Duco allows you to apply rules in order to facilitate the matching of values that would otherwise be unmatched. Such rules are often necessary where two data sets contain values that while nominally "matching", are not completely identical.
For example, two data sets may both contain a "Company Name" field, but differences in the formatting used means one side's field contains the value "Barclays Securities Ltd" and the other "BARCLAYS SECURITIES LTD". Duco would consider this a break, as the two values are not identical. To address this would require a rule associated with the "Company Name" field that instructs Duco to compare values in a case-insensitive way.
Duco supports a wide range of rules, including the ability to ignore punctuation, tolerate differences in numerical values, define equivalence tables, etc.
It is worth noting that a matching rule does not change the input values, it only affects the way in which input values are compared.