From: Michael Dyck <MichaelDyck@home.com>

Date: Sat, 03 Mar 2001 11:04:47 -0800

Message-ID: <3AA1404F.FBF7EFA6@home.com>

To: Peter Fankhauser <fankhaus@darmstadt.gmd.de>

CC: www-ql@w3.org

Date: Sat, 03 Mar 2001 11:04:47 -0800

Message-ID: <3AA1404F.FBF7EFA6@home.com>

To: Peter Fankhauser <fankhaus@darmstadt.gmd.de>

CC: www-ql@w3.org

Peter Fankhauser wrote: > > > So that got me wondering: if we have the Algebra, why do we need > > XQuery? > > The algebra and XQuery tackle the design space from different angles. Then I guess I'm thinking: maybe they shouldn't; or maybe they don't need to; or maybe there's a hyperplane through the design space that contains both angles :) > The main goal of the algebra working draft is to provide a > formal framework for specifying the dynamic and static > (type) semantics of the query language(s). > ... > Some of the additional goals of XQuery are > (see http://www.w3.org/TR/xquery/#section-Introduction) are > conciseness and understandibility, and human readability, even > for rather complex queries. Okay, so the main goal of the Algebra is straightforward formalizability, whereas XQuery has a goal of conciseness/readability. But I'm not convinced that these goals are mutually exclusive. In fact, it seems to me that (to a large extent) the Algebra and XQuery are *both* straightforwardly formalizable, and *both* concise & readable. So rather than develop them as separate languages (with the duplication of effort and the synchronization problems), wouldn't it be less work overall to "merge" them? Granted, there are cases where an XQuery operation is more concise & readable than its Algebra-equivalent. So in merging the two languages, one would face the question: "Do we add this operator to the language (sacrificing formal simplicity for readability), or leave it out (sacrificing readability for formal simplicity)?" But I think the Algebra has already dealt with this problem, by supplying "reducible expressions", which are defined by equivalence to expressions using lower-level operators from the "core" Algebra. (http://www.w3.org/TR/query-algebra/#sec_equivlaws) Thus, the Algebra achieves both readability (allowing you to use the nice operators) and formalizability (defining them by straightforward transformation, without increasing the set of core operators). -Michael DyckReceived on Saturday, 3 March 2001 14:08:44 GMT

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