Whether you realize it or not, every single tweet that is being sent out has a set of instructions or rules integrated into the back-end. The instructions are known as structured metadata that are part of an annotations.
Here’s another way of looking at it. When you send out a tweet, there is a unique ID number that is associated with the tweet that gets noted. Where the tweet came from is noted (i.e. the web, TweetDeck, Tweetie, Hootsuite, Seesmic, etc). The time it was created is noted. Even the longitude and the latitude of every tweet is noted if the user opts in for that feature. These tweet properties have a special character name within Twitter’s database that is being accessed by developers through the use of APIs.
The reason why knowing this is a big deal is because Twitter will soon be allowing developers to create their own Annotations and have them created on the fly when reporting tweets being sent out. Annotations are expected to be available this fall.
So what are the existing character names that developers can access through APIs and what do they do? Raffi Krikorian, a member of the API/Platform team at Twitter created a map of Twitter Status Objects and posted it on his Posterous account. Below is the document he created, hosted on Scribd.