In order for the collaborative filtering system to work with multiple vote sources, there must be a naming convention to describe and identify each vote source. Uniform Resource Locators (URLs) [2] provide such a mechanism so vote sources are referred to by their URL. URLs are especially convenient for vote sources as they contain both the address of the information and an access method. For example, a vote file with a local name of /usr/maltz/votes available by anonymous ftp from intrepid.xerox.com would have the URL ftp://intrepid.xerox.com/usr/maltz/votes. A vote server that listened for TCP connections at port 3636 of host news.xerox.com would be known as telnet://news.xerox.com:3636.
While sites are assumed to have a local vote server whose URL is well known at that site, some method must exist for informing users of the URL for a vote file. Any of several approaches could be used for informing other users where a person's vote file lives. We think of the location of a person's vote file as just another piece of localizing information similar to a telephone number.
The simplest mechanism for finding a person's vote file would be to ask them personally. This mechanism is identical to the way phone numbers and email addresses are frequently exchanged. A more complicated mechanism would be for users to include the URL for their vote file as an extra header line in their posts to Net News - many people already distribute their phone numbers and addresses in this fashion. News reader programs could take advantage of the extra header line by extracting the URL from articles the user liked. These URLs might then be added to the list of sources the user uses to filter Net News. Another option might be the creation of new newsgroups where users exchange URLs and perhaps discuss which vote files and URLs are the best for filtering various newsgroups.