Abstract: A method at a controller (112) of a database network (110) is provided. The controller (112) receives (S100) a request for a first set of data entries (200a). The request comprises a public identifier and an identifier of a first database (111a) of the plurality of databases (111) from which the first set of data entries (200a) is to be retrieved, each data entry (210) in the first set of data entries (200a) comprising a respective raw value for each of a plurality of attributes (220). The controller (112) retrieves the first set of data entries (200a) and uses the public identifier to transform (S120) the raw values of at least a first attribute (220a) of the plurality of attributes (220) into respective synthetic values. The controller (112) generates (S130) and outputs (S140) a first dataset (300a) comprising data entries having the synthetic values for the first attribute (220a) and the raw values for at least one of the attributes (220).

Abstract: A method of determining an indication of an intersection between a first dataset and a second dataset, the first and second datasets each holding entries in association with at least one key, the method comprising: generating for the at least one key in the first dataset location information in a first binary structure by applying a deterministic function to the entries associated with the key; transmitting the first binary structure to a comparison stage; generating for the at least one key in the second dataset, location information in a second binary structure by applying the same deterministic function to the entries associated with the key; and comparing, at the comparison stage, the location information in the first and second binary structures to determine the indication of the intersection between the first dataset and second dataset.

Abstract: A method of joining a first dataset configured to store a set of data entries each identified by a respective key of a first type and a second dataset configured to store a second set of data entries identified by a respective key of a second type, the method comprising: selecting an intermediate mapping entity from a set of possible intermediate mapping entities, each mapping entity storing association between keys of the first type and keys of the second type; providing the selected intermediate mapping entity for use in joining the first data set with the second data set; wherein the step of selecting the intermediate mapping entity is based on the intersection weight between the first and second data sets via each of the intermediate mapping entities, wherein the intersection weight is the proportion of overlapping data entries between the first and second datasets.

Abstract: A method of accessing a dataset to fulfil a query over an intended audience is provided. A user interface comprises input means for a user to select an intended audience dataset from a plurality of datasets which the user has permission to access. The user interface is configured to receive from the user a query defining an intended operation to be performed on entries of the intended audience dataset to generate the target audience. The query is received from the user and a supporting candidate dataset is selected. It is determined whether the selected supporting candidate dataset comprises entries which enhance the entries of the audience dataset for performing the intended operation. If so, the candidate dataset and the audience dataset are selected to contribute to performance of the operation. If not, a next candidate dataset is selected, and the determining step is repeated.

Abstract: Methods and devices for controlling access to sensitive data stored in a computer system are provided. For at least some data entries in a dataset, each identified by a respective key, an indicator of which zero or more conditions of a plurality of queries are satisfied by that data entry is generated. The keys are grouped into cohorts based on the indicators, at least some of the cohorts comprising keys identifying data entries satisfying the same zero of more conditions. A first output is transmitted to the first computing device comprising an identifier of a first cohort and an indication of a condition which is satisfied by data entries identified by keys in the first cohort. A second output is transmitted to a second computing device comprising an identifier of the first cohort and a set of keys corresponding to the data entries in the first cohort.

Abstract: A method of determining a further dataset to be joined with a source dataset having a plurality of data entries each identified by a respective key. An identifier of the source dataset is received, and an intersection weight between the source dataset and each of a plurality of possible further datasets is determined based on the number of common keys between the source dataset and each respective possible further dataset. An output is then generated based on the intersection weights for use in selecting one of the plurality of possible further datasets to be joined with the source dataset.

Abstract: A method of accessing a dataset to fulfill a query over an intended audience is provided. A user interface comprises input means for a user to select an intended audience dataset from a plurality of datasets which the user has permission to access. The user interface is configured to receive from the user a query defining an intended operation to be performed on entries of the intended audience dataset to generate the target audience. The query is received from the user and a supporting candidate dataset is selected. It is determined whether the selected supporting candidate dataset comprises entries which enhance the entries of the audience dataset for performing the intended operation. If so, the candidate dataset and the audience dataset are selected to contribute to performance of the operation. If not, a next candidate dataset is selected, and the determining step is repeated.

Abstract: A method of accessing multiple independent databases with a single query having multiple expressions involves deriving from a single query at least one filtering query, searching a first one of the multiple independent databases using the at least one filtering query, applying identifiers only of the filtering set of target entries and the target query to a second one of the multiple independent databases and generating a set of result entries from the second database which thereby satisfy the filtering expression and the target expression.

Abstract: Systems and methods of determining, from an identity database, raw identifiers of entities satisfying a set of attributes. The identity database does not hold the set of attributes in association with any identifiers in the identity database. An interrogation data structure is provided which represents encoded identifiers of entities satisfying the at least one attribute. The interrogation data structure is applied to encoded identifiers held in the identity database in association with respective raw identifiers to determine any raw identifiers which correspond to the encoded identifiers in the interrogation data structure.