In programming your chatbot, it is important to realize the complexity of language that you will need to address using your AIML code. This is achieved by composing categories that will match each formulation of the question you desire to answer. Using simple text matching, this is indeed a daunting task. However, AIML provides a number of approaches to streamline your coding task.

The first of these is the introduction of wildcard characters to the category pattern. AIML uses two different wildcard characters, the asterisk * and the underscore character _. Both of these characters can be used to match either single words or multiple-word strings. The difference between them is the priority or order in which they are selected in a text-matching sequence.

An underscore is processed first, before any additional exact pattern match is sought. If no pattern with a matching underscore sequence is identified among the coded AIML categories, then an exactly matching text string is sought. Finally, if no matching text string is located, a pattern match using an asterisk is sought.

The following provides an example of how this could work. Let’s say the customer asks the question, “Do you have ebooks?” You want to respond with the template message <template>We do not currently offer ebooks.</template>. You can use a number of different pattern formulations in order to generate the desired template.

First and most simply, you could program the pattern using two underscore characters around the abbreviation “EBOOK.” This would cue a response with the desired template, but would also respond with this same template to all instances of comments or questions about e-books, not just about their availability. An alternative would be to use the asterisk in the same position. Changing the underscore to an asterisk allows you to continue to catch the same wildcard matches, but also allows you to program specific responses to different text matches should you wish. Table 3.2 illustrates this.

Suffice it to say, in order to avoid many pattern matching-problems, it’s safer to use the asterisk than the underscore in most instances.

The value provided for an asterisk wildcard character in the question pattern can also be repeated in the answer template using a <star/> tag. This is a single tag that is used to repeat whatever text is matched by the pattern asterisk in the template. This can be extremely valuable in clarifying the intent of the customer or providing options for further interaction.

In the following example, an asterisk is inserted to allow the question to ask about any person. By repeating the name in the template response, the potential search parameters are clarified.

<category>

<pattern>DO YOU KNOW WHO * IS</pattern>

<template>Would you like me to search for <star/>?</template>

</category>

In the above example, to the question “Do you know who Melvil Dewey is?” the chatbot will respond, “Would you like me to search for Melvil Dewey?”

It is also possible to implement pattern/template pairs containing multiple wildcard strings. In such cases, it is important to identify which asterisk string is to be repeated in the template. This is done by assigning each asterisk in the sequence an index value equal to its ordinal position in the sequence. The first asterisk will match index 1, the second index 2, etc. Using this scheme, it is possible to further simplify the above code as follows:

<category>

<pattern>* WHO * IS</pattern>

<template>Would you like me to search for <star index=”2”/>?</template>

</category>

Another option for making coding more efficient is to use <srai> tags. SRAI stands for “symbolic reduction artificial intelligence.” This tag option allows you to replicate a given template response to multiple pattern inputs without writing each of these out in full. To use SRAI, you must first create a unique pattern that is unlikely to be matched by a simple text-matching scheme. It is often best to use a sequence of letters and numbers to name these patterns. Having chosen a pattern sequence for your SRAI element, you then compose the template for this sequence. Once this base category is created, you can then refer to it in the template of any other category you wish to make respond the same way.

<category>

<pattern>LIB2FINES</pattern>

<template>Fines for overdue books are ten cents per day</template>

</category>

<category>

<pattern>What are library fines for books?</pattern>

<template><srai> LIB2FINES </srai></template>

</category>

<category>

<pattern>How much are library fines?</pattern>

<template><srai> LIB2FINES </srai></template>

</category>

The <srai> efficiency option focused on offering the same response (or template) to multiple questions (or patterns). The <random> option provides a way to offer multiple responses to a single question. It is, in design, similar to HTML list formatting. For a given pattern to which you wish to offer multiple responses, simply insert into the template a <random> tag followed by <li> tags for each formulation of the response you wish to offer. Be certain to close each <li> tag with </li>, and the <random> tag with </random>.

<category>

<pattern>I like the library.</pattern>

<template>

<random>

<li>I’m glad you like our services!</li>

<li>Thank you! We aim to please.</li>

<li>I’m happy to hear that!</li>

</random>

<template>

</category>