> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf
> Of Ovidiu Predescu
> Sent: maandag 10 december 2001 23:12
> To: Berin Loritsch
> Cc: [EMAIL PROTECTED]
> Subject: Re: [RT] Managing Flow and Resources
<snip/>
> When you have forms whose result can branch the flow, you can use the
> control flow statements, like "if", "while" etc. Here's a non-trivial
> example of continuations at work.
>
> function shopping-cart()
> {
> set-default-pipeline("my-pipeline");
> send-page("show-shopping-cart.xml");
> operation = request.getParameter("operation");
> if (operation == "continue-shopping")
> send-page("continue-shopping");
> else if (operation == "buy")
> buy();
> else if (operation == "update-quantities")
> update-quantities();
> }
>
> function buy()
> {
> credentials = get-user();
> ship-to-address(credentials);
> charge-credit-card(credentials);
> }
>
> function get-user()
> {
> // get-user() returns only with valid credentials.
> // If no valid credentials are found, this function never returns.
>
> for (count = 0; count < 3; count++) {
> send-page("get-username.xml");
>
> user = request.getParameter("username");
> passwd = request.getParameter("password");
>
> usersDB = UsersDatabase.newConnection();
> if (!usersDB.isUserKnown(user, passwd))
> registration();
> else
> return userDB.credentialsForUser(user, passwd);
> }
>
> // This shows the user a sorry page with a single link that
> points to Home.
> // This is an example of a non-local exit, where the computation will
> // continue at a different location in the program.
> send-page("sorry-page.xml");
> }
>
> function ship-to-address(credentials)
> {
> send-page("ship-to-address", "my-pipeline",
> {"address" = credentials.getAddress()});
> change = request.getParameter("change");
> if (change)
> return change-address(credentials);
> else
> return credentials.getAddress();
> }
>
> function registration()
> {
> // Register a new user
> send-page("register.xml");
>
> while (true) {
> username = request.getParameter("username");
> if (usersDB.isUserKnown(username))
> send-page("user-already-known.xml", {"username" = username});
> else
> break;
> }
>
> passwd = request.getParameter("password");
> usersDB.registerNewUser(username, password);
>
> send-page("registration-successful.xml"});
> }
>
> function change-address(credentials)
> {
> // Function to change the address. Returns the address the user chose
> ...
> }
>
> function charge-credit-card(credentials)
> {
> // Charge the credit card of the user
> ...
> }
>
> function update-quantities()
> {
> ...
> }
>
> This example shows how Java objects are used to perform critical
> functions like connecting to the user's databases, checking for new
> users and registering them.
<snip/>
> Also I don't like to express logic in XML, it's not what it was
> designed for. We need a programming language, so why use an XML syntax
> to express this? The attempts to use XML to implement a programming
> language are taking XML too far, where it wasn't designed to work.
If and when our little flowmap specification language remains as beautifully
terse and human-readable as Ovidiu's example above, I do not see a need for an
XML syntax. What we could do to support user adoption is provide plenty of
already implemented functions, and perhaps maybe later a Visio-like GUI to
draw the flow.
I must say I prefer this instead of convoluting the sitemap with Actions &
redirects, even though I haven't figured out Velocity in this new grand Scheme
(hehe) of things.
We're allowed to change opinions over here, no? ;-)
Nice work!
</Steven>
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, email: [EMAIL PROTECTED]
