xmlns:tbx TBX Namespace Declaration

This is not an attribute, but the namespace pseudo-attribute. The value provides a prefix and URI to use for the TBX elements. All namespace prefixes must be associated with a URL. This namespace is required on a top-level element if the TBX-namespaced elements are to be used.
FIXED (not settable) on many elements; click for list and usage
Value Meaning
urn:iso:std:iso:30042:ed-1 The URI that goes with the “tbx” prefix.
Restriction This attribute has a fixed value which may not be changed in the XML document.