There are many different Message Exchange Patterns you can use in messaging. This concept is also demonstrated in WSDL and JBI’s MEPs.
From there Enterprise Integration Patterns the common examples are
Event Message (or one way)
In Camel we have an
org.apache.camel.ExchangePattern enumeration which can be configured on the exchangePattern property on the Message Exchange indicating if a message exchange is a one way Event Message (InOnly) or a Request Reply message exchange (InOut).
For example to override the default pattern on a JMS endpoint you could use this URI