...@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 <mb...@apache.org>>
Sent: Thursday, January 4, 2024 8:27 AM
To: users@daffodil.apache.org<ma...@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 <co...@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 <co...@mitre.org>>
Sent: Thursday, January 4, 2024 6:49 AM
To: users@daffodil.apache.org<ma...@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 <mb...@apache.org>>
Sent: Tuesday, January 2, 2024 8:32 AM
To: users@daffodil.apache.org<ma...@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 <co...@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
Re: How to count the number of child elements of the root element?
Posted by Mike Beckerle <mb...@apache.org>.
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 <co...@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 <mb...@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 <co...@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 <co...@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 <mb...@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 <co...@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
>
>
>
>
Re: How to count the number of child elements of the root element?
Posted by Roger L Costello <co...@mitre.org>.
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 <mb...@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 <co...@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 <co...@mitre.org>>
Sent: Thursday, January 4, 2024 6:49 AM
To: users@daffodil.apache.org<ma...@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 <mb...@apache.org>>
Sent: Tuesday, January 2, 2024 8:32 AM
To: users@daffodil.apache.org<ma...@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 <co...@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
Re: How to count the number of child elements of the root element?
Posted by Mike Beckerle <mb...@apache.org>.
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 <co...@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 <co...@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 <mb...@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 <co...@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
>
>
>
>
RE: How to count the number of child elements of the root element?
Posted by Roger L Costello <co...@mitre.org>.
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 <co...@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 <mb...@apache.org>>
Sent: Tuesday, January 2, 2024 8:32 AM
To: users@daffodil.apache.org<ma...@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 <co...@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
Re: How to count the number of child elements of the root element?
Posted by Roger L Costello <co...@mitre.org>.
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 <mb...@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 <co...@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