W3C home > Mailing lists > Public > www-svg@w3.org > July 2008

Re: dilemma of cache: two types of image

From: David Woolley <forums@david-woolley.me.uk>
Date: Sun, 27 Jul 2008 21:29:49 +0100
Message-ID: <488CDABD.3070503@david-woolley.me.uk>
To: www-svg <www-svg@w3.org>

Jonathan Chetwynd wrote:

Firstly this isn't really specific to SVG and the concepts could do with
clarifying in a more general context before one tries to consider any
SVG specifics.

> the naive user may seek and find a picture of the sun, they copy and 

I think you are using "naive" as a euphemism.  I suspect you are really
talking about people who have difficulty thinking about times other than
now and places other than here, and would have difficulties with
abstractions that involve these dimensions, like weather and national dress.

> paste it into a document, and send it to a friend.

I think you are talking about copying links, rather than copying the
images.  This whole problem seems to be about the concept of indirection.

One problem that you have is that, without explicit permission, really
copying the resource is illegal and copying an image link (when one
divorces it from any message that the host site is conveying, or the 
surrounding advertising) is, at least, unethical (I'm not a lawyer, but 
I suspect one might be able to make a case that it constitutes theft of 
service).

(Even if the image is static, you may find that the site takes 
countermeasures and actually serves a different, possibly embarrassing, 
resource, when one accesses it out of context.  Such countermeasures 
might be introduced at any time.  Quite a common tactic with HTML is to 
force you to the home page if you enter with a deep link.)

> when it arrives it is a cloud...

There seem to be two basic approaches.

1) Supervision by someone who does understand copyright and abstraction.

2) Additional meta data to indicate copyright licensing and some measure 
of abstraction (maybe more than one dimension).

The problem with the second option is that most authors won't use 
either, and, at least with respect to copyright, browsers don't enforce 
the default copyright permissions, i.e. they allow you to copy a link by 
default even though copyright requires explicit permission.

My guess is that only those people likely to give an explicit copyright 
permission, are likely to provide abstraction level metadata.

Moreover, I think those who permitted use and were prepared to provide 
metadata, would also provide libraries of static images that would not 
need the metadata.  I think they would also be likely to use client side 
redirection to ensure that the URL that actually got displayed was 
always static.

I'm also not convinced that you can define a unique ordering amongst 
abstraction levels, and given that all images are abstractions, no 
resource will have zero abstraction.  Even static images can change 
because the author thinks they have found an image that better 
represents the concept that the image conveys.  Unless the person 
"borrowing" the image used in it with identical meaning and in an 
identical visual context, the result may no longer be valid.

Although you introduced caching, I don't really see that this has 
anything to do with caching.  In an ideal world one might infer 
abstraction in the time dimension by cache control metadata, but in 
practice designers seem to have rejected the idea of caching, and try to 
completely defeat it for primary content.  That is often to ensure that 
different advertisements are served each time, rather than because the 
editorial content is time varying - although time varying content does 
encourage repeat visits, so is often sought out.
> 
> if this explanation is not sufficient, please follow the screencast:
> http://www.youtube.com/watch?v=v_GAB3jRj6U

I don't have Flash on the Linux system.

-- 
David Woolley
Emails are not formal business letters, whatever businesses may want.
RFC1855 says there should be an address here, but, in a world of spam,
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Received on Sunday, 27 July 2008 20:28:46 GMT

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