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From Stefano Mazzocchi <stef...@apache.org>
Subject Re: Attribute and Element
Date Fri, 19 May 2000 10:33:35 GMT
"K.C. Jones" wrote:
> 
> Interesting discussion with lots of helpful tips and points
> to consider -- even if it is off-topic.
> 
> Anyway, I'm beginning to understand that there are simply no
> hard and fast rules here.  

You are right. Many believe that element vs. attribute is a religious
issue, not much different from browser wars, editor wars or os wars.

> Consider SVG.  SVG encodes vector
> path information like:
>         <path d="M316.32 120.153l11.443 12.706" style="&st2;"/>
> Where the 'd' attribute encodes the pen movement somehow.
> Lots of learned XML-DEV experts had a cow about how long the
> attributes were (the example is a very small one), how
> unparsable and un XSLT-transformable the important path data
> was.  But the ruling requirement for SVG was compactness and
> speed.  I think they were right.

I don't.

People believe that XML is verbose and will load their bandwidth. This
is the _totally_ wrong. In fact, it can be proved (based on pure
information theory) that XML conveys more structured information, then,
if the schema is a available at both ends, a schema-aware compressor is
able to compress the XML entropy stream with _LESS_ bits than an
equivalent xml-unaware compressor.

The XMill people showed they achieve 5% more compression over BZip by
simply using the XML syntax... they didn't even had to go down to
schema.

But they achieve this compression over the compressed text and I totally
agree that a pure binary vector format (with a tuned-for compressor)
would blow XML by an order of magnitude (like binary VRML showed).

So binary is always smaller than text-encoded formats, but the point is
XML verbosity and this doesn't count if a good compressor is used.

Unfortunately, very few understand XML verbosity is, from an information
point of view, fake.

> So bear in mind that attributes can be long if need be.  And
> that the structure and relationships that come with entity
> hierarchies come with some performance and efficiency costs
> when compared to use of attributes.

The use of entities is a form of compression and everyone knows that
doing compression over compression is not a good thing to do.

The SVG people clearly failed to understand the basics of network
layering and compression.

-- 
Stefano Mazzocchi      One must still have chaos in oneself to be
                          able to give birth to a dancing star.
<stefano@apache.org>                             Friedrich Nietzsche
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