Thursday, April 2nd, 2009
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.
The big news for the week of March 23rd is that SVG can once again be included directly in HTML 5 documents served as text/html:
I've made the following changes to HTML5:
- Uncommented out the XXXSVG bits, reintroducing the ability to have SVG content in text/html.
- Defined
<script> processing for SVG <script> in text/html by deferring to the SVG Tiny 1.2 spec and blocking synchronous document.write(). The alternative to this is to integrate the SVG script processing model with the (pretty complicated) HTML script processing model, which would require changes to SVG and might result in a dependency from SVG to HTML5. Anne would like to do this, but I'm not convinced it's wise, and it certainly would be more complex than what we have now. If we ever want to add async="" or defer="" to SVG scripts, then this would probably be a necessary part of that process, though.
- Added a paragraph suggesting: "To enable authors to use SVG tools that only accept SVG in its XML form, interactive HTML user agents are encouraged to provide a way to export any SVG fragment as a namespace-well-formed XML fragment."
- Added a paragraph defining the allowed content model for SVG
<title> elements in text/html documents.
r2904 (and, briefly, r2910) give all the details of this solution. There are still a number of differences between the text in HTML 5 and the proposal brought by the SVG working group. Some of these are addressed further down in the announcement:
- SVG-in-XML is case-preserving; SVG-in-HTML is not.
- SVG-in-XML requires quoted attribute values; SVG-in-HTML does not.
- When SVG-in-XML uses CDATA blocks, they show up as CDATA nodes in the DOM; when SVG-in-HTML uses CDATA blocks, they show up in the DOM as conventional text nodes. [Clarified based on Henri's feedback]
- The
<svg> element can not be the root element of a text/html document.
Doug Schepers, who has been the SVG working group's HTML 5 liason, does not like this solution:
To be honest, I think it's not a good use of the SVG WG's time to provide feedback when Ian already has his mind made up, even if I don't believe that he is citing real evidence to back up his decision. What I see is this: one set of implementers and authors (the SVG WG) and the majority of the author and user community (in public comments) asking for some sort of preservation of SVG as an XML format, even if it's looser and error-corrected in practice, and a few implementers (Jonas and Lachy, most notably) disagreeing, and Ian giving preference to the minority opinion. Maybe there is sound technical rationale for doing so, but I haven't been satisfied on that score.
Turning to technical matters, one of the features of web forms in HTML 5 is allowing the attributes for form submission on either the <form> element (as in HTML 4) or on the submit button (new in HTML 5). Originally, the attributes for submit buttons were named action, enctype, method, novalidate, and target, which exactly mirrored the attribute names that could be declared on the <form> element.
However, in January 2008, Hallvord R. M. Steen (Opera developer) noted that "INPUT action [attribute] breaks web applications frequently. Both GMail and Yahoo mail (the new Oddpost-based version) use input/button.action and were seriously broken by WF2's action attribute."
Following up in November 2008, Ian Hickson replied, "I notice that Opera still supports 'action' and doesn't seem to have problems in GMail; is this still a problem?" to which Hallvord replied, "GMail fixed it on their side a while ago. It is still a problem with Yahoo mail, breaking most buttons in their UI for a browser that supports 'action'. We work around this with a browser.js hack. ('Still a problem' means 'I tested this again a couple of weeks ago and things were still broken without this patch'.)"
Ian replied, "This is certainly problematic. It's unclear what we should do. It's hard to use another attribute name, since the whole point is reusing existing ones... can we trigger this based on quirks mode, maybe? Though I hate to add new quirks." Hallvord did not like that idea: "In my personal opinion, I don't see why re-using attribute names is considered so important if we can find an alternative that feels memorable and usable. How does this look? <input type="submit" formaction="http://www.example.com/">"
Finally, in March 2009, Ian replied:
That seems reasonable. I've changed "action", "method", "target", "enctype" and "novalidate" attributes on <input> and <button> to start with "form" instead: "formaction", "formmethod", "formtarget", "formenctype" and "formnovalidate".
And thus we have r2890: Rename attributes for form submission to avoid clashes with existing usage.
Other interesting changes this week:
- r2889 adds support for
select.add(e) and select.options.add(e) with no second argument.
- r2888 defines how to determine the character encoding of Web Worker scripts. Briefly, it says to look for a Byte Order Mark, then look at the Content-Type HTTP header, then fall back to UTF-8.
- r2898, r2899, r2901, r2914, and r2916 define a locking mechanism to allow thread-safe read/write access to
document.cookie and .localStorage. The lock is acquired during page fetching (which sets the cookie based on HTTP headers) and released once the cookie is set. It is also released automatically whenever something modal happens (such as window.alert()). (I first mentioned the discussion of this issue in episode 27. The problem is that Web Workers allows threaded client-side script execution, which means access to shared storage like document.cookie needs to be made explicitly thread-safe with some sort of locking mechanism.)
Tune in next week for another exciting episode of "This Week in HTML 5."
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Thursday, April 2nd, 2009
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. In this episode, I'd like to highlight some of the discussions that I've missed in previous episodes.
- Greg Millam writes, "I'm one of the main engineers responsible for captioning support on YouTube, and I've joined the Chrome team at Google to attempt to help drive video captions and subtitling forward." Henri Sivonen replies, "I agree it makes sense to start with something simple. The markupless flavor of SRT would be such a format. However, supporting the formatting tags in later flavors of SRT is a can of worms." [full thread: Captions, Subtitles, and the Video Element]
- Robert O'Rourke writes, "Are there any plans to bring list headers from HTML3 into HTML5?" Ian Hickson replies, "You can do this in HTML5, using <figure> and <legend>." The thread continues in a number of directions. Marcus Ernst writes, "Anyway I would consider it even more appropriate to allow the list inside a paragraph," to which Ian replies, "We had this in the spec originally, but we dropped it due to a variety of issues (it made life harder for editors, it didn't work in text/html even when it looked like it did, people got confused...)." [full thread: List Headers]
- Drew Wilson writes, "There's currently no way to set or get cookies from workers, which makes various types of cookie-based operations problematic." Jonas Sicking replies, "Allowing cookie to be set would unfortunately create a synchronous communication channel between the worker and the main window." The discussion continues, focusing on issues of multi-threaded updates to
document.cookie. Drew Wilson again: "Following up on this. I created two pages, one that tests cookies in a loop, and one that sets cookies in a loop, and ran them in separate windows in Firefox 3, IE7, and Chrome. Chrome and IE7 currently allow concurrent modification of document.cookies (i.e. the test loop throws up an alert). Firefox does not." [full thread: Accessing cookies from workers]
- There have been a number of overlapping discussions on whether and how to allow authors to embed RDFa in HTML 5 documents. See 1, 2, 3, and followups. Besides the technical arguments about how it would work, much of the discussion centers around the concept of distributed extensibility, which I've touched on before. For example, here is Chris Wilson (of the Microsoft IE development team): "We have had (in the past as well, imo, in the future) a requirement for decentralized extensibility - that is, that document/content authors can extend the set of elements with their own semantic or behavioral elements. I continue to think there is a requirement for that. (One might well ask why we didn't implement full XML in that case; I'll politely not answer from a historical context, but will point out that the draconian error handling and poor fallback story make delivering content in XML in the browser a poor solution in the ecosystem today.)"
- Steven Faulkner writes, "I have ... taken a stab at a RFC 2119 compatible definition for table summaries: http://esw.w3.org/topic/HTML/SummaryForTABLE/SummarySpecification." [full thread: Draft text for summary attribute definition, continued in March archives]
There has also been a vigorous debate about the license of the specification itself.
- Sam Ruby writes, "In my discussions with Ian and at Mozilla, I gathered that it was a shared understanding that by October that the license for the W3C license would be somehow open source friendly, and specifically that a Creative Commons Attribution license was something that was of common and general interest." The "open source friendly" clause is a reference to the fact that the spec does actually contain some code (in the form of WebIDL declarations), and vendors of open source browsers would like to include this code (or derive code from it) into their products.
- After much discussion, Philippe Le Hegaret (of the W3C) writes, "In response to requests from developers to make it easier to include portions of W3C specifications in software documentation, bug reports, code, and test cases, W3C have drafted a new Excerpt & Citation License. ... Uses like forking of a specification would remain prohibited to protect the due process and the consensus found in a chartered Working Group."
- Ian Hickson immediately replies, "Increasing license proliferation is a really bad idea here. I would be opposed to introducing yet another license. ... [The forking] use case is the main one that I'm concerned about, FWIW."
- Jonas Sicking explains his reasoning about allowing forking: "I think it would gain W3C a tremendous amount of trust if it were to allow [forking]. To many people, me included, having the gurentee that W3C can't go off 'into the weeds' means that I have don't have to worry about my time being wasted when I contribute. I think many people feel the same when they contribute to the forkable software I represent."
- Philippe notes that the W3C "isn't used to the concept of allowing a fork" of their specifications, which is one of the requirements of any "open source friendly" license.
- I believe Maciej Stachowiak (WebKit developer at Apple) best summarized the group's objections: "1) Preventing specification forks is not achievable through license terms; a sufficiently motivated party can create a new spec from scratch. 2) Preventing specification forks is probably not necessary; the one time it happened, the outcome was good and the effort merged back into a realigned W3C. 3) Due to 1 and 2, we should give more consideration to LGPL/GPL compatibility than prevention of forks via licensing terms."
- Ian Hickson agrees: "I do agree that the original use cases are (intentionally and explicitly) not all met by the proposal that was put forward, and I do think the original use cases were an accurate portrayal of the use cases that this working group has consensus on. Compatibility with open source (including GPL and LGPL projects), clear license terms (ideally reusing an existing license), and the ability to fork are all issues that working group members discussed and considered important previously."
[Further reading: Discussions with plh, Draft W3C Excerpt License]
Tune in next week for another exciting episode of "This Week in HTML 5."
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Thursday, April 2nd, 2009
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.
The big news for the week of March 16th is this announcement from Ian Hickson:
I've now split out the Server-sent Events and Storage APIs out of HTML5, and I've removed the text for Web Sockets, which was split out earlier. By popular demand I've also done some tweaks to the styling of these specs.
- HTML5
- http://dev.w3.org/html5/spec/
- Server-Sent Events
- http://dev.w3.org/html5/eventsource/
- Web Storage
- http://dev.w3.org/html5/webstorage/
- Web Workers
- http://dev.w3.org/html5/workers/
- Web Sockets
- http://dev.w3.org/html5/websockets/
http://tools.ietf.org/html/draft-hixie-thewebsocketprotocol
It is my understanding that the desire is to publish the Server-Sent Events, Web Storage, Web Workers, and Web Sockets specs through the Web Apps working group, so that is what I put into the "status of this document" sections.
I would like to be able to put more permissive licenses (ideally MIT) on these drafts, rather than the W3C license.
The following sections still haven't been split out:
- URLs
- I'll remove this section as soon as DanC's draft is published.
- Content-Type sniffing
- I'll remove this section once Adam's draft is on a standards track.
- Timeout API
- This section is lacking an active editor.
- Origin
- I'm unsure what will happen with this section.
In IRC, Ian explained that all of these documents are generated from one master file:
# [21:02] <hixie> the source document is run through a bunch of scripts to generate the output documents
# [21:03] <hixie> from that one file i now generate one whatwg spec, four w3c specs, and an rfc
In other news, r2876 (WARNING: VERY LARGE) adds user stylesheets to the HTML 5 specification itself. If you view it in a browser that support switching stylesheets (such as Firefox, under the View → Page Style submenu), you can choose between "Complete specification" (default), "Author documentation only," or "Highlight implementation requirements." The "Author documentation only" stylesheet hides all of the client parsing algorithms and focuses on the elements, attributes, and scripting features that web authors need to know about.
For example, the "author documentation" of the <img> element highlights the required attributes, how to create a new Image() dynamically, and the detailed requirements for providing alternate text, while completely hiding any mention of how image fetching fits into the client's task queue, the gory details of how clients resolve image URLs, or the security risks of allowing pages on the public internet to attempt to load images on the local network. On the flip side, "highlight implementation requirements" highlights these exact issues.
Critics who complained that the HTML 5 specification should be "just a markup language" will be able to have their cake and eat it too. Those who complained that HTML 5 was "too bloated" will have a little less to complain about now that several parts of it have been published as separate documents. On the other hand, critics who complained about these things as a cover for other agendas will have to continue complaining a little while longer.
Tune in next week for another exciting episode of "This Week in HTML 5."
Posted in Weekly Review | 2 Comments »