EUROPEAN BUSINESS SCHOOL

XML Schema or just RELAX?

by

Thomas Kramer

2001

Table of contents

1 Introduction ... 1

2 E-commerce requirements ... 2

3 The impact of DTD and XML on Internet commerce ... 3

4 The need for schema ... 6

5 Evaluation of the XML Schema recommendation ... 6
5.1 Schema and schema languages ... 6
5.2 XML Schema recommendation ... 7
5.3 Contrasting XML Schema against DTDs ... 8

6 RELAX as an alternative schema language ... 10
6.1 Why alternative schemas were born ... 10
6.2 RELAX grammar definition ... 11
6.3 The better schema: RELAX versus XML Schema ... 12

7 Summary and conclusion ... 15

Table of abbreviations
API Application Programming Interface
B2B Business-to-Business
DOM Document Object Model
DTD Document Type Definitions
EAI Enterprise Application Integration
EDI Electronic Data Interchange
ERP Enterprise Resource Planning
HTML Hyper Text Markup Language
IOTP Internet Open Trading Protocol
IT Information Technology
RDF Resource Description Framework
RELAX Regular Language Description for XML
SCM Supply Chain Management
SGML Standard Generalized Markup Language
W3C World Wide Web Consortium
XLS Extensible Style Sheet Language
XLST Extensible Style Sheet Transformations
XML Extensible Markup Language

1 Introduction

Today′s e-business consists largely of interactive marketplaces and portals which offer services to their customers. Especially in the field of Business-to-Business (hereafter referred as to B2B) commerce vertical and horizontal interoperability between the heterogeneous IT systems and platforms of trading partners are essential for business endeavours in order to automate transactions and to cut costs respectively.¹ With technologies such as XML (Extensible Markup Language) or DTD (Document Type Definitions) disparate systems of stakeholders can be integrated into the corporate value chain, thus eliminating human interaction by describing and interpreting the content of the data exchanged between them.² However, due to the lack of one agreed-upon format or schema standard transenterprise communications remains a sophisticated challenge for e-commerce businesses.³ The attempt of developing a standard schema language has been one of the most watched efforts in the last couple of years. Recently, the W3C Consortium has released XML Schema, which is supposed to facilitate the data exchange among trading partners.⁴ During its development phase, the need for interoperability among e-businesses grew to the extend that other organizations came up with alternative schema languages such as RELAX.⁵ However, the variety of emerging schema languages caused XML Schema not becoming a standard yet.⁶

The intention of this paper is to show how schema languages emerged from the need of interoperability and how they solve many challenges presented by e-commerce requirements. Furthermore the ideas and philosophies behind two significant schemas for XML, the XML Schema and RELAX, are highlighted and contrasted against each other and against the intention of DTDs. The question to be answered is whether XML Schema can compete against alternative schemas in the long run and whether it can still become a widespread standard within the rapidly growing e-commerce environment.

The main part of this paper is divided into four core parts. The first section will give the reader an overview about the current e-commerce needs and requirements, followed by a critically evaluation of DTD (Document Type Definitions) and XML (Extensible Markup Language) as considerable options to attempt meeting the e-businesses requirements presented earlier. The next section will introduce a recent advance in XML technology, the Schema language, whose contribution and utility for e-commerce will be highlighted. In particular XML Schema as the W3C recommendation will be evaluated and critically compared with its significant competitor RELAX in the fourth section. The last part comprises a critically discussion about the schemas′ potential of becoming an enterprise-wide standard for XML document description. The end of this paper constitutes a summary of the results presented and conclusions drawn.

2 E-commerce requirements 

In the nineties the Internet revolutionized the Information age in many ways.⁷ In its first generation (circa 1993-1997) Internet applications were basically focussed on simple browsers and static web sites. Web content was rather unstructured and presented in HTML. Later, between 1997 and 1999, the emphasis of the second generation of Internet applications was tending more on interactive applications, enterprise integration and application servers. As the number of commercial activities over the Internet, the number of trading partners as well as the sophistication of Internet applications increased significantly, businesses which deployed e-commerce systems started stressing the importance of transenterprise communication and harmonizing business models, processes and representation formats.⁸ The idea of unifying the heterogeneous platforms, applications and frameworks between trading partners changed the views of ecommerce. Frictionless e-transactions and sustainable network relationships with trading partners would add significant value to customers since real-time data could be collected from them, thus being able to respond better and faster to their needs. In addition smooth transactions over the Web would increase productivity and improve data mining among the involved organizations. The need for interoperability among systems deployed by businesses engaged in commerce on the Internet became ubiquitous: “Your business simply won’t scale if you have to handle orders manually.”⁹

[...]

1 Holland, 2001; Gregory, 2000; Liebmann, 2000; Smith, 1999

2 TIBCO, 2000; Liebmann, 2000; Klarlund, 2000; Holland, 2001; Floyd , 1999; Walsh, 1999

3 Holland, 2001; Gregory, 2000; O′Kelly, 2000

4 O′Kelly, 2000; Girishankar, 2000; Dyck, 2001; Dyck, 2000

5 Levitt, 2000; Sliwa, 2000 [1]; Dotts, 2001; Ogbuji, 2000; Klarlund, 2000; Alschuler, 2000

6 Holland, 2001; O′Kelly, 2000; Patrizio, 2001; Dyck, 2001; Alschuler, 2000

7 O′Kelly, 2000; Robie, 2000; Shantaram, 2001

8 O′Kelly, 2000; Smith, 1999

9 Liebmann, 2000