In this paper we attempt to construct a dynamic model of discourse management, a version of Mental Space Theory, modified to accommodate dialogic discourse by incorporating a memory management system. We posit a cognitive interface between linguistic expression and knowledge-base. This interface contains pointers or indices linked to addresses in the knowledge base, controlling access paths to the data in the base. Utterances in a dialogue exchange can be redefined as input-output operations via this interface: registering, searching, editing, etc. The main theses of our approach to discourse management are as follows: The operations coded in the various forms are to be defined as performing input-output operations on the database of the speaker and not that of the hearer's model in the speaker. It is argued that the hearer's model in the speaker is not only unnecessary but also harmful in the description of sentence forms. We divide the interface into two components, I-domain and D-domain. The former is linked to temporary memory, houses the assumptions and propositions newly introduced to the discourse yet to be incorporated into the database and can be accessed only indirectly by inferences, logical reasoning, hearsay, and data search. The latter is linked to the permanent memory, houses information already incorporated in the database and can be directly accessible by simple memory search like pointing to an index. New information passes through only via I-domain. We will demonstrate that our approach solves problems in mutual knowledge but also provides a powerful tool in the description of some of the most recalcitrant phenomena in natural language.