easy_nlu

A Natural Language Understanding (NLU) toolkit for Flutter.

This is a direct port of https://github.com/kolloldas/EasyNLU

easy_nlu is a combinatory categorial grammar (CCG) library written in pure Dart. It is capable of transforming natural language utterances such as:

meet Alice Monday night for dinner

into a canonical, structured form like:

{
    "task": "meet Alice", 
    "auxtask": "dinner",
    "startTime": {
        "dow": 1,
        "shift": "night"
    }
}

Capabilities

The high level steps to integrating an NLU capability, broadly are the following:

1. Define the rules for the parser
2. Collect labeled samples and train the parser
3. Write a resolver to convert the strcutured form into task specific objects
4. Integrate into the mobile app

Parsing

As a toy example, we can define a task such as turning on and off phone features like Bluetooth, Wifi and GPS.

i.e.:

{"feature": "bluetooth", "action": "enable}

A few sample inputes could be:

• turn off Bluetooth
• bt on
• enable wifi
• kill GPS

Defining Rules

We can say that at the top level, we have a command that must have a feature and an action. We can capture this as

Rule r1 = Rule.fromStrings("\$Setting","\$Feature \$Action");
Rule r2 = Rule.fromStrings("\$Setting","\$Action \$Feature");

A rule contains a left hand side (LHS) and right hand side (RHS) at a minimum. By convention, we prepend a "$" to a word to indicate it denotes a category. A category represents a collection of words or other categories. We can capture our target words like "bluetooth", "bt", "wifi", etc as lexical rules, normalized for variations and structured into sub-features:

List<Rule> featureRules = [
        Rule.fromStringWithParsedTemplate("\$Feature", "\$Bluetooth", "{\"feature\": \"bluetooth\"}"),
        Rule.fromStringWithParsedTemplate("\$Feature", "\$Wifi", "{\"feature\": \"wifi\"}"),
        Rule.fromStringWithParsedTemplate("\$Feature", "\$Gps", "{\"feature\": \"gps\"}"),
        Rule.fromStrings("\$Bluetooth", "bt"),
        Rule.fromStrings("\$Bluetooth", "bluetooth"),
        Rule.fromStrings("\$Wifi", "wifi"),
        Rule.fromStrings("\$Gps", "gps"),
        Rule.fromStrings("\$Gps", "location"),
];

For our actions:

List<Rule> actionRules = [
Rule.fromStringWithParsedTemplate(
            "\$Action", "\$EnableDisable", "{\"action\": \"@first\"}"),
        Rule.fromStringWithParsedTemplate(
            "\$EnableDisable", "?\$Switch \$OnOff", "@last"),
        Rule.fromStringWithParsedTemplate(
            "\$EnableDisable", "\$Enable", "enable"),
        Rule.fromStringWithParsedTemplate(
            "\$EnableDisable", "\$Disable", "disable"),
        Rule.fromStringWithParsedTemplate("\$OnOff", "on", "enable"),
        Rule.fromStringWithParsedTemplate("\$OnOff", "off", "disable"),
        Rule.fromStrings("\$Switch", "switch"),
        Rule.fromStrings("\$Switch", "turn"),
        Rule.fromStrings("\$Enable", "enable"),
        Rule.fromStrings("\$Disable", "disable"),
        Rule.fromStrings("\$Disable", "kill")
];

The "?" in the third rule means that the category is optional.

To determine if a parse is successful, the parser looks for a special category called the root category. It is denoted as "$ROOT".