Saxon tries to be helpful if the value of a to be
created attribute contains double quotes and encloses
the value in single qoutes.
Especially when dealing with server side scripting one
could create (X)HTML which is valid only after having
been parsed by the server.
<% get_image_info(1, "src"); %>'>
After parsed by server:
which wouldn't be valid (X)HTML anymore.
IMHO an option (with a reasonable default) to configure
the quoting behavior would enable to create such
documents in a way which should cover all cases.