XML Schema: Is Extensible Value List A Right Design?

XML Schemas provide precise definition of the XML used to exchange the data. It is possible to have a list of enumerated values for any field. Having such a restricted list of values adds further semantics so that all parties exchanging the documents know exactly what the value means.

VisualSchema had a problem of identifying the list of values for the currency fields in the OAGIS standards. Upon further investigation, it was found that the currency type of OAGIS is actually a Union of two simple types, one with a fixed list of values while the other is a free form.

The pros of this approach is that say a new currency is introduced all of a sudden, it is possible to make the xml documents work with the new currency without having to wait till the standards have been modified. In case of a currency code or any other lov that is based on a ISO standard or other well accepted standards, then one can expect everyone to use the same value with the same semantic meaning. Otherwise, this extra flexibility of being able to adopt immediately to the changes may have incompatibility issues.

VisualSchema has been enhanced to display the enumerations even if it’s also possible to specify any other value.


Visual Schemas For XML Schemas (XSDs)

The specification of XML Schema is quite complex and understanding it to make sense out of the XML Schema of an XML is no easier task. Ofcourse, some XML Schemas are much simpler than the other. However, many real life XML Schemas providing open standards tend to be quite complex. This is understandable because the open standards try to offer the most generic solutions that can hopefully cover all the possible scenarios. Hence, a purchase order document even in the best of the enterprise applications can span only a few dozens of tables, the OAGIS definition has more than two thousand elements (in most cases each element maps to a table when no shortcuts are taken).

VisualSchema.com is a website that provides these complex open standards XML Schemas as easily navigable HTML forms that people are familiar in enterprise applications making it easy even for the non-technical people to understand the XML Schema definitions.

At present, the site provides Visual Schemas for OAGIS and GS1’s GDSN standards.