By default, matching is case sensitive, but this is attribute may be configured using the Case Sensitive property in the extension’s Offnormal Algorithm and Fault Algorithm container slots.
In addition to the standard alarm properties, this extension supports these properties.
| Property | Value | Description |
|---|---|---|
| Expression | a value of: .* | This is the regexp value for any text. |
| Normal On Match | true, false |
Matches when the condition is in the specified limits. |
| Case Sensitive | true (default), false |
Matching defaults to case sensitive. |
By default, status remains ok until an edit is made to one or both properties above.
A hospital emergency room desires an alarm created whenever the moon enters a "full moon" phase. A StringWritable is created and given a StringChangeOfValueAlarmExt. In this extension:
Expression property, the following string is entered: Full Moon.Normal On Match is set to false, and Case Sensitive is left at true. In the station's WeatherService, a WeatherProvider has a MoonPosition component, which serves as the link source. A link is made from the MoonPosition's Phase property to the In16 slot of the StringWritable. On all phases of the moon but one, the StringWritable has a normal status. When MoonPosition's phase changes to Full Moon, the StringWritable alarms, and remains in alarm until the next moon phase (Waning Gibbous).
Expression string entry was simply: Moon, alarms would occur during both phases that include the string "Moon", namely "Full Moon" and
"New Moon".
The Expression property in both the Offnormal Algorithm and Fault Algorithm containers can process a simple string value, as in the example. The Expression property also processes a value using regular expression (regexp) syntax. This provides even more flexibility, such as with
use of "or" operators, among others.
Regexp syntax is beyond the scope of this document, but a few regexp examples are listed below:
(.*)(alarm)(.*)
(.*)(offnormal)¦(fault)(.*)
(1¦0){3}(1)(1¦0){3}(1)
^$
.*
This is the default Expression property value, that is in an extension copied from the alarm palette.