Zone File Checking Tools.
Let's add some information to the current debate on zone file checking: There is a variety of free tools available which performs many checks like the ones mentioned in IANA's FAQ on TLD zone file access. Examples include dnswalk, dlint, doc.
Unless IANA is actually using one (or several) of the tools listed above in order to check TLD zone files, it would most likely be a great service to the community if they'd publish the software they are currently using to check zone files - I don't believe they are inspecting TLD zone files manually. Such a tool could be helpful to those who (as opposed to large ccTLDs) still edit zone files manually.
