Shown is an improved method and system for implementing and building messages, such as HL7-based messages. Messages are constructed in a format-independent manner, in which a message is built by instantiating and linking Java classes. Metadata for the message specifications are used to construct the Java class libraries. Signature of the classes automatically cause the messages to be constructed with correct syntax, structure, and restrictions. Thus, the correctness of the constructed messages can be enforced at compile time. Moreover, a developer can construct a specification-specific message without having to know XML.