An embodiment of the invention comprises, providing an initial object graph to a database, the initial object graph being generated by applying a set of rules to resources included in a resource set at a specified time, or by revising a previous object graph at the previous time, the resource set at the specified time comprising an initial resource set. The method includes providing the initial object graph to a working memory, maintained in separation from the database; discovering a changed fact associated with one of the resources of the initial resource set; and upon discovering the changed fact, determining modifications required by the changed fact to the initial object graph. If modifications are required, the initial object graph is revised in the working memory to include such modifications. The same revisions are then made to the initial object graph in the system database.