Subject: RE: [xsl] Can sets have order? From: "Michael Kay" <mhkay@xxxxxxxxxxxx> Date: Wed, 31 Jan 2001 16:14:01 -0000 |
> In fact, in databases, relations are *multisets*, allowing for > duplicates. I.e., tuples with the same values but different > internal row-ids are allowed. In Codd's relational model, relations are sets. In SQL, relations are multisets, because a relation can contain two tuples that are indistiguishable. In every real RDBMS that I know of, relations are sets, because two tuples in the same relation are always distinguishable by some kind of id, which means that the relation no longer contains duplicates. > For XPath/XSL I would say that it is somewhere between sets and > multisets since a result set can contain the same values several times Unlike the pure relational model, but like most relational implementations, nodes in XPath/XSLT have identity, so a node-set cannot contain "the same node" twice. It can contain two nodes that are equal, but not two that are identical. Mike Kay XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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