PIQUE(ID:5277/piq001)
for Pits QUEry language
data querying language for the PITS dbms at Stony Brook
(PITS for Pie-In-The-Sky)
"QUEL-like syntax, tuple variables are implicitly bound to windows, rather than explicitly bound to relations, thus removing range statements and join conditions."
Related languages
References:
Maier, David "The Theory of Relational Databases" Computer Science Press, Rockville, Md., 1983 view details
Maier, David; Rozenshtein, David and Warren, David S. "Windows on the world", Proceedings of the 1983 ACM SIGMOD international conference on Management of data, May 23-26, 1983, San Jose, California view details
Abstract: We discuss the philosophy, history and theory of window functions. Window functions (sometimes called connections) are a means to treat a relational database as a semantic whole, rather than as an arbitrary collection of relations. Simply stated, a window function maps a database state and a relation scheme to a relation over the scheme. Window functions are the basis for all existing universal scheme interfaces. We present an assumption inherent in universal scheme interfaces, the unique role assumption.Window functions have evolved along two paths, giving rise to computational definitions and weak instance definitions. We examine several examples of each type of window function, with special attention to the association-object window function of PIQUE. We then look at properties we feel a reasonable window function should satisfy, notably the containment condition and faithfulness. We also define implicit objects, which are relation schemes that a window function treats in a special manner, and which are useful for describing the behavior of window functions.
DOI
Extract: Current Work
We are now adding more semantic information than simply associations and objects to our data model, and considering ways of using the information to extend the PIQUE window function. Such extensions require connections to be made by means other than just natural joins. A simple extension is to aggregate attributes; for example,
"date" might be composed of "month," "day," and "year." A more complex extension is the inclusion of a role or "ISA" hierarchy on attributes.
Such a semantic structure is essential to recover information on relatabihty of attributes that is lost when attributes are renamed in order to satisfy URSA. We extend the set of object relations by making connections with equijoins on compatible attributes in the hierarchy. There are difficulties with this approach, as care must be taken that object relation formed with equijoins not clash with one formed with natural joins. These extensions to the model are leading us to believe that relational algebra may not be a sufficiently powerful system with which to compute window functions. Therefore, we are investigating logic programming languages as an alternative.
Maier, David; Ullman, Jeffrey D. "Maximal objects and the semantics of universal relation databases", ACM Transactions on Database Systems (TODS), v.8 n.1, p.1-14, March 1983 view details
Maier, David; Ullman, Jeffrey D.; Vardi, Moshe Y. "On the foundations of the universal relation model" ACM Transactions on Database Systems (TODS), v.9 n.2, p.283-308, June 1984 view details
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