Page Two: U.S. Federal XML guidelines
Reuse, reuse, and reuse again
The guidelines encourage agencies at several points to try to meet their business needs with existing XML solutions before writing their own. For schemas and data items within schemas, the guidelines require agencies to search the Federal XML Registry (FXR) for existing suitable components in other federal applications. Agencies also need to search for suitable commercial vocabularies that can apply to their business needs. Some XML business vocabularies, such as Extensible Business Reporting Language and Human Resources XML, have been developed with participation from the public sector.
The guidelines consider data components suitable if they meet the needs of the business domain and follow the prescribed naming conventions. And if agencies decide to use data components from other federal schemas, they need to register their use of those components with the FXR. Royal says the FXR will be an important part of XML development in the federal government, but noted that it is still in development. The guidelines document will fill in the details about the FXR once it is operational.
But if you do need to develop your own solutions...
If an agency needs to develop its own schema, the guidelines encourage it to engage program managers and business domain experts in the task along with IT specialists, and it encourages initial business process modeling to better understand data exchange requirements. The document does not require a specific modeling method but says agencies may use the Unified Modeling Language (UML) for this purpose. The guidelines mention no other modeling methods.
Royal said the UML recommendations in the guidelines are aimed more at developers than program managers, in order to provide them with a common modeling language. The guidelines may need to clarify this point further, given that some agencies have recently found UML lacking (see Interoperate or Evaporate, 12 December 2001).
If agencies need to create their own vocabularies, the document offers detailed guidance on element naming. The guidelines recommend using the naming conventions found in ISO standard 11179, Specification and Standardization of Data Elements. That standard divides data elements into three parts:
- Object class —a set of ideas or artifacts that can be identified and delineated, and with properties or behaviors that follow the same rules;
- Property —a common condition found all members of an object class;
- Representation —describes the manifestation of values in the element, such as datatype or unit of measure
ISO 11179 uses periods as delimiters between units, but the Federal XML guidelines recommend the approach used by Electronic Business XML (ebXML) core components that puts the three parts together as one string. The document specifies camel case for Federal XML components, with upper camel case (UpperCamelCase) assigned to elements and lower camel case (lowerCamelCase) applying to attributes.
What, no acronyms?
The document's naming conventions also follow ebXML's recommendation to avoid acronyms in tag names. It leaves the decision on the use of acronyms to the program managers rather than systems designers, and it urges that the decision-maker consider the need for communicating across multiple communities of interest. Well known federal agency acronyms, such as NASA and FBI, would likely survive in federal schemas.
The guidelines discuss the use of XML elements and attributes in schemas. The document advises agencies to use attributes only for metadata that will not be parsed and to provide additional business meaning for the element. Also, attributes should be short, not subject to further subdivision, apply to the entire contents of the element structure (including child elements), not contain data specific to a particular application or database.
While the document contains a lot of normative content (the thou-shalts and thou-shalt-nots with XML), most of the guidelines consist of explanations and examples. The drafters have cast the guidelines as a tool to encourage the use of XML to promote interoperability among federal systems. It's noted that the document will probably evolve over time.
The XML Work Group deserves credit for taking on many tough questions. Providing guidance means agreeing on rules and making choices, which are rarely easy tasks. The question now is whether the group made the right choices.
Sidebar: e-GIF, an alternative approach for XML in government
The United Kingdom has taken a more assertive and encompassing approach than the U.S. toward the use of XML in government systems. The U.K. has established an e-Government Interoperability Framework (e-GIF) that spells out technical policies and specifications for achieving interoperability across the public sector. In the U.K., e-GIF "defines the essential pre-requisite for joined-up and web enabled government. It is a cornerstone policy in the overall e-government strategy."
The main focus and objective of e-GIF is to adopt Internet and Web specifications for all government systems, with XML and XSL specifically noted as the core standards for data integration and representation. The goal of e-GIF is to adopt XML specifications that are already well adopted in the marketplace, to reduce the cost and risk for government systems, while keeping them aligned with global developments.
The e-GIF specifications deal mainly with infrastructure, but a team has also developed a core set of XML schemas for business use in public agencies. The Government Schemas Group, as it is called, also works with and monitors key standards bodies such as the W3C, IETF, and OASIS, much like its counterpart in the U.S., the XML Work Group.
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Copyright 2002, reprinted with permission. Alan Kotok is a Washington, DC-based reporter and writer on technology, business, and public policy, editor of "E-Business Standards Today" and Chief Editorial Officer of "Technology News and Literature." This article originally appeared on XML.com.
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