NamespaceName + Symbol is a globally unique ID for an entry – just as the UL is (when the UL is treated appropriately e.g. ignoring certain bytes of the UL when making comparisons).

So, NamespaceName sets the scope within which a Symbol is unique.


NamespaceName must be specified for every entry in every Register.

The value of NamespaceName is controlled / pre-determined for entries with SMPTE-controlled ULs.

Entries in Classes 13 and 14 (that are controlled by Class 13/14 Registrants) can use any valid absolute URI (see RFC3986) for NamespaceName as long as:

  • they have permission to use that URI from the owner of the URI’s “authority” / “host” / “domain name”
  • the NamespaceName is different to those used for SMPTE-controlled entries in the Registers

A unique “default” NamespaceName value is offered to Class 13/14 Registrants at the point of registration which they can optionally use.

It is strongly recommended that no NamespaceName value is used in more than one Register.

Use of NamespaceName as an XML namespace: Reg-XML etc

In the Registers, NamespaceName is simply a string (a URI) that defines the scope of Symbol uniqueness. It is not, as such, directly anything to do with XML namespaces.

However, the established practice is to make use of the NamespaceName when creating Reg-XML assets from the Registers:

  • one Reg-XML Extension MetaDictionary is created per NamespaceName value
  • The NamespaceName value is used for the SchemeURI in this Extension MetaDictionary
  • It is in turn used as the targetNamespace in the Reg-XML XML Schema that is generated from this Reg-XML Extension MetaDictionary

These Reg-XML assets are auto-generated from the Registers and available from the Registers Development Website.

Note: the “AAF” “baseline” in SMPTE ST 2001-2 does not follow this practice but uses an independent URI for SchemeURI / XML namespace.

This means that NamespaceName values in the Registers must not be used as XML namespaces (e.g. as the targetNamespace in an XML Schema) in any other kind of XML document / Schema (e.g. not even in Reg-XML v2, should that ever exist) because then there would be multiple incompatible XML Schemas in existence with the same XML namespace (leading to interoperability problems).