Document Type

Book Chapter

Publication Date



One way of dealing with an important aspect of the natural language barrier that researchers m artificial intelligence have been wrestling with for more than two decades is to normalize the expression of the logical structure of legal rules.

The computer program, NORMALIZER, will enable a legal analyst to automatically generate Normalized Versions of legal rules and Outlines of them from Parenthesized Logical Expressions of their structure and Marked Versions of the Original Text of the rules. In brief:

Parenthesized Logical Expression & Marked Version = = > Outline & Normalized Version.

The Parenthesized Logical Expression of a normalized rule is a statement that expresses the logical structure of the rule in brief notation. The Marked Version of the Original Text of a rule divides that text into constituent sentences and associates a short name with each of them. The short names of the sentences in the Marked Version are used in the Parenthesized Logical Expression to represent those sentences. In the Parenthesized Logical Expression, the logical structure of the Normalized rule is presented in a single dimension -- horizontally. In the Outline of the Normalized rule, the logical structure is presented in two dimensions -- both horizontally and vertically. In the Outline, short names are used to represent the constituent sentences, but in the Normalized Version the short names are replaced by the sentences themselves. In the Normalized Version, the logical structure of the rule is presented in two dimensions -horizontally and vertically by means of defined (and signalled) structural terminology.

Unpacking the logical structure of a Normalized rule into progressively more basic structural terms is done automatically by part of NORMALIZER. A completely unpacked rule (an elementary normalized one) will be expressed in terms of three of the four basic structural terms (AND OR NOT and IF· THEN) and will be in the form of a conjunction of elementary norms. Although some drafters may prefer to use advanced Normalized Versions, probably the most frequently used ones will be clear Normalized Versions and basic Normalized Versions.

In using NORMALIZER a legal analyst must first specify the Parenthesized Logical Expression and Marked Version of the legal rule being normalized, and then NORMALIZER can be used to generate the Outline and Normalized Version of the rule. Thus, the interpretation of the Original Text is a result of the expertise of the human analyst, while the formatting of the expression of that interpretation is done automatically by the program. The program can also automatically generate equivalent Normalized Versions that are expressed in logically more basic form (and also the reverse).


Use is with the permission of Thomson Reuters. All rights reserved. Originally published as Allen, Layman E. and C. S. Saxon. "Computer-Aided Normalizing and Unpacking: Some Interesting Machine-Processable Transformations of Legal Rules." In Computing Power and Legal Reasoning, edited by C. Walter, 495-572. St. Paul: West Pub. Co., 1985.