The New Language Of Embedded Devices

June 18, 2001

Embedded network appliances usher in a new level of compatibility through the use of standards-based protocols and data formats. At the center is XML, the Extended Markup Language. It's the basis for protocols, such as the Simple Object Access Protocol (SOAP), that in turn are used with the Universal Plug and Play (UPNP) device discovery protocol. It's also the basis for XHTML, the heir apparent to HTML.

Current Internet appliances typically have a Web server that presents a configuration and status interface using HTML pages. A Web browser is used to view the pages and configure the device. This works well when a user is configuring or using the device. But the same interface is very difficult to use when another device is trying to perform this configuration because parser HTML is a rather tedious task at best. XML documents have a much simpler and consistent structure compared to HTML.

XML documents, with the exception of XHTML, try to keep presentation information separate from content. HTML normally mixes both in one document. XHTML includes some formatting in the document.

The SOAP protocol uses XML documents. SOAP is used to communicate between devices. It isn't as efficient as the Simple Network Management Protocol (SNMP), but it's more extensible. SOAP also is used as the basis for a variety of control and data-exchange protocols for which SNMP is unsuitable.

More information on XML, XHTML, SOAP, and related standards can be found at www.w3c.org.

HTML—Hypertext Markup LanguageAdvantages

Works with almost any browser
Well-documented
Extensive HTML tool support

Disadvantages

Combines content and formatting
Browser-dependent presentation
Difficult to parse

XML—Extended Markup LanguageAdvantages

User-definable tags and attributes
Supports arbitrary data structures
Separates data from formatting
Sophisticated style-sheet support

Disadvantages

Requires XML parser
Performance limited by hardware

SOAP—Simple Object Access ProtocolAdvantages

Simple transaction protocol
Based on XML and HTTP
Extensible

Disadvantages

Requires XML support
Limited embedded implementations at this time

About the Author

William G. Wong | Senior Content Director - Electronic Design and Microwaves & RF

I am Editor of Electronic Design focusing on embedded, software, and systems. As Senior Content Director, I also manage Microwaves & RF and I work with a great team of editors to provide engineers, programmers, developers and technical managers with interesting and useful articles and videos on a regular basis. Check out our free newsletters to see the latest content.

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I earned a Bachelor of Electrical Engineering at the Georgia Institute of Technology and a Masters in Computer Science from Rutgers University. I still do a bit of programming using everything from C and C++ to Rust and Ada/SPARK. I do a bit of PHP programming for Drupal websites. I have posted a few Drupal modules.

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