Re: [xml-dev] Schematron Best Practice: A Schematron schema's area of re

["bryan rasmussen" <rasmussen.bryan@gmail.com>]

Probably, I don't have a lot of familiarity with BPEL, from what I
have seen I think there is some overlap between XML pipelines and
BPEL, but I think that pipelines have the following benefits:
1. less verbose
2. more generic and  composable?
3. therefore more comprehensible for a programmer.

These are just impressions however, the time I looked at BPEL I
believe I said something like "god save me".
This could just be because I was having to deal with a lot of the
language of UBL, ebxml at the time and maybe the part of the brain
devoted to business processes was already filled up. not hard for me
to do.

cheers,
Bryan Rasmussen




On 6/30/07, Trapp, Tobias <Tobias.Trapp@sys.aok.de> wrote:
> Hi Bryan,
>
> the data exchange scenario you described reminds me of a process that could be described in a language (think of BPEL) and executed by a BPEL engine because the validation steps you mentioned can be seen as services. Perhaps the BPEL model is equivalent to a pipeline model and could be translated back and forth between two models.
>
> The process model should be a part of a data exchange scenario and the concrete steps (think of Schematron validation) could be a part of the specification too. Of course the process model should have "user exits" for customer specific tailoring.
>
> But I think now I'm getting slightly off topic.
>
> Cheers
> Tobias
>
> AOK Systems GmbH - Mülheimer Str. 3-7 - 53840 Troisdorf-Handelsregister Siegburg HRB 5373 - Geschäftsführer: Klaus Schmitt, Rüdiger Bräuling
> -----Ursprüngliche Nachricht-----
> Von: bryan rasmussen
> Gesendet: Samstag, 30. Juni 2007 11:47
> An: Costello, Roger L.
> Cc: xml-dev@lists.xml.org
> Betreff: Re: [xml-dev] Schematron Best Practice: A Schematron schema's area of responsibility?
>
> I would agree to that. I suppose also when the datatype definition
> language is finished that the rule will be define algorithms etc. as
> datatypes, do grammar in grammar language, datatypes in datatype
> language,  dependency constraints in language for checking these..
> probably along the lines of what James Clark said about markup
> languages being constrained to doing one thing (Im on an italian
> computer with slow dialup connection so Im not going to look up
> precise quotes here!)
>
> I think though that the process the XML document if all validation
> steps return valid is too strict a view on things, I think you may
> well, in various applications, process XML documents in different ways
> dependent on how a particular validation step has failed. Especially
> with Schematron (although I suppose a lot of the schematron scenarios
> for handling failures would then be to say well that does not raise an
> error, it raises a warning).
>
> This comes into the part where we have to think about pipelines of validations.
>
> Example: UBL in a national profile, such as Denmarks.
>
> ways to handle could be:
> 1. valid UBL comes in, does not follow national rules, send back error report.
> 2. valid UBL comes in, does not follow national rules, enter data
> provisionally for ok by Human, send back error report requesting
> update to sent document with national rules adhered to.
> 3. valid UBL comes in, valid by national rules, raises warnings
> (country element not filled out in Sender), starts pipeline to find
> country for Sender, adds data, validates, enter data provisionally for
> ok by human.
>
> and so forth.
>
> Cheers,
> Bryan Rasmussen
>
>
>
>
>
>
>
>
>
>
>
> On 6/29/07, Costello, Roger L.  wrote:
> > Thanks Bryan.  As always, excellent input.
> >
> > I would like to extend my question a bit.
> >
> > Consider this sequence of activities:
> >
> > XML instance --> grammar-based validation --> rule-based validation -->
> > process the XML document
> >
> > Read as: first validate an XML instance document using a grammar-based
> > language (e.g. DTD, Relax NG, XML Schema), then validate using a
> > rule-based language (i.e. Schematron) and then if both validations are
> > successful process the XML document.
> >
> > Is this sequence of activities best practice for assessing the
> > constraints in an XML document?
> >
> > Does this mean that a Schematron schema may assume that any grammar
> > type of constraints have already been validated?
> >
> > For example, consider the classification attribute on this Para
> > element:
> >
> >     <Para classification="unclassified">
> >           One if by land, two if by sea;
> >     </Para>
> >
> > The value of the classification attribute is legal only if it is one of
> > top-secret, secret, confidential or unclassified.
> >
> > This constraint can be implemented using a grammar-based language, e.g.
> > here's how to do it using XML Schema:
> >
> > <attribute name="classification">
> >    <simpleType>
> >        <enumeration value="top-secret" />
> >        <enumeration value="secret" />
> >        <enumeration value="confidential" />
> >        <enumeration value="unclassified" />
> >    </simpleType>
> > </attribute>
> >
> > But it can also be easily implemented using Schematron.
> >
> > However, if best practice is the sequence shown above (i.e. perform
> > grammar-based validation and then perform Schematron validation) then a
> > Schematron schema can safely leave the job of validating the value of
> > the classification attribute to the grammar-based validation, and focus
> > on what it does best (co-constraint checking, cardinality checking,
> > algorithmic checking).
> >
> > What do you think about these as recommended best practices:
> >
> > 1. Validate the grammar of XML instance documents using a grammar-based
> > schema language, and then validate co-constraints, data cardinality,
> > and algorithmic checks using a Schematron schema.
> >
> > 2. A Schematron schema may safely assume all grammar type of
> > constraints have already been implemented and validated by a
> > grammar-based validation.
> >
> > 3. A Schematron schema should focus on just implementing
> > co-constraints, data cardinality checks, and algorithmic checks (things
> > that grammar-based languages can't express).
> >
> >
> > /Roger
> >
> >
> >
> >
> >
> >
> > -----Original Message-----
> > From: bryan rasmussen
> > Sent: Thursday, June 28, 2007 12:03 PM
> > To: Costello, Roger L.
> > Cc: xml-dev@lists.xml.org
> > Subject: Re: [xml-dev] Schematron Best Practice: A Schematron schema's
> > area of responsibility?
> >
> > Well, questions to ask about languages when they are equivalent in
> > abilities are which one would it be easiest to implement it in. Which
> > one would be easiest to maintain and extend.
> >
> > one might be able to put this kind of co-constraint thing into a
> > grammar based language but you would tie yourself in knots to do it.
> > it would make your grammar based language difficult to maintain, just
> > as doing many grammar things in schematron would make it difficult to
> > maintain.
> >
> > cheers,
> > Bryan Rasmussen
> >
> > On 6/28/07, Costello, Roger L. wrote:
> > > ISSUE
> > >
> > > When implementing an XML instance document's set of constraints, what
> > > is a Schematron schema's area of responsibility?
> > >
> > > EXAMPLE
> > >
> > > Consider this XML instance document:
> > >
> > > <?xml version="1.0"?>
> > > <Document classification="secret">
> > >     <Para classification="unclassified">
> > >           One if by land, two if by sea;
> > >     </Para>
> > > </Document>
> > >
> > > Schematron is very well-suited for implementing this co-constraint:
> > >
> > > Security Classification Policy: For the instance document to be valid
> > > no <Para> element may have a classification value higher than the
> > > <Document>'s classification value.
> > >
> > > The implementation of this co-constraint is shown at the bottom of
> > this
> > > message.
> > >
> > > RESPONSIBILITY OF A SCHEMATRON SCHEMA
> > >
> > > The implementation makes some assumptions.  For example, it assumes
> > > that the classification attributes have already been verified to have
> > > legal values (top-secret, secret, confidential, and unclassified).
> > >
> > > The Schematron schema *could* validate that the classification
> > > attributes have legal values.  But so could a grammar-based schema
> > > language (e.g. Relax NG, XML Schema).
> > >
> > > QUESTIONS
> > >
> > > 1. What is the responsibility of a Schematron schema?
> > >
> > > 2. Should a Schematron schema implement constraints that could be
> > done
> > > by a grammar-based schema language?
> > >
> > > 3. Should a Schematron schema implement only those constraints which
> > > cannot be implemented by a grammar-based schema languages such as
> > > co-constraints, data cardinality checks, and algorithmic checks?
> > >
> > > 4. How much intersection should there be between the set of
> > constraints
> > > implemented by a Schematron schema and the set of constraints
> > > implemented by a grammar-based schema?
> > >
> > > IMPLEMENTATION OF THE SECURITY CLASSIFICATION POLICY
> > >
> > >    <sch:pattern name="Security Classification Policy">
> > >
> > >       <sch:p>A Para's classification value cannot be more sensitive
> > >              than the Document's classification value.</sch:p>
> > >
> > >       <sch:rule context="Para[@classification='top-secret']">
> > >
> > >          <sch:assert test="/Document/@classification='top-secret'">
> > >              If there is a Para labeled "top-secret" then the
> > Document
> > >
> > >              must be labeled top-secret
> > >          </sch:assert>
> > >
> > >       </sch:rule>
> > >
> > >       <sch:rule context="Para[@classification='secret']">
> > >
> > >          <sch:assert test="(/Document/@classification='top-secret')
> > or
> > >                            (/Document/@classification='secret')">
> > >              If there is a Para labeled "secret" then the Document
> > >              must be labeled either secret or top-secret
> > >          </sch:assert>
> > >
> > >       </sch:rule>
> > >
> > >       <sch:rule context="Para[@classification='confidential']">
> > >
> > >          <sch:assert test="(/Document/@classification='top-secret')
> > or
> > >                            (/Document/@classification='secret') or
> > >
> > (/Document/@classification='confidential')">
> > >              If there is a Para labeled "confidential" then the
> > > Document
> > >              must be labeled either confidential, secret or
> > top-secret
> > >          </sch:assert>
> > >
> > >       </sch:rule>
> > >
> > >    </sch:pattern>
> > >
> > > /Roger
> > >
> > >
> > >
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