Cart
|
[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: [SML] Whether to support Attribute or not?
On Fri, 26 Nov 1999, Don Park wrote:
> I believe it is now time to address the question of
> whether Attribute should be supported in SML or not.
Summary:
Attributes cannot be eliminated without
providing a suitable replacement.
Discussion:
The reason why SGML/XML/SML is so powerful is
that it accurately reflects the dual nature
of reality. Code has two aspects -- it is
edited as data and run as instructions.
This pattern is recursive. Witness yet another
compiler ("yacc"), it is code which instructs the
generation of code.
XML is powerful beacuse it recognizes that there are
_always_ two simotanenous contexts that must be
distinguished: data and markup.
Attributes are the result of applying this same
pattern recursively on the markup itself. Thus, a
given tag can have instructions (the attribute) and
data for those instructions (the attribute's value).
Attributes therefore, allow a second order approximation
to the recursive pattern:
[Attribute]
/
[Markup]
/ \\
/ [Value]
[Document]
/ [Attribute]
\\ [Markup]
\\ / \\ [Value]
[Content]
\\
[Content] ...
Unfortunately, as pointed out on this list many, many
times -- by having a different syntax, attributes do
not allow for further recursion. Thus, there is an
entire realm of reality which cannot be described
using XML, since attributes cannot have children.
Thus, I really doubt that it is possible to have
a meaningful markup language without attributes --
however, finding a recursive replacement would
be very good.
Consider:
<element att="val"> <content/> </element>
If attributes were eliminated, this would be mapped to:
<element> <att>val</att> <content/> </element>
Possibility #1:
Use a hard-coded namespace,
<element> <attribute:att>val</attribute:att> <content/> </element>
Possibility #2:
Use a marker,
<element> <$att>val</$att> <content/> </element>
Possibility #3:
Use another type of brackets,
<element> {att}val{/att} <content/> </element>
Possibility #4:
Use a divider,
<element> <att>val</att> <|> <content/> </element>
In any case, replacing the attribute mechanism with
one that allows for recursion would allow for
stuff like:
<para alt="<b>alt</b>"> para </para>
To be legally expressed (using syntax #4):
<para> <alt><b>alt</b></alt> <|> para </para>
Hmm. Thoughts?
Clark
xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@i...
Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ and on CD-ROM/ISBN 981-02-3594-1
To unsubscribe, mailto:majordomo@i... the following message;
unsubscribe xml-dev
To subscribe to the digests, mailto:majordomo@i... the following message;
subscribe xml-dev-digest
List coordinator, Henry Rzepa (mailto:rzepa@i...)
|
PURCHASE STYLUS STUDIO ONLINE TODAY!Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced! 
Download The World's Best XML IDE!Accelerate XML development with our award-winning XML IDE - Download a free trial today! Subscribe in XML format
|
|||||||||
