Disallowing code points

[Chris Wright]

There have been some discussions lately about explicitly disallowing specific code points

I believe that the decisions to disallow specific code points should be kept to an absolute minimum, with strong technically justifiable reasons being required for specific singling out of code points. Again these are in the end 'policy' based decisions that have the potential to impact languages not yet even considered. Registries are required by ICANN/IANA to identify the list of 'characters' that they will allow to be used for registration of domain names in each particular language they would like to support. As per my previous post, Registries are not in the business of doing things to jeopardised the security and stability of their own namespaces. We have the rule system, that is Unicode independent for determining the protocol status of each code point and barring the exceptions, this should be sufficient. If we must make comment on other code points, as per context rules, we should discuss these in the context of Best Common Practices and set forth recommendations for registries to follow about which code points that they should consider 'dangerous' and not allow in the definition of their languages.

If we take a single code point like Tatweel, for example, and argue that it's not required to be used anymore and thus should be disallowed, then why not take the whole class of 'dead' languages and disallow those? I have to ask what is the harm in keeping those code points PVALID? At least this is the most flexible approach going forward, and doesn't force us to make decisions now that we may not necessarily have all the information about.  We can publish a BCP discussing the issues with specific code points and educate the registries as to the right thing to do.

Thanks

Chris Wright
Chief Technology Officer
AusRegistry Pty Ltd