content element-qualifier* (is | isnt) (content-type | content-type-list)

Tests an element's declared content type or content model type. It can also be used to determine if an element has a conref attribute, in which case the element is effectively EMPTY, no matter what its declared type is.

The content type can be:

• any -- indicates an element with a content model of ANY.
• empty -- indicates an element with a declared content of EMPTY.
• cdata -- indicates an element with a declared content of CDATA.
• rcdata -- indicates an element with a declared content of RCDATA.
• element -- indicates an element with a content model that allows other elements but does not allow #PCDATA.
• mixed -- indicates an element declared with a content model that allows #PCDATA or a content model of ANY. (The content model ANY allows #PCDATA.) Elements declared with a content model of ANY satisfy the tests for both MIXED content models and the ANY content model. So if ANY and MIXED are to be distinguished, any should be tested before mixed. In essence, any overrides mixed.
• conref -- indicates an element for which a CONREF attribute has been specified.

A content-type-list is a list of content types separated by or or "|", or by and or "&".

If element qualifiers are specified, the test applies to the qualified element. Otherwise, the current element is tested.

The following down-translate program illustrates how content is tests can be used to provide an analysis of every element in a document:

  down-translate

  element #implied
     output "%n<%q>: "
     do when content is element
       output "element"
     else when content is any
       output "any"
     else when content is mixed
       output "mixed"
     else when content is cdata
       output  "cdata"
     else when content is rcdata
       output "rcdata"
     else when content is empty
       output "empty"
     done
     output " (conref)" when content is conref
     output "%n"

     ; Finally, process the content:
     output "%c"