Since UMDL cannot know at design-time what services will be available in the future or what the best negotiation mechanisms are for any given situation, its languages and protocols have been designed for flexibility and extensibility. In the case of negotiation mechanisms, UMDL uses a generalized auction specification to allow goods and services to be offered under a wide variety of terms .
While generalized auctions are not the only possible kinds of negotiation mechanisms, they offer many advantages. They provide a structured, yet flexible market infrastructure promoting automated negotiation due to the following characteristics:
Auction specifications consist of parameters which can be tuned to reflect the type of good being sold, timing requirements or mechanism properties desired. For example, a query planning service might be sold differently depending on how it is bundled (e.g., per-query, subscription), characteristics (topic, audience, timeliness), terms (redistribute, read-only) or to whom it is sold (individual, library, group). Different kinds of auctions will have advantages and disadvantages for different types of information goods and services.
Although evaluating tradeoffs between desirable properties of different auction types is important, the role of UMDL is not to require that a particular auction be used in a given circumstance, but rather to provide an open framework whereby the use of these market facilitator agents is supported. To automate the creation and management of auctions as much as possible, we use a system agent called the Auction Manager Agent.