At ASHRAE’s 2010 Winter Conference held recently in Orlando, the BACnet committee approved final publication of eight addenda to the ANSI/ASHRAE Standard 135, A Data Communication Protocol for Building Automation and Control Networks. The addenda are expected to be available by the end of February.
The addenda include a specification for a standard way of representing data in XML that will give BACnet new capabilities for communications between a wide range of applications. The Extensible Markup Language (XML) is a popular technology in the data processing and communications worlds, due to its capability to model complex data and its flexibility to be transformed and extended.
“With this new IT-friendly way of representing building data, BACnet will open up new ways to communicate. XML can be used for exchanging files between systems, communicating with the Smart Grid, and expanding enterprise integration with richer Web services,” said Dave Robin, chair of the BACnet committee.
The XML syntax is intended to be the core data representation for a variety of uses:
- New Web services that are capable of efficient exchange of complex structured data.
- An electronic version of a BACnet PICS document, consumable by workstations and other tools, to describe the capabilities of a device.
- An “as built” description of a deployed device, distributed either as a separate file or as a BACnet File object resident in the device itself.
- Descriptions of proprietary objects, properties, and data types, which may be simple for basic data sharing purposes, or extremely rich, providing complete descriptions of the meaning and usage of the data in multiple human languages.
- An export/import format for tools and workstations to publish their knowledge of a complete system of devices and networks.
- An XML version of an EPICS, including the complete test database and other test-oriented data.
In addition to the new “computer language” of XML, another addendum has added an important new capability for human languages as well. When the Unicode character set was created many years ago, it was constructed to be universal set of characters to support most of the world’s languages together in one stream. However, its original 2-byte encoding caused trouble with many existing systems that were designed to process only the 1-byte characters common in Western languages. The “UTF-8” encoding was created to solve this problem and quickly became a very popular method of conveying international text on the World Wide Web. BACnet has also embraced this standard and uses it in a way that fully takes advantage of its compatibility with the existing and ubiquitous ANSI/ASCII character set.
BACnet has also added support for more data types as well. A set of new “Value” objects rounds out BACnet’s ability to represent different data types in a uniform and standard way. Added to the original Analog, Binary and Multi State Value objects, are new Value objects for every primitive datatype that BACnet supports, including support for character strings and large numerics.