Such string pattern is a regular expression that allows or prohibits parsing of a string.
Example 28.1. String Format
If an input file contains a string field and Format property is \\w{4} for this field,
only the string whose length is 4 will be parsed.
Thus, when a Format property is specified for a string,
Data policy may cause fail of the graph (if Data policy is Strict).
If Data policy is set to Controlled or Lenient,
the records in which this string value matches the specified Format property are read, the others are skipped
(either sent to Console or to the rejected port).