There is a very large set of possible types that may be used to pass data between elements. Indeed, each new element that is defined may use a new data format (though unless at least one other element recognises that format, it will be most likely be useless since nothing will be able to link with it). In order for types to be useful, and for systems like autopluggers to work, it is neccessary that all elements agree on the type definitions, and which properties are required for each type. The &GStreamer; framework itself simply provides the ability to define types and parameters, but does not fix the meaning of types and parameters, and does not enforce standards on the creation of new types. This is a matter for a policy to decide, not technical systems to enforce. For now, the policy is simple: Do not create a new type if you could use one which already exists. If creating a new type, discuss it first with the other &GStreamer; developers, on at least one of: IRC, mailing lists, the &GStreamer; wiki. Try to ensure that the name for a new format is as unlikely to conflict with anything else created already, and is not a more generalised name than it should be. For example: "audio/compressed" would be too generalised a name to represent audio data compressed with an mp3 codec. Instead "audio/mp3" might be an appropriate name, or "audio/compressed" could exist and have a property indicating the type of compression used. Ensure that, when you do create a new type, you specify it clearly, and get it added to the list of known types so that other developers can use the type correctly when writing their elements.