RE: Content constructors and sequences

.. From: "Michael Kay" <michael.h.kay@xxxxxxxxxxxx>
.. Subject: RE:  Content constructors and sequences
.. Date: Wed, 9 Jan 2002 14:43:48 -0000
..
.. Yes, it is defined in the data model to work in terms of copying. So
.. conceptually, you create a sequence of child nodes, then you add these nodes
.. to a new parent element or document, which is done by creating copies of the
.. child nodes. So in principle, mutability shouldn't be a problem if you
.. follow this model: any variables are left pointing to the child node as it
.. was before you made the copy, and the value of count($v/ancestor::*) doesn't
.. change.
..
.. So another way of expressing my worries is, that if you actually have to
.. make a physical copy, and give each node a new identity, then it's going to
.. be horribly expensive. Perhaps there's an implementation solution based on
.. reference counting - you only need to actually copy a node if there are
.. variables that reference it - but I'd like to be convinced.
..

Seems you could implement the copies as pointers to the original node, with
the pointers containing the (new) identity.

--jeff




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