7. An apparatus for generating a recommendation, the apparatus comprising: a processor; and a memory to store computer program instructions, the computer program instructions when executed on the processor cause the processor to perform operations comprising: receiving a user-defined recommendation request issued by a user as a user query; receiving a user-defined declarative community definition; selecting a sampling group belonging to a community defined by the declarative community definition; for each particular member in the sampling group, retrieving, from a recommendation database, a particular rating data of each particular member based on the user-defined recommendation request; for each particular rating data, generating a particular perturbed rating data, such that there is a predetermined probability that the particular perturbed rating data is different from a respective particular rating data; aggregating all the particular perturbed rating data into a plurality of perturbed rating data; and generating the recommendation based on the plurality of perturbed rating data.
7. An apparatus for generating a recommendation, the apparatus comprising: a processor; and a memory to store computer program instructions, the computer program instructions when executed on the processor cause the processor to perform operations comprising: receiving a user-defined recommendation request issued by a user as a user query; receiving a user-defined declarative community definition; selecting a sampling group belonging to a community defined by the declarative community definition; for each particular member in the sampling group, retrieving, from a recommendation database, a particular rating data of each particular member based on the user-defined recommendation request; for each particular rating data, generating a particular perturbed rating data, such that there is a predetermined probability that the particular perturbed rating data is different from a respective particular rating data; aggregating all the particular perturbed rating data into a plurality of perturbed rating data; and generating the recommendation based on the plurality of perturbed rating data. 10. The apparatus of claim 7 , the operations further comprising: receiving a user-defined recommendation algorithm; and generating the recommendation based on the user-defined recommendation algorithm.