Re: [xml-dev] XML Design Guidelines for Facilitating the Creation and Pr

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

Hi Roger,

Your stated example below (XHTML with embedded MathML) is the kind of
example that is often given for a compound document, and it has a
slightly different set of needs than your example instance given
earlier. The example instance given earlier (the classic 'marking up a
book' example) does not state explicitly its use but it implies it
because of the way that example is often used - it is an example of
marking up data that will be typically used for such things as
querying, exchange of data, and perhaps transformation to a
presentation format.

The example of XHTML and embedded mathml is of an XML format that has
an end media purpose - it should be presented in some way (although
others may argue that this is wrong) - thus the problem there is - how
to combine markup without explicit presentational parameters with
markup that does have explicit presentational parameters for actual
presentation.

I believe these problems to be slightly different.

reasons for the difference:

The output of the merged markups for presentation is given directly to
a human - and humans can hopefully determine if a presentation is
incorrect - thus in many cases of incorrect combinations of data the
human can discern there has been an error (at any rate this is the
naive hope I still have for humanity, that there can be some leeway
for error), whereas the merged data markups are fed into a program
which will have a harder time to determine the correctness of what
they're dealing with.

This difference can be seen in how browsers handle unknown markup and
how databases handle unknown data. (of course this example is somewhat
overblown)

Cheers,
Bryan Rasmussen

On Fri, Mar 6, 2009 at 9:17 PM, Costello, Roger L. <costello@mitre.org> wrote:
> Hi Rob,
>
>> How are you defining compound documents?
>
> By compound documents I mean two or more independent XML vocabularies combined into a single XML instance document. A common example is combining the XHTML vocabulary with the MathML vocabulary to create an XHTML document with embedded MathML.
>
> /Roger
>
>
>> -----Original Message-----
>> From: Robert Koberg [mailto:rob@koberg.com]
>> Sent: Friday, March 06, 2009 1:21 PM
>> To: Costello, Roger L.
>> Cc: 'xml-dev@lists.xml.org'
>> Subject: Re: [xml-dev] XML Design Guidelines for Facilitating
>> the Creation and Processing of Compound Documents
>>
>> How are you defining compound documents? Do you want different media
>> types in a document or are you talking about including XML
>> 'components' (that might include other components and so on)?
>>
>> What is compound about your examples?
>>
>> best,
>> -Rob
>>
>>
>>
>> On Mar 6, 2009, at 1:11 PM, Costello, Roger L. wrote:
>>
>> >
>> > Hi Folks,
>> >
>> > What guidelines would you recommend to someone who:
>> >
>> >   - wants to create an XML vocabulary,
>> >
>> >   - that will be combined with other XML vocabularies to create a
>> > compound instance document,
>> >
>> >   - which will be processed by applications?
>> >
>> > In other words, what XML designs will facilitate the creation and
>> > processing of compound documents?
>> >
>> > Below is a list of guidelines that I have come up with. Are there
>> > other guidelines that you recommend?
>> >
>> >
>> > ----------------------------------------------
>> >   GUIDELINES FOR FACILITATING THE
>> >      CREATION AND PROCESSING
>> >       OF COMPOUND DOCUMENTS
>> > ----------------------------------------------
>> >
>> > Namespaces are key to creating compound documents that can be
>> > effectively processed. Applications can partition compound
>> documents
>> > along the lines identified by namespaces, thus enabling module-
>> > specific processing.
>> >
>> >
>> > 1. When designing a schema, associate the XML vocabulary it
>> creates
>> > with a namespace. Thus the first guideline is to identify each XML
>> > vocabulary via a namespace. Here's an example of a Book XML
>> > vocabulary identified by the http://www.book.org namespace:
>> >
>> >    <Book xmlns="http://www.book.org";>
>> >         <Title>Illusions</Title>
>> >         <Author>Richard Bach</Author>
>> >         <Date>1977</Date>
>> >         <ISBN>0-440-34319-4</ISBN>
>> >         <Publisher>Dell Publishing Co.</Publisher>
>> >    </Book>
>> >
>> > Conversely, do not identify the XML vocabulary by embedding
>> a unique
>> > identifier inside an element or attribute. Here's an
>> example of the
>> > Book XML vocabulary identified using a GUID embedded inside an
>> > element:
>> >
>> >    <Book>
>> >
>> <Identifier>fc48ee30-0a6b-11de-8c30-0800200c9a66</Identifier>
>> >         <Title>Illusions</Title>
>> >         <Author>Richard Bach</Author>
>> >         <Date>1977</Date>
>> >         <ISBN>0-440-34319-4</ISBN>
>> >         <Publisher>Dell Publishing Co.</Publisher>
>> >    </Book>
>> >
>> >
>> > 2. If the schema language used to create the XML vocabulary
>> provides
>> > the option of namespace-qualifying all elements or namespace-
>> > qualifying only global elements, choose the former. For
>> example, the
>> > W3C XML Schema language allows you to specify "all elements
>> must be
>> > qualified in the instance document" by setting:
>> >
>> >    elementFormDefault="qualified"
>> >
>> > Conversely, it allows you to specify "only qualify globally
>> declared
>> > elements in the instance document" by setting:
>> >
>> >    elementFormDefault="unqualified"
>> >
>> > Don't use the latter as it destroys the value of namespaces.
>> > Instead, use the former as it maximizes the value of namespaces.
>> >
>> >
>> > 3. Use standard filename suffixes: .xsd (W3C XML Schema),
>> .rng (ISO
>> > RELAX NG), .sch (ISO Schematron), .dtd (W3C DTD). Although it is
>> > technically accurate to, say, suffix an XML Schema file with .xml,
>> > it is preferable to use .xsd as the latter enables applications to
>> > more easily recognize an XML vocabulary's schema language.
>> >
>> >
>> > 4. Design your schema maximizing the use of globally declared
>> > elements. Each globally declared component is a potential compound
>> > document component. For example, with this schema both
>> BookStore and
>> > Book can be used as a component in a compound document:
>> >
>> >    <element name="BookStore">
>> >        <complexType>
>> >            <element ref="Book" maxOccurs="unbounded" />
>> >        </complexType>
>> >    </element>
>> >
>> >    <element name="Book"> ... </element>
>> >
>> > Conversely, this schema only allows BookStore to be used as a
>> > component in a compound document:
>> >
>> >    <element name="BookStore">
>> >        <complexType>
>> >            <element name="Book" maxOccurs="unbounded"> ...
>> </element>
>> >        </complexType>
>> >    </element>
>> >
>> >
>> > What else would you add to this list?
>> >
>> > /Roger
>> >
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