FIELD: information technologies.
SUBSTANCE: on an information server a query is configured to execute referencing, including an identifier of a referenced object, which a query receiver shall address to make an information source provide information when receiving such a query without referring to additional sources of information. This query is sent to a source of information. After reception of a query by an information source, the query is verified to determine whether information shall be provided by the source of information in response to this query without reference to additional sources of information. If it is determined that information shall be provided, information is provided.
EFFECT: function to extract information on presence from sources of information on presence by means of query for referencing execution.
