Re: [EXTERNAL] - Getting rid of @sequence="true/false"?

I like that Gerrit,

+1 it is

just to make sure...
this implies dropping @sequence ?,
this implies @sequence = true() assumed always (be it the @sequence is dropped) ?
this implies @as is optional and mainly useful if we need to restrict what comes in?

----- Oorspronkelijk bericht -----
Van: "gerrit imsieke" <gerrit.imsieke@le-tex.de>
Aan: "XProc Dev" <xproc-dev@w3.org>
Verzonden: Maandag 25 september 2017 12:58:29
Onderwerp: Re: [EXTERNAL] - Getting rid of @sequence="true/false"?

I don’t think it will fit well into content-types.

But we can think of allowing the as attribute also on input and output 
ports, like this:

<p:input port="source" as="document-node(element(*))*"/>

or

<p:output port="result as="document-node()"/>

As long we don’t permit arbitrary XDM items on ports, we need to raise 
an error though (statically?) if the declared sequence type is atomic, a 
map, or anything else except item() or document-node().

Gerrit

On 25.09.2017 12:45, Kraetke, Martin, le-tex wrote:
> Naturally, sequence is the default for 3.0 but I agree that pipeline 
> authors should have the chance to change this. However, there are cases 
> where you want to specify the number of possible documents more 
> precisely. I would suggest that we drop the sequence attribute and 
> instead specify that a pipeline author can add the operators "?", "*" 
> and "+" to the content-type attribute, e.g:
> 
> <p:output port="result" content-type="text/xml+"/>
> 
> best, Martin
> 
> Am 23.09.2017 um 08:06 schrieb Imsieke, Gerrit, le-tex:
>> The weird errors are probably the processor’s fault. A processor should
>> be able to tell you (and should in fact tell you) which step in which
>> pipeline expected a sequence / a single document and which input that it
>> received or emitted violated this restriction.
>>
>> -----
>>
>> If we think that “zero to many documents arriving on a port” is the new
>> normal: What about keeping the sequence attribute on p:input and
>> p:output but make it true by default?
>>
>> Gerrit
>>
>> On 22.09.2017 15:21, Ari Nordström wrote:
>>> Hi,
>>>
>>> Getting rid of @sequence seems like a good idea to me. I know I've had
>>> it set to false on numerous occasions, only to get weird errors and an
>>> 'oh' moment when realising why. Having everything be a sequence makes
>>> sense to me.
>>>
>>> Having said that, I like #3 but need to think about it more.
>>>
>>> Thanks,
>>>
>>> /Ari
>>>
>>>
>>> On 22 September 2017 at 15:05, Vojtech Toman <vtoman@opentext.com
>>> <mailto:vtoman@opentext.com>> wrote:
>>>
>>>     I think removing sequence=true/false is a good idea. In the ideal
>>>     world, everything is a sequence :)
>>>
>>>     My personal favorite is option 2. (To be honest, I don't quite
>>>     understand option 1 - is this some sort of backward compatibility
>>>     mode for old XProc 1.0 pipelines?)
>>>
>>>     Option 3 (implicit looping) looks fancy but I think it would work
>>>     only with simple steps that have only one input port. For steps that
>>>     have multiple non-sequence input ports, it is far from clear to me
>>>     how it could work. Would it loop? Would it loop over all
>>>     combinations of the inputs (implications on streaming)? Etc. Also,
>>>     there would probably have to be some mechanism to tell the processor
>>>     whether it should loop over a port or not (because sometimes you do
>>>     want to pass a sequence of items to the step). Consider, for
>>>     example, the p:xquery step: it takes a sequence of documents on the
>>>     "source" port (the default collection) and the XQuery on the "query"
>>>     port. You definitely don't want to loop over "source" but you may or
>>>     may not want to looping over "query".
>>>
>>>     Regards,
>>>     Vojtech
>>>
>>>     -----Original Message-----
>>>     From: Achim Berndzen [mailto:achim.berndzen@xml-project.com
>>>     <mailto:achim.berndzen@xml-project.com>]
>>>     Sent: Friday, September 22, 2017 2:41 PM
>>>     To: XProc Dev
>>>     Subject: [EXTERNAL] - Getting rid of @sequence="true/false"?
>>>
>>>     Hi all,
>>>
>>>     A while ago, @ndw and I had a mail conversation about sequence ports
>>>     in XProc 3.0. In order to make it easier to learn XProc, we
>>>     discussed about elimination non-sequence ports and @sequence, so
>>>     that in XProc 3.0 all steps accept sequences on all ports.
>>>
>>>     Following this line of thought, some options are possible:
>>>
>>>     1. Nothing changes: All steps accepting sequences on a port in XProc
>>>     1.0 will do so in XProc 3.0. Steps that do not accept a sequence
>>>     will only raise an error, when an empty sequence is delivered. If
>>>     not, they we process the first document in the sequence as described
>>>     and discard all others.
>>>
>>>     2. We simply move task of raising an error to the step and its
>>>     semantic: Instead of having one global error (XD0006) we could have
>>>     more informative errors like (XS????: It is a dynamic error if not
>>>     exactly one document appears on port "stylesheet"
>>>     of p:xslt).
>>>
>>>     3. Implicit looping: One possible consequence I personally like very
>>>     much is the idea, that some steps (like p:add-attribute, p:delete,
>>>     p:insert etc.) do an implicit looping for the sequence. This might
>>>     be more natural the XProc newbies and may appear attractive to
>>>     current users, because in some cases you will not need "p:for-each"
>>>     any more. This would be inline with p:viewport in XProc 3.0 with
>>>     does implicit looping. For other steps, where implicit looping does
>>>     not make sense (e.g. p:compare or p:http-request) we could choose
>>>     option (1) or (2).
>>>
>>>     4. Bad idea, keep it like it is: You might say that the distinction
>>>     between a document and a sequence of documents is very easy to grasp
>>>     and that it is perfectly established in XSLT, XQuery and other
>>>     X-technologies. Also you might argue, that in XProc 3.0 we will have
>>>     mixed sequences with XML and non-XML documents and we would need a
>>>     special treat when p:add-attribute is applied to a sequence of xml
>>>     documents, JPEGs and texts.
>>>
>>>     What do you think?
>>>
>>>     Greetings from Germany,
>>>     Achim
>>>     ------------------------------------------------
>>>     Achim Berndzen
>>>     achim.berndzen@xml-project.com
>>> <mailto:achim.berndzen@xml-project.com>
>>>
>>>
>>> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.xml-2Dproject.com&d=DwIFAg&c=ZgVRmm3mf2P1-XDAyDsu4A&r=aJZr6mdNzy-qsGbVYWF8KIxwje5rrbk2V7QfMr35EhU&m=cPHeErshVOYtQvSxAMDAic7JkUGz2HP66H7HpBWsndQ&s=mHiMaFmT9YqrWTQHwBnXpOa4VbbxxpA4Y2cOjvacjmY&e= 
>>>
>>>
>>>
>>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.xml-2Dproject.com&d=DwIFAg&c=ZgVRmm3mf2P1-XDAyDsu4A&r=aJZr6mdNzy-qsGbVYWF8KIxwje5rrbk2V7QfMr35EhU&m=cPHeErshVOYtQvSxAMDAic7JkUGz2HP66H7HpBWsndQ&s=mHiMaFmT9YqrWTQHwBnXpOa4VbbxxpA4Y2cOjvacjmY&e=> 
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
> 

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Received on Monday, 25 September 2017 13:24:16 UTC