1. A computer implemented method for enabling invocation of an external service at a service provider server from a database in a database computer system, comprising: accessing from over a network a published description of the external service published by the service provider external to the database, wherein the published description includes a definition defining operations performed by the external service in a service description language, wherein the database manages data and includes a database engine to perform queries; parsing the accessed published description to determine one of the operations contained in the published description; deriving a user defined function name for one of the determined operations from the accessed published description of the external service; generating a conversion between a database language statement and the service description language for the determined operation; generating database language statements defining the user defined function executable by the database to invoke the external service, wherein the user defined function resides on the database; invoking, by the database, the user defined function by executing the database language statements including the user defined function within the database to invoke the external service and perform a query with respect to the external service, wherein the user defined function invokes the external service by accepting as input parameters a network address of the external service, a name of the external service, and a name of an operation to be performed; and receiving, at the database, data from the external service in response to invoking and interacting with the external service, wherein the user defined function returns the result of the invocation.