Search engine

A method as claimed in any preceding claim, comprising outputting the user identifier data item for each returned search result to a client device.

A method as claimed in any preceding claim, wherein in the event the search results comprise multiple candidate user identifier data items, the method comprises receiving partial data relating to the user identifier data item from a client device and using the partial data to filter the candidate user identifier data items to form a filtered set of user identifier data items.

A method as claimed in any preceding claim, comprising storing the set of data items as a new data record within the first data store.

A method as claimed in any preceding claim, wherein the received set of data items comprises a plurality of identifier proxy data items.

A method as claimed in any preceding claim, comprising analysing the plurality of data items to determine the identifier proxy data category most frequently associated with a user identifier data item.

A method as claimed in any preceding claim, wherein the user interaction comprises a transaction at a point of sale system.

A method as claimed in any preceding claim, wherein the first data store comprises historic transaction data.

A method as claimed in any preceding claim, wherein the second data store comprises transaction data relating to a current transaction.

A method as claimed in any preceding claim, wherein the user identifier data item comprises an email address for the user.

A method as claimed in any preceding claim, wherein the identifier proxy data item comprises one or more selected from:

• a primary account number of a transaction card belonging to the user;
• a masked primary account number of a transaction card belonging to the user;
• a loyalty card number of a loyalty card belonging to the user.

A method as claimed in any preceding claim, wherein the computing device comprises a server.

A search engine module for identifying a user from a first data store, the first data store comprising a plurality of data records, each data record comprising an identifier proxy category for an identifier proxy data item and an associated user identifier category for a user identifier data item, the module comprising:

• an input arranged to receive a set of data items relating to a user interaction, the set of data items comprising an identifier proxy data item;
• a processor arranged to formulate an identifier search query comprising the received identifier proxy data item and send the identifier search query to the first data store containing the plurality of data records, the input being further arranged to receive search results from the first data store in the form of one or more data records in which the identifier proxy data item within each returned search result matches the identifier proxy data item in the search query;
• and an output arranged to output a user identifier data item from the returned search results.