In line with Nirenburg and Raskin's paradigm of ontological semantics, we adhere to the basic tenet that natural language semantics needs to be captured with respect to an explicitly formalized ontology. Many researchers in computational semantics, however, have neglected the ontological aspects of meaning representation, and even more have neglected aspects of meaning representation related to domain-independent ontologies, i.e. foundational or upper-level ontologies. In this paper we argue for a stronger integration of foundational ontologies in computational semantics. We show that relying on foundational ontologies can, on the one hand, lead to a clean separation between domain-specific and domain-independent components of natural language processing systems. On the other hand, we show how the interplay between foundational, domain ontologies and lexical semantics resources can elegantly account for disambiguation as well as allow to draw non-trivial inferences. Further, a temporal theory compliant with the foundational ontology is absolutely necessary for supporting temporal reasoning in natural language understanding.