Using regular expressions to summarize a format

The first new format is the ``ReferBibliographic'' type which is the format that the refer program uses to represent bibliography information. To recognize that a file is in this format, we'll use the convention that the filename ends in ``.referbib''. So, we add that naming heuristic as a type recognition customization. Naming heuristics are represented as a regular expression against the filename in the lib/byname.cf file:

        ReferBibliographic      ^.*\.referbib$

Now, to write a summarizer for this type, we'll need a sample ReferBibliographic file:

        %A A. S. Tanenbaum
        %T Computer Networks
        %I Prentice Hall
        %C Englewood Cliffs, NJ
        %D 1988

Essence summarizers extract structured information from files. One way to write a summarizer is by using regular expressions to define the extractions. For each type of information that you want to extract from a file, add the regular expression that will match lines in that file to lib/quick-sum.cf. For example, the following regular expressions in lib/quick-sum.cf will extract the author, title, date, and other information from ReferBibliographic files:

        ReferBibliographic      Author                  ^%A[ \t]+.*$
        ReferBibliographic      City                    ^%C[ \t]+.*$
        ReferBibliographic      Date                    ^%D[ \t]+.*$
        ReferBibliographic      Editor                  ^%E[ \t]+.*$
        ReferBibliographic      Comments                ^%H[ \t]+.*$
        ReferBibliographic      Issuer                  ^%I[ \t]+.*$
        ReferBibliographic      Journal                 ^%J[ \t]+.*$
        ReferBibliographic      Keywords                ^%K[ \t]+.*$
        ReferBibliographic      Label                   ^%L[ \t]+.*$
        ReferBibliographic      Number                  ^%N[ \t]+.*$
        ReferBibliographic      Comments                ^%O[ \t]+.*$
        ReferBibliographic      Page-Number             ^%P[ \t]+.*$
        ReferBibliographic      Unpublished-Info        ^%R[ \t]+.*$
        ReferBibliographic      Series-Title            ^%S[ \t]+.*$
        ReferBibliographic      Title                   ^%T[ \t]+.*$
        ReferBibliographic      Volume                  ^%V[ \t]+.*$
        ReferBibliographic      Abstract                ^%X[ \t]+.*$

The first field in lib/quick-sum.cf is the name of the type. The second field is the Attribute under which to extract the information on lines that match the regular expression in the third field.