In Mule 3, users had to contend with learning both the Mule Expression Language (MEL) and DataWeave. MEL forced users to convert their payloads from binary data, such as XML or JSON documents, into Java objects, so they could write expressions which access that data, for example when routing to a specific location. In Mule 4, DataWeave is now the default expression language. Combined with the built-in streaming capabilities, this simplifies many common tasks: Events can be routed based on payload data, without first needing to convert them to Java objects. Binary data can easily be queried from an expression anywhere in your flow, for example, when logging. Larger than memory access to data happens transparently. DataWeave 2.0 also features many improvements: Language simplifications. Everything is now a function. DataWeave scripts can now be packaged and reused, via the new imports and modules features. Support for multi-line comments. Support for calling static Java methods directly from DataWeave.