Information ChannelsThe Buzz uses channels to describe the various pieces of information that it will display. Each channel tells The Buzz what data to gather from some Internet publisher and how to display it on the screen. In this way, each channel is like a TV channel that you can control. You can have a channel for international news headlines from the BBC, or just technology news, or from the New York Times instead of the BBC. You can subscribe to channels about your favorite baseball or hockey teams, or even pictures shared by other people running The Buzz.
What's in a ChannelEach channel serves two primary tasks: to describe the data that the publisher provides and how to present that data. The Buzz uses data gatherers to collect data from the publisher and visualizers to draw a representation of that data to the screen. Normally, you don't need to know anything about data gatherers or visualizers. You can just subscribe to the many channels that others have made to create your own personal channel lineup. But if you ever want to create your own channel, you'll need to know a little bit about gatherers.
Data GatherersData gatherers are responsible for collecting the data published by the content provider. The Buzz provides several types of gatherers for some common formats on the Internet. The first of these is the RSS or Atom Gatherer. If the publisher provides such a feed (usually identified by the feed icon), then you can just use the RSS or Atom Gatherer and enter the URL for the feed. The Buzz can also gather data:
Scrapers and FiltersMany of these gatherers use the concepts of scrapers and filters. For example, by default, the RSS gatherer will simply extract each article in the RSS feed you select. Usually that's what you want, but sometimes the RSS feed might not contain all of the information that you want the channel to show. For example, the BBC News publishes some fantastic RSS feeds of their news articles, but the feed does not include any of the images in the article. The scraper allows you to overcome this limitation. While the gatherer handles talking to the publisher, the scraper is what extracts the data for each article or web page. To get the images from the BBC news articles, you can change the scraper from one that extracts images from the RSS entry to one that extracts images from the web page found by following the link associated with the RSS entry.
While scrapers are responsible for extracting the relevant data from a web page or RSS feed, filters are responsible for discarding the other data. For example, you may wish to scrape all of the pictures on a web page, only to find that there are a bunch of small buttons and ads in addition to the images you care about. You can use a filter to skip any images based on their size or aspect ratio (how square or rectangular they are).
Last modified 14 May 2007 at 3:33 pm by eaganj