Look way up. Knowing the location of a resource on the web tells us nothing about what it is or how to make use of it. But if the resource is a software component, its interface needs to be known for it to be of any use. A component interface is a contract that makes available the component s services. It is a virtual set of knobs and buttons that allow you to use the component.
Components provide methods to users.
Methods either return data, alter the state of the component, or both. Methods may require the user to provide data in order to function. The IDL document tells the user how this information needs to be formatted in order to be understood by the dictionary. On receiving the information, the rhyming dictionary adds the word, finds every other word that rhymes, and then creates a new document containing this information. The user again needs to refer to the IDL in order to find out how the new document has been formatted in order to understand it.