[whatwg] Trying to work out the problems solved by RDFa
Calogero Alex Baldacchino
alex.baldacchino at email.it
Sat Jan 3 11:22:25 PST 2009
Dan Brickley ha scritto:
> On 3/1/09 14:02, Julian Reschke wrote:
>> Tab Atkins Jr. wrote:
>>> The most successful alternative is nothing at all. ^_^ We can
>>> extract copious data from web pages reliably without metadata, either
>>> using our human senses (in personal use) or natural-language-based
>>> processing (in search engine use). It has not yet been established
>>> that sufficient and significant enough problems *exist* to justify a
>>> solution, let alone one that requires an addition to html. That is
>>> what Ian is specifically looking for.
>> That's what you and Ian claim. Many disagree.
> My main problem with the natural language processing option is that it
> feels too close to waiting for Artificial Intelligence. I'd rather add
> 6 attributes to HTML and get on with life.
> But perhaps a more practical concern is that it unfairly biases things
> towards popular languages - lucky English, lucky Spanish, etc., and
> those that lend themselves more to NLP analysis. *The Web is for
> everyone*, and people shouldn't be forced to read and write English to
> enjoy the latest advances in *Web automation*. Since HTML5 is going
> through W3C, such considerations need to be taken pretty seriously.
My concern is: is RDFa really suitable for everyone and for Web
automation? My own answer, at first glance, is no. That's because RDF(a)
can perhaps address nicely very niche needs, where determining how much
data can be trusted is not a problem, but in general misuses AND
deliberate abuses may harm automation heavily, since an automaton is
unlikely to be able to understand whether metadata express the real
meaning of a web page or not (without a certain degree of AI).
If an external mechanism is needed to determine trust level for
metadata, that is to establish when an automation results are good or
bad, such a mechanism may involve human beings at some stage, thus
breaking automation (this is somehow similar to the problem of defining
an "oracle machine" described by Turing, according to whom such a
machine isn't an automaton).
On another hand, a very custom model thought for very custom needs (and
not requiring wide support) may be less prone to abuses, since it's
unlikely to find someone willing to cheat himself. Thus, having third
parties agreeing a certain model and related APIs, and implementing APIs
on their own sides, might be more reliable in some cases (anyway, third
parties should agree their respective metadata are reliable and find a
way to evaluate they really are).
Dan Brickley ha scritto:
> On 3/1/09 16:54, Håkon Wium Lie wrote:
>> Also sprach Dan Brickley:
>> > My main problem with the natural language processing option is
>> that it
>> > feels too close to waiting for Artificial Intelligence. I'd
>> rather add 6
>> > attributes to HTML and get on with life.
> Another thought re NLP. RDFa (and similar, ...) are formats that can
> be used for writing down the conclusions of NLP analysis. For example
> here see the BBC's recent Muddy Boots experiment, using DBPedia
> (Wikipedia in RDF) data to drive autoclassification / named entity
> recognition. So here we can agree with Ian and others that text
> analysis has much to offer, and still use RDFa (or other semantic
> markup - i'll sidestep that debate for now) as a notation for marking
> up the words with a machine-friendly indicator of their NLP-guessed
>> Personally, I think the 'class' attribute may still be a more
>> compelling option in a less-is-more way. It already exists and can
>> easily be used for styling purposes. Styling is bait for authors to
>> disclose semantics.
> I'm sure there's mileage to be had there. I'm somehow incapable of
> writing XSLT so GRDDL hasn't really charmed me, but 'class' certainly
> corresponds to a lot of meaningful markup. Naturally enough it is
> stronger at tagging bits of information with a category than at
> defining relationships amongst the things defined when they're
> scattered around the page. But that's no reason to dismiss it entirely.
> Did you see the RDF-EASE draft,
> http://buzzword.org.uk/2008/rdf-ease/spec? From which comes: "Ten
> second sales pitch: CSS is an external file that specifies how your
> document should look; *RDF-EASE is an external file that specifies
> what your document means.*"
> RDF-EASE uses CSS-based syntax. More discussion here,
> including question of whether it ought to be expressed using
My question is: how often can I trust such a file specifies what your
document really means, without evaluating its content?
I'd distinguish two cases (not pretendig to make a complete classification),
- The semantics described by metadata is used for server-side
computations: there's no need to evaluate content (since I'm trusting to
you when navigating your site, and it's unlikely to find you purposedly
messing with yourself), as well as to have client-side support for such
metadata (by the UA). This is the case of a centralised database.
For instance, a *pedia page may send queries to the server, which
elaborates them and sends results back the the user.
- The UA must understand metadata and automatically gather informations
meshed-up in a page from several sources: each source must be actively
evaluated and trusted (a bot can't do such). This is the case of a
For instance, that's easy to think of a spamming advertiser who
apparently puts honest content into your pages (which maybe take
reliable content from dbpedia), whereas he uses fake metadata to cheat
my browser and send me irrelevant informations (or infos I'm not
interested in) when I ask for related content , perhaps without you
even guessing what's going on (and you may be loosing visitors because
For obvious reasons, a trust evaluation mechanism can't be as easy as
getting/creating a signature to be used in a secure connection, because
someone must actively evaluate at least two things:
- the metadata really reflects a resource content, and
- the metadata is properly used with respect to an external schema
involved to model data (otherwise, no relationship would be reliable --
however, such might be a minor concern from a certain angle, since
misused metadata might be less harmful than deliberately abused ones).
The result can be very expensive (as certifying a driver or an
application for a certain platform), or lead to a free choice to avoid
any evaluation and instead to trust to any third parties. Both solutions
may work, perhaps, for niche/limited cases, but I don't think such may
be a good base for a "global" - and general purpose - automation.
 That's not the same as using the @rel attribute without any
relationship with other metadata: a UA may just provide a link somehow
described as pointing to a related resource with respect to the
surrounding content, so that I can choose to follow such a link or not;
if the @rel attribute is used by an automated mechanism in response to a
query and with respect to other metadata, the UA must decide on its own
if a link is worth to be followed or not, and I don't think there is any
easy way to take automated decisions involving trust.
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