Introduction

• Important note
• Basics
• Terminology

Important note

This documentation covers a specific version of the LaSt engine and may not applicable to previous or later versions. Also note that this is work in progress, and specification may be subject to change without notice. Please report any errors or shortcomings in this documentation to radioweb-at-upm@clip.dia.fi.upm.es. When reporting errors, also include the version date for this manual.

Basics

The LaSt engine is a LaSt language interpreter specialized for RadioWeb, a project aimed at producing dynamic web solutions for the radio broadcasting industry. The LaSt engine is specialized in the sense that it provides interfaces to other RadioWeb components, but not in the sense that it sacrifices LaSt language generality.

The LaSt engine is completely written in Prolog, and in particular using the Ciao Prolog system [Gro97] and the PiLLoW library [CHV99]. The engine produces one or more HTML output files from a RadioWeb document, a form of template that may contain dynamic objects. Each object is processed separately and representations of data or database queries can be stored within the object. During the processing one or more LaSt packages will be used to create the output, and data may be looked up in databases. The LaSt engine may also be supplied with reader preferences affecting the results of the processing.

All data lookups are managed through the WSDL interface, an abstract data type allowing access to structured data. This interface permits several types of implementation, but for the RadioWeb project the WSDL interface should be connected to appropriate WOFs that generate the data needed.

The LaSt language is used for creating a presentable layout and style from the structured data, but is not the topic of this documentation. See the separate documentation for the specification of the LaSt language [Ct99].

Terminology

The terminology so far has probably already been confusing and misleading, so below is a list of some of the more important terms in the following documentation.

RadioWeb

A project aimed at producing dynamic web content for radio stations (as defined in [Par97]).

RadioWeb document

A special document containing dynamic objects which may need data and/or formatting updates.

LaSt language

The Layout & Style language [Ct99], describing transformations of data into a presentable form. The LaSt language contains several parts; rules, templates, default values and constraints.

LaSt engine

An interpreter of the LaSt language, providing interfaces to the outer world. Also the topic of this documentation.

LaSt package

A file containing the LaSt rules, templates, etc. The packages are identified by their file names.

Choices

A way to set variable values in LaSt packages. Normally this is used for storing preferences for certain options.

Go to the first, previous, next, last section, table of contents.