While quot;nowquot; is expressed in SQL as CURRENT-TIMESTAMP within queries, this value cannot bestored in the database … database-resident variables, such asquot;now,quot; quot;until-changed,quot; quot;acirc; ,quot; quot;@quot; and quot …;-.quot; Time variables are very desirable, but their usealso leads to a new type of database, consisting of tuples with variables …

The concept of an historical database is introduced as a tool formodelling the dynamic nature of some part of the real … semantics of the relational database model,intensional logic is presented as an analogous formalism for expressing … andunderstanding the temporal semantics involved in an historical database.The various components of the relational model, as extended …

unlimitedsecondary storage at affordable prices. Database applicationscan be expected to take advantage of this expanded storagecapacity … timeand the other stored data items.We present such a model, the Historical Database Model (HDBM),and define its semantics in … Richard Montague's higher-orderlambda calculus with intensions. The HDBM is defined as anextension of the relational database …

target applicationdomain is an historical database, we present the essential features of the Historical RelationalDatabase …;cent;Acirc;not;Acirc;? semantics into a database at the conceptual level. We thenpresent the essential features of QE-III, a formally defined English … database query languagewhose semantic and pragmatic theory, based on a Montague-type semantics, makes explicitreference to the …

Much recent research in the database community focuses on ways toexpand the modelling capabilities of database … data. In thispaper we examine how these enhanced modelling capabilities will increasethe functionality of the database …

. We introduce the notion of reference time - the timethat any operation is applied to the database state - and provide a …