3.1.1 Abstract Data Model
This section describes a conceptual model of possible data organization that an implementation maintains to participate in this protocol. The described organization is provided to facilitate the explanation of how the protocol behaves. This document does not mandate that implementations adhere to this model as long as their external behavior is consistent with that described in this document.
An abstract construct referred to as the advanced flow-control object (AFCO) is used in this section to describe the advanced flow-control extension (AFCE) to web services reliable messaging protocol (WSRM) on the reliable messaging destination (RMD).
The AFCO maintains the following data elements:
Buffer Remaining: A 32-bit integer value that indicates the number of messages the RMD can to receive. The value of Buffer Remaining is non-negative.
The following figure shows a hypothetical implementation of the AFCO and the events that control its state on a hypothetical implementation-specific RMD.

Figure 2: State diagram of the AFCO on the RMD