fn:unparsed-text-available

fn:unparsed-text-available($href as xs:string?) as xs:boolean

fn:unparsed-text-available(
    $href as xs:string?, 
    $encoding as xs:string
) as xs:boolean

This function is deterministic, context-dependent, and focus-independent. It depends on static base URI.

The fn:unparsed-text-available function determines whether a call on the fn:unparsed-text function with identical arguments would return a string.

If the first argument is an empty sequence, the function returns false.

In other cases, the function returns true if a call on fn:unparsed-text with the same arguments would succeed, and false if a call on fn:unparsed-text with the same arguments would fail with a non-recoverable dynamic error.

The functions fn:unparsed-text and fn:unparsed-text-available have the same requirement for determinism as the functions fn:doc and fn:doc-available. This means that unless the user has explicitly stated a requirement for a reduced level of determinism, either of these functions if called twice with the same arguments during the course of a transformation must return the same results each time; moreover, the results of a call on fn:unparsed-text-available must be consistent with the results of a subsequent call on unparsed-text with the same arguments.

This requires that the fn:unparsed-text-available function should actually attempt to read the resource identified by the URI, and check that it is correctly encoded and contains no characters that are invalid in XML. Implementations may avoid the cost of repeating these checks for example by caching the validated contents of the resource, to anticipate a subsequent call on the fn:unparsed-text or fn:unparsed-text-lines function. Alternatively, implementations may be able to rewrite an expression such as if (unparsed-text-available(A)) then unparsed-text(A) else ... to generate a single call internally.

Since the function fn:unparsed-text-lines succeeds or fails under exactly the same circumstances as fn:unparsed-text, the fn:unparsed-text-available function may equally be used to test whether a call on fn:unparsed-text-lines would succeed.