managing side-effects in XSLT

Dimitre's warning about the sequential occurrence of code in
XSLT templates not implying sequential execution of side-effects
(if any) is still spinning in my mind. I am doing quite a bit
of interaction with the real world in my XSLT work and one of
those is JDBC access. I am assuming XSLT v2.0 and XPath v2.0 as
implemented in Saxon 7.

Here is some use cases and I simplify the JDBC API a lot to avoid
cluttering the point. I will use the following namespace prefixes:

DriverManager
Connection
PreparedStatement
ResultSet

void DriverManager.registerDriver('my.Driver');
Connection conn = DriverManager.getConnection('jdbc:my:address');
PreparedStatement stmt =
   conn.prepareStatement('SELECT * FROM ANSWERS WHERE QUESTION=?');
void stmt.setString(1,'HOWSITGOING') // returns value that set before
ResultSet rset = stmt.executeQuery();

- static functions returning void
- static functions returning an object
- method functions returning an object
- method functions returning irrelevant stuff

As I noted earlier, to make sure that thing happen in this
order, I want to define variables for most of these steps and
link them together. For the very little that I comprehend of
the very little that I had taken the time to read about monads,
this notion of a variable representing an action (once it is
being evaluated) is somewhat related to monads.

I welcome other suggestions, Dimitre mentioned continuation
passing, and it would be nice to see an example of that.

<xsl:variable name="drivers-registered"
   select="DriverManager:registerDriver('my.Driver')"/>

and now I would like to have a nice form that allows me to say that
first I need to have the drivers-registered and then I need to
get the connection.

<xsl:variable name="connection"
   select="..."/>

     if(empty($drivers-registered))
       then DriverManager.getConnection(...)
       else false()

this is because Saxon returns an empty sequence when a function returns
void. But this looks silly, so at least I could define a function
aliasing empty as "ensured"

     if(ensured($drivers-registered))
       then DriverManager.getConnection(...)
       else false()

but what's ugly here is that I need this "else" part, which really
doesn't make sense, instead of "else" I'd need to fail.

Another way of doing it would be to construct a sequence and then
pick the last value. This is sort of reminescent of the LISP
PROG form:

but there is no last function for sequences standard in XPath, also,
this would not even ensure that the $drivers-registered are ever
evaluated because they are never asked for. The trick here is,
as I understand it, to make a form that would be guarranteed
executed in the order given.

which, again, like LISP, would evaluate each argument and return the
value of the last.

Wouldn't it be nice if something like that was part of XSLT/XPath?
It seems that this needs to be a primitive function, because
nothing really guarantees this behavior in the general case.

thanks,
-Gunther

--
Gunther Schadow, M.D., Ph.D.                    gschadow@xxxxxxxxxxxxxxx
Medical Information Scientist      Regenstrief Institute for Health Care
Adjunct Assistant Professor        Indiana University School of Medicine
tel:1(317)630-7960                         http://aurora.regenstrief.org