In sparsely populated mobile ad-hoc networks (MANETs) communication has to cope with mobility and in particular interruptions of connections. The lack of continuous network connectivity is addressed by Delay Tolerant Network (DTN) protocols. DTNs are characterized by varying delays and the fact that a successful delivery of data is not guaranteed. However, today no DTN protocol that functions autonomously and transparently for the application level is available in the related literature.This paper introduces a new approach for store-carry-forward communication in DTNs. In contrast to existing protocols such as the Bundle Protocol, here store-carry-forward communication is supported transparently without the need for application changes. In addition, the decision on whether or not to use store-carry-forward is no longer delegated to user applications. Instead, the decision is taken autonomously by MANET nodes based on the data to be send. The approach requires only local changes on the nodes that are part of the store-carry-forward communication path. Furthermore, it avoids interfering with traditional MANET routing by separating wireless routing from store-carry-forward (DTN) routing. Evaluations using epidemic, history-based and oracle-based DTN routing techniques illustrate successful operation of the introduced approach.

In this paper we provide a categorical interpretation of the first-order Hoare logic of a small programming language by giving a weakest precondition semantics for the language. To this end, we extend the well-known notion of a (first-order) hyperdoctrine to include partial maps. The most important new aspect of the resulting partial (first-order) hyperdoctrine is a different notion of morphism between the fibres. We also use this partial hyperdoctrine to give a model for Beeson's Partial Function Logic such that (a version of) his axiomatization is complete with respect to this model. This shows the usefulness of the notion, independent of its intended use as a model for Hoare logic.

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