Extensibility, HTML, and the Web ecosystem
Extensibility, HTML, and the Web ecosystem
Theresa O'Connor
BarCamp San Diego 5
There are at least 32.89 billion web pages.
HTML
the language of the Web
angle brackets
elements and attributes
<a href>, <img src alt>,
etc.
Why was HTML so wildly successful?
1. view source
2. cut & paste
3. F5
engine of generativity
[Generativity is] the ability of a self-contained system to provide an independent ability to create, generate or produce content without any input from the originators of the system.
Generativity on Wikipedia
HTML is a controlled vocabulary
What if that's not enough?
Extending HTML
1. alter meaning of existing els/attrs
layer additional meaning
@class, @id, @rel,
meta@name
<ul class="blogroll">
<em
class="RFC2119">MUST</em>
Avoiding collisions
apple: computer or fruit?
word sense disambiguation
centralized
(pre-defined @rel /
meta@name values)
coordinated (microformats)
distributed: head@profile
<html>
<head profile="http://example.com/RFC2119"/>
…
</head>
<body>
…
<em class="RFC2119">MUST</em>
…
</body>
</html>distributed: JFGI
2. Adding new elements and attributes
There are only two hard things in Computer Science: cache invalidation and naming things.
centralized v. distributed
centralized: HTML WG
distributed: ?
distributed extensibility
(ISSUE-41)
the promise of XHTML, circa 1998
<aside>: XML
elements and attributes
also angle brackets
<foo bar="baz"/>
looks so much like HTML
looks are deceiving!
</aside>
Distributed extensibility ends up reducing to a power-struggle between browser vendors who want to dictate what the vocabulary of the Web is—and content creators who do not want to cede this right entirely to the browser.
TV Raman, W3C TAG
There is no vast, browser-wing conspiracy. Really. Honest.
<apple>: computer or fruit?
Coping mechanisms
1. punt
<blink> & <marquee>
<canvas>
We're stuck with them.
2. Sufficiently Interesting(TM) prefixes
<moz-blink>,
<ms-marquee>,
<apple-canvas>
(Think Python package names)
-moz-border-radius
3. Controlled prefix minting
DNS
(Java package names)
<com.netscape.tags.blink>
<com.microsoft.tags.marquee>
<com.apple.tags.canvas>somewhat ugly
4. URI-based qualification
foo
becomes
{http://example.com/ns#, foo}
Names become {uri, term} pair
Gets ugly FAST
<{http://example.com/ns1#, foo}>
<{http://example.com/ns2#, bar}
{http://example.com/ns3#, baz}="quux"/>
</{http://example.com/ns1#, foo}>Namespaces in XML
Prefix-based indirection
<foo xmlns="http://example.com/ns1#"
xmlns:alpha="http://example.com/ns2#"
xmlns:beta="http://example.com/ns3#">
<alpha:bar beta:baz="quux"/>
</foo>Common case
<foo>
<alpha:bar beta:baz="quux"/>
</foo>Prefix is ephemeral
<foo xmlns="http://example.com/ns1#"
xmlns:alpha="http://example.com/ns1#">
<bar/>
<alpha:bar/>
</foo>Lifts part of element name into metadata
Data and metadata
the accuracy of metadata is inversely proportional to the square of the distance between the metadata and the data which it proports to describe.
HTTP headers
v.
<meta name="http-equiv">
document fragments
1. view source
2. cut & paste
3. F5
engine of metacrap
There is no such thing as risk-free copy and paste.
Disambiguation redux
The only risk is copying and pasting them into a document that doesn't provide namespace definitions for the prefixes[...]
[... or are] you thinking that someone will be using different namespaces but the same prefix? Come on — do you really think that will happen?
Yes. Yes, it will.
SearchMonkey v1: hard-coded prefixes
Google's handling of RDF blocks for license declarations is all done with regular expressions instead of actually parsing the namespaces[...]
Feed parsing
And frankly, few people will be doing copying and pasting. Most metadata will probably be added either as part of an underlying tool[...]
argumentum
ad adminiculum
the tools won't
save us
[E]arly adopters having difficulties is indicative of a feature that will be significantly more problematic when used by the (less well informed/competent) population of authors as a whole.
Web Environmentalism
Would the Web platform be better if <canvas> were <apple:canvas xmlns:apple="http://www.apple.com/2004/07/namespaces/webkit/dashboard#"> instead of <canvas>?
Design for Bob
Varieties of disambiguation and extensibility worth wanting
benefits: how well do they allow author to express novel semantics and how well can we avoid collisions
costs: how badly do they harm the Web
1. Adding elements and attributes:
Prefix-based indirection within a URI-based extensibility scheme: benefits not worth the cost
2. Augmenting existing elements and attributes
Profiling is overkill; head@profile unused in
practice by the very communities it was for
Sufficiently-Interesting, Google-able, semantic class names appear to get us all the disambiguation we need
Java-style DNS-derived names for the extra-paranoid
Upcoming microdata
attribues @item, @itemprop,
@subject avoid colloding with class names in the
wild
Look ma, no namespaces
thank you