Concept for handling requests for data

A query handler device for accessing data, the query handler device comprising:

• at least one interface configured to communicate with a requester device and with a plurality of data provider devices;
• and
• processing circuitry configured to:
• obtain a request for data from the requester device, wherein the request includes a reference to a classification result, with the data being requested being relevant for machine learning with respect to the classification result,
• wherein the data being requested is at least one of a) sensor data or an abstraction of sensor data of at least one of an object, person, event, scene, activity, and act being classified, b) data relevant with respect to machine-learning and c) data relevant for classification,
• determine an access policy for the requester device based on a negotiation with the requester device,
• impose rate limiting on requests from the requester device, wherein the rate limiting refers to a scope of the requests per requester device across an index of possible classifications to prevent index building by the requester device, wherein the processing circuitry is configured to discard requests that violate the rate limiting to prevent the requester device from discovering which of the plurality of data provider devices have data according to different classifications, and
• forward the request with information on the access policy to the plurality of data provider devices, to instruct the plurality of data provider devices to provide the data to the requester device according to the access policy,
• wherein the data provider devices are configured to provide the data to the requester device without involving the query handler device such that the query handler device does not know which data provider devices provide data in response to the request.