Comparing mod_accessibility to Betsie

The BBC Betsie program is probably the nearest comparison to mod_accessibility. We believe mod_accessibility has very substantially more to offer than betsie, and have prepared a brief comparison.

Subject Betsie mod_accessibility
Installation Runs as CGI and requires some site-specific configuration. It is well-commented, but requires some basic familiarity with CGI. Requires only a simple configuration directive. Site-specific configuration is available but not necessary.
Performance: Initial Overhead A Perl script running as CGI incurs a basic performance penalty with every hit, in addition to the processing it performs. An Apache module incurs no overhead other than the processing it performs.
Performance: Parser Overhead Performs Perl pattern-manipulation and text substitutions on the entire document, requiring it to hold the whole document in memory, parse and rewrite it several times, and slowing substantially for larger documents. Runs a lean and efficient SAX parser (written in C), requiring just a single pass through the document. No performance penalty even for the largest documents.
Performance: Cacheability As far as I can tell, Betsie output is not cacheable. Output from mod_accessibility mostly preserves the cacheability of the original contents.
Parser Ad-hoc Perl text manipulation (commonly known as "tag soup" parsing). A markup-aware SAX parser based on the htmlParser module of libxml2.
Compatibility: Webservers Runs on any server that supports CGI and has Perl available. Runs only on Apache 2.0. Can be used with other servers by deploying Apache as a proxy.
Compatibility: Dynamic or non-local contents Runs as CGI, so using it with another content-generator (such as another CGI script, PHP, mod_xml, or in a proxy server) requires a significant hack, such as an entire new HTTP request. Works out-of-the-box with any content generator. No hacks required.
User Choices Appears to offer superficial configuration options (such as fonts and colours) that rely on deprecated markup to work, and are in any case generally available as browser options. Offers different views on page structure, complementing rather than duplicating normal browser functions. Available views include Betsie emulation.