RDFa Basics video (8 minutes)

Finished an RDFa Basics video this weekend. It attempts to
explain RDF,
CURIEs, N3 and basic RDFa in 8 minutes:

http://www
.youtube.com/watch?v=ldl0m-5zLz4

Thought some of you would want to learn about some of the
upcoming
features of XHTML2 as well as compare and contrast how RDFa
differs from
Microformats.

Constructive feedback would be great, as I'll probably be
doing the
"advanced" RDFa tutorial in a month or so, and
will need to know what
worked and what didn't in the RDFa Basics video.

A high-bitrate version, along with all source material, will
be uploaded
and put on the Digital Bazaar wiki tomorrow:

http://w
iki.digitalbazaar.com/en/rdfa-basics

-- manu

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Manu Sporny wrote:
> Constructive feedback would be great, as I'll probably
be doing the
> "advanced" RDFa tutorial in a month or so,
and will need to know what
> worked and what didn't in the RDFa Basics video.
>
>   
I'm relatively new to RDFa and this is a great introduction.
I'm 
probably going to say things you've already heard, so please
bear with me.
For someone like me who has learnt to value the
accessibility of 
standards, the brutally honest takeaway of your introduction
is that 
RDFa does what microformats do and probably more (otherwise
why would it 
exist?), but not clear what exactly and plus it requires
XHTML 2.0 and 
complex syntax. So, when comparing uf and RDFa, adopting
RDFa seems a 
huge leap of faith and a lot of work considering it requires
XHTML 2.0 
and your introduction does not mention any application
supporting RDFa...
So, if the goal of this video is to evangelize RDFa to a
large audience, 
I think it would be great to explain why (ex. why id, class
and 
a/href/rel haven't been leveraged more to represent RDF
triples) and 
also explain how an implementation can best leverage the 
backward-compatibility/evolutionary benefits of microformats
with the 
RDFa more formalist and consistency with other w3
standards.
Last, if you believe like me that applications drive
standards, not the 
reverse, then I think what will ultimately get people
excited is to have 
a demonstration of how this content can be leveraged by an
application 
once published and gathered in a RDF store. In an ideal
world, putting a 
aside resource constraints issues, if I had to evangelize
RDFa, I would 
start with the application, for instance showing content in
a browser, 
then showing how it's possible to type queries against this
content in a 
browser plugin. Then only I would show the implementation,
and at the 
end possibly, adoption numbers such as how many people have
downloaded 
the plugin so far.
My 2 cents.
Guillaume
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Guillaume Lebleu wrote:
> Manu Sporny wrote:
>> Constructive feedback would be great, as I'll
probably be doing the
>> "advanced" RDFa tutorial in a month or
so, and will need to know what
>> worked and what didn't in the RDFa Basics video.
>>   
> I'm relatively new to RDFa and this is a great
introduction. I'm
> probably going to say things you've already heard, so
please bear with me.

Any feedback is really appreciated, so I thank you for
taking the time
to write out your thoughts on the video[1] 

> So, when comparing uf and RDFa, adopting RDFa seems a
> huge leap of faith and a lot of work considering it
requires XHTML 2.0

Ooops, looks like my post lead to some confusion. RDFa works
with any
version of XHTML. You can write valid RDFa today. t's not an
"it's going
to happen in the future" thing - you can author RDFa
today (for example,
Operator already has RDFa support).

> and your introduction does not mention any application
supporting RDFa...

That's true, there aren't many applications that use RDFa
today...
mostly because the standard is just being finalized. The
semantic web
stuff has been brewing in academia for almost a decade. We
have the
Microformats community to thank for getting the message
about why
semantics are important in web pages... so, I think that
we're really at
the cusp of this stuff taking off.

> So, if the goal of this video is to evangelize RDFa to
a large audience,

Hmm... the goal of the video wasn't necessarily to
evangelize RDFa - it
was to educate web developers about some basic semantic web
concepts. It
was supposed to teach people very briefly about the power of
RDF, what a
CURIE is, what N3 notation is, and how you can express
semantic
information in XHTML web pages using RDFa. Do you think it
achieved that
goal, or did it fall short for some reason? Was there too
much going on
in each part of the video?

> I think it would be great to explain why (ex. why id,
class and
> a/href/rel haven't been leveraged more to represent RDF
triples)

[FULL DISCLOSURE: I am on the W3C RDFa task force... take
what I have ]
[                 to say with a grain of salt.              
         ]

I'll explain here, just so you know. I don't know how many
people know
this, but XHTML is extensible in that you can add modules to
extend
XHTML. These modules define new attributes and tags that can
be used in
a valid XHTML document. RDFa is an extension to XHTML, and
works with
all current browsers that support XHTML.

id
isn't used because it must be unique to a page. It also
already had
a different set of semantics associated with it in XHTML and
it doesn't
allow CURIEs, AFAIK. about is used instead.

class wasn't used because they didn't want to stomp
on the Microformats
community's implementation, among other reasons. In certain
RDFa
implementations, bad things happened when you mixed RDFa
and
Microformats on the same page. about is used instead.

href
and rel were re-used. href is used to denote a
object, while
rel
is used to denote predicates.

The current implementation makes sure to take the semantics
of the
pre-existing XHTML standard into account, the following
attributes were
used from XHTML:

rel,
rev,
href, src

These attributes were added in XHTML+RDFa:

about, instanceof, resource, property,
datatype, content

I should mention that while RDFa may seem more complex than
Microformats
(and in some cases it is)... there are no issues with ABBR
or title
mis-use/abuse. These endless debates we seem to have over
"where do we
place the ISO machine readable data in the
Microformat?", are a
non-issue in RDFa.

> also explain how an implementation can best leverage
the
> backward-compatibility/evolutionary benefits of
microformats with the
> RDFa more formalist and consistency with other w3
standards.

Thanks for the suggestion - I'll try to put that in the next
video, or a
video comparing/contrasting Microformats and RDFa. We need
both... like
any syntax, each has its benefits and drawbacks.

> Last, if you believe like me that applications drive
standards, not the
> reverse, then I think what will ultimately get people
excited is to have
> a demonstration of how this content can be leveraged by
an application
> once published and gathered in a RDF store. 

You're right, the proof of the greatness of any technology
is in it's
adoption rate and the number of applications that are
written using that
technology.

> if I had to evangelize RDFa, I would
> start with the application, for instance showing
content in a browser,
> then showing how it's possible to type queries against
this content in a
> browser plugin. Then only I would show the
implementation, and at the
> end possibly, adoption numbers such as how many people
have downloaded
> the plugin so far.

We hope to do just that this year... using the hAudio
Microformat as
well as hAUdio RDFa. I guess we have to start somewhere, and
this video
was an attempt at just that...

Thanks a bunch for your feedback, Guillaume - it is
definitely
appreciated 

-- manu

[1] http://www
.youtube.com/watch?v=ldl0m-5zLz4

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On Jan 7, 2008, at 1:31 PM, Manu Sporny wrote:

> class wasn't used because they didn't want to stomp
on the  
> Microformats
> community's implementation, among other reasons. In
certain RDFa
> implementations, bad things happened when you mixed
RDFa and
> Microformats on the same page.

Can you maybe elaborate on the "bad things" you
mention here?  There  
should be nothing about microformats that prevented RDFa
from using  
the class attribute, as there's no monopoly on the class
attribute.   
Were those implementations that didn't involve any
namespaces nor  
profiles?  I don't see how there could be any conflict with
namespaces  
(since microformats have no namespaces), and a lack of
namespaces  
seems antithetical to my understanding of RDF.

Peace,
Scott

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