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XHTML5 in a nutshell

Sunday, July 25th, 2010

The WHATWG Wiki portal has a nice section describing HTML vs. XHTML differences, as well as specifics of a polyglot HTML document that also would be able to serve HTML5 document as valid XML document. I'd like to review what it takes to transform an HTML5 polyglot document into a valid XHTML5 document: it appears, finally the 'XHTML5' has become an official name.

The W3C first public working draft of "Polyglot Markup" recommendation describes polyglot HTML document as a document that conforms to both the HTML and XHTML syntax by using a common subset of both the HTML and XHTML and in a nutshell the HTML5 polyglot document is:

Polyglot document could serve as either HTML or XHTML, depending on browser support and MIME type. A polyglot HTML5 code essentially becomes XHTML5 document if it is served with the XML MIME type application/xhtml+xml . In a nutshell the XHTML5 document is: Finally, the basic XHTML5 document would look like this:
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title></title>
<meta charset="UTF-8" />

</head>

<body>
<svg xmlns="http://www.w3.org/2000/svg">
<rect stroke="black" fill="blue" x="45px" y="45px" width="200px" height="100px" stroke-width="2" />
</svg>
</body>
</html>

The XML declaration <?xml version=”1.0” encoding=”UTF-8”?> is not required if the default UTF-8 encoding is used: an XHTML5 validator would not mind if it is omitted. However it is strongly recommended to configure the encoding using server HTTP Content-Type header, otherwise this character encoding could be included in the document as part of a meta tag <meta charset="UTF-8" />. This encoding declaration would be needed for a polyglot document so that it will be treated as UTF-8 if served as either HTML or XHTML.

The Total Validator Tool - Firefox plugin/desktop app has now the user-selectable option for XHTML5-specific validation.

I would say that the main advantage of using XHTML5 would be the ability to extend HTML5 to XML-based technologies such as SVG and MathML. The disadvantage is the lack of Internet Explorer support, more verbose code, and error handling. Unless we need that extensibility, HTML5 is the way to go.

Posted in Syntax, What's Next, WHATWG | 26 Comments »

HTML5 Rationale document

Monday, May 10th, 2010

I've started a page on the wiki to document the rationale for the decisions made about the HTML specification.

There are two goals for this document:

  1. Explain why things are the way they are
  2. Explain the difference between multiple similar elements by providing example usages.

One person can not possibly write the entire thing so I hope that this becomes a group process where anyone interested can contribute so go sign up, log in, and edit.

Posted in Syntax, WHATWG | 5 Comments »

HTML5 at Last Call

Tuesday, October 27th, 2009

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 »

Usability testing HTML5

Sunday, October 4th, 2009

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:

  1. One based on what the spec said (documentation)
  2. 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)
  3. 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:

  1. Read and comment on a couple of motivating slides explaining why one would care about microdata
  2. Read the provided documentation for the variant being tested
  3. Look at and comment on the animals example with microdata (variant 2, variant 3)
  4. Exercise: try to extract the data from the "flickr" example (variant 2, variant 3)
  5. Exercise: try to annotate the blog example (variant 2, variant 3)
  6. Exercise: try to annotate the review example (variant 2, variant 3)
  7. 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:

  1. Read and comment on a couple of motivating slides explaining why one would care about microdata
  2. Read the provided documentation for the variant being tested
  3. Look at and comment on the animals example with microdata
  4. Exercise: try to extract the data from the "flickr" example
  5. Exercise: try to extract the data from the review example
  6. Exercise: try to annotate the blog example
  7. 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 »

Spelling HTML5

Thursday, September 10th, 2009

What’s the right way to spell “HTML5”? The short answer is: “HTML5” (without a space).

People in the WHATWG community have commonly referred to HTML5 as “HTML5” for quite a while. However, when the W3C HTML WG voted on adopting “Web Applications 1.0” the question about the title said “HTML 5”. Thus, the W3C HTML WG voted to adopt “HTML 5” as the title, but it wasn’t a vote for or against the space but about “HTML” and “5” in contrast to e.g. “Web Applications 1.0”. Anyway, as a result, the spec was retitled literally “HTML 5”.

This lead to inconsistency. Sometimes people kept writing “HTML5” and sometimes “HTML 5” (even on whatwg.org). This kind of inconsistency is bad for branding. The Super Friends pointed this issue out as the first thing they pointed out.

Now both the WHATWG Draft Standard and W3C Editor’s Draft spell it “HTML5”.

Posted in WHATWG | 29 Comments »