I will try to briefly articulate why I feel an _official_ EAD W3C/RelaxNG
schema would be useful. I agree with Stephen that enhanced datatype
support doesn't bring much to EAD, particularly at the level of the
official DTD. However, the advantages to be gained by namespace support in
XML Schema and RelaxNG are great. An official W3C XML Schema for EAD
would, for example, greatly facilitate interoperabilty with other digital
library standards, particularly METS. Documents in other namespaces could
include elements (say the <did> element) from a properly designed EAD
schema and elements from other schemata (MARCXML, or EAC were it to be
expressed as a W3C Schema, for instance) could be incorporated in EAD
instances. I'd believe use of an official EAD for these purposes would be
better idea than reliance on ad hoc versions of EAD.
Further, wouldn't it be easier and cleaner to modify an official EAD W3C
and/or RelaxNG schema at the local, consortial, or other level, adding
constraint and extensions in a modular way than for all to roll their own?
Not to overly rely on a "keeping up with the Joneses" argument, but should
it not be considered that of the major digital library standards being
used and developed (METS, MODS, MARCXML, TEI), EAD is one of the only
standards expressed only in DTD?
This is all said in full recognition of what Stephen has already wisely
stated: this will all require a lot of thought, analysis, and, I may add,
discussion. All the more reason to proceed "officially" as a community.
On Thu, 3 Jun 2004, Stephen Yearl wrote:
> Perhaps schema proponents can better articulate why they need an _official_
> reworking of EAD in their schema language of choice?
> I stress official. EAD is more than the DTD: in fact it is not even
> the DTD, it just so happens that the common currently shared formal
> definition of EAD is expressed by DTD syntax (and not just for XML, you
> will remember). Like Clay and many others, I too use formal grammars (and
> rules-based validation mechanisms) that are impossible to achieve express
> in a DTD. But really, who cares by what means these constraints are
> enforced? My investment is in the markup, not the formal expression of it
> A locally derived schema (RELAX NG, XML-verbose) is in heavy use in my unit
> at Yale, and has more than realized the effort involved in crafting it.
> But it is used just for local purposes. It constrains an instantiation of
> EAD that is specific to our needs, a subset of EAD proper. There are many,
> many benefits to our use of this schema, but it remains a utilitarian tool
> targeted for specific use. Schema benefits are all on the "processing"
> rather than the "exchange" side of things: There is no mechanism for
> formally validating an XML instance against a schema for instance. The XML
> spec will tell you, amongst other things, that the root node (ead) must
> match that of the document type declaration, and that the document type
> declaration must contain a reference to a grammar that is expressed in DTD.
> How to do this _portably_ with schema?
> I'm a big fan of schemas (shemata), and would be further out to sea than
> I'd be happy about without RNG, but I would imagine that our community
> (which is exceedingly diverse) needs to better understand the nature of the
> advanced constraining features that schemata allow for. Example: should we
> impose a schema constraint that date@normal be ISO 8601? Then, as Mary Lacy
> pointed out in a recent message to this list, how to express distant, BCE
> dates? Now your Julian date@normal
> <http://scienceworld.wolfram.com/astronomy/JulianDate.html> are invalid.
> Creating an official schema is not going to be as simple as letting loose
> one of the very many DTD to schema converters on the EAD 202 DTD; it's
> going to require a lot of thought and analysis. Locally however, or for
> consortial arrangements, schema are invaluable-- they are the mechanical
> best practise guidelines, if you will.
> just my $0.2.
> Stephen Yearl
> Systems Archivist
> Yale University Library::Manuscripts and Archives
> At 05:24 PM 6/2/2004, you wrote:
>> Thanks to Clay for bringing this up.
>> I'd also be VERY interested in finding out the current status of an
>> official EAD W3C XML/RelaxNG schema. Like Clay, I'd be willing to do what
>> ever I could to assist in the effort.
>> On Wed, 2 Jun 2004, Clay Redding wrote:
>>> I, as well as several list members and institutions, have now converted
>>> the EAD 2002 DTD to XML Schema for local development with XForms,
>>> InfoPath, OAI, JAXB, etc. I'm curious where the provision of an
>>> official EAD 2002 XML Schema stands. I have heard that one is in
>>> development, as well as a Relax NG schema. When might we expect these?
>>> I'll be glad to lend a helping hand if possible to help accelerate the
>> Terry Catapano
>> Special Collections Analyst/Librarian
>> Columbia University Libraries Digital Program
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Special Collections Analyst/Librarian
Columbia University Libraries Digital Program
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