Optimistic synchronization is considered an effective means for supporting Parallel Discrete Event Simulations. It relies on a speculative approach, where concurrent processes execute simulation events regardless of their safety, and consistency is ensured via proper rollback mechanisms, upon the a-posteriori detection of causal inconsistencies along the events' execution path. Interactions with the outside world (e.g. generation of output streams) are a well-known problem for rollback-based systems, since the outside world may have no notion of rollback. In this context, approaches for allowing the simulation modeler to generate consistent output rely on either the usage of ad-hoc APIs (which must be provided by the underlying simulation kernel) or temporary suspension of processing activities in order to wait for the final outcome (commit/rollback) associated with a speculatively-produced output.

A rational territorial management requires that all the amount of geographical data (maps, aerophotos, satellite images but also statistics, etc ...) be unified and made accessible to the decisional entities, which can use them as means for an adequate planning of the actions to undertake. Therefore the concept of data base (or DB) and the relative techniques offer the suitable means, as they give to the user a clear view of the data, an access and computational language oriented to the user, and the capability to support in a simple way the process (often heuristic) of solution of the management problems.The extended relational model [1] is adequate for this kind of problems for its simplicity, semantic completeness, and descriptive power. The access language to the DB represents an extension of AQL [2] that, besides supporting the DB management operations and the possibilities of interactive computation of AQL, offers the integration with the geographical operations and data geographical type. The proposal is illustrated by means of a series of examples of inquiry against a geographical DB.