A method in which an array identifier for a chemical array with probes at multiple feature locations is retrieved from a memory or read. The array identifier, a request for a test which requires an instruction on reading or processing the signal data read from the array, and payment information, are all forwarded to a remote location. A method is also provided which includes retrieving an instruction on reading or processing signal data read from a chemical array. This is retrieved from a memory using a test request and which memory carries one or more instructions for the array each retrievable with a different test request. Apparatus and computer program products are further provided.