Abstract
Data with plural sources are handled in an extended relational model under a modal logic approach. A source of information corresponds to a possible world and relationships between sources are expressed by an accessibility relation. An attribute value in a database relation is the triplet that consists of a set of possible worlds, an accessibility relation and a set of value assignment functions. A tuple in a relation consists of a tuple value and a membership attribute value to which the tuple value belongs to the relation. The degree, not always equal to 1 or 0, comes from different values being obtained from plural sources. Furthermore, the degree is expressed by two approximate values; namely, one is a degree in the lower limit that means necessity; the other is a degree in the upper limit that means possibility. This comes from sources having some relationships with others. Simple queries containing elementary formulas and logical operators are shown in the extended relational model.
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Nakata, M., Murai, T., Resconi, G. (2001). Handling Data with Plural Sources in Databases. In: Ziarko, W., Yao, Y. (eds) Rough Sets and Current Trends in Computing. RSCTC 2000. Lecture Notes in Computer Science(), vol 2005. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-45554-X_50
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DOI: https://doi.org/10.1007/3-540-45554-X_50
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