Information is increasingly being created, exchanged and stored in
the eXtensible Markup Language (XML). In this paper, we propose
XTreeNet, an XML overlay network that efficiently supports XML content
access and distribution. XTreeNet unifies two major content
access models, namely, publish/subscribe model and query/response
model, based on the conceptual ideas of (i) content descriptors (CDs),
which describe the information consumers want to receive and producers
generate, and (ii) core-based CD distribution trees, which connect
producers and consumers interested in the same CD. We provide a
detailed
description of the XTreeNet protocols and then evaluate its performance
through extensive simulations. Our results suggest that XTreeNet
performs very well compared to existing systems proposed in the
literature.