The Antelope Interface to PHP and Applications: Web-based Real-time Monitoring

Abstract

The World Wide Web has become a de facto standard for the distribution of wide varieties of data, including monitoring information from real-time systems. The Antelope Environmental Monitoring System (AEMS) is one such system widely used in seismology (Boulder Real Time Technologies 2007). The open architecture of the Antelope system has made it possible to write numerous open-source extensions. The current work describes one such open-source extension specifically designed for the Web. Figure 1. Schematic of the underlying software layers. Data are retrieved from Datascope databases and Antelope orbservers by the Antelope libds.so and liborb.so shared-object libraries, respectively. These native Antelope libraries are linked to the PHP interpreter by the new Datascope.so and Orb.so PHP extension libraries, allowing data to be displayed on Web pages using PHP code embedded in HTML. A parallel sysinfo.so extension library provides access to a number of Antelope system-information utilities. The PHP Hypertext Processor language (referred to by the recursive acronym PHP) is a popular server-side processing language embedded within hypertext markup language (HTML) (PHP 2007; Lerdorf and Tatroe 2002). As an open-source middle layer between Web server and Web client, PHP provides a platform for integrating third-party extensions as dynamically loaded shared objects. The underlying Zend engine (Zend 2007) provides an architecture for easily implementing such extensions (Golemon 2006). Extensions have been developed for a wide variety of purposes, including database connectivity ( e.g. , MySQL and PostgreSQL) and access to services ( e.g. , Mail, FTP, LDAP, and SNMP). These extensions include the many PHP utilities under the PECL online repository (PECL 2007) and reusable applications and components under the PEAR repository (PEAR 2007). We have combined these two technologies (AEMS and Zend) to produce an Antelope interface in the PHP language (figure 1). Initial versions of the interface were written in PHP 4; we …