An encoding module generates metadata descriptions for unique combinations of subset of fields of data structures that define for the receiver how to decode data in the corresponding subset of fields of that data structure included in messages; generates a unique metadata description identification for each different metadata description; includes metadata descriptions in the messages as well as the corresponding metadata description identifications when the receiver has not previously received those metadata descriptions. A decoding module stores metadata descriptions in a metadata description data structure as they are received, where each metadata description is associated with a metadata description identification, whereby the metadata description data structure is progressively populated with metadata for data structures as messages are received that include metadata descriptions; and decodes those messages received that do not include metadata descriptions based on the stored metadata descriptions that correspond with the metadata description identifications included in these messages.