A data warehouse (DW) is a large centralized database that stores data integrated from multiple, usually heterogeneous external
data sources (EDSs). DW content is processed by so called On-Line Analytical Processing applications, that analyze business trends, discover anomalies and hidden dependencies between data. These applications are part of decision support systems. EDSs constantly change their content and often change their structures. These changes have to be propagated into a DW, causing its evolution. The propagation of content changes is implemented by means of materialized views. Whereas the propagation of structural changes is mainly based on temporal extensions and schema evolution, that limits the application of these techniques. Our approach to handling the evolution of a DW is based on schema and data versioning. This mechanism is the core of, so called, a multiversion data warehouse. A multiversion DW is composed of the set of its versions. A single DWversion is in turn composed of a schema version and the set of data described by this schema version. Every DW version stores a DW state which is valid within a certain time period. In this paper we present: (1) a formal model of a multiversion data warehouse, (2) the set of operators with their formal semantics that support a DW evolution, (3) the impact analysis of the operators on DW data and user analytical queries. The presented formal model was a basis for implementing a multiversion DW prototype system.
The analysis of the Italian preposition su in spatial contexts (static, involving undirectional movement or dynamic) leads to the conclusion that su engenders support and contiguity schema interpretation in whatever context it appears. The term support implies terms such as surface and contiguity (contact). In both static and dynamic contexts the location of a trajector is visualized as contigously situated on the surface of the landmark. In both cases the landmark is an idealized plane whose boundaries are perceptively unimportant in a given configuration, even though in the real world they are clearly cut. The boundaries, which are not focalized, render possible the temporal uses of the unit su with the meaning of an approximate location in time.
The Polish equivalents of su phrases are the following: na+loc, na+acc, po+loc, około(koło)+gen. The structures na+loc, na+acc involve the support and contiguity schema. The construction około(koło) +gen can be analyzed with near – far schema and applies to the approximate location in space and time in Polish. The schematic meaning is conveyed not only by prepositional units but also by inflectional case governed by prepositions. Usually such a case is convergent with dynamic (accusative) or static (locative, genitive) predication.