Artificial Intelligence Markup Language

Categories in AIML form the fundamental unit of knowledge. A category consists of at least two further elements: the pattern and template elements. Here is a simple category:

<category>
  <pattern>WHAT IS YOUR NAME</pattern>
  <template>My name is Michael N.S Evanious.</template>
</category>

When this category is loaded, an AIML bot will respond to the input "What is your name" with the response "My name is Michael N.S Evanious."

A pattern is a string of characters intended to match one or more user inputs. A literal pattern like

WHAT IS YOUR NAME

will match only one input, ignoring case: "what is your name". But patterns may also contain wildcards, which match one or more words. A pattern like

WHAT IS YOUR *

will match an infinite number of inputs, including "what is your name", "what is your shoe size", "what is your purpose in life", etc.

The AIML pattern syntax is a very simple pattern language, substantially less complex than regular expressions and as such less than level 3 in the Chomsky hierarchy. To compensate for the simple pattern matching capabilities, AIML interpreters can provide preprocessing functions to expand abbreviations, remove misspellings, etc.

The AIML syntax itself is at least as complex as finite state machines and as such at least of level 3 in the Chomsky hierarchy. This is because a state correlates to one topic. To implement that behavior, the topic should have a "*" Pattern to make sure, that the state is not left accidentally. A state transit is implemented with the <think><set name="topic">state2</set></think> Tag. This way, the bot will be able to "remember" the topic talked about or even user privileges, which are gained during the chat.

A template specifies the response to a matched pattern. A template may be as simple as some literal text, like

My name is John.

A template may use variables, such as the example

My name is <bot name="name"/>.

which will substitute the bot's name into the sentence, or

You told me you are <get name="user-age"/> years old.

which will substitute the user's age (if known) into the sentence.

Template elements include basic text formatting, conditional response (if-then/else), and random responses.

Templates may also redirect to other patterns, using an element called srai (Symbolic Reduction in Artificial Intelligence). This can be used to implement synonymy, as in this example (where CDATA is used to avoid the need for XML escaping):

<category>
  <pattern>WHAT IS YOUR NAME</pattern>
  <template><![CDATA[My name is <bot name="name"/>.]]></template>
</category>
<category>
  <pattern>WHAT ARE YOU CALLED</pattern>
  <template>
    <srai>what is your name</srai>
  </template>
</category>

The first category simply answers an input "what is your name" with a statement of the bot's name. The second category, however, says that the input "what are you called" should be redirected to the category that matches the input "what is your name"—in other words, it is saying that the two phrases are equivalent.

Templates can contain other types of content, which may be processed by whatever user interface the bot is talking through. So, for example, a template may use HTML tags for formatting, which can be ignored by clients that don't support HTML.