[saml-dev] Encoding of URI in "Alternative SAML Artifact Format"

Dear experts,

chapter 9 of the Bindings document introduces an alternative format for the Assertion Artifact:

TypeCode          := 0x0002
RemainingArtifact := AssertionHandle SourceLocation
AssertionHandle   := 20-byte_sequence
SourceLocation    := URI


To create the artifact, Base64 is to be applied to the concatenation of TypeCode and RemainingArtifact.
Base64 uses Bytes as input.

The specification does not specify how to convert the character-like URI into bytes. 
On an ASCII machine, the letter "A" within the URI will map to byte value 65, but on an EBCDIC machine the byte value will be 193.

Is UTF-8 the recommended choice?
Should it be explicitly expressed in the specification?

Juergen Kremp,
SAP AG