Middleware Overview

• Object Oriented Perl CGI programs
• Set of DLPS-written Perl applications that also use:
  • DLPS-written class, subclass and library modules
  • Perl modules found in the standard distribution (information on current Perl version in installation notes)
  • Additional Perl modules freely available through CPAN
  • HTML pages and HTML templates
• Interacts, through DBI, with various DLXS-related databases
• Basic flow of middleware:
  • Take user input for search
  • Fork off an XPAT process
  • Creates as many XPAT queries as needed to retrieve results
  • Gather up SGML results
  • Process HTML templates; that is, replace parts of templates with the search results after filtering them to HTML. This creates the final server delivered HTML
• Through the above modules and databases, the middleware keeps track of collection and user information (either through a session object or a database):
  • search history
  • bookbag / portfolio
  • collection information needed for single collection or cross-collection searching and display behavior
• Pageviewing handled through a separate CGI program which interacts with a database of page metadata and which uses image conversion software to convert archived TIFF files into GIF or PDF formats on the fly