1. A non-transitory computer readable medium including program code for providing a message-based interface for exchanging information about goods and activity confirmation inventory change items, the medium comprising: program code for receiving via a message-based interface derived from a common business object model, where the common business object model includes business objects having relationships that enable derivation of message-based interfaces and message packages, the message-based interface exposing at least one service as defined in a service registry and from a heterogeneous application executing in an environment of computer systems providing message-based services, a first message for querying about an overview of goods and activity confirmation inventory change items, the first message including a first message package hierarchically organized in memory, the first message package including: at a first hierarchical level in the first message package, a goods and activity confirmation inventory change item overview simple by elements query sync message entity; at the first hierarchical level in the first message package, a goods and activity confirmation inventory change item overview simple selection by elements package including, at a second hierarchical level in the first message package, a goods and activity confirmation inventory change item overview simple selection by elements entity, wherein the goods and activity confirmation inventory change item overview simple selection by elements entity includes, at a third hierarchical level in the first message package, at least one of the following: at least one selection by inventory location inventory type code, at least one selection by inventory location location universal unique identifier (UUID), at least one selection by inventory location location identifier (ID), and at least one selection by inventory location custodian party UUID; and at the first hierarchical level in the first message package, a processing conditions package including, at the second hierarchical level in the first message package, a processing conditions entity; processing the first message based on the hierarchical organization of the first message package, where processing the first message includes unpacking the first message package based on the first message package's structure and the first message package's derivation from the common business object model, wherein the particular structure of the first message package is used at least in part to identify the purpose of the first message; and program code for sending a second message to the heterogeneous application responsive to the first message, where the second message includes a second message package derived from the common business object model to provide consistent semantics with the first message package.