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Self-Describing Data

Self-describing data is data that has been annotated by the producer, so all consumers can interpret and use the data properly. Every message and every message field consists of self-describing data. Table 4 presents the annotations that augment data so it is self-describing.

Table 4 Self-Describing Data 

Element	Description
Field Annotations
type	Producers must designate the type of every message field. Rendezvous software uses a set of wire-format datatype designations to characterize data by type and size. For example, the type TIBRVMSG_I32ARRAY denotes an array of 32-bit integers.
count (number of elements)	Producers must specify the length of all array data—that is, the number of elements in an array.
field name	Producers can label the fields of a message with names. Consumers use field names to select specific fields from messages.
field identifier	Producers can label the fields of a message with numeric identifiers. Consumers can use field identifiers to select specific fields from messages. All field identifiers in a message must be unique within that message.
Message Annotations
subject name	Producers must label every outbound message with a send subject name (also called the send subject name), which describes its content and destination set.
reply subject name	Producers can label an outbound message with a reply subject name, to which consumers can send reply messages.

See Also

Data

Subject Names

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