Several industry and government initiatives are now gaining momentum in their goal to craft guidelines and rules for naming XML components: XML namespace names, types, elements, attributes, schema modules, code list enumerations, domain models, etc.
Most of these initiatives have identical or similar goals, aimed at optimizing semantic interoperability, modularity, extensibility, maintainability, and data element re-use through best-practice design of business components.
One indication of increased interest in XML naming design rules/guidelines is seen in the three most recent meeting agendas of the XML.gov XML Community of Practice: the June, July, and August meetings have included major presentations by practitioners and other interested stakeholders who are seeking to design component naming models that interoperate inside and outside their domains.
Some of the current design initiatives have their historical roots in the UN-CEFACT/ISO ebXML Core Components Technical Specification (CCTS) and in the ebXML Technical Architecture Specification. The latter, for example, provides for consistent capitalization and naming convention across all family specifications, using "Upper Camel Case" (UCC) for XML elements [and types] and "Lower Camel Case" (LCC) for XML attribute names.
The UBL NDR specification, like that published by UN/CEFACT, assigns a Rule Prefix to each of its rules, in one of of eighteen (18) categories. A survey of these category labels provides a summary of concerns addressed by several of the NDR specifications: ATD: Attribute Declaration; ATN: Attribute Naming; CDL: Code List; CTD: ComplexType Definition; DOC: Documentation; ELD: Element Declaration; ELN: Element Naming; GNR: General Naming; GTD: General Type Definition; GXS: General XML Schema; IND: Instance Document; MDC: Modeling Constraints; NMC: Naming Constraints; NMS: Namespace; RED: Root Element Declaration; SSM: Schema Structure Modularity; STD: SimpleType Definition; VER: Versioning.
The following summary of design initiatives reveals the growing concern for semantic clarity through the use of recognized naming conventions and for naming architectures that provide a sound basis for extension of XML schemas and XML-based business vocabularies. The order of presentation below is (plausibly) alphabetic, but not chronological.
Danish XML Project: OIOXML Naming and Design Rules
A Danish XML project now available through the Danish OIO (Offentlig Information Online) is Version 3.0 of the OIOXML Naming and Design Rules (OIOXML NDR). The set of rules laid down by the OIOXML NDR 3.0 "provides the foundation for the approval process for OIOXML schemas used in public government data provider solutions. The OIOXML NDR only allows one to use a subset of the XML Schema specification and also endorses certain schema patterns to avoid ambiguities and to maximize interoperability. Denmark has adopted XML as a key to the information architecture in support of E-Government. The philosophy of the Danish E-Government strategy is based on government wide co-operation and reuse, and supports also cooperation with both the private sector and with a wider international community. The Danish XML project focuses on coordination and supports the development and standardization of XML interfaces and vocabularies."
EPA Exchange Network XML Design Rules and Conventions
The EPA Exchange Network is a secure Internet- and standards-based approach for exchanging environmental data and improving environmental decisions. In December 2004, the EPA Schema Review Work Group under the Technical Resource Group (TRG) prepared a documentation package designed to help Partners "initiate their schema development effort based on the Exensible Markup Language (XML) Design Rules and Conventions (DRC), existing schema, documented elements from the Environmental Data Registry (EDR), Environmental Data Standards Council (EDSC) data standards, and modularity defined by the Core Reference Model (CRM). These are critical for schema designed to flow data within the Exchange Network. The XML Design Rules and Conventions (DRCs) provides rules and guidelines for the creation and use of XML schema and schema components for use in the Exchange Network. Schema design has important implications for the reusability of schema and schema components in data exchanges. It provides an opportunity to promote the Exchange Network's goals of improved data quality and efficient data exchanges."
Federal XML Naming and Design Rules Project
A Federal XML Naming and Design Rules Project is hosted at CORE.GOV, and is directed by Mark Crawford and Tim Mathews. The draft Federal XML Naming and Design Rules and Guidelines document is designed to "provide a set of rules and guidelines that will enable development of: (1) a flexible federal modularity model that defines the structure for creating interoperable schema and schema modules; (2) a clearly defined namespace scheme that ensures consistency across Agencies; (3) a versioning scheme that will support consistency in versioning of government schema; (4) a Federal canonical schema for base Data Types; (5) specific NDR's by government agencies or communities of practice that build on this document; (6) a reference to use for a mapping of different agency NDR's to each other; (7) consistent, reusable XML components that may be made available for reuse such as: Schema; Schema Modules such as reusable code lists and identifier lists; Simple and Complex Types; Elements; Attributes; (8) a set of tools to facilitate ease of development, validation, and interoperability."
Global Justice XML Data Model (GJXDM) Naming and Design Rules
The Global XML Structure Task Force (GXSTF) was formed under The Global Justice Information Sharing Initiative to "identify data requirements, explore XML concepts, and apply XML best practices to the design and implement of the Global Justice XML Data Model (Global JXDM). A draft GJXDM NDR document corresponding to the GJXDM Version 3.1 specification is focused on providing: (1) a definition of GJXDM-conformant schemas; (1) a definition of GJXDM-conformant reference schemas, on which schemas that are simply conformant are based; (3) a definition of subsetting methodology, through which conformant schemas are built from conformant reference schemas; (4) naming of content to ensure understandability and reuse; (5) documentation of content to ensure comprehension; definition of GJXDM-conformant instances, which contain additional validation requirements, such as types associated with references and relationships."
Hong Kong OGCIO Interoperability Framework for E-Government
The Office of the Government Chief Information Officer (Government of the Hong Kong Special Administrative Region) has published an XML Schema Design and Management Guide through the Interoperability Framework (IF). This IF, "including the technical specifications, is managed by the Interoperability Framework Co-ordination Group (IFCG). Part II of the Guide "XML Schema Design Guide" includes a Section 5 on "XML Schema Definition Development". It documents a mechanism that programmers should follow to convert information models, which are prepared by business analysts, into XSDs. XML naming rules are also discussed. In addition, this section provides guidelines on namespace assignment, versioning, and meta-data documentation of schema documents. Attribute names use the lower camel case convention (currencyCode); complex types and elements use the upper camel case convention (PurchaseOrder).
IRS XML Naming and Design Rules
The US Department of the Treasury, Internal Revenue Service, with a long history of SGML/XML adoption, is developing an IRS XML Naming and Design Rules (NDR) specification. The EDMO effort recognizes that "effective XML management requires a balance between diversity and conformity recognizing that diversity can impose increased transformation costs and performance penalties. The principal objective of all the XML naming and design rules is to facilitate consistency and interoperability across the IRS and with its data exchange partners." Similar to other NDRs based upon UBL, the IRS NDR rules have a Rule Prefix Token corresponding to the rule category: ATD: Attribute Declaration; CDL: Code List; COM: ComplexType; CVR: Component Versioning; DOC: Artifact Documentation; ELD: Element Declaration; FRM: Forms; GNR: General Naming; GXS: General Construct; IMP: Schema Import; IND: Instance Document; NMP: Namespace Prefix; NMS: Namespace; SCF: Schema File; SCH: Schema Organization; SIM: SimpleType; SSM: Schema Modularity; STA: Standards Adherence; VER: Schema Versioning.
OAGIS Naming and Design Rules (NDR)
"The Open Applications Group, Inc. (OAGi) is a not-for-profit open standards group building process-based XML standards for both B2B and A2A integration. OAGIS 9.0 is a major release that includes full support for the UN/CEFACT/ISO Core Components Technical Specification, CCTS 2.01, harmonized Core Components from UN/CEFACT TBG17, a great deal of new content, and technical improvements to better support Web Services and to make OAGIS easier to use. OAGIS 9 "incorporates today's best practices for XML and continues to take full advantage of XML Schema. It uses primarily global elements, incorporating UN/CEFACT ATG 2 Naming and Design Rules (ISO 11179; long tag names; use of UpperCamelCase for Elements and Types; use of lowerCamelCase for attributes; makes use of XML Schemas Typing to define types for everything to inherit common pieces of the component and Noun definitions, minimizing the number of definitions and the amount of code needed to process the standard; all Types end with the word 'Type'."
OASIS LegalXML Exchange Document Methodology, Naming, and Design Rules (MNDR) Subcommittee
The Exchange Document Methodology, Naming, and Design Rules (MNDR) Subcommittee is a workgroup of the OASIS LegalXML Integrated Justice Technical Committee. The MNDR Subcommittee was chartered to "develop and document (1) A methodology for the construction of GJXDM-conformant exchange documents; (2) Naming and design rules for the artifacts called for by the methodology; (3) Guidelines for the customization of GJXDM schema structures; (4) Context drivers for integrated justice. Draft versions of "Schema Set Naming and Design Rules" and "Instance Naming and Design Rules" are available. The purpose of the MNDR deliverable is: (1) to "improve interoperability by promoting consistent use of GJXDM in constructing schemas; (2) to lower risk and improve efficiency of projects to establish exchanges between justice partners, by disseminating best practices; (3) to reduce the effort involved in identifying exchange document development best practices, by consolidating them in, or at least referencing them from, one single place; (4) where possible, to provide a formal, normative standard that exchange partners can use to establish criteria for quality assurance — for example, in contracts with system integration vendors."
Universal Business Language (UBL) Naming and Design Rules
The Universal Business Language (UBL) specification is being developed through an international effort to define a royalty-free library of standard electronic XML business documents such as purchase orders and invoices. In December 2004 the OASIS membership voted to approve the Universal Business Language (UBL) Naming and Design Rules specification as an OASIS Standard. This specification "conveys a normative set of XML schema design rules and naming conventions for the creation of business based XML schema for business documents being exchanged between two parties using XML constructs defined in accordance with the ebXML Core Components Technical Specification." Finalization of the naming and design rules for UBL 2.0 is [2005-08] gaining momentum with the appointment of Michael Grimley of the US Department of the Navy to the UBL NDR editorial team. Grimley has played a pivotal role in the development of both UBL and DON NDR, and his appointment to UBL NDR editorship will help ensure their continued alignment. Key changes under consideration for UBL 2.0 NDR are the adoption of the UN/CEFACT Core Component Type schema module and the UN/CEFACT Unqualified Datatype schema module. Additionally, for version 2.0 the UBL NDR requires that all attributes must be globally declared, including ID and Code.
UN/CEFACT XML Naming and Design Rules Technical Specification
The UN/CEFACT — XML Naming and Design Rules Technical Specification "describes and specifies the rules and guidelines that will be applied by UN/CEFACT when developing XML schema. The specification provides a way to identify, capture and maximize the re-use of business information expressed as XML schema components to support and enhance information interoperability across multiple business situations." As of 2005-08-16, the UN/CEFACT NDR specification was still in the implementation verification stage, but the development team expected that period to be finished prior to the 7th UN/CEFACT Forum Convention (Lyon, France) meeting in September 2005. Together with the OASIS UBL NDR specification, this document is one of the foundational NDRs developed in accordance with the UN/CEFACT Core Components Technical Specification (CCTS). Mark Crawford (Project Team Leader) serves on several of the NDR working groups, and has worked to harmonize them as far as possible.
US Department of the Navy XML Naming and Design Rules
In January 2005 the US Department of the Navy CIO approved the latest version [Version 2.0] of the DON XML Naming and Design Rules. These rules... provide for implementation of ISO 11179 concepts and ISO 15000-5 ebXML Core Components in XSD Schema. The XML NDR provides the DON XML developer with a clear and comprehensive set of development rules and guidance that will standardize XML across the DON and promote global interoperability. NDR Version 2.0 complies with joint requirements as embodied in DoD's net-centric data strategy, helps FORCEnet architects and system developers to achieve their requirement for a common structure and language for information handling, and enables the discovery and use of common data across the naval enterprise." The U.S. Department of the Navy (DON) XML naming and design rules are based on the work of the OASIS UBL Technical Committee. Michael Grimley is the official DON representative to the UBL TC and played a significant role in the alignment of the DON NDR with the UBL NDR.