Distributed WWW Programming using (Ciao-)Prolog and the PiLLoW library

TL;DR

This paper introduces PiLLoW, a library for LP/CLP systems that simplifies distributed WWW programming by providing tools for document access, HTML/XML manipulation, form handling, and client-server interaction, modeled as terms.

Contribution

The paper presents PiLLoW, a novel library that models HTML/XML as terms and supports distributed WWW programming in LP/CLP systems, including concurrency and client-side code execution.

Findings

PiLLoW simplifies WWW programming in LP/CLP systems.

It models HTML/XML as terms for easier manipulation.

Supports concurrency and client-side code execution.

Abstract

We discuss from a practical point of view a number of issues involved in writing distributed Internet and WWW applications using LP/CLP systems. We describe PiLLoW, a public-domain Internet and WWW programming library for LP/CLP systems that we have designed in order to simplify the process of writing such applications. PiLLoW provides facilities for accessing documents and code on the WWW; parsing, manipulating and generating HTML and XML structured documents and data; producing HTML forms; writing form handlers and CGI-scripts; and processing HTML/XML templates. An important contribution of PiLLoW is to model HTML/XML code (and, thus, the content of WWW pages) as terms. The PiLLoW library has been developed in the context of the Ciao Prolog system, but it has been adapted to a number of popular LP/CLP systems, supporting most of its functionality. We also describe the use of concurrency and a high-level model of client-server interaction, Ciao Prolog's active modules, in the context of WWW programming. We propose a solution for client-side downloading and execution of Prolog code, using generic browsers. Finally, we also provide an overview of related work on the topic.