Filter
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D
EFINING
F
ILTER
F
ORMULAS
7-7
Defining Filter Formulas
Filters may be defined for any log process. A filter sets the conditions that determine if data received by the Log
Manager will be saved into the log database. A filter is defined in the Filter field of the Log Information dialog box
(i.e., the dialog box opened when you create or edit a log process). If no filter is defined, then all the data received
is automatically logged.
Filter Formula
The filter formula uses Backus-Naur Form (BNF) as follows:
Filter::= SimpleExpression|
ComplexExpression|
<NULL> -- Nothing
SimpleExpression::=Variable rel_op Value
Variable::= "VALUE"|
--Value of the data
"DATE"| --Date the data arrives
"TIME"| --Time the data arrives
rel_op::= ">"| --Greater than
"<"| --Less than
">="| --Greater than or Equal to
"<="| --Less than or Equal to
"=="| --Equal
"!="| --Unequal
Value::=<INTEGER VALUE>| --Number represented in decimal digits, within the range
of a 4-byte unsigned integer.
<yymmdd>| --Eight digits representing a date.
<hhmmss> --Eight digits representing a time, in 24 hour format
ComplexExpression::=
"(" SimpleExpression ")" |
"(" ComplexExpression ")"|
ComplexExpression logic_op ComplexExpression
logic_op::="AND"|"OR"