Index To XML Schema Papers¹

John I. Bobbitt

POSC

Abstract: POSC has developed papers dealing with best practices in XML. Other groups have also done work in this area. This page serves as an introduction to the POSC papers, and contains an list of references to other groups.

1.Introduction

XML offers a wide variety of ways to develop exchange sets using XML schema. In fact, it offers too many alternatives.

The last three years have seen many groups attempting to pare down the possible ways of doing XML schema. These generally result in a set of guidelines that define the way things will be done within some development scope. POSC also has developed a set of guides.

The guides are not independent. The groups, when developing their guidelines, tend to “look over each other's shoulders” to see what everyone else is doing. For that reason, there has tended to be increasing agreement with respect to some of the practices.

But for many reasons, there tends to be a lack of agreement in other areas. The purpose of this paper is not to analyze the reasons for the differences, but merely to point out that they do exist.

POSC has, like many other groups, developed its own set of guidelines to control development of XML schema within its boundaries. But POSC has also developed a series of discussion papers that describe various issues along with recommendations for best practices. These issues are, in many cases, unresolved, undiscussed, and often unrecognized within the industry. Section 3 will give a brief summary of the issues, and how the various papers relate to these issues.

2.Outside References

The first part of the References section, Section 5, contains outside references. These are a sampling of papers that deal with XML, and with guidelines and practices in XML. It is not intended to be comprehensive. However, the various sites will lead you to other sites which are appropriate.

3.The POSC Papers

The over-riding goals in the POSC approach to XML schema are interoperability, usability, and predictability. The interoperability will be seen in attempts to use and re-use the same structures over-and-over in many different places. The usability will be seen in many papers which make it easy for users to incorporate the POSC schema parts into their overall schema, and to extend the usage of developed schemas without a long, involved updating process. The predictably will be seen in simple rules, such as the use of upper camel case for elements, and lower camel case for attributes.

The guidelines document [Guidelines] is comparable to many of those given in the outside references. The document is based on another guidelines document [UKGuide] from an outside group. This document was chosen because it did not seem to be overly prescriptive like many of the others, and did not concen itself with the details of internal file systems and such. The Guidelines document is a good starting place for POSC Best Practices.

3.1.Papers on Modules

POSC is developing re-usable schemas. At the level of a business object, the re-usable schema is referred to as a module. To further explain this architecture, and how it is to be used in conjunction with other schemas, POSC has developed a series of papers.

Introduction to Modules [IntroModules] is a high-level view of how modules are used as illustrated by an example. A description of how modules fit into the overall architecture is also given.
A second paper, Modules, Profiles, and Application Schemas [ProfilesAppSchema], give a more detailed view of the POSC architectural model.
A third paper, Build a Module [BuildModule] takes you through the steps of building a simple XML module. It introduces some of the issues that a schema developer must consider when building a re-usable module.
Another part of the architecture is Tables, which are described in XML Tables [xmlTables].

3.2.Making it Usable

A module must be usable by another group. To be used, the other group must particularize it for their use - a process which includes several different concept.

The concept of profiling and using a module, as defined by POSC is described in the paper, Policies on Modules [ModulePolicies].
A module may have a relationship to another module. A user community should not be restricted to only POSC modules. They should be able to unplug a POSC module, and substitute in another module for the same purpose. The paper on Importing Modules [importModule] gives a best practice for allowing this to be done.
A schema can also restrict the values of an element through the use of an enumerated list (and/or patterns). While most user communities greatly value this concept, they do not always agree on the particular set of values to go into the enumerated list. POSC can give a set of values it feels appropriate. But the user community may wish to extend this set of values, either by allowing additional values, or by going into greater depth. The best practices for reference values (value sets, enumerated lists) is discussed in great detail in the paper, Reference Data and Enumerated Lists Implemented in XML [ReferenceData].
As mentioned earlier, a module may have relationships to other modules (or other blocks of schema). POSC gives three methods of implementing these relationships in its paper, Relationships in XML [Relationships]².

3.3.Additional Papers

There are some papers that do not fit into the neat categories above, but are worth including. The first is the paper on Units of Measure [UOMRecs], which was developed in conjunction with several other groups. The purpose was to get a common way to handle values which require a unit of measure.

A second paper is on dictionaries, or registries [Dictionaries]. This paper was developed to demonstrate how XML can access information that is in other files or databases, using standard XML technology (ie., XML and XSLT). The strength of this method is that it allows a business object to be referenced without having to include the whole set of information about the object.

4.Glossary

XML involves a whole new set of terms that can be put into a glossary. The use of XML in the POSC environment introduces an additional set of terms. It's use in other groups generally elicits even more terms.

It is not reasonable to cover the whole gamut of terms in this index, or in the various papers. As part of a total package, POSC will maintain a separate glossary file that can be referenced from the various papers.

As of September 2003, the glossary is still under construction.

5.References

5.1.Outside References

[ANSIX12] X12 Reference Model for XML Design, 2002-10, produced by the ANSI X12 committee, obtainable at http://www.x12.org/x12org/.

[BestPractices] Best Practices Homepage, developed and maintained by XML-dev and Mitre, obtainable at http://www.xfront.com/BestPracticesHomepage.html.

[ComProServ] PIDX XML Standards Master, Version 1.0, RP 3901, produced by PIDX, obtainable at http://committees.api.org/business/pidx/standards.htm.

[EBCCNAM] ebXML RT - Naming Convention for Core Component, 2001-05-10, produced by the ebXML group, obtainable at http://www.ebxml.org/specs/index.htm#technical_reports.

[ebTechArch] ebXML Technical Architecture Specification V1.0.4, 2001-02-16, produced by the ebXML group, obtainable at http://www.ebxml.org/specs/ebTA.pdf.

[FedDevGuide] Draft Federal XML Developer's Guide, 2002-04 (work in progress), produced by the Federal CIO Council, obtainable at http://xml.gov/documents/in_progress/developersguide.pdf.

[FedTagStds] Federal Tag Standards for Extensible Markup Language, 2001-06, produced by LMI, not obtainable from the internet.

[HKGuide] XML Schema Design and Management Guide, (4 parts), Draft versions dated in summer, 2003. Produced by Hong Kong Information Services Technology Division. Available at http://www.itsd.gov.hk/itsd/english/infra/eif.htm.

[IETFKeywords] Key Words for Use in RFCs to Indicate Requirement Level, 1997-03, obtainable at http://www.ietf.org/rfc/rfc2119.txt.

[ISO8601] International Standard Date and Time, 2001-11-10, produced by ISO. A web page that explains the formats is http://www.cl.cam.ac.uk/~mgk25/iso-time.html.

[ISO11179] ISO 11179 Part 5 - Naming and Identification, 1995-12, produced by ISO, obtainable at http://fdr.faa.gov/iso/ISO11179page.htm. There is a later version, that is available from the ISO website,

[UKGuide] e-Government Schema Guidelines for XML, 2002-12, produced by United Kingdom e-Envoy, obtainable at http://www.e-envoy.gov.uk/Resources/Guidelines/fs/en.

[Unicode] Unicode Charts, available at http://www.unicode.org/charts/.

[W3CSchemaDatatypes] W3C Schema Datatypes, 2001-05-02, produced by W3C, obtainable at http://www.w3.org/TR/xmlschema-2.

[W3CNamespaces] Namespaces in XML, 1999-01-14, produced by W3C, obtainable at http://www.w3.org/TR/REC-xml-names/.

[W3CSchemaPrimer] W3C Schema Primer, 2001-05-02, produced by W3C, obtainable at http://www.w3.org/TR/xmlschema-0.

[W3CSchemaStructures] W3C Schema Structures, 2001-05-02, produced by W3C, obtainable at http://www.w3.org/TR/xmlschema-1.

[Xlink] W3C XLink Specification, 2001-06, produced by W3C, obtainable at http://www.w3.org/TR/xlink/.

[Xpath] W3C XPath Specification, 1999, produced by W3C, obtainable at http://www.w3.org/TR/xpath/.

[XSL] W3C XSL and XSLT Specifications, produced by W3C, obtainable at http://www.w3.org/Style/XSL/.

5.2.POSC References

POSC references are available in the following formats:

[html] html format readable by browsers

[doc] MS Word 97/2000/XP

[sxw] OpenOffice writer, v1.0

1Copyright 2004, Petrotechnical Open Standards Consortium, Inc. All rights reserved. All access, receipt, and/or use of this document is subject to the POSC Product Licensing Agreement posted on the POSC Web site at http://www.posc.org/about/license.shtml.

2As of the end of August 2003, this paper was still being developed. The paper is included even though it is still under construction.

2003-09-03 Index to Papers in XML Schema Page 1 / 1