Mac OS X Leopard - ARCAism

Publication Subscription
Syndication is old technology that’s recently taken the Web by storm. It works by letting people
subscribe to web feeds—lightweight versions of their favorite web sites. These feeds can then be
aggregated using specialized applications, like NewsGator’s NetNewsWire, shown in Figure 24-11.
Apple and others have expanded on syndication and found novel uses for its technology. In
addition to Safari’s subscription feature, iTunes’s podcasts and iPhoto’s album sharing are implemented
using syndication.
Figure 24-11. NetNewsWire aggregates web content using syndication.
The bad news about syndication is that it encompasses several competing standards, such
as RSS and ATOM. There are also different versions within each standard, such as RSS 0.9,
RSS 1.0, and RSS 2.0. The good news is you don’t need to care, thanks to Leopard’s new Publication
Subscription framework, known simply as PubSub.
PubSub handles the details of monitoring, downloading, and updating feeds, and then notifying
interested applications when something changes. Because it’s a central database for all
syndication information, you can also ask PubSub for other people’s feeds. For example, if
you’re interested in what feeds your user has bookmarked in Safari, PubSub can tell you.
Feeds are typically implemented in XML, and Cocoa’s XML framework is quite good. Still,
PubSub lets you treat the XML as an implementation detail, giving you a single, object-oriented
interface to syndicated data regardless of the vagaries of format. Even if you don’t subscribe to a
feed, you can still use PubSub to parse it.
Spotlight
CHAPTER 24 MAC OS X DEVELOPMENT: THE APPLICATION FRAMEWORKS 433
If you’ve been using a Mac (or reading this book), you know about Spotlight: Apple’s integrated
search utility that reunites users with their data across the vast cluttered landscape of their hard
drives. To Mac developers, Spotlight presents a responsibility, as well as opportunity.