How to use binary data with XML?
chris at w3.org
Wed Apr 21 01:02:13 BST 1999
"Roger L. Costello" wrote:
> I have a few questions on using binary data (e.g., gif, jpeg images)
> with XML.
> (1) Binary data isn't actually put in an XML file, correct? i.e., the
> binary data is _not_ inline, correct?
Not usually, although it is arguable (in terms of document object
modelks) that notation does exactly that; however in practice no, you
don't physically put jpeg-compressed bytes into the middle of your
> An XML file just contains ASCII text, correct?
No, and XML file contains Unicode text, which is one reason why lieral
insertion of binary data would be difficult.
> (2) Just like in HTML, binary data is _referenced_ by the XML document,
That is the most sensible way to do it, It allows independent revision,
and independent re-use, and facilitates cacheing.
> (3) Is this the correct way of using binary data:
> <!NOTATION jpeg PUBLIC "JPEG">
> <!NOTATION gif PUBLIC "GIF">
> <!ENTITY bostonGIF SYSTEM "http://www.maps.com/boston.gif" NDATA gif>
> <!ENTITY bostonJPEG SYSTEM "http://www.maps.com/boston.jpeg" NDATA jpeg>
> <!ELEMENT map (image)>
> <!ELEMENT image EMPTY>
> <!ATTLIST image
> src ENTITY #REQUIRED
> desc CDATA #IMPLIED>
> <image src="bostonGIF"
> desc="Map of Boston"/>
Its one way. It works in some viewers. Its rather sub-html, though -
there is no content, not even a measly alt attribute, let along actual
structured text alternatives.
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