For a brief period today, there were no outstanding e-mails or bugs on the specs, and so I took that opportunity to transition us here at the WHATWG to the next stage of HTML5's development: Last Call! This affects three specs at the WHATWG:
There's also a version of the spec called Web Applications 1.0 (for nostalgic reasons) that has all of the above as well as a number of other specs, namely Web Storage, Web Database, Server-sent Events, and the Web Sockets API and protocol, all together in one document. With the exception of the Web Database spec, they're all now in last call at the WHATWG.
So if you've been waiting to see if someone else would report the problem that you had seen, well, if it's not fixed, they didn't! So you should now send that feedback in yourself.
There's two ways to send feedback. If your feedback is something short and simple, you can just load up the spec in your browser, click on the section with the problem, then type in your message using the review comments box that appears at the bottom of the window, and hit the "Submit Review Comments" button. This works for the HTML5 and Web Applications 1.0 specs. (Thanks to the W3C HTML Working Group for making their bug database available to us for this purpose.)
If your feedback is more elaborate, then you should subscribe to the mailing list and then send your feedback there.
Note: Lest there be any confusion, the W3C HTML WG has not yet transitioned HTML5 to Last Call at the W3C. HTML5 is a joint effort of W3C and WHATWG groups, but we have different issues lists and different criteria for going to Last Call. For more details on the W3C HTML WG's processes, see the W3C HTML WG charter.
Posted in WHATWG | 16 Comments »
Welcome back to "This Week in HTML 5," where I'll try to summarize the major activity in the ongoing standards process in the WHATWG and W3C HTML Working Group.
This week, there were some more refinements to microdata. r4139 changes the names of the DOM properties that reflect microdata markup. r4140 renames the content
property to itemValue
Since no browser has actually implemented this API yet, these changes shouldn't make any difference. Standards are like sex; one mistake, and you're stuck supporting it forever! r4141 and r4147 fix up some microdata examples, in particular this example from Gavin Carothers about marking up O'Reilly's book catalog. Hooray for real-world examples!
There were also some noteworthy changes to the <video>
and <audio>
API. r4131 says that setting the src
attribute on one of those elements should call its load()
method. r4132 removes the load
event for multimedia elements, and r4133 removes the "in progress" events (loadstart
, loadend
, and progress
) that used to be fired while the video/audio file was downloading.
Other noteworthy changes this week:
- r4097 defines fallback content for the obsolete
<applet>
element.
- r4098 "dramatically simplifies
<script defer>
and <script async>
handling." [Background: bug 7792]
- r4106 makes the step argument to the
<input>
element's stepUp()
and stepDown()
methods optional.
- r4111 removes
<link rel=feed>
. As I documented earlier this year, rel=feed
was a reasonable idea that never took off. Only one browser ever implemented it, and in a survey of 3 billion pages I could only find a single page that used it.
- r4126 lists suggested default encodings for different locales. [Background: RE: HTML5 Issue 11 (encoding detection): I18N WG response...]
- r4138 drops support for non-UTF-8 encodings in Web Workers. [Background: [whatwg] Please always use utf-8 for Web Workers]
- r4099 marks the creation of Web Applications 1.0, a super-spec that contains HTML5, pre-defined microdata vocabularies, Web Workers, Web Storage, Web Database, Server-sent Events, and Web Sockets. This marks the first time that some of those specs have been published by the WHATWG, rather than the W3C, and therefore the first time that said specs have been published under a Free-Software-compatible license. (The W3C is still deciding whether to use such a license.)
Around the web:
Tune in next week for another exciting edition of "This Week in HTML5."
Tags: applet, licensing, microdata, thisweekinhtml5, video
Posted in Weekly Review | 5 Comments »
The big news this week is microdata. Google sponsored a usability study on microdata syntax, which resulted in significant changes to the spec [r4066]. Also related: r4067 fixes a microdata example, r4068 updates the algorithm for extracting RDF triples from microdata, r4069 does some spec cleanup, and r4070 splits out the predefined microdata syntaxes into their own specs:
There was also work on events this week. r4032 defines what events are involved in copy and paste, closing bug 7668. r4037 defines when the reset
event fires, closing bug 7699. r4039 defines when the abort
event fires, closing bug 7700.
This week brings another milestone, one which went mostly unremarked in mailing lists, blogs, and IRC chatter. As with any large project, Ian Hickson has maintained an informal wishlist of things he would like to clarify, define, or otherwise include in HTML5. The list has grown and shrunk over the years. The list was stored in HTML comments, so it has never been visible unless you viewed the source of the HTML5 specification itself. And as with any large project, there comes a time when you realize you're not going to get to everything on your wishlist.
This week, the wishlist shrunk a lot, as Ian finally "punted" on several issues. Some of them may be tackled in HTML6. (Of course, if someone feels strongly enough, they can certainly argue that an issue still needs to be tackled in HTML5.) r4023 shows the deletions from the wishlist, including: "ability for a web app to save a file to the local disk," proposals for new attributes on the <title>
element, partial form validation, multi-column select widgets, auto-formatting of number fields (like many spreadsheet programs do), relative dates, input controls for repeating dates (like anniversaries or other repeating events), and input controls for currency.
Other noteworthy changes this week:
- r4011 syncs with the latest Origin spec, closing bug 7599.
- r4031 allows user agents to explicitly disable
<canvas>
support.
- r4042 limits
PUT
and DELETE
actions on web forms to the same origin as the page. This is similar to the restriction on XMLHttpRequest
.
- r4057 defines
<applet>
.
- r4076 disallows the backtick (
`
) character in unquoted attribute values, because Internet Explorer will treat it as an attribute value delimiter.
- r4082 adds the
document.head
property, which makes me very happy.
- r4083 states that an
<audio>
element without controls should always be hidden. (You can still make a visible <audio>
element; just give it a controls
attribute.)
- r4086 tries to clarify the ever-elusive
WindowProxy
object.
- r4091 registers the various HTTP headers that are used in the new features of HTML5, including
Ping-From
and Ping-To
.
- r4092 and r4094 add a non-normative index of HTML elements and attributes. Think of it as an "HTML5 cheat sheet." Various third parties have attempted such a list, but none have been able to keep up with the maintenance required as HTML5 evolved.
Around the web:
Tune in next week for another exciting edition of "This Week in HTML5."
Tags: Events, microdata, thisweekinhtml5
Posted in Weekly Review | 2 Comments »
Over the past few weeks, Google has been preparing and then running a usability study to test the microdata feature of HTML5.
Methodology
We first created three different variants based on the original microdata proposal:
- One based on what the spec said (documentation)
- One trying to put types in an explicit
itemtype=""
attribute and moving "about" to item=""
, and replacing itemfor=""
with just having multiple item=""
s with the same name (documentation)
- One trying to remove types altogether and using
item
as a boolean attribute. (documentation)
Our plan was to run six studies, two for each variant, with each participant running through the following steps:
- Read and comment on a couple of motivating slides explaining why one would care about microdata
- Read the provided documentation for the variant being tested
- Look at and comment on the animals example with microdata (variant 2, variant 3)
- Exercise: try to extract the data from the "flickr" example (variant 2, variant 3)
- Exercise: try to annotate the blog example (variant 2, variant 3)
- Exercise: try to annotate the review example (variant 2, variant 3)
- Compare and contrast the "yelp" example with microdata to the equivalent of one of the other two variants (variant 2, variant 3)
We made some changes along the way. After the first three, it became clear that "about" was a very confusing term to use for giving the item's global identifier, and so we changed the documentation and examples to use "itemid" instead (which turned out to be much less confusing). Early on we also introduced some documentation text to explain the differences between the variants in the last exercise, because just showing them the two side by side wasn't getting us anything useful (1 to 3, 2 to 1, 2 to 3, 3 to 1).
After our sixth participant canceled on us, we decided to create a fourth variant (documentation) based on what we'd learnt with the first five, and to get two more participants to test this variant specifically. For these participants, we used the following methodology:
- Read and comment on a couple of motivating slides explaining why one would care about microdata
- Read the provided documentation for the variant being tested
- Look at and comment on the animals example with microdata
- Exercise: try to extract the data from the "flickr" example
- Exercise: try to extract the data from the review example
- Exercise: try to annotate the blog example
- Exercise: try to annotate the "yelp" example
Conclusions
Some interesting things came out of this study. First, as mentioned above, the term "about" turns out to be highly non-intuitive. I originally took the word from RDFa, on the principle that they knew more about this than I did, but our participants had a lot of trouble with that term. When we changed it to "itemid", there was a marked improvement in people's understanding of the concept.
Second, people were much less confused about types than I thought they would be. In preparing for this study I discussed microdata with a number of people, and I found that one major area of confusion was the concept of types vs the concept of properties. This is why variant 3 has no types: I wanted to find out whether people had trouble with them or not. Well, not only did people not have problems with types, several participants went out of their way to specify the type of an item, for example using the attribute name "type" instead of "item" in variant 1.
It seems that while reasoning about types at the theoretical level is somewhat confusing, it isn't so confusing that the concept should be kept out of the language. Instead, types should just be more explicitly mentioned. This is why we renamed "item" to "itemtype".
Third, people were confused by the scoping nature of the "item" attribute. Some of our participants never understood scoping at all, and most of the participants who understood the concept were still quite confused by the "item" attribute. We were encouraged, however, by one variant 1 participant's sudden enlightenment when they saw variant 3's "itemscope" attribute, and by the reaction of the variant 3 participant to the "itemscope" attribute compared to the reactions that the other two variants' participants had to their "item" attributes. This is why we split "item" into "itemtype" and "itemscope", instead of just using "itemtype".
We found that people who understood microdata's basic features also understood "itemfor", but while we were doing the study, it was pointed out on the WHATWG list that "itemfor" makes it impossible to find the properties of an item without scanning the whole document. This is why we tested the <itemref> idea in variant 4. People were at least as able to understand this as "itemfor".
In general, the changes we made for variant 4 were all quite successful. With one exception, that's what HTML5 now says. The one exception is that I hoisted the "itemid" property to an attribute like "itemtype", based on the argument that if people want to scan a document for the item with a particular "itemid", <itemref> would make it impossible to do it for the property without creating the microdata graph for the entire page.
One thing we weren't trying to test but which I was happy to see is that people really don't have any problems dealing with URLs as property names. In fact, they didn't even complain about URLs being long, which reassured me that microdata's lack of URL shortening mechanisms is probably not an issue.
Overall, this was a good and useful experience. I hope we can use usability studies to test other parts of HTML5 in the future.
Update
(Added based on Twitter feedback.) Some people have asked to see the raw data we collected in this study. I've uploaded the raw files as they were at the end of each participant's one-hour session. This data on its own isn't especially useful; what matters is how the participants reached their conclusions. There are seven hours' worth of video to document that, but we can't publish the video online, since that would be a violation of the legal agreement we have with the participants to protect their privacy.
The study was conducted by one of Google's usability study moderators, and the participants were screened and recruited by a separate team of usability study recruiters specifically for this study. Our criteria were intended to find Web developers who were somewhat comfortable with HTML and who had at most a passing knowledge of the HTML5 effort.
Bear in mind, when looking at the raw data, that the participants had just one hour to go from not knowing about this at all, to being expected to read and write code in a new syntax, with no hints other than the examples and the documentation (which most only glanced at!).
Posted in WHATWG | 7 Comments »
I recently found myself testing how browsers sniff for RSS 1.0 feeds that are served with an incorrect MIME type. (Yes, my life is full of delicious irony.) I thought I'd share my findings so far.
Firefox
Firefox's feed sniffing algorithm is located in nsFeedSniffer.cpp
. As you can see, starting at line 353, it takes the first 512 bytes of the page, looks for a root tag called rss
(for RSS 2.0), atom
(for Atom 0.3 and 1.0), or rdf:RDF
(for RSS 1.0). The RSS 1.0 marker is really a generic RDF marker, so it then does some additional checks for the two required namespaces of an RSS 1.0 feed, http://www.w3.org/1999/02/22-rdf-syntax-ns#
and http://purl.org/rss/1.0/
. This check is quite simple; it literally just checks for the presence of both strings, not caring whether they are the value of an xmlns
attribute (or indeed any attribute at all).
Firefox has an additional feature which tripped up my testing until I understood it. IE and Safari both have a mode where they essentially say "I detected this page as a feed and tried to parse it, but I failed, so now I'm giving up, and here's an error message describing why I gave up." Firefox does not have a mode like this. As far as I can tell, if it decides that a resource is a feed but then fails to parse the resource as a feed, it reparses the resource with feed handling disabled. So an non-well-formed feed served as application/rss+xml
will actually trigger a "Do you want to download this file" dialog, because Firefox tried to parse it as a feed, failed, then reparsed it as some-random-media-type-that-I-don't-handle. A non-well-formed feed served as text/html
will actually render as HTML, but only after Firefox silently tries (and fails) to parse it as a feed.
There's nothing wrong with this approach; in fact, it seems much more end-user-friendly than throwing up an incomprehensible error message. I just mention it because it tripped me up while testing.
Internet Explorer
Internet Explorer's feed sniffing algorithm is documented by the Windows RSS team. About RSS 1.0, it states:
IE7 detects a RSS 1.0 feed using the content types application/xml
or text/xml
. ... The document is checked for the strings <rdf:RDF
, http://www.w3.org/1999/02/22-rdf-syntax-ns#
and http://purl.org/rss/1.0/
. IE7 detects that it is a feed if all three strings are found within the first 512 bytes of the document. ... IE7 also supports other generic Content-Type
s by checking the document for specific Atom and RSS strings.
Now that I understand IE's algorithm, I have to concede that this documentation is 100% accurate. However, it doesn't tell the full story. Here's what actually happens. If the Content-Type
is
application/xml
text/xml
application/octet-stream
text/plain
text/html
- the empty string, or
- missing altogether
...then IE will trigger its feed sniffing. Once IE triggers its feed sniffing, it will never change its mind (unlike Firefox). If feed parsing fails, IE will throw up an error message complaining of feed coding errors or an unsupported feed format. The presence or absence of a charset
parameter in the Content-Type
header made absolutely no difference in any of the cases I tested.
And how exactly does IE detect an RSS 1.0 feed, once it decides to sniff? The documentation on MSDN is literally true: "The document is checked for the strings <rdf:RDF
, http://www.w3.org/1999/02/22-rdf-syntax-ns#
and http://purl.org/rss/1.0/
. IE7 detects that it is a feed if all three strings are found within the first 512 bytes of the document." Combined with our knowledge of which Content-Type
s IE considers "generic," we can conclude that the following page, served as text/html
, will be treated as a feed in IE:
<!-- <rdf:RDF -->
<!-- http://www.w3.org/1999/02/22-rdf-syntax-ns# -->
<!-- http://purl.org/rss/1.0/ -->
<script>alert('Hi!');</script>
[live demonstration]
Why Bother?
I am working with Adam Barth and Ian Hickson to update draft-abarth-mime-sniff-01 (the content sniffing algorithm referenced by HTML5) to sniff RSS 1.0 feeds served as text/html
. It is unlikely that we will adopt IE's algorithm, since it seems unnecessarily pathological. I am proposing the following change, which would bring the content sniffing specification in line with Firefox's sniffing algorithm:
In the "Feed or HTML" section, insert the following steps between step 10 and step 11:
10a. Initialize /RDF flag/ to 0.
10b. Initialize /RSS flag/ to 0.
10c. If the bytes with positions pos to pos+23 in s are exactly equal to 0x68, 0x74, 0x74, 0x70, 0x3A, 0x2F, 0x2F, 0x70, 0x75, 0x72, 0x6C, 0x2E, 0x6F, 0x72, 0x67, 0x2F, 0x72, 0x73, 0x73, 0x2F, 0x31, 0x2E, 0x30, 0x2F respectively (ASCII for "http://purl.org/rss/1.0/"), then:
- Increase pos by 23.
- Set /RSS flag/ to 1.
10d. If the bytes with positions pos to pos+42 in s are exactly equal to 0x68, 0x74, 0x74, 0x70, 0x3A, 0x2F, 0x2F, 0x77, 0x77, 0x77, 0x2E, 0x77, 0x33, 0x2E, 0x6F, 0x72, 0x67, 0x2F, 0x31, 0x39, 0x39, 0x39, 0x2F, 0x30, 0x32, 0x2F, 0x32, 0x32, 0x2D, 0x72, 0x64, 0x66, 0x2D, 0x73, 0x79, 0x6E, 0x74, 0x61, 0x78, 0x2D, 0x6E, 0x73, 0x23 respectively (ASCII for "http://www.w3.org/1999/02/22-rdf-syntax-ns#"), then:
- Increase pos by 42.
- Set /RDF flag/ to 1.
10e. Increase pos by 1.
10f. If /RDF flag/ is 1, and /RSS flag/ is 1, then the /sniffed type/ of the resource is "application/rss+xml". Abort these steps.
10g. If pos points beyond the end of the byte stream s, then continue to step 11 of this algorithm.
10h. Jump back to step 10c of this algorithm.
Further Reading
You can see the results of my research to date and test the feeds for yourself. Because my research results are plain text with embedded HTML tags, I have added 512 bytes of leading whitespace to the page to foil browsers' plain-text-or-HTML content sniffing. Mmmm -- delicious, delicious irony.
Update: Belorussian translation is available.
Tags: feeds, rss, sniffing
Posted in Browsers | 4 Comments »