A pattern is a user-defined sequence of subpatterns. A subpattern consists of three items :
- a set designator
- a minimum number of occurrences of elements of that set
- a maximum number of occurrences of elements of that set
Or, a subpattern is a minimum and maximum number of occurrences of elements of a set. A variable can also be used as the subpattern's set. The sets or variables used by a pattern must therefore be defined before the pattern can be defined.
To define or modify a pattern :
- Select the Definitions | Patterns menu option.
- In the Patterns dialog, select the pattern name (tag) - if adding a new pattern, enter the new pattern tag.
- Press the Enter key or the Select button.
- A second dialog will appear with the user-defined pattern tag at the top :
In the second dialog, enter the subpatterns that constitute the pattern. Enter the minimum (Min) and maximum (Max) number of expected occurrences of each set / variable. The minimum can be zero. The maximum must be greater than or equal to the minimum.
In the above example pattern WS1-X (one or more whitespaces) is defined as 1-100 occurrences of members of the "ws" (whitespace) set. Pattern WS0-X, zero or more whitespaces, could be defined in a similar manner by changing the minimum from 1 to 0.
Data Splitter checks that Min is less than or equal to Max. If either is undefined the default is zero. If both Min and Max are unspecified, or zero, the entry for that Set will be ignored.
A pattern is said to be recognized if all of its subpatterns are recognized, sequentially, in the input stream.