XML - Gateway to interoperability
Ian Martin
Program Manager, Technical Services Analytical Surveys, Inc.
11900 Crownpoint Drive, Suite 100 San Antonio, TX 78233
Telephone: (210) 657-1500, Innovative Technologies: (210) 862-9232, Fax: (210) 657-1304
Email: imartin@anlt.com
Abstract
Integrating applications is a common and necessary function of most GIT project
implementations. Designing application data gateways between Geographic Information Systems
(GIS), Outage Management Systems (OMS), and other related business process applications is
key to the successful enterprise GIT implementation.
Extensible Markup Language (XML) is a set of rules for designing text-based structured data
formats that is fast emerging as the standard for structured data exchange on the Internet.
Standard enterprise data interchange formats based on XML and related technologies like
XLINK, XSL, and XSLT can be utilized to create an enterprise data interoperability framework
that can streamline and simplify the task of application data integration.
In addition, XML can be used to take application integration to the "next level", and extend a
structured interoperability framework into a real-time data exchange between related GIT
systems. Finally, XML can be used to streamline future GIT platform upgrades by providing
structured source data formats that are more easily integrated into the target GIT data model.
Introduction
There is truly an alphabet soup of technical acronyms in the data interoperability and Web
services programming arena. The goal of this paper is to introduce the consumer to the enabling
technology with the stated goals being to help build an understanding of the concept of data
interoperability; to learn how XML and related technologies can contribute to application and
platform interoperability; and to discover how XML can streamline future data migration
processes.
XML and related technologies are fast emerging as the standard for structured data exchange on
the Internet, and comprise the backbone, the enabling technology behind web services and
lightweight application interoperability frameworks. Proposed application interoperability
standards, like MultiSpeak, GML and LandXML, rely heavily on XML schemas and Document
Type Definitions (DTDs) to define how applications can communicate and share object
information in a structured manner.
Technology Standards?
All of the standards that define the various languages, formats and protocols specific to
application and data interoperability were conceived and developed by the World Wide Web
Consortium (W3C). The W3C is a joint venture of MIT, CERN, DARPA, and the European
Commision. Establised in 1994, the W3C now includes over 500 member organizations
committed to promoting the evolution and interoperability of the World Wide Web.
What follows is an introduction to the technology standards which is, admittedly, very much
influenced by the W3C website and technical papers. In keeping with the goals of this
presentation, the information has been simplified to faciliate greater understanding by a wider
audience. In all cases, references to original definitions and technical works are documented.
XML
XML is a W3C recommendation that describes a subset of Standard Generalized Markup
Language (SGML) (ISO 8879). XML has been designed for ease of implementation and for
interoperability with both SGML and HTML (W3C, 2000).
XML is a text-based, structured file format that presents a method for storing and exchanging
data between disparate applications. XML has grown from its markup and document
presentation roots into a nearly-ubiquitous format for data storage and information exchange.
Related technologies such as XML Schema, the Document Object Model (DOM), and the
Simple API for XML (SAX) have given Web programmers, administrators and content
managers the ability to present structured XML files as interfaces between disparate systems and
to better manage and extend the capabilities of legacy systems as well as develop next-generation
applications and web services.
XML Schema
XML Schema is a W3C recommendation for describing complex restrictions on elements and
attributes (W3C, 2001). Schemas describe what constitutes a well-formed XML document in
much the same way that a DTD does, but a schema can be extended and combined with other
schemas to validate multiple XML formats and the relationships between the elements in an
XML file (Harold and Means, 2002).
The XML Schema recommendation is a powerful tool for maintaining data quality and ensuring
applications do not fail due to data or schema problems. While users have relied on DTDs in the
past to fill this role, DTDs cannot inherently validate complex relationships or custom data types.
In data-centric applications, XML documents can be validated against one-to-many XML
Schemas to ensure that the data contained in the document meets certain criteria or adhere to
customized business rules. This makes XML Schema a key part of any scalable, data-centric
XML application.
DOM
The Document Object Model (DOM) defines an Application Program Interface (API) for
accessing and manipulating XML documents as tree structures (Harold and Means, 2002). DOM
Level 2 is a W3C recommendation for expressing the structure and content of documents in a
hierarchical, object-oriented framework.
