<P> Well - formed documents also bring into focus the issue of valid versus correct XML . According to the W3 Organization, valid documents are those that validate against a DTD . The rules of validity mean that a document complies with the restraints stated within a DTD . Thus, tags or entities must be in conformity to the rules and relations established within a DTD . However, there is no control on whether a tag or entity is correct . Thus a first level head tag could be applied to a second level head object and be valid, while incorrect . </P> <P> The emphasis on well - formed documents has developed within the publishing industry where the use of left and right angle bracket delimited information has become problematic . Emphasis on the well - formed document allows for the definition, delimiting, and nesting of content to be managed within programs that are not XML, per se, but exhibit the characteristics or potential for being well formed . </P> <P> There are several tools available to determine if a given XML document is well formed . One example is: </P> <Ul> <Li> W3 Schools XML Validator </Li> </Ul>

Which of the following are characteristic of well-formed xml documents