Re: P work in new charter

Alex Rousskov wrote:

 > Let's call the service-configuration language "S". Suppose we have
 > service "foo", with three parameters: "a", "b", and "z".

What about something like

     // P code starts here
     if (message meets criteria) then {
         service := services.find("foo");
	call service(message.body, 1, 2, message.size);
     }

assuming the service is defined as a function with four input 
parameters, e.g foo(body, a, b, z).

> You do not foresee something like the "encapsulated" code below, do
> you?
> 
>     // P code starts is here
>     if (message meets criteria) then {
>         service := services.find("foo"); // still P code
>         service.configure(<![SCODE[>     // P code ends here
>             a = 1;               // S code to be passed to the service
>             b = 2;               // S code
>             z = message.size;    // S code accessing P objects??
> 	<]SCODE]>);                      // P code resumes here
> 	call service(message.body);      // P code
>     }

The approach with "encapsulated" code would allow me to program the 
entire service in "P", i.e. using "encapsulated" code to write a virus 
scanner or anything I want, and then just call a service that does 
nothing else then executing the "encapsulated" code fragment - not a 
good idea, IMHO.

> Or is there a better way? Please give an example of how to configure a
> dynamically selected service in S without tainting P.

Maybe we were talking about diferent things... When you talk about 
"customizing a service", do you mean "passing dynamic input parameters 
to a service"? If yes, I think we're aligned - I would assume that 
this is possible (see my example above). If it also includes passing 
code fragments to the service for execution, I start feeling 
uncomfortable.

> Here is another example calling (and configuring) an HTTP-unaware
> content scanning service that needs to know the content MIME type:
> 
>   if (http.message.mime == "application/exe") then
>     call services.scan("Windows binary", http.message.body);
>   else
>   if (http.message.mime == "text/html") then
>     call services.scan("HTML page", http.message.body);
>
> How can the above selection/configuration be done without tainting P?

That makes sense to me and seems to be pretty much in line with the 
example I gave above. I would consider this ok - this is just calinbg 
a service with the correct parameters.

-Markus