Once again, public identifiers are a trick inherited from SGML that are probably only useful to people who already have working SGML software installed. Remember that if you use public identifiers within your own organization, that's perfectly OK, but if you want to interchange XML documents with anybody external, they have the right to demand, and you have the obligation to provide, a working system identifier (URI) for each external entity.
Copyright © 1998, Tim Bray. All rights reserved.