Browsing by Subject "Object oriented databases"

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    Incremental materialization of object-oriented views
    (Elsevier, 1999) Alhajj, R.; Elnagar, A.
    We present an approach to handle incremental materialization of object-oriented views. Queries that define views are implemented as methods that are invoked to compute corresponding views. To avoid computation from scratch each time a view is accessed, we introduce some deferred update algorithms that reflect for a view only related modifications introduced into the database while that view was inactive. A view is updated by considering modifications performed within all classes along the inheritance and class-composition subhierarchies rooted at every class used in deriving that view. To each class, we add a modification list to keep one modification tuple per view dependent on that class. Such a tuple acts as a reference point that marks the start of the next update to the corresponding view. © 1999 Elsevier Science B.V. All rights reserved.
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    Query model for object-oriented databases
    (IEEE, 1993-04) Alhajj, Reda; Arkun, M. Erol
    A query language should be a part of any database system. While the relational model has a well defined underlying query model, the object-oriented database systems have been criticized for not having such a query model. One of the most challenging steps in the development of a theory for object-oriented databases is the definition of an object algebra. A formal object-oriented query model is described here in terms of an object algebra, at least as powerful as the relational algebra, by extending the latter in a consistent manner. Both the structure and the behavior of objects are handled. An operand and the output from a query in the object algebra are defined to have a pair of sets, a set of objects and a set of message expressions where a message expression is a valid sequence of messages. Hence the closure property is maintained in a natural way. In addition, it is proved that the output from a query has the characteristics of a class; hence the inheritance (sub/superclass) relationship between the operand(s) and the output from a query is derived. This way, the result of a query can be persistently placed in its proper place in the lattice.
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    Reusability and schema evolution in object - oriented query models
    (ASME, New York, NY, United States, 1996) Polat, F.; Alhajj, R.
    In this paper, we have benefited from having an object algebra maintaining closure that makes it possible to have the output from a query persistent in the hierarchy. Based on this, it is possible to maximize reusability in object-oriented databases. Furthermore, we show how the object algebra is utilized to handle basic schema evolution functions without requiring any special set of built-in functions to serve the purpose. The invariants and the conflict resolving rules are specified. It is also shown how other schema functions are derivable from the basic ones.