= QCG-Notification Main Features = From the architecture perspective, QCG-Notification exposes a well-defined Web Service interface corresponding to the role of Notification Broker as well as it offers other standard interfaces for managing Subscriptions and Pull Points. It supports advanced two-layer notification filtering based on hierarchical topic namespaces and XPath queries on the content of messages. All funtions offered by QCG-Notification can be invoked using different transport protocols. Currently, our system on a server side supports the SOAP communication over HTTP, HTTPS, and XMPP. In turn, the client side (Publisher side) of the system is based on dynamically loaded plugins. Currently QCG-Notification offers here SOAP over HTTP, HTTPS and XMPP as well as SMTP (e-mail) protocol. Thanks to the XMPP based communication, all notification parties, namely Subscribers, Publishers, Notification Consumers and QCG-Notification itself, can be located behind firewalls with only well defined outgoing TCP/IP port open for the XMPP transport communication. [[Image(QCG-Notification-Architecture-v2.png,400px,center)]] The low-level architecture of QCG-Notification is based on highly efficient mechanisms and data structures. We compared the three notification systems that confirmed the good performance of our sollution. See [[benchmarks|Benchmarks]] for details.