1. MXV NDR 2.1 Overview

2. Decoupling from XSD enumerated code lists referenced by the UN/CEFACT UDT Unqualified Data Type Schema Module XSD

MXV, the first version of this UML model-driven XML Schema Vocabulary Design solution, was originally based on UBL NDR 2.0, OASIS' first approved XML Schema Naming and Design Rules standard.

In 2010, OASIS has published OASIS UBL 2.1 (*) work in progress. Its outputs are well documented on the OASIS website.

In parallel, Data Management Solutions has upgraded MXV to stay aligned with OASIS UBL NDR 2.1. (*)

Since October 2010, the latest MXV Productivity Tools are applying the MXV methodology v2.1, which emulates OASIS UBL NDR 2.1 (*).

OASIS UBL NDR 2.1 (*) delivers two major improvements:

• Decoupling from XSD enumerated code lists referenced by the UN/CEFACT UDT Unqualified Data Type Schema Module XSD

• A much simpler XML Library Schema Module structure

NDR 2.0:

The problem: With NDR 2.0, the schema designer cannot modify the UN/CEFACT inbuilt code value lists for Country, Currency, Unit of Measure and MIME type.

This may lead to major processing issues when one of above code value list changes over time.

OASIS states: "The W3C Schema 1.0 expression of code list value constraints in the UN/CEFACT UDT Unqualified Data Type Schema Module XSD based on CCTS 2.01 and used in UBL 2.0 has been proven not to support the objective in UBL 2.1 of validating instances of UBL 2.0 and UBL 2.1. See the case study of different currency codes for Turkey at the dates of the releases of UBL 2.0 and UBL 2.1 in the two threads starting at http://lists.oasis-open.org/archives/ubl/200904/msg00015.html and http://lists.oasis-open.org/archives/ubl-dev/200905/msg00002.html."

NDR 2.1: 

UBL NDR 2.1 (*) eliminates the described restriction, and provides full flexibility on all code lists. For details, see the OASIS STGT strategy document at http://www.oasis-open.org/committees/document.php?document_id=35864

MXV NDR 2.1 provides the same code list flexibility as UBL by adopting the same data type schema modules as UBL 2.1

NDR 2.1 benefit:

• Complete control over all code list changes, including the NDR 2.0 inbuilt UN/CEFACT code lists Country, Currency, Unit of Measure and MIME type, without the need for issuing new schema versions.

NDR 2.0:

The following diagram depicts the Library Schema Module import structure of UBL NDR 2.0 and MXV NDR 2.0:

NDR 2.1:

The same high level of componentisation and re-use can be achieved in MXV NDR 2.1 by using the new UBL NDR 2.1 (*) library schema module structure, which by the way is backward-compatible with any NDR 2.0 instance document:

NDR 2.1 benefits:

• The total number of XML Library Module schemas is reduced from 9 to 6

• The total number of nested schema imports is reduced from 15 to 8

• The simpler XML Schema import structure reduces complexity for developers

• Less schemas and namespaces result in simpler messaging server and XML catalogue configuration

• The size of the XML Library schemas is reduced by approx. 0.6 MB

• Smaller operational footprint leads to better performance

• The QDT Library Module Schema has become virtually maintenance-free

• Only two of the Library Schema Modules require the administrator's maintenance: CBC and CAC Library Schema Modules

• Simpler and faster schema maintenance for the administrator has reduced the release turn-around time

• Simpler schemas and import structures reduces the risk of errors

• Cost savings in design, implementation and operation of XML Schemas

• Transparent upgrade from an instance document perspective, i.e. a 2.0 instance document will validate against a 2.1 document schema (provided this contains no business-driven backward-incompatible changes)

UBL NDR 2.1 (*) delivered many benefits, yet apart from the one-off migration to NDR 2.1 no real disadvantages.

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