Jane -
I've been down this track a couple of times so have one comment to add:
There is one way only in W3C XML Schema of defining
an element from which other elements can be derived
which can have either simpleContent or complexContent -
that is to declare an element with anyType that acts
as the head of a substitution group:
either
<element name="DCField" type="anyType"/>
or
<element name="DCField"/>
where in the latter construction the type is implied.
Then any other element of any type can be declared
to be in its substitution group, e.g.
<element name="DCDate" type="date" substitutionGroup="DCField"/>
where "date" is a built-in simpleType from XML Schema, or
<element name="DCCoverage" type="your:favoriteCoverageEncodingType"
substitutionGroup="DCField"/>
where favoriteCoverageEncodingType is a complexType in "your" namespace.
But don't try deriving simpleContent types by restriction from
an anyType parent - there is "magic" involved in deriving the
simpleTypes side of the type hierarchy which is not to be
exposed in real schema documents!
Also, do not make the mistake of defining an empty complexType
and then trying to add simpleContent - it doesn't work.
And you also cannot derive specific simpleContent types
from string, unless using lexical patterns is acceptable.
And even the correct XML Schema syntax for deriving types
by restriction from anySimpleType is muddy - different
schema validators seem to have different interpretations
of the spec (there is a bug in XML Spy, for example -
I can forward my correspondence with Altova if anyone is interested!)
_____
[log in to unmask] CSIRO Exploration & Mining
26 Dick Perry Avenue, Kensington WA 6151
PO Box 1130, Bentley WA 6102 AUSTRALIA
T: +61 (8) 6436 8639 F: +61 (8) 6436 8555 C: +61 (4) 0330 2672
http://www.csiro.au/page.asp?type=resume&id=CoxSimon
> -----Original Message-----
> From: Automatic digest processor [mailto:[log in to unmask]]
> Sent: Tuesday, 12 March 2002 8:01 AM
> To: Recipients of DC-ARCHITECTURE digests
> Subject: DC-ARCHITECTURE Digest - 10 Mar 2002 to 11 Mar 2002
> (#2002-35)
>
>
> There are 6 messages totalling 1037 lines in this issue.
>
> Topics of the day:
>
> 1. Public Comment on DC-simple XML Schema declaration within OAI (5)
> 2. Public Comment on DC-simple XML Schema
> declaration within OAI
>
> ----------------------------------------------------------------------
>
> Date: Mon, 11 Mar 2002 10:15:20 +1000
> From: Jane Hunter <[log in to unmask]>
> Subject: Re: Public Comment on DC-simple XML Schema
> declaration within OAI
>
> Dear all,
>
> My original concern with using the 'string' datatype was not just with
> the need for more complex structured derivations but also with the
> inability to derive other simple and commonly-required datatypes such
> as URIs (for dc:identity) or dates (for dc:date) from 'string'.
>
> I'm by no means an XML Schema expert but, one suggestion is that you
> consider using 'anySimpleType' rather than 'string':
>
> http://www.w3.org/TR/xmlschema-2/#built-in-datatypes
>
> At least then users can derive some other useful datatypes.
>
> And just to clarify, the current proposal is to have 3 XML Schemas?
>
> 1. An XML Schema for 'simple DC' - using either 'string' or
> 'anySimpleType' for the element types
>
> 2. An XML Schema from which 'complex DC' and application profiles can
> be derived - using 'anyType' for the element types
>
> 3. An XML Schema for 'qualified DC'.
>
> jane
>
> > I'll add my pat on the back to this. I think that Andy has
> successfully put the cap on this discussion.
> >
> > I raised the xHTML possibility to test the waters on
> whether HTML falls into the realm of lingua franca that serve
> as 'appropriate literals' for DCMI. This was inspired by the
> fact that xs:string in xml land is not the good old 7-bit
> ASCII that we know and love but unicode, which is a big step
> up the complexity ladder. I wasn't sure that adding html
> tagging to that stepped out of bounds, but figured it was
> worth asking. I withdraw that shredded trial balloon.
> >
> > Moral of the story: you've got to draw the line somewhere
> and I think that Andy's argument is as good as it gets.
> >
> > Carl
> >
> > > -----Original Message-----
> > > From: Dan Brickley [mailto:[log in to unmask]]
> > > Sent: Saturday, March 09, 2002 4:55 AM
> > > To: [log in to unmask]
> > > Subject: Re: Public Comment on DC-simple XML Schema
> declaration within
> > > OAI
> > >
> > >
> > > This is one of the clearest articulations of the problem I've
> > > heard in a long while.
> > >
> > > We know how to deal with simple string values, and how to
> qualify them
> > > (subproperties and datatypes, in RDF-ese). We don't know
> yet how to
> > > preserve widearea interoperability and data re-use as we move
> > > from this
> > > realtively well understood realm towards more complex, highly
> > > strucured
> > > multi-namespace data exchange. It's OK, that's a
> difficult problem for
> > > everyone...
> > >
> > > Dan
> > >
> > > On Sat, 9 Mar 2002, Andy Powell wrote:
> > >
> > > > On Fri, 8 Mar 2002, Carl Lagoze wrote:
> > > >
> > > > > Andy, is there any reason in your mind why we should NOT
> > > allow xHTML
> > > > > in the values of the simple schema. My first
> reaction is that it
> > > > > opens the door sufficiently to allow things like MathML
> > > but does not
> > > > > push it wide open into unrestricted land.
> > > >
> > > > I'm not really sure... but my feeling is that 'simple DC'
> > > means simple
> > > > literal string values and *nothing* else.
> > > >
> > > > Here's my thinking...
> > > >
> > > > We need to have a shared understanding of what we mean by a
> > > 'simple DC'
> > > > application.
> > > >
> > > > Currently, that understanding has to work across
> > > applications that are not
> > > > based on XML. I'm thinking here about applications that
> > > carry metadata
> > > > using non-XML encodings such as HTML4/meta, Z39.50/GRS-1,
> > > Z39.50/MARC, ...
> > > >
> > > > Any two 'simple DC' applications should be able to exchange
> > > all their
> > > > metadata. Anything encoded in one 'simple DC' application,
> > > should be able
> > > > to be encoded in another with no loss of data.
> > > >
> > > > 'Simple DC' is our most dumbed-down form of metadata. It
> > > provides our
> > > > base level of interoperability between different services.
> > > (Simple DC is
> > > > the equivalent of the plain text rendered by, say, lynx -
> > > not the (X)HTML
> > > > page on which that rendering is based).
> > > >
> > > > XHTML carried in DC element values does *not* feel like
> > > 'simple DC' to me.
> > > > I completely agree that it would be a useful thing to be
> > > able to do (and
> > > > at least one of the services I'm involved in would like to
> > > be able to do
> > > > it!) - but I wouldn't call it 'simple DC' and I don't think
> > > support for it
> > > > should appear in a 'simple DC' XML schema.
> > > >
> > > > Finally, as an aside...
> > > >
> > > > It seems to me that the problems associated with trying to embed
> > > > structured content within DC element values is the aspect
> > > of DC that we
> > > > understand least currently. I think we now have a good
> > > understanding of
> > > > qualified DC in terms of element refinement and encoding
> > > schemes. But we
> > > > still don't know how to handle structured content very
> > > well. For example,
> > > > we have the rather messy situation in which it is not clear
> > > if the DCMI
> > > > Box encoding scheme is a 'formatted string' or an 'XML
> > > application' or
> > > > both. I think this stems from an acknowledgement that
> we can do some
> > > > things in XML-based applications that we can't do in text-based
> > > > applications but without being quite sure how to handle
> > > that properly in
> > > > practice.
> > > >
> > > > Andy.
> > > >
> > > > > > -----Original Message-----
> > > > > > From: Roland Schwaenzl
> > > > > > [mailto:[log in to unmask]]
> > > > > > Sent: Friday, March 08, 2002 1:17 PM
> > > > > > To: [log in to unmask]
> > > > > > Subject: Re: Public Comment on DC-simple XML Schema
> > > declaration within
> > > > > > OAI
> > > > > >
> > > > > >
> > > > > > > From [log in to unmask] Fri Mar 8
> > > 16:30 MET 2002
> > > > > > > content-class: urn:content-classes:message
> > > > > > > MIME-Version: 1.0
> > > > > > > X-MimeOLE: Produced By Microsoft Exchange V6.0.5762.3
> > > > > > > Thread-Topic: Re: Public Comment on DC-simple XML
> > > > > > Schema declaration
> > > > > > > within OAI
> > > > > > > Thread-Index: AcHGrDpz/EG80hNpQAmDGuSf4riG1QACWQMg
> > > > > > > Date: Fri, 8 Mar 2002 10:30:05 -0500
> > > > > > > From: Carl Lagoze <[log in to unmask]>
> > > > > > > Subject: Re: Public Comment on DC-simple XML Schema
> > > > > > declaration within OAI
> > > > > > > Comments: cc: Herbert Van de Sompel
> <[log in to unmask]>
> > > > > > > To: [log in to unmask]
> > > > > > > Content-Transfer-Encoding: 8bit
> > > > > > > X-MIME-Autoconverted: from quoted-printable to 8bit by
> > > > > > scarlett.mathematik.Uni-Osnabrueck.DE id QAA20116
> > > > > > >
> > > > > > > Roland,
> > > > > > >
> > > > > > > Regarding point 1: The prohibition as you state it sound
> > > > > > pretty draconian; seems like some of the people originally
> > > > > > motivated OAI (eprints folks) would want mathML. Remind me
> > > > > > again, is there a solution that allows things like
> mathML but
> > > > > > forbid arbitrary other XML?
> > > > > >
> > > > > > >
> > > > > >
> > > > > > Sure, you could (!) do that. W3C's xml-schema-primer has an
> > > > > > example, with content restricted to XHTML:
> > > > > > http://www.w3.org/TR/xml-schema-0 sec.5.5. It's
> the example
> > > > > > preceding the textType example.
> > > > > > In particular table 4 in that section is quite useful as
> > > > > > summary of built in facilities.
> > > > > > There's a similar technique with attributes.
> > > > > >
> > > > > > One could try: http://www.w3.org/1998/Math/MathML for a
> > > namespace URI.
> > > > > >
> > > > > > There's some use of MathML embedded into XHTML -
> > > > > > (cf. processContents="skip" in the example cited above)
> > > > > >
> > > > > >
> > > > > > rs
> > > > > >
> > > > > >
> > > > > >
> > > > > > > Carl
> > > > > > >
> > > > > > > I've copied to Herbert Van de Somple because the MathML
> > > > > > thing might be of concern to him also.
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > > -----Original Message-----
> > > > > > > > From: Roland Schwaenzl
> > > > > > > > [mailto:[log in to unmask]]
> > > > > > > > Sent: Friday, March 08, 2002 9:19 AM
> > > > > > > > To: [log in to unmask]
> > > > > > > > Subject: Re: Public Comment on DC-simple XML Schema
> > > > > > declaration within
> > > > > > > > OAI
> > > > > > > >
> > > > > > > >
> > > > > > > > Dears,
> > > > > > > >
> > > > > > > > with us it's now the time for reports rather than
> > > development.
> > > > > > > > I'll not be able to follow this discussion the
> coming week.
> > > > > > > >
> > > > > > > >
> > > > > > > > Let me try to summarize, what i understand
> currently from
> > > > > > the dc-xml
> > > > > > > > discussion.
> > > > > > > >
> > > > > > > >
> > > > > > > > 1. In OAi the use of dc:elements with the xml- simple
> > > > > > > > dataType "string" will (continue to) be required in
> > > > > > > > the mandatory part of OAi.
> > > > > > > > It could be, that OAi allows a dataType extension by
> > > > > > > > the xml:lang attribute.
> > > > > > > >
> > > > > > > > [In particular no mark-up from W3C's MathML or Ruby will
> > > > > > be allowed in
> > > > > > > > oai-dc records].
> > > > > > > >
> > > > > > > > 2. There are mixed views on (details of)
> > > requirements, design
> > > > > > > > and coding
> > > > > > > > for dcmi supported "plain-xml"-schemes.
> > > > > > > >
> > > > > > > >
> > > > > > > > Please correct me on mistaken points.
> > > > > > > >
> > > > > > > >
> > > > > > > > Best,
> > > > > > > > rs
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > > > Andy
> > > > --
> > > > Distributed Systems, UKOLN, University of Bath, Bath,
> BA2 7AY, UK
> > > > http://www.ukoln.ac.uk/ukoln/staff/a.powell +44
> 1225 383933
> > > > Resource Discovery Network http://www.rdn.ac.uk/
> > > >
> > >
>
> ------------------------------
>
> Date: Mon, 11 Mar 2002 10:08:53 +0000
> From: Rachel Heery <[log in to unmask]>
> Subject: Re: Public Comment on DC-simple XML Schema
> declaration within OAI
>
> On Mon, 11 Mar 2002, Jane Hunter wrote:
>
> >
> > And just to clarify, the current proposal is to have 3 XML Schemas?
> >
> > 1. An XML Schema for 'simple DC' - using either 'string' or
> > 'anySimpleType' for the element types
> >
> > 2. An XML Schema from which 'complex DC' and application
> profiles can
> > be derived - using 'anyType' for the element types
> >
> > 3. An XML Schema for 'qualified DC'.
>
>
> If we are going this multipe schema route I think an
> additional schema for
> unqualified Dc i.e. v1.1 15 elements plus 'audience' should
> be a priority.
> With same element type as 'simple DC'.
>
> Rachel
>
> >
> > jane
> >
> > > I'll add my pat on the back to this. I think that Andy
> has successfully put the cap on this discussion.
> > >
> > > I raised the xHTML possibility to test the waters on
> whether HTML falls into the realm of lingua franca that serve
> as 'appropriate literals' for DCMI. This was inspired by the
> fact that xs:string in xml land is not the good old 7-bit
> ASCII that we know and love but unicode, which is a big step
> up the complexity ladder. I wasn't sure that adding html
> tagging to that stepped out of bounds, but figured it was
> worth asking. I withdraw that shredded trial balloon.
> > >
> > > Moral of the story: you've got to draw the line somewhere
> and I think that Andy's argument is as good as it gets.
> > >
> > > Carl
> > >
> > > > -----Original Message-----
> > > > From: Dan Brickley [mailto:[log in to unmask]]
> > > > Sent: Saturday, March 09, 2002 4:55 AM
> > > > To: [log in to unmask]
> > > > Subject: Re: Public Comment on DC-simple XML Schema
> declaration within
> > > > OAI
> > > >
> > > >
> > > > This is one of the clearest articulations of the problem I've
> > > > heard in a long while.
> > > >
> > > > We know how to deal with simple string values, and how
> to qualify them
> > > > (subproperties and datatypes, in RDF-ese). We don't
> know yet how to
> > > > preserve widearea interoperability and data re-use as we move
> > > > from this
> > > > realtively well understood realm towards more complex, highly
> > > > strucured
> > > > multi-namespace data exchange. It's OK, that's a
> difficult problem for
> > > > everyone...
> > > >
> > > > Dan
> > > >
> > > > On Sat, 9 Mar 2002, Andy Powell wrote:
> > > >
> > > > > On Fri, 8 Mar 2002, Carl Lagoze wrote:
> > > > >
> > > > > > Andy, is there any reason in your mind why we should NOT
> > > > allow xHTML
> > > > > > in the values of the simple schema. My first
> reaction is that it
> > > > > > opens the door sufficiently to allow things like MathML
> > > > but does not
> > > > > > push it wide open into unrestricted land.
> > > > >
> > > > > I'm not really sure... but my feeling is that 'simple DC'
> > > > means simple
> > > > > literal string values and *nothing* else.
> > > > >
> > > > > Here's my thinking...
> > > > >
> > > > > We need to have a shared understanding of what we mean by a
> > > > 'simple DC'
> > > > > application.
> > > > >
> > > > > Currently, that understanding has to work across
> > > > applications that are not
> > > > > based on XML. I'm thinking here about applications that
> > > > carry metadata
> > > > > using non-XML encodings such as HTML4/meta, Z39.50/GRS-1,
> > > > Z39.50/MARC, ...
> > > > >
> > > > > Any two 'simple DC' applications should be able to exchange
> > > > all their
> > > > > metadata. Anything encoded in one 'simple DC' application,
> > > > should be able
> > > > > to be encoded in another with no loss of data.
> > > > >
> > > > > 'Simple DC' is our most dumbed-down form of metadata. It
> > > > provides our
> > > > > base level of interoperability between different services.
> > > > (Simple DC is
> > > > > the equivalent of the plain text rendered by, say, lynx -
> > > > not the (X)HTML
> > > > > page on which that rendering is based).
> > > > >
> > > > > XHTML carried in DC element values does *not* feel like
> > > > 'simple DC' to me.
> > > > > I completely agree that it would be a useful thing to be
> > > > able to do (and
> > > > > at least one of the services I'm involved in would like to
> > > > be able to do
> > > > > it!) - but I wouldn't call it 'simple DC' and I don't think
> > > > support for it
> > > > > should appear in a 'simple DC' XML schema.
> > > > >
> > > > > Finally, as an aside...
> > > > >
> > > > > It seems to me that the problems associated with
> trying to embed
> > > > > structured content within DC element values is the aspect
> > > > of DC that we
> > > > > understand least currently. I think we now have a good
> > > > understanding of
> > > > > qualified DC in terms of element refinement and encoding
> > > > schemes. But we
> > > > > still don't know how to handle structured content very
> > > > well. For example,
> > > > > we have the rather messy situation in which it is not clear
> > > > if the DCMI
> > > > > Box encoding scheme is a 'formatted string' or an 'XML
> > > > application' or
> > > > > both. I think this stems from an acknowledgement that
> we can do some
> > > > > things in XML-based applications that we can't do in
> text-based
> > > > > applications but without being quite sure how to handle
> > > > that properly in
> > > > > practice.
> > > > >
> > > > > Andy.
> > > > >
> > > > > > > -----Original Message-----
> > > > > > > From: Roland Schwaenzl
> > > > > > > [mailto:[log in to unmask]]
> > > > > > > Sent: Friday, March 08, 2002 1:17 PM
> > > > > > > To: [log in to unmask]
> > > > > > > Subject: Re: Public Comment on DC-simple XML Schema
> > > > declaration within
> > > > > > > OAI
> > > > > > >
> > > > > > >
> > > > > > > > From [log in to unmask] Fri Mar 8
> > > > 16:30 MET 2002
> > > > > > > > content-class: urn:content-classes:message
> > > > > > > > MIME-Version: 1.0
> > > > > > > > X-MimeOLE: Produced By Microsoft Exchange V6.0.5762.3
> > > > > > > > Thread-Topic: Re: Public Comment on DC-simple XML
> > > > > > > Schema declaration
> > > > > > > > within OAI
> > > > > > > > Thread-Index: AcHGrDpz/EG80hNpQAmDGuSf4riG1QACWQMg
> > > > > > > > Date: Fri, 8 Mar 2002 10:30:05 -0500
> > > > > > > > From: Carl Lagoze <[log in to unmask]>
> > > > > > > > Subject: Re: Public Comment on DC-simple XML Schema
> > > > > > > declaration within OAI
> > > > > > > > Comments: cc: Herbert Van de Sompel
> <[log in to unmask]>
> > > > > > > > To: [log in to unmask]
> > > > > > > > Content-Transfer-Encoding: 8bit
> > > > > > > > X-MIME-Autoconverted: from quoted-printable to 8bit by
> > > > > > > scarlett.mathematik.Uni-Osnabrueck.DE id QAA20116
> > > > > > > >
> > > > > > > > Roland,
> > > > > > > >
> > > > > > > > Regarding point 1: The prohibition as you
> state it sound
> > > > > > > pretty draconian; seems like some of the people originally
> > > > > > > motivated OAI (eprints folks) would want mathML.
> Remind me
> > > > > > > again, is there a solution that allows things
> like mathML but
> > > > > > > forbid arbitrary other XML?
> > > > > > >
> > > > > > > >
> > > > > > >
> > > > > > > Sure, you could (!) do that. W3C's
> xml-schema-primer has an
> > > > > > > example, with content restricted to XHTML:
> > > > > > > http://www.w3.org/TR/xml-schema-0 sec.5.5. It's
> the example
> > > > > > > preceding the textType example.
> > > > > > > In particular table 4 in that section is quite useful as
> > > > > > > summary of built in facilities.
> > > > > > > There's a similar technique with attributes.
> > > > > > >
> > > > > > > One could try: http://www.w3.org/1998/Math/MathML for a
> > > > namespace URI.
> > > > > > >
> > > > > > > There's some use of MathML embedded into XHTML -
> > > > > > > (cf. processContents="skip" in the example cited above)
> > > > > > >
> > > > > > >
> > > > > > > rs
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > > Carl
> > > > > > > >
> > > > > > > > I've copied to Herbert Van de Somple because the MathML
> > > > > > > thing might be of concern to him also.
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > > > -----Original Message-----
> > > > > > > > > From: Roland Schwaenzl
> > > > > > > > > [mailto:[log in to unmask]]
> > > > > > > > > Sent: Friday, March 08, 2002 9:19 AM
> > > > > > > > > To: [log in to unmask]
> > > > > > > > > Subject: Re: Public Comment on DC-simple XML Schema
> > > > > > > declaration within
> > > > > > > > > OAI
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > Dears,
> > > > > > > > >
> > > > > > > > > with us it's now the time for reports rather than
> > > > development.
> > > > > > > > > I'll not be able to follow this discussion
> the coming week.
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > Let me try to summarize, what i understand
> currently from
> > > > > > > the dc-xml
> > > > > > > > > discussion.
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > 1. In OAi the use of dc:elements with the xml- simple
> > > > > > > > > dataType "string" will (continue to) be required in
> > > > > > > > > the mandatory part of OAi.
> > > > > > > > > It could be, that OAi allows a dataType
> extension by
> > > > > > > > > the xml:lang attribute.
> > > > > > > > >
> > > > > > > > > [In particular no mark-up from W3C's MathML
> or Ruby will
> > > > > > > be allowed in
> > > > > > > > > oai-dc records].
> > > > > > > > >
> > > > > > > > > 2. There are mixed views on (details of)
> > > > requirements, design
> > > > > > > > > and coding
> > > > > > > > > for dcmi supported "plain-xml"-schemes.
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > Please correct me on mistaken points.
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > Best,
> > > > > > > > > rs
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > > > Andy
> > > > > --
> > > > > Distributed Systems, UKOLN, University of Bath, Bath,
> BA2 7AY, UK
> > > > > http://www.ukoln.ac.uk/ukoln/staff/a.powell +44
> 1225 383933
> > > > > Resource Discovery Network http://www.rdn.ac.uk/
> > > > >
> > > >
> >
>
>
> --------------------------------------------------------------
> -------------
> Rachel Heery
> UKOLN
> University of Bath tel: +44
> (0)1225 826724
> Bath, BA2 7AY, UK fax: +44
> (0)1225 826838
> http://www.ukoln.ac.uk/
>
> ------------------------------
>
> Date: Mon, 11 Mar 2002 06:59:45 -0500
> From: Carl Lagoze <[log in to unmask]>
> Subject: Re: Public Comment on DC-simple XML Schema
> declaration within OAI
>
> Hi Jane,
>
> Its not clear to me that there is a clear proposal for the number of =
> schema (schemata?), except for the fact that there will be more than =
> one. The one we know about at this time is "simple dc'.
> There may be a =
> schema for qualified dc, the conceptual basis of which is [1], where =
> qualification is fairly tightly constrained. The answer to whether =
> there will be other schema for a much fuzzier area that you
> are calling =
> complex dc is unclear. =20
>
> Your message implies that such a schema is necessary for application =
> profiles but that leads to a much more expansive view of applicaiton =
> profiles than I understand. For example, it is possible to write a =
> schema based on the simple dc schema for an app profile
> defined as "must =
> include one dc creator element and on dc title element and three =
> elements from FGDC". Your definition of application profile
> seems to =
> include more complex structures such as dc elements rooting
> sub-trees =
> comprised of elements from mixed namespaces. Its not clear
> to me that =
> we understand this world yet and how to control it.
>
> Finally, regarding anySimpleType: I had not heard of such an animal =
> until your email but went and found it in the datatype part
> of the xml =
> schema spec. I played with it in xml spy just to check it
> out. From my =
> brief look around it indicates that it has no real effect on
> the derived =
> instance documents relative to xs:string. Is then your intention to =
> make it possible for deriving schema (those that import it)
> to have an =
> adequate restriction base?
>
> Carl=20
>
>
> [1] http://dublincore.org/documents/2000/07/11/dcmes-qualifiers/
>
> > -----Original Message-----
> > From: Jane Hunter [mailto:[log in to unmask]]
> > Sent: Sunday, March 10, 2002 7:15 PM
> > To: [log in to unmask]
> > Subject: Re: Public Comment on DC-simple XML Schema
> declaration within
> > OAI
> >=20
> >=20
> > Dear all,
> >=20
> > My original concern with using the 'string' datatype was
> not just with
> > the need for more complex structured derivations but also with the
> > inability to derive other simple and commonly-required
> datatypes such
> > as URIs (for dc:identity) or dates (for dc:date) from 'string'.
> >=20
> > I'm by no means an XML Schema expert but, one suggestion is that you
> > consider using 'anySimpleType' rather than 'string':
> >=20
> > http://www.w3.org/TR/xmlschema-2/#built-in-datatypes
> >=20
> > At least then users can derive some other useful datatypes.
> >=20
> > And just to clarify, the current proposal is to have 3 XML Schemas?
> >=20
> > 1. An XML Schema for 'simple DC' - using either 'string' or
> > 'anySimpleType' for the element types
> >=20
> > 2. An XML Schema from which 'complex DC' and application
> profiles can
> > be derived - using 'anyType' for the element types
> >=20
> > 3. An XML Schema for 'qualified DC'.
> >=20
> > jane
> >=20
> > > I'll add my pat on the back to this. I think that Andy has=20
> > successfully put the cap on this discussion.
> > >
> > > I raised the xHTML possibility to test the waters on=20
> > whether HTML falls into the realm of lingua franca that serve=20
> > as 'appropriate literals' for DCMI. This was inspired by the=20
> > fact that xs:string in xml land is not the good old 7-bit=20
> > ASCII that we know and love but unicode, which is a big step=20
> > up the complexity ladder. I wasn't sure that adding html=20
> > tagging to that stepped out of bounds, but figured it was=20
> > worth asking. I withdraw that shredded trial balloon.
> > >
> > > Moral of the story: you've got to draw the line somewhere=20
> > and I think that Andy's argument is as good as it gets.
> > >
> > > Carl
> > >
> > > > -----Original Message-----
> > > > From: Dan Brickley [mailto:[log in to unmask]]
> > > > Sent: Saturday, March 09, 2002 4:55 AM
> > > > To: [log in to unmask]
> > > > Subject: Re: Public Comment on DC-simple XML Schema=20
> > declaration within
> > > > OAI
> > > >
> > > >
> > > > This is one of the clearest articulations of the problem I've
> > > > heard in a long while.
> > > >
> > > > We know how to deal with simple string values, and how to=20
> > qualify them
> > > > (subproperties and datatypes, in RDF-ese). We don't know=20
> > yet how to
> > > > preserve widearea interoperability and data re-use as we move
> > > > from this
> > > > realtively well understood realm towards more complex, highly
> > > > strucured
> > > > multi-namespace data exchange. It's OK, that's a=20
> > difficult problem for
> > > > everyone...
> > > >
> > > > Dan
> > > >
> > > > On Sat, 9 Mar 2002, Andy Powell wrote:
> > > >
> > > > > On Fri, 8 Mar 2002, Carl Lagoze wrote:
> > > > >
> > > > > > Andy, is there any reason in your mind why we should NOT
> > > > allow xHTML
> > > > > > in the values of the simple schema. My first=20
> > reaction is that it
> > > > > > opens the door sufficiently to allow things like MathML
> > > > but does not
> > > > > > push it wide open into unrestricted land.
> > > > >
> > > > > I'm not really sure... but my feeling is that 'simple DC'
> > > > means simple
> > > > > literal string values and *nothing* else.
> > > > >
> > > > > Here's my thinking...
> > > > >
> > > > > We need to have a shared understanding of what we mean by a
> > > > 'simple DC'
> > > > > application.
> > > > >
> > > > > Currently, that understanding has to work across
> > > > applications that are not
> > > > > based on XML. I'm thinking here about applications that
> > > > carry metadata
> > > > > using non-XML encodings such as HTML4/meta, Z39.50/GRS-1,
> > > > Z39.50/MARC, ...
> > > > >
> > > > > Any two 'simple DC' applications should be able to exchange
> > > > all their
> > > > > metadata. Anything encoded in one 'simple DC' application,
> > > > should be able
> > > > > to be encoded in another with no loss of data.
> > > > >
> > > > > 'Simple DC' is our most dumbed-down form of metadata. It
> > > > provides our
> > > > > base level of interoperability between different services.
> > > > (Simple DC is
> > > > > the equivalent of the plain text rendered by, say, lynx -
> > > > not the (X)HTML
> > > > > page on which that rendering is based).
> > > > >
> > > > > XHTML carried in DC element values does *not* feel like
> > > > 'simple DC' to me.
> > > > > I completely agree that it would be a useful thing to be
> > > > able to do (and
> > > > > at least one of the services I'm involved in would like to
> > > > be able to do
> > > > > it!) - but I wouldn't call it 'simple DC' and I don't think
> > > > support for it
> > > > > should appear in a 'simple DC' XML schema.
> > > > >
> > > > > Finally, as an aside...
> > > > >
> > > > > It seems to me that the problems associated with
> trying to embed
> > > > > structured content within DC element values is the aspect
> > > > of DC that we
> > > > > understand least currently. I think we now have a good
> > > > understanding of
> > > > > qualified DC in terms of element refinement and encoding
> > > > schemes. But we
> > > > > still don't know how to handle structured content very
> > > > well. For example,
> > > > > we have the rather messy situation in which it is not clear
> > > > if the DCMI
> > > > > Box encoding scheme is a 'formatted string' or an 'XML
> > > > application' or
> > > > > both. I think this stems from an acknowledgement that=20
> > we can do some
> > > > > things in XML-based applications that we can't do in
> text-based
> > > > > applications but without being quite sure how to handle
> > > > that properly in
> > > > > practice.
> > > > >
> > > > > Andy.
> > > > >
> > > > > > > -----Original Message-----
> > > > > > > From: Roland Schwaenzl
> > > > > > > [mailto:[log in to unmask]]
> > > > > > > Sent: Friday, March 08, 2002 1:17 PM
> > > > > > > To: [log in to unmask]
> > > > > > > Subject: Re: Public Comment on DC-simple XML Schema
> > > > declaration within
> > > > > > > OAI
> > > > > > >
> > > > > > >
> > > > > > > > From [log in to unmask] Fri Mar 8
> > > > 16:30 MET 2002
> > > > > > > > content-class: urn:content-classes:message
> > > > > > > > MIME-Version: 1.0
> > > > > > > > X-MimeOLE: Produced By Microsoft Exchange V6.0.5762.3
> > > > > > > > Thread-Topic: Re: Public Comment on DC-simple XML
> > > > > > > Schema declaration
> > > > > > > > within OAI
> > > > > > > > Thread-Index: AcHGrDpz/EG80hNpQAmDGuSf4riG1QACWQMg
> > > > > > > > Date: Fri, 8 Mar 2002 10:30:05 -0500
> > > > > > > > From: Carl Lagoze <[log in to unmask]>
> > > > > > > > Subject: Re: Public Comment on DC-simple XML Schema
> > > > > > > declaration within OAI
> > > > > > > > Comments: cc: Herbert Van de Sompel=20
> > <[log in to unmask]>
> > > > > > > > To: [log in to unmask]
> > > > > > > > Content-Transfer-Encoding: 8bit
> > > > > > > > X-MIME-Autoconverted: from quoted-printable to 8bit by
> > > > > > > scarlett.mathematik.Uni-Osnabrueck.DE id QAA20116
> > > > > > > >
> > > > > > > > Roland,
> > > > > > > >
> > > > > > > > Regarding point 1: The prohibition as you
> state it sound
> > > > > > > pretty draconian; seems like some of the people originally
> > > > > > > motivated OAI (eprints folks) would want mathML.
> Remind me
> > > > > > > again, is there a solution that allows things like=20
> > mathML but
> > > > > > > forbid arbitrary other XML?
> > > > > > >
> > > > > > > >
> > > > > > >
> > > > > > > Sure, you could (!) do that. W3C's
> xml-schema-primer has an
> > > > > > > example, with content restricted to XHTML:
> > > > > > > http://www.w3.org/TR/xml-schema-0 sec.5.5. It's=20
> > the example
> > > > > > > preceding the textType example.
> > > > > > > In particular table 4 in that section is quite useful as
> > > > > > > summary of built in facilities.
> > > > > > > There's a similar technique with attributes.
> > > > > > >
> > > > > > > One could try: http://www.w3.org/1998/Math/MathML for a
> > > > namespace URI.
> > > > > > >
> > > > > > > There's some use of MathML embedded into XHTML -
> > > > > > > (cf. processContents=3D"skip" in the example cited above)
> > > > > > >
> > > > > > >
> > > > > > > rs
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > > Carl
> > > > > > > >
> > > > > > > > I've copied to Herbert Van de Somple because the MathML
> > > > > > > thing might be of concern to him also.
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > > > -----Original Message-----
> > > > > > > > > From: Roland Schwaenzl
> > > > > > > > > [mailto:[log in to unmask]]
> > > > > > > > > Sent: Friday, March 08, 2002 9:19 AM
> > > > > > > > > To: [log in to unmask]
> > > > > > > > > Subject: Re: Public Comment on DC-simple XML Schema
> > > > > > > declaration within
> > > > > > > > > OAI
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > Dears,
> > > > > > > > >
> > > > > > > > > with us it's now the time for reports rather than
> > > > development.
> > > > > > > > > I'll not be able to follow this discussion the=20
> > coming week.
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > Let me try to summarize, what i understand=20
> > currently from
> > > > > > > the dc-xml
> > > > > > > > > discussion.
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > 1. In OAi the use of dc:elements with the xml- simple
> > > > > > > > > dataType "string" will (continue to) be required in
> > > > > > > > > the mandatory part of OAi.
> > > > > > > > > It could be, that OAi allows a dataType
> extension by
> > > > > > > > > the xml:lang attribute.
> > > > > > > > >
> > > > > > > > > [In particular no mark-up from W3C's MathML
> or Ruby will
> > > > > > > be allowed in
> > > > > > > > > oai-dc records].
> > > > > > > > >
> > > > > > > > > 2. There are mixed views on (details of)
> > > > requirements, design
> > > > > > > > > and coding
> > > > > > > > > for dcmi supported "plain-xml"-schemes.
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > Please correct me on mistaken points.
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > Best,
> > > > > > > > > rs
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > > > Andy
> > > > > --
> > > > > Distributed Systems, UKOLN, University of Bath, Bath,=20
> > BA2 7AY, UK
> > > > > http://www.ukoln.ac.uk/ukoln/staff/a.powell +44=20
> > 1225 383933
> > > > > Resource Discovery Network http://www.rdn.ac.uk/
> > > > >
> > > >
> >=20
>
> ------------------------------
>
> Date: Mon, 11 Mar 2002 15:52:46 -0000
> From: Pete Johnston <[log in to unmask]>
> Subject: Re: Public Comment on DC-simple XML Schema
> declaration within OAI
>
> Apologies... I've been away from this for a couple of days and I'm
> struggling to absorb it all, but just picking up one point here...
>
> Jane said:
>
> > I'm by no means an XML Schema expert but, one suggestion is
> > that you consider using 'anySimpleType' rather than 'string':
> >
> > http://www.w3.org/TR/xmlschema-2/#built-in-datatypes
> >
> > At least then users can derive some other useful datatypes.
> >
> > And just to clarify, the current proposal is to have 3 XML Schemas?
> >
> > 1. An XML Schema for 'simple DC' - using either 'string' or
> > 'anySimpleType' for the element types
>
> Is there not a problem that the current "base" element type in the
> simpledc schema isn't a simpleType? i.e. if we allow the use of the
> xml:lang attribute (which was part of the initial proposal for "simple
> DC", and I don't _think_ has been rejected along the way?), I
> think that
> makes the "base" element type a "complexType" in XML Schema
> terms, which
> introduces the problem pointed out by Roland here
>
> http://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=ind0203&L=dc-archi
> tecture&F=
> &S=&P=7240
>
> of deriving simpleTypes from that starting point.
>
> Does this mean we need separate "per-DC-element" types, where some
> elements have complexTypes permitting xml:lang and others have only
> simpleTypes based only on "anySimpleType"?
>
> Pete
>
> ------------------------------
>
> Date: Mon, 11 Mar 2002 18:24:43 -0000
> From: Pete Johnston <[log in to unmask]>
> Subject: Re: Public Comment on DC-simple XML Schema
> declaration
> within OAI
>
> Rachel said:
>
> > What I would like to see is one XML schema for all DC
> > terms... given that we now have elements in 2 different
> > namespaces I think we have to accept the need for a schema
> > containing all terms.... surely it will be a nonsense to have
> > a schema with qualifiers and one element??
>
> Andy said:
>
> > If a schema representing all DCMI terms is a useful building block,
> > then fine, lets create an XML schema for it that others can import.
> > But I'm not convinced it is BTW.
>
> My understanding is that because of the way XML Schema works with XML
> namespaces, it's not possible to model elements/attributes from two
> namespaces within one XML Schema. So we will necessarily have
> a minimum
> of two "base schemas" for DCMI, one each for the elements in the two
> namespaces http://purl.org/dc/elements/1.1/ and
> http://purl.org/dc/terms/ This contrasts with RDF Schema where you
> could put the descriptions of the terms in the two namespaces in one
> file (if you really wanted to do so!)
>
> So I don't think Rachel's requirement can be realised directly.
>
> And following Carl and Andy's messages at
>
> http://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=ind0203&L=dc-archi
> tecture&F=
> &S=&P=8602
>
> http://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=ind0203&L=dc-archi
> tecture&F=
> &S=&P=8322
>
> I think we're saying that, given the need for different datatyping
> requirements for using elements from the _same_ namespace in
> _different_
> application contexts, there may be a requirement for multiple XML
> Schemas to represent the terms in one namespace.
>
> What I'm still not sure about is whether these multiple schemas for,
> say, http://purl.org/dc/elements/1.1/ are to be completely independent
> of each other, or whether we should try to build explicit
> relationships
> between them, or more specifically between the datatypes used within
> them.
>
> My understanding is that we can do the former quite easily, but trying
> to do the latter introduces some (for me, at least) quite difficult
> questions of datatype hierarchies.
>
> Cheers
> Pete
>
> ------------------------------
>
> Date: Tue, 12 Mar 2002 09:26:43 +1000
> From: Jane Hunter <[log in to unmask]>
> Subject: Re: Public Comment on DC-simple XML Schema
> declaration within OAI
>
> Dear Pete,
>
> Sorry I missed that point raised by Roland - but I'm not sure you're
> right. Its certainly more complex but you can apply restrictions to
> complexTypes. I think you can do the following but I need to test it
> with XML Spy:
>
> In the 'simple DC' XML Schema DCMI namepace you define the generic
> elementType:
>
> <complexType name="elementType"
> <simpleContent>
> <extension base="anySimpleType">
> <attribute ref="x:lang" use="optional"/>
> </extension>
> </simpleContent>
> </complexType>
>
> <element name="date" type="elementType/>
>
>
> Then if a user wants their date element to use the 'date' datatype,
> they define their own element based on the dc:elementType, in
> their own
> schema:
>
> <element name="myDate">
> <xs:complexType>
> <xs:simpleContent>
> <xs:restriction base="dc:elementType">
> <simpleContent>
> <extension base="date">
> <attribute ref="x:lang" use="optional"/>
> </extension>
> </simpleContent>
> </xs:restriction>
> </xs:simpleContent>
> </xs:complexType>
> </xs:element>
>
>
> This is pretty complex, so I'm starting to think the pure and simple,
> string and vanilla (sounds like a song) approach is the easiest. If
> anyone wants anything other than strings, or facets of strings, then
> they have to declare their own element, but we could consider
> providing
> a 'semantics' attribute which can be included in the user's
> definition,
> to point to the DC element definition:
>
> <element name="myDate" type="xsd:date" xx:semantics=
> "http://www.dublincore.org/documents/1999/07/02/dces/#date"/>
>
> Since the semantic definition of each element is the important stable
> part of DC, then this seems a sensible approach (to me at least).
>
> jane
>
> > Is there not a problem that the current "base" element type in the
> > simpledc schema isn't a simpleType? i.e. if we allow the use of the
> > xml:lang attribute (which was part of the initial proposal
> for "simple
> > DC", and I don't _think_ has been rejected along the way?),
> I think that
> > makes the "base" element type a "complexType" in XML Schema
> terms, which
> > introduces the problem pointed out by Roland here
> >
> >
http://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=ind0203&L=dc-architecture&F=
> &S=&P=7240
>
> of deriving simpleTypes from that starting point.
>
> Does this mean we need separate "per-DC-element" types, where some
> elements have complexTypes permitting xml:lang and others have only
> simpleTypes based only on "anySimpleType"?
>
> Pete
------------------------------
End of DC-ARCHITECTURE Digest - 10 Mar 2002 to 11 Mar 2002 (#2002-35)
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