discussion of the Creative Commons Metadata work

[David Wendt <dcrkid AT optonline.net>]

Nathan R. Yergler wrote:

Sounds like an interesting idea; is there a reason to define a new chunk
type (ccMd) instead of using a tEXt chunk with the specification defined
'Copyright' keyword (http://www.w3.org/TR/PNG/#11Chunks)?  

Nathan R. Yergler
Software Engineer
Creative Commons

On Sun, 2004-11-07 at 18:31 -0500, David Wendt wrote:
  

After reading some parts of the W3C's spec for PNG, it seems easy enough 
to create a chunk for licence metadata that could then easily fit into a 
PNG file (photo, webcomic) for tagging files. The contents of the chunk 
would be the same as the mp3 data, although if you really wanted we 
could stick some RDF in there.

How to encode metadata: The chunk will be an ancillary private 
safe-to-copy chunk named ccMd (the capitalization is important) that 
will contain data in the format used for MP3-tagging:

[copyright notify] [license url] verify at [claim url]

The 2 important URLs are next to the words 'verify at', that is, the URL 
to the left of 'verify at' is the licence URL, the right of 'verify at' 
is the claim url. The software will then check the claim url for the 
verifing RDF, checking it against the licence referred to in the licence 
url.

It's important you read and understand part 5 of the W3C PNG spec:

http://www.w3.org/TR/PNG/#5DataRep

Read that entire part, it will show you what I'm talking about.

Comments, critiques, flames?
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Yes, however we would have to change the internal text to:

copyright [copyright notify] [licence url] verify at [claim url]

although if we did then it would be harder to differentiate between metadata and normal text blocks, since now we have to check the message as well as the chunk, and PNG engines will differentiate by chunk name, which means searching every tEXt chunk. It's doable, but may be a little more work then if we were to put it in a seperate chunk type.