1. A method comprising: storing a representation of a service in a repository, the service comprising handling of a request for a context-dependent data set derived from one or more collections of data elements, the data set being requested for one of a plurality of data fields based on values for other ones of the plurality of data fields, the representation comprising a database table including a plurality of records comprising: a specification of a first data field of the plurality of data fields; a specification of an input data structure comprising the first data field and a plurality of second data fields of the plurality of data fields, the second data fields defining a context for the first data field; a specification of an output data structure for the context-dependent data set; and a name of a service provider; receiving a request for the service from a software entity, the request comprising an instance of the input data structure, the instance of the input data structure comprising values for the second data fields; comparing the request to the representation of the service; selectively sending the request to the service provider only if the request complies with at least one of the records; receiving one or more instances of the output data structure from the service provider based on the values for the second data fields; generating the context-dependent data set comprising a list of non-repeating values for the first data field, based on the one or more instances of the output data structure; and sending the context-dependent data set to the software entity.