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 in TextClass is handled through a separate CGI program
which interacts with the Pageview table (in the dlxs database) of
page metadata and which uses image conversion software to convert
archived TIFF files into GIF or PDF formats on the fly