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Other Voices: An HTML5 Primer


A lot of what people think is HTML5, is actually CSS3, which is itself a collection of sub-specifications. These are in various states of completion and browser implementation. For example, CSS Animations and CSS Transitions are sub-specs that provide rich dynamic 2D animations and effects for elements. CSS 3D and 2D Transformations provide animations for boxed content. The CSS3 spec family also includes standards for richer layout control, borders and backgrounds (the highly desired "rounded corners" ). It also includes more niche capabilities such as Ruby (not the language, Ruby with a small "r" means visual hints for meaning or pronunciation often used in ideogram based languages), aural style sheets and scrolling marquees.

Web Workers

Web Workers let an application spawn tasks for the browser to work on in the background without freezing the execution of the main application. There are a few types of workers that can be created with slightly different behavior. The intent of web workers is to give application developers the ability to specify what tasks within the application are parallelizeable (in the small), so that the browser can better schedule work for the rapidly increasing core count of today's (and tomorrow's) multi-core processors.

Web Storage and Web SQL

Web Storage is one of the more exciting parts of the HTML5 Family. Web Storage allows a page to store string data in a key-value pair database, specific to that domain. There are two varieties of Web Storage, the first is sessionStorage, that persists data only for a single session (think of it as a more functional cookie storage mechanism). The second is localStorage which allows a domain to store data locally across browser sessions (and system reboots). When you add localStorage to the cache manifest from the main HTML5 spec, you have the ability to run an offline application. The Web Storage spec is itself separate from the Web SQL Database spec which provides for a full SQL-addressable database that is accessible offline. Although varieties of this spec are in implementation by browser makers, the standardization process is blocking on the need for a second interoperable implementation that is not based on SQLite (which all the current versions are.)

Web Sockets

The Web Sockets protocol is in the first stage of the standards process and has also been submitted as an IETF draft because it is a networking protocol. It defines a non-http-based asynchronous client/server protocol that can be used in place of the current AJAX methods for asynchronous server communication. It uses an initial http: request to bootstrap the new protocol.

And all the others…

Geolocation is a simple spec that provides a built-in a geolocation object that scripts can query. It also provides methods for defining location cache freshness requirements. This is fairly non-controversial and already in new browsers. File API allows single and multiple file uploads from the user desktop. It's unclear exactly who will support this, but there doesn't seem to be much confusion about what it's supposed to do. Microdata is a mechanism to allow communities of interest to mark up content with semantic tags (for example, tags that identify an address or a resume.) It doesn't specify what these semantic tags are, just how they should be implemented. Device APIs that allow web browser access to devices such as cameras, BlueTooth etc, are still an early work in progress. These hope to define standardized access to native hardware and sensitive data from web applications. Highest priority are a camera API, and APIs for contact list, SMS history etc. on mobile devices. From Google I/O it appears that Google is going to ship something sooner rather than later that allows camera access from a Chrome web application, but there have been no further details on this.

HTML5 Summed Up

It's easy to get lost in the welter of standards enumerated above. But stepping back you should get the sense that the HTML5 Family authors are on a mission to make web applications as powerful as native applications when it comes to user interface richness, offline capability and hardware access. Since HTML5 family apps will be deployed on the web, they'll have the added benefits that the web has always brought, which are:

  • A universal client that works cross platform
  • Easy searchability and indexing (including deep linking)
  • The ability to trivially include third party services and mashups
  • Zero hassle deployment and updating (after all, it's just on the web)

We're excited by our initial HTML5-based development, and we eagerly await these new features as they are implemented and stabilized in the latest browsers.

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