BAS communication standards - Intelligent Buildings and Building Automation - page 91

UDDI. These technologies are designed on the basis of existing web techno-
logies. Web Services are self-contained, self-describing, modular applications
that can be published, located and invoked across the Web. The core techno-
logies of Web Services are as follows:

1 XML: XML is developed first, and a Web Service is developed on the
basis of XML. All Web Service definitions and message are in the form
of XML.
2 Universal Description, Discovery and Integration (UDDI): UDDI pro-
vides the protocol to register and find a Web Service in a public UDDI
directory.
3 Web Service Definition Language (WSDL): WSDL is an XML Document
Type Definition (DTD) that defines the standard format of describing a
Web Service. Documenting a Web Service in WSDL provides plenty of
scope for future automatic client site Web Service stub generation or using
graphical user interface (GUI) applications to configure or plug in a Web
Service.
4 Simple Object Access Protocol (SOAP): SOAP is also an XML DTD that
defines how a message is sent over the line. As long as you send a service
request in SOAP, no matter how the Web Service is constructed, it will
serve you. SOAP offers vendor, platform and language independence.
With SOAP, developers can easily bridge applications written with COM,
CORBA or Enterprise JavaBeans.

Web Services adopts common Internet protocols (e.g. HTTP, HTTPS and
SMTP) as its basic communication framework. These protocols' ports usually
have a firewall, so Web Services are Internet-friendly. Using the Web Service
technology, BAS systems from different vendors, even on different platforms,
can be integrated easily, as illustrated in Figure 5.9.
As shown in Figure 5.9, the portal application can access different BAS

BAS 1 BAS 2

Integration
Application
Portal

Web Services Web Services

BAS 3 Weather Report

Figure 5.9 BAS systems integration using Web Services.