In a computerized system, a sending computer system and recipient computer system exchange an interchange format message in a resource-efficient manner. For example, a transformation writer at the sending computer system selects and transforms only one or few of a plurality of units of the message at the time. The transformed message units are then streamed to the recipient computer system in accordance with a relevant transformation standard, such as the canonicalization standard in the case of XML messages. A transformation reader at the recipient computer system transforms the messages using a buffer big enough for received message units, and passes the transformed units to a file. Thus, the transformation writer acts as a stream writer to pass a message, and the transformation reader acts as a stream reader at the recipient computer system.