Browsing by Author "Tin, E."
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Item Open Access A comparison of historical relational query languages(ASME, 1994-07) Tansel, Abdullah Uz; Tin, E.We introduce a historical relational data model in which N1NF relations are used and 1-level of nesting is allowed. Attributes can either be atomic or temporal atom. An atomic attribute represents a time invariant attribute. A temporal atom consists of two components, a value and a temporal set, which is a set of times denoting the validity period of the value. We define a relational tuple calculus for this model. We follow a comparative approach towards completeness of historical query languages.Item Open Access The expressive power of temporal relational query languages(IEEE, 1997) Tansel, A. U.; Tin, E.We consider the representation of temporal data based on tuple and attribute timestamping. We identify the requirements in modeling temporal data and elaborate on their implications in the expressive power of temporal query languages. We introduce a temporal relational data model where N1NF relations and attribute timestamping are used and one level of nesting is allowed. For this model, a nested relational tuple calculus (NTC) is defined. We follow a comparative approach in evaluating the expressive power of temporal query languages, using NTC as a metric and comparing it with the existing temporal query languages. We prove that NTC subsumes the expressive power of these query languages. We also demonstrate how various temporal relational models can be obtained from our temporal relations by NTC and give equivalent NTC expressions for their languages. Furthermore, we show the equivalence of intervals and temporal elements (sets) as timestamps in our model. © 1997 IEEE.Item Open Access Towards situation-oriented programming languages(ACM, 1995) Tin, E.; Akman, V.; Ersan, M.Recently, there have been some attempts towards developing programming languages based on situation theory. These languages employ situation-theoretic constructs with varying degrees of divergence from the ontology of the theory. In this paper, we review three of these programming languages.