Service API Patterns, Protocols, Coupling Types, Metrics > Service API Design Patterns > Messaging Metadata
How can service APIs be designed to process activity-specific data at runtime?
Since Web-based messaging does not rely on persistent connections between the service and consumer, it can be difficult to manage state and context data related to the current service activity.
The Messaging Metadata pattern can be applied to supplement messages with activity-specific metadata that can be interpreted and processed by conversing participants at runtime. The application of the Messaging Metadata pattern requires a messaging framework that supports the processing of messages with headers or properties.
With the Messaging Metadata pattern, meaningful contextual metadata is conveyed in the message header that accompanies the message payload.
The HTTP protocol provides for both standardized and proprietary metadata to be conveyed in the HTTP header. The metadata is represented as key value pairs. For example, “Accept: text/plain” indicates that the service consumer desires the format of the response to be provided in plain text format. HTTP headers are utilized by REST services.