ulink.hyphenate — Allow URLs to be automatically hyphenated
If not empty, the specified character (or more generally,
content) is added to URLs after every character included in the string
ulink.hyphenate.chars parameter (default
is “/”) to enable hyphenation of ulinks. If the character
in this parameter is a Unicode soft hyphen (0x00AD) or Unicode
zero-width space (0x200B), some FO processors will be able to
reasonably hyphenate long URLs.
Note that this hyphenation process is only applied when the ulink element is empty and the url attribute is reused as the link text. It is not applied if the ulink has literal text content. The same applies in in DocBook 5, where ulink was replaced with link with an xlink:href attribute.