[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: xPath 2.0, XSLT 2.0 ... size increase over v1.0
From: "Murali Mani" <mani@C...> > > Regarding mathematical properties: in particular, closure properties. > > The operations being closed under regular tree languages might be > desirable property.. > > I have seen two kinds of operations under which regular tree languages are > not closed.. that is the result is not a regular tree language.. > > (a) Consider the schema: > S -> s (A, S, B) | s () > A -> a () > B -> b () > > if we write a query like // (a | b) -- the result is (a^n b^n) which is > not regular tree language.. The result is not a tree, it is a sequence (a()^n, b()^n). The result is not a property of the query but of the schema. The schema, a regular tree grammar, describes the derivation tree of the context-free language: s -> s-> a s b where s is non-terminal and a,b are terminals, which is the set of strings a^n, b^n, n >= 0. So it is not surprising that the query result sequence is the same set of strings. Bob > (b) Consider > S -> s (A*) > A -> a () > > consider the query > for $x in //a > return <b/> > for $x in //a > return <c/> > > the result is (b^n c^n) > > The question is has the new constructs in XPath made it not closed or > not.. It might have.. If someone has studied these aspects, then we can > know if XPath 2.0 is different from XPath 1.0 in these respects also.. > > cheers and regards - murali. > > > ----------------------------------------------------------------- > The xml-dev list is sponsored by XML.org <http://www.xml.org>, an > initiative of OASIS <http://www.oasis-open.org> > > The list archives are at http://lists.xml.org/archives/xml-dev/ > > To subscribe or unsubscribe from this list use the subscription > manager: <http://lists.xml.org/ob/adm.pl> > >
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