Practical PostgreSQL

Chapter 13. LXP

LXP (or mod_lxp) is an Application Server designed as an Apache Module. LXP is used to broker and dynamically format HTML content through a process called server-side inclusion. This involves assembling HTML output from a variety of sources, which can include HTML source files, XML files, or even data within a PostgreSQL database.

LXP’s content inclusion is performed entirely on the server, ensuring the same output regardless of the web browser. LXP is intended to behave more intuitively, seamlessly, and comprehensively than other available content inclusion methods via its unique mark-up based approach and native PostgreSQL connectivity.

LXP uses a unique form of programmatic mark-up tags, which are interpreted entirely on the server and translated into standard HTML output before being sent to the client. While the effects of these tags are programmatic in nature, they differ from a “scripting language” such as PHP or Perl, by relying for their implementation on the same structural concepts as those behind HTML and XML for their implementation.

One of the goals of LXP is to provide dynamic, conditional capabilities that do not violate the syntax and methodology of a mark-up–based document. An LXP document should be readable to anyone fluent in HTML, though the meaning of the extra tags may not be immediately obvious. Simultaneously, experienced programmers can take advantage of the more advanced features within the content model of LXP.