All cells in the i2b2 hive must communicate using standard i2b2 XML messages. This message specifies certain properties that are common to all cells and are essential to the administration tasks associated with sending, receiving and processing messages.
All requests are sent using a <request> tag and responses are returned using a <response> tag. The same <message_header> tag is used for both. The <request_header> is used for requests but may be echoed back (optionally) in the response. The response must include a <response_header>.
The XSD specification of the i2b2 message permits individual cells to add cell-specific XML in the <message_body> tag. This cell-specific XML does not need to extend the i2b2 message schema since the i2b2 schema will allow insertion of tags from any namespace into the <message_body> tag.
The following image illustrates the basic top-level elements contained within the request and response messages.