The System
The system comprises 7 modules:
a) The Search module
b) Database index
c) Query software parser
d) String handling
e) Navigation module
f) Target database xml output
g) combination engine

The Search module
This module handles presentation of the options to the user. In the case of the example interface this provides a simple search dialogue box with selection of type of information in the result. A browsable interface could also be used as is the case of ELAND where multilingual retrieval is neccessary. Here one keyword can issue a search for language equivalents. To improve performance these searches can be asssembled prior to the user requesting them. Therefore a static page combining results may have been prepared and be linked from the keyword.
The search module passes the query string and data type parameters to the query software parser.

Database index
This index is the handling for information on each database. This is currently a database drectory on the server containing individual scripts for each database. As the system is scaled up this could become a database containing parameter information about the database such as software platform, string handling rules and query parameters.

Query software parser
This module controls the commands issued to the target database. Unlike other systems this does not require host databases to adopt an xml compatible search system but uses the existing database query with a new results format.

String handling
This sub module of the query handling contols boolean operators and truncation. This replaces standard notation with the relevant commands for the target database, e.g. & is replaced by and / by or as necessary. This will often be more complex as subfelds may be used to pass multiple criteria in the search.

Navigation module
This module controls navigation through the resuts pages of the chosen databases. it stores the relevant query strings for passing to the query module and allows the user to browse through databases. The system needs to highlight the selected database and provide a search box using the search module script.

Target xml output
This is the only component which needs to be setup on the participating database. It is not specific to this software and can be used for other purposes, exchanging data with other systems, providing versatile display in conjunction with XSL orcascading stylesheets to different users. It simply requires the construction of a new results page script which inserts xml code in place of the html code.

Combination engine
This script combines the xml results pages into one file, this then uses the properties of the attached stylesheet to sort and display the data. data can thus be sorted by any field and presented in any design depending on the choice of stylesheet which can be declared in the header of the xml file when this is generated. For demonstration purposes the raw xml file is generated for display with Internet explorer 5.