How to set variables with default values in AIML?

Question

I want to set some variables to default values, so if the user never supplies, say, their username, my responses won't have odd empty spaces in them.

Sample of what I tried but didn't work:

<set name="name">user</set>
<category>
<pattern>HELLO</pattern>
<template>
Hello, <get name="name"/>.
</template>
</category>

Answer 1

The description of <get /> leads to the .pdefaults file.

Instead of

<set name="name">user</set>

in the UDC, the following single line in .pdefaults gets the result you want

[["name", "user"]]