Echelon i.LON 100 e2 Internet Server - Manual (Page 18)

i. LON 100 Internet Server Programmer’s Reference 3-1
3 Monitoring and Controlling Data Points with the
SOAP/XML Interface
Any i. LON 100 user can make use of the SOAP/XML interface, even those who do not plan
on using it to configure the applications of their i. LON 100. The SOAP interface includes
functions that read and write the values of the data points defined on the i. LON 100. These
functions do not affect the configuration of the i. LON 100 applications. You can use them to
create applications to monitor and control data in the control network attached to your
i. LON 100.
This chapter provides an overview of data points, and the functions you can use to read and
write their values. It also describes the syntax of each of these functions, and a programming
sample written in Microsoft Visual Basic .NET that may assist you when using these
functions.
NOTE: You can use the functions described in this chapter to read or write to the value of a
single data point at a time. This may create unnecessary network traffic if you use it to read
or write to a large number of data points over a short period of time. The Data Server SOAP
interface includes functions you can use to read or write to multiple data points at a time.
These functions are described in Chapter 5, Data Server. However, you should review
Chapter 4, i.LON 100 Applications and the SOAP/XML Interface, before attempting to use
any of the functions described in Chapter 5.
3.1 Overview of Data Points
The i.LON 100 uses the concept of a data point to map logical names to i. LON 100 system
variables, network variables defined on the i.LON 100 LonTalk interface, and explicitly
addressed network variables. Data points provide the i. LON 100 applications and Web
server a generic, open way to handle any piece of information from any type of network, such
as the current value of a network variable in an LNS managed network, or a network
variable on a self-installed node in a closed L ON W ORKS system.
This document describes how to use two kinds of data points:
• NVL data points for network variables that are local to the i. LON 100
• NVC data points for i. LON 100 system variables that maintain constant values
The i.LON 100 Data Server handles all the details of each data point that the various
applications require, such as how often the value of a data point should be polled, its default
value, its heartbeat, its current status, and its value.
At the Data Server layer, all data points have the same set of properties, regardless of which
network or device they are local to. This made possible by the drivers that exist for each
separate data point type, which handle all communication between the i. LON 100 Data
Server and the network each data point is local to. Each driver on the i. LON 100 must be
configured using a standard network management tool for that particular point type.
For example, you could use an LNS-based network management tool to configure the NVL
points on the
i. LON 100. The abstraction layer between the drivers and the Data Server
provides a mechanism for all i. LON 100 applications to use data points of all types and from
all devices in the same way.
One of the most important properties stored in the Data Server for each data point is the
property. The property contains the current value of the data