Website
histpop online/ website technical
Design and application
This website is the visible front-end of an online repository containing over a million presentable images and a large quantity of related metadata. It was possible to make a million images available because rather than using scalable JPGs we have chosen to use the PNG format for the images, and for each page from the Census or Registrar-General reports we present five digital images of different sizes. The site makes use of the latest open source software technologies and uses open standards for the presentation of the available resources.
User requirements
To use the site users only need a standards compliant web browser. The minimum browser requirements and configurations are as follows:
- Support for XHTML 1.x transitional;
- Support for Cascading Style Sheets (CSS 1 and some CSS 2.1);
- No client-side Javascript needed;
- Support for PNG image viewing;
- Minimum physical screen size is 800 x 600 (Recommended screen size 1024 x 768);
- Web browsers supported include:
- Opera 7.5 or later (Windows, Linux, Mac OS X);
- Firefox 1.x or later (all platforms);
- Internet Explorer 6.x or later (Windows);
- Mozilla 1.7.x or later (all platforms);
- SeaMonkey 1.0 or later (all platforms);
- Konqueror (Linux KDE 1.5 or later).
This means, to all intents and purposes, that most users will be able to use this site with any standard web browser and not lose any functionality.
Web server
The web server is a database-driven system. To the end-user it presents itself as a collection of dynamically generated web pages which are organized in a hierarchical structure. The top-level pages are easily accessible via main menu tabs. From there it is possible to browse into lower-level pages which provide more detailed content on requested resource material. The lower-level navigation is done through tree-style menus.
Main features
The main features offered by this website include Browse and Search functionalities, tables of contents for the volumes, a target page image browser, as well as some Help and Project pages.
Some technical information
The main front end consists of the Apache web server (Version 2.0.x) which serves all incoming requests. Most requests are being forwarded to a back end Tomcat (Version 5.5.x) J2EE Servlet which is responsible for generating the dynamic web pages. This includes looking up the necessary metadata from a MySQL (Version 5.0.x) database. The main Apache server also contains plug-ins for PHP (Version 5.0.x) and Pearl (Active Pearl Version 5.8) for enabling server-side scripts which provide additional features such as a remote database management tool, the presentation of rotated images, or for showing web site visitor statistics. The whole server software is installed on multiple server machines which are then load balanced to scale up to higher traffic volumes.
Server architecture
The J2EE Java-Servlet follows the Model-View-Controller architecture and communicates with the Apache front-end via TCP (Transmission Control Protocol). The following diagram illustrates the n-level architecture, where red arrows denote TCP or UDP (User Datagram Protocol) and black arrows denote local communication paths.
