A data store for a modular assembly system is described. The data store comprises a number of records, each record relating to a physical module in the modular assembly system and comprising a module ID, an owner ID for the module and one or more properties fields. The properties field(s) define any property of the module and different records may define different properties. At least one of the fields in each data record (e.g. the module ID or owner ID) is verified by an authentication service. A user assembles two or more modules into a coherent physical whole object to act as a user input device to an interactive software experience. The data store communicates with the interactive software experience and causes a change in behavior of the interactive software experience in response to a check of the data records for each of the modules in the object.