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I should clarify that I used rdfs:seeAlso specifically because (as I
understand it) it is one of the few RDF predicates where it is
acceptable for the object to not be another RDF resource. See
<a class="moz-txt-link-freetext" href="http://www.w3.org/TR/rdf-schema/#ch_seealso">http://www.w3.org/TR/rdf-schema/#ch_seealso</a> and various other
discussions on the web as to why seeAlso was defined this way. Thus,
it isn't clear to me that creating a "hasPDF" predicate is a good idea
because it might send an uninformed client on a wild-goose chase for
non-existent RDF. I believe that the idea behind seeAlso was that
clients were on their own in figuring out the meaning of what they get
as the result of following the seeAlso link. <br>
Steve<br>
<br>
Peter DeVries wrote:
<blockquote
cite="mid:AANLkTi=D_55_rNiy4jvaZ7cyhU7a0yZ_G=5EF9Uzstqp@mail.gmail.com"
type="cite">I guess the question is do you want to use a generic
seeAlso which most crawlers follow, vs some more specific predicate
that says "here is the PDF"
<div><br>
</div>
<div>My reluctance was more about minting my own vs. finding some
other vocabulary which has a similar predicate.</div>
<div><br>
</div>
<div>With the <b>hasPDF</b> predicate it would be pretty easy to
query for all species concepts that have a linked original description
PDF etc.</div>
<div><br>
</div>
<div>I suspect that some standard predicate will eventually become
accepted since it is very useful to have something more specific than
foaf:Document.</div>
<div><br>
</div>
<div>Respectively,</div>
<div><br>
</div>
<div>- Pete</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
<br>
<div class="gmail_quote">On Wed, Jan 5, 2011 at 6:54 PM, Paul Murray <span
dir="ltr"><<a moz-do-not-send="true"
href="mailto:pmurray@anbg.gov.au">pmurray@anbg.gov.au</a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div style=""><br>
<div>
<div>On 06/01/2011, at 7:48 AM, Peter DeVries wrote:</div>
<br>
<blockquote type="cite">
<div>Also, although I like a lot of what Steve says, I think that
most existing crawlers expect that a seeAlso link is to some html, xml,
rdf type thing and will</div>
<div>not be able to handle a multi-megabyte PDF.</div>
<div><br>
</div>
<div>This is why I reluctantly minted the predicate "hasPDF"</div>
</blockquote>
<br>
</div>
<div>Hmm. This is an issue with linkeddata: when you fetch a URI
while crawling the semantic web, if it redirects, then it's an "other
resource" and you get RDF. If not, then you are potentially pulling a
multimegabyte "information resource" across the wire.</div>
<div><br>
</div>
<div>A solution is to use an HTTP "HEAD" request when you do the
initial URI fetch. If it's an "other resource", the HEAD return will be
a 303 and contain redirect that you want in the "Location" header, and
that's all you need. If not, the 200 result will contain the content
type and possibly even the size, which is what you need to know before
you GET it.</div>
<div><br>
</div>
So .. the problem that "hasPDF" is meant to address might be
addressable by the crawlers just being a bit smarter about how they
browse the semweb.
<div class="im">
<div><br>
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</blockquote>
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<br>
<br clear="all">
<br>
-- <br>
---------------------------------------------------------------<br>
Pete DeVries<br>
Department of Entomology<br>
University of Wisconsin - Madison<br>
445 Russell Laboratories<br>
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