ion principle) while OSI RM The OSI upper-layer architecture is described by the OSI RM. ACSE ("association control ser- vice element") and ROSE ("remote operation service element") are generic parts of this archi- tecture. A third generic part is called RTSE ("reliable transfer service element"). RTSE seems to be a function that compensates for the lack of transparency in the OSI application layer, as regards the OSI presentation and session layers. Since we believe that this is a reason as good as any for abandoning these layers completely, we can disregard RTSE in this discussion. 6.2 OSI Upper-Layer Architecture defines a generic layer model only for its application layer, a number of architec- tural principles differ. In summary: The actor-agent separation principle does not exist in OSI. The identification of something similar to the abstract protocol in AMLn is defined only for the OSI application layer (layer 7), which (in OSI) is a software layer by definition. Encoding is dealt with in different ways. In AMLn it is a task that is performed by agent layers within every (OSI) layer. In OSI it is a task performed by a sepa- rate OSI layer (the presentation layer, layer 6) on behalf of only one specific layer: the application layer. Dialogue handling is performed in the OSI session layer (layer 5) and in ROSE (layer 7). In AMLn, the corresponding function is regarded as a part of the layer state machine (LSM) of a control layer since dialogue handling is assumed to be more or less unique for a specific application. Allocating LSM dialogue han- dling in the layer protocol machine (LPM), as is done in ROSE, is avoided in AMLn, to make LPMs more generally applicable. In the AMLn sense, the OSI application layer is a control layer. There is no sim- ple way to map between an AMLn control layer and the OSI RM upper layer archi- tecture, however. An intuitive comparison is made in Fig. 6.1. OSI RM A layer Common agent AP-instance element Mapping invokes AP-instance on messages Association handling Encoding T-ROa P