We propose a formalism to model database-driven systems, called database manipulating systems (DMS). The actions of a (DMS) modify the current instance of a relational database by adding new elements into the database, deleting tuples from the relations and adding tuples to the relations. The elements which are modified by an action are chosen by (full) first-order queries. (DMS) is a highly expressive model and can be thought of as a succinct representation of an infinite state relational transition system, in line with similar models proposed in the literature. We propose monadic second order logic (MSO-FO) to reason about sequences of database instances appearing along a run. Unsurprisingly, the linear-time model checking problem of (DMS) against (MSO-FO) is undecidable. Towards decidability, we propose under-approximate model checking of (DMS), where the under-approximation parameter is the "bound on recency". In a k-recency-bounded run, only the most recent k elements in the current active domain may be modified by an action. More runs can be verified by increasing the bound on recency. Our main result shows that recency-bounded model checking of (DMS) against (MSO-FO) is decidable, by a reduction to the satisfiability problem of MSO over nested words.

We consider the verification problem for Dynamic Register Automata (DRA). DRA extend classical register automata by process creation. In this setting, each process is equipped with a finite set of registers in which the process IDs of other processes can be stored. A process can communicate with processes whose IDs are stored in its registers and can send them the content of its registers. The state reachability problem asks whether a DRA reaches a configuration where at least one process is in an error state. We first show that this problem is in general undecidable. This result holds even when we restrict the analysis to configurations where the maximal length of the simple paths in their underlying (un)directed communication graphs are bounded by some constant. Then we introduce the model of degenerative DRA which allows non-deterministic reset of the registers. We prove that for every given DRA, its corresponding degenerative one has the same set of reachable states. While the state reachability of a degenerative DRA remains undecidable, we show that the problem becomes decidable with nonprimitive recursive complexity when we restrict the analysis to strongly bounded configurations, i.e. configurations whose underlying undirected graphs have bounded simple paths. Finally, we consider the class of strongly safe DRA, where all the reachable configurations are assumed to be strongly bounded. We show that for strongly safe DRA, the state reachability problem becomes decidable.