RE: [xml-dev] Xml Revisited

["Jim Tivy" <jimt@bluestream.com>]

[<JT>] Names and how they are woven into the story is important.
When I re-read this part of the XML Rec I still find it a rather daunting
explanation for something so elegant and simple as XML.

As Per Version 5 of the XML Rec:
"
Each XML document has both a logical and a physical structure. Physically,
the document is composed of units called entities. An entity may refer to
other entities to cause their inclusion in the document. A document begins
in a "root" or document entity. Logically, the document is composed of
declarations, elements, comments, character references, and processing
instructions, all of which are indicated in the document by explicit markup.
The logical and physical structures MUST nest properly, as described in 
4.3.2 Well-Formed Parsed Entities."


After reading this I still didn't have a clue.  To me Xml is physical - for
example a file/buffer or stream of markup - mostly what would be called the
physical layout in a database system. Or a group of files that have some
"inclusion" relationship to each other - to me that is physical.  InfoSet or
DOM is more the "logical" level, and perhaps that is what is being said -
but in the revisit leave that to InfoSet.
Perhaps it is not so much the use of the word Entity but the way it is
defined.
As well, the above paragraph does not talk about Entity definitions and
Entity usages - perhaps use of the definition/declaration language would
help.

Comments below:

-----Original Message-----
From: rjelliffe@allette.com.au [mailto:rjelliffe@allette.com.au] 
Sent: Monday, August 24, 2009 9:11 PM
To: 'XML Developers List'
Subject: Re: [xml-dev] Xml Revisited


> I kept wondering how something so simple could use such convoluted terms.
> An entity to me was something in Entity Relationship modeling.  A file was
> something you included.  A compiland (Pascal) was something you imported -
> or a package in Java.

What is your point: there should only ever be one name for anything, and
it should be the same name that you use? I know COBOL people who get upset
that SGML uses "attribute" and "element" so incorrectly.  Actually, maybe
you do have a point: maybe standards should have an explicit note about
terms that have multiple uses in the wild (ISO standards all have a terms
and definitions section for this purpose.)

That entities are not what we would expect is not a compelling reason for
not having them, is it? (Indeed, the failure of XInclude may show that the
entity mechanism was in fact pretty practical and could be usefully
revived.)
[<JT>] 
I live in a content world where XInclude is very alive (DocBook) and
"transclusion" mechanisms like content references in DITA are very much
alive.  In both these cases Entities were not chosen.
If you want to look at SOAP attachments Entities were not used...

> Also the name Extensible Markup Language is a misnomer.  XML is not a
> language but a general meta grammar for creating and number of
> "languages".

Well, it certainly is a language in CS terms, because a formal language is
just syntactic, and XML certainly is a grammar.

Cheers
Rick

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