The message body contains data specific to the particular message.
Many messages share a common set of tags. For example, all of the order-related messages contain tags that identify the trader and trading account information. To help identify these shared components, TT FIX groups the shared tags into the following groups:
Component blocks can also differ based on the source of the message, whether a request from a FIX client or a response from TT FIX. For example, an instrument component block comprises FIX tags that fully define a product, including its identity, characteristics, and price data. When submitting a request, you need to include only enough tags in the instrument component block to identify uniquely the instrument. When TT FIX sends the response, it includes all of the tags - unlike the request which includes only enough tags to uniquely identify the instrument with the requested information.
Each FIX message can contain zero or more component blocks. The FIX Protocol uses the component blocks as a convenient way to group a set of FIX tags that might appear in multiple messages.
TT FIX supports the following component blocks in a message body: