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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Making a silk purse out of the schema sows ear - was[xml-d
bryan rasmussen wrote:
> Well, looking at what you pointed to the first example also has
> sorting, which is somewhat outside the bounds of what anyone has
> discussed as validation before. As for the other ones I'm not exactly
> sure what you're validating (maybe due to not having time to learn ASL
> syntax)?
the type simply checks that the value of the attribute is an xs:int
if it is not, an error will be reported
additionally, it builds a data model that is customizable
>
> Actually this one
> http://reflex.gforge.inria.fr/tutorial/weather-report/schema2.asl
> looks like you're changing the value of the temp attributes if scale
> attribute equals the Fahrenheit scale.
in fact, it doesn't change the attribute value (but it could), it just
changes the typed data value which is bound to the attribute
I think it's important for the attribute to keep its value as is ; I
don't think that the role of a schema is to change the XML document
anyway, if some people really want to change the document, they could
replace the <xcl:update> instruction with :
<xcl:attribute referent="{ asl:element() }" name="temp" operand="{
(value( . ) - 32) * 5 div 9 }"/>
<xcl:attribute referent="{ asl:element() }" name="scale" value="°C"/>
...which really converts <town temp="32" scale="°F"> to <town temp="0"
scale="°C">
notice that XCL is not part of ASL : it's a general-purpose language
that can be advantageaously used in ASL, but more traditional
applications (web app, batch scripts) can also be considered with XCL
ASL is part of a wider framework that I called "Active Tags", that
allows to design native XML programs ; ASL is a module (a library) of
Active Tags, XCL (the XML Control Language) is another, and there is
also a library for accessing RDBMS ; thus, if you have an attribute
which values must be one the result of an SQL query, you can express it :
http://disc.inria.fr/perso/philippe.poulard/xml/active-tags/active-schema/active-schema.html#N401309
>
> Another in the list of schema languages that people don't note too
> often is DSD http://www.brics.dk/DSD/
I'll have a look at it
>
> Cheers,
> Bryan Rasmussen
>
>
>
> On 2/9/06, Philippe Poulard <Philippe.Poulard@s...> wrote:
>
>>This is a remark that has been made in comp.text.xml
>>
>>Unlike schematron, ASL computes content models, which allow
>>tools such as editors to predict which element is allowed ; schematron
>>is not predictive, it can only warn that a rule has not been followed
>>AFTER the user has made the mistake, for example by inserting an element
>>that is not allowed.
>>
>>There is a great difference between a tool such as schematron that
>>checks if everything is right in the XML document, and other schema
>>technologies (DTD, RelaxNG, WXS, ASL) that are able to draw up a
>>contextual list of XML material (attributes, elements, text) that is
>>legal to use. You can consider that the Active Schema Language is like a
>>deep integration of known schemata (DTD, RNG, WXS) with an assertion
>>language such as schematron ; a deep integration goes further than using
>>schematron in WXS or RNG because even if they are located in the same
>>XML instance, they are processed separately.
>>
>>Here is a mix of RNG + schematron :
>><?xml version="1.0" encoding="UTF-8"?>
>><grammar ns="" xmlns="http://relaxng.org/ns/structure/1.0"
>> xmlns:sch="http://www.ascc.net/xml/schematron">
>> <start>
>> <element name="table">
>> <oneOrMore>
>> <element name="column">
>> <sch:pattern name="Check to have the same number of cells in
>>each column" id="cells">
>> <sch:rule context="column">
>> <sch:assert test="count(../column[1]/cell) =
>>count(cell)">The number of cells in this
>> column should be the same as in the firtst column,
>>expected <sch:value-of
>> select="count(../column[1]/cell)"/> but got
>><sch:value-of select="count(cell)"/>.
>> </sch:assert>
>> </sch:rule>
>> </sch:pattern>
>> <oneOrMore>
>> <element name="cell">
>> <empty/>
>> </element>
>> </oneOrMore>
>> </element>
>> </oneOrMore>
>> </element>
>> </start>
>></grammar>
>>
>>Anyway, another point that is not covered by schematron is the
>>capability to design smart data types such as semantic data types, as
>>shown in this example :
>>http://reflex.gforge.inria.fr/tutorial.html#N800F69
>>This is a very basic problem that known schematas can't resolve.
>>I think that neither WXS nor schematron could perform the same result
>>(just tell me how if I'm wrong)
>>
>>bryan rasmussen wrote:
>>
>>>In Schematron - however going for xslt implementation of schematron by
>>>using the current function:
>>>
>>><sch:rule context="table/column[1]">
>>> <sch:report
>>>test="following-sibling::column[count(cell)>current()[count(cell)]]"
>>> >cells need to be the same number per column
>>></sch:report>
>>>
>>></sch:rule>
>>>
>>>Cheers,
>>>Bryan Rasmussen
>>>
>>>
>>>
>>>
>>>On 2/9/06, Philippe Poulard <Philippe.Poulard@s...> wrote:
>>>
>>>
>>>>hi,
>>>>
>>>>IMHO, the main difficulty that schema technologies encounter is their
>>>>poor capabilities to express constraints because they are hard-coded in
>>>>the schema. This is the case for occurrence constraints and content
>>>>model definitions.
>>>>
>>>>I have experimented a schema language that allows to compute the
>>>>occurrence constraints dynamically and that allows to switch from a
>>>>declarative language to an imperative one, which increases dramatically
>>>>the expressiveness of the schema. The idea is to push back the limits of
>>>>the declarative language when they are reached.
>>>>
>>>>An example :
>>>>a RelaxNG user was complaining about a constraint that he couldn't
>>>>express : he had to design a <table> with any <column>s but <column>s
>>>>should have the same number of <cell>s
>>>>
>>>>I respond that he could consider an alternative schema technology, such
>>>>as these that I designed :
>>>><asl:element name="column">
>>>> <asl:sequence>
>>>> <xcl:if test="{ asl:element()/preceding-sibling::column }">
>>>> <xcl:then>
>>>> <asl:element ref-elem="cell" min-occurs="{
>>>> $asl:max-occurs }" max-occurs="{ count( asl:element()/../column[1]/cell
>>>> ) }"/>
>>>> </xcl:then>
>>>> <xcl:else>
>>>> <asl:element ref-elem="cell" min-occurs="1"
>>>> max-occurs="unbounded"/>
>>>> </xcl:else>
>>>> </xcl:if>
>>>> </asl:sequence>
>>>></asl:element>
>>>>The full schema and the running results are available here :
>>>>http://groups.google.com/group/comp.text.xml/browse_thread/thread/d97cd4adf1964fdb/2f92e65b7ad48dff?hl=en#2f92e65b7ad48dff
>>>>
>>>>This demonstrates that a simple if-then-else statement allows to build a
>>>>made-to-measure content model with dynamic occurrence constraints.
>>>>
>>>>I named that schema language the Active Schema Language and I have an
>>>>almost full implementation of it in Java, called RefleX :
>>>>http://disc.inria.fr/perso/philippe.poulard/xml/active-tags/active-schema/active-schema.html
>>>>http://reflex.gforge.inria.fr/
>>>>You can read the examples, download the tool and play with it.
>>>>
>>>>Moreover, ASL allows to design smart data types ; there is a tutorial in
>>>>the RefleX web site that shows a semantic data type : the "temperature"
>>>>data type, which is able to parse "32°F" and "20°C" ; as this type is
>>>>used to augment the amount of information of the XML document, we can
>>>>sort a list of attributes of this type not on the string values but on
>>>>the typed values
>>>>http://reflex.gforge.inria.fr/tutorial.html#N800F69
>>>>
>>>>It is worth seeing because all the problems you consider in your message
>>>>are pointed out and solutioned in ASL.
>>>>
>>>>Michael Champion wrote:
>>>>
>>>>
>>>>>I think the reality is that lots of people flipped the Bozo Bit on the
>>>>>XSD spec in 1999-2000. They went in different directions, however:
>>>>>Some to alternative schema languages, some to radical simplification of
>>>>>XML to de-emphasize schemas altogether.
>>>>>
>>>>>
>>>>>
>>>>>In hindsight, had people foreseen today's reality that we're stuck with
>>>>>XSD as what the mainstream user thinks of as the "real standard",
>>>>>clearly the energy would have been better spent debugging the wretched
>>>>>thing rather than trying to pretend it doesn't exist or trying to drive
>>>>>a stake thru its heart. I'm more interested in discussing what to do
>>>>>going forward given the current mess. The problems I see are:
>>>>>
>>>>>
>>>>>
>>>>>- The W3C is more interested in moving the XSD spec forward than fixing
>>>>>its numerous ambiguities. (Their pushback is that the people who want
>>>>>to fix it are not represented on the WG, and the people who have skin in
>>>>>the game want to move forward).
>>>>>
>>>>>- RELAX NG is clearly "better" for textual documents but doesn't have
>>>>>much support for the data-oriented use cases. (Sure you can plug in the
>>>>>XSD type system, but that's a big part of the problem). We now have an
>>>>>unpleasant situation of fragmentation where there's little mainstream
>>>>>tool support for RELAX NG due to lack of demand, exploitation of its
>>>>>geek chic (partly to strike a blow against the empire, I suppose), with
>>>>>the result that the normative definitions of Atom and ODF can't be used
>>>>>with most commercial XML tools. Maybe a good guerilla tactic in the
>>>>>open source wars, but for the moment it's the innocent who suffer the
>>>>>collateral damage.
>>>>>
>>>>>
>>>>>
>>>>>- Schematron is moving forward as an ISO standard and has some good
>>>>>implementations but has few normative references in vertical industry
>>>>>standards nor mindshare. (Correct me if I'm wrong about the normative
>>>>>references).
>>>>>
>>>>>
>>>>>
>>>>>- Lots of people complain about the limitations of XSD that Schematron
>>>>>addresses and the W3C doesn't plan to, especially the lack of occurrence
>>>>>constraints.
>>>>>
>>>>>The best way forward that I can see is to encourage end users to
>>>>>employ XSD + Schematron as necessary, and encourage W3C to address XSD's
>>>>>bugs and ambiguities before adding more onto an unstable foundation.
>>>>>What does that miss that the world actually values? (as much as it
>>>>>depresses me to say it, the world doesn't seem to value RELAX NG's
>>>>>elegance and mathematical foundation very much).
>>>>>
>>>>
>>>>--
>>>>Cordialement,
>>>>
>>>> ///
>>>> (. .)
>>>> --------ooO--(_)--Ooo--------
>>>>| Philippe Poulard |
>>>> -----------------------------
>>>> http://reflex.gforge.inria.fr/
>>>> Have the RefleX !
>>>>
>>>>-----------------------------------------------------------------
>>>>The xml-dev list is sponsored by XML.org <http://www.xml.org>, an
>>>>initiative of OASIS <http://www.oasis-open.org>
>>>>
>>>>The list archives are at http://lists.xml.org/archives/xml-dev/
>>>>
>>>>To subscribe or unsubscribe from this list use the subscription
>>>>manager: <http://www.oasis-open.org/mlmanage/index.php>
>>>>
>>>>
>>>-----------------------------------------------------------------
>>>The xml-dev list is sponsored by XML.org <http://www.xml.org>, an
>>>initiative of OASIS <http://www.oasis-open.org>
>>>
>>>The list archives are at http://lists.xml.org/archives/xml-dev/
>>>
>>>To subscribe or unsubscribe from this list use the subscription
>>>manager: <http://www.oasis-open.org/mlmanage/index.php>
>>>
>>>
>>
>>--
>>Cordialement,
>>
>> ///
>> (. .)
>> --------ooO--(_)--Ooo--------
>>| Philippe Poulard |
>> -----------------------------
>> http://reflex.gforge.inria.fr/
>> Have the RefleX !
>>
>
>
> -----------------------------------------------------------------
> The xml-dev list is sponsored by XML.org <http://www.xml.org>, an
> initiative of OASIS <http://www.oasis-open.org>
>
> The list archives are at http://lists.xml.org/archives/xml-dev/
>
> To subscribe or unsubscribe from this list use the subscription
> manager: <http://www.oasis-open.org/mlmanage/index.php>
>
>
--
Cordialement,
///
(. .)
--------ooO--(_)--Ooo--------
| Philippe Poulard |
-----------------------------
http://reflex.gforge.inria.fr/
Have the RefleX !
|
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