1. A non-transitory computer readable medium including program code for providing a message-based interface for exchanging information about financial instrument impairment calculations, the program code executed by at least one processor associated with the medium, the program code causing the medium to perform operations including: 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 for calculations of an impairment amount and an unwinding amount for a financial instrument, including calculations for analyzing effects by different calculation parameters on risk provisions and accounting balances, the first message including a first message package hierarchically organized in memory based on and derived from the common business object model, the first message package including: at a first hierarchical level in the first message package, a financial instrument impairment calculation financial services calculate query message entity; and at the first hierarchical level in the first message package, a financial instrument impairment calculation package, wherein the financial instrument impairment calculation package includes, at a second hierarchical level in the first message package, a financial instrument impairment calculation entity and a parameters package, wherein the parameters package includes, at a third hierarchical level in the first message package, a parameters entity, wherein the parameters entity includes, at a fourth hierarchical level in the first message package, a set of books identifier, a date, a currency code, a financial instrument impairment exposure amount, an effective interest percent, a financial instrument write down amount, and an unwinding amount calculation requested indicator; 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 hierarchical organization of the first message package, the specific grouping and order of the hierarchcial elements in the first message package, and the first message package's derivation from the common business object model, wherein the particular hierarchical organization of the first message package and the specific grouping and order of the hierarchical elements in the first message package are used at least in part to identify the purpose of the first message; and 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, the second package hierarchically organized in memory based on and derived from the common business object model, the first message package including: at a first hierarchical level in the second message package, a financial instrument impairment calculation financial services calculate response message entity, and at the first hierarchical level in the second message package, a result package, the result package including, at a second hierarchical level in the second message package, a result entity, wherein the result entity includes, at a third hierarchical level in the second message package, a financial instrument impairment amount.