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Library for creating state-machine-based chatbots.

Project description

State Transition Dialogue Manager

Defines a dialogue management framework based on state machines and regular expressions.

Class DialogueFlow is the main class to initialize. It defines a state machine that drives natural language conversation. State transitions in the state machine (alternately) represent either system or user turns.

dialogue_manager = DialogueFlow('start') initializes a new DialogueFlow object with 'start' as the initial state of the state machine.

All states must be specified before they are used in a transition by calling the .add_state(state) method. Each state is defined as a string literal like the following:


Alternatively, multiple states can be added at once using the .add_states(states) method where states is a list of string literals, like the following:

dialogue_manager.add_states(['feelings_pos', 'feelings_pos_reason'])

To add transitions, use: .add_transition(source, target, NLU, NLG_list) method like the following:

    'feelings_pos', 'feelings_pos_reason',
    '{(what, &feelings_positive, {part, most, best}),'
    '(you, &feelings_positive)}',
    ['what excites you the most']

where the first two arguments are the source and target states of the transition, the third argument is a string that defines a set of natural language expressions given by a user that satisfy the transition (see below), and the fourth argument is a list of natural language expressions that the system selects as a response when taking this transition during its turn.

If you want to define a function that is used to evaluate satisfaction of the transition, instead of (or in addition to) the natural language expressions, you can pass the function name in as the optional fifth parameter evaluation_function of the .add_transition method.

Similarly, if you want to define a function that is ran upon selection of a transition, such as to update the current variables (see below), you can pass the function name in as the optional sixth parameter selection_function of the .add_transition method.

A user turn can be taken, updating state, using


where input is a string representing the user utterance.

A system turn can be taken using


NLU Expressions

Strings created for transition NLU define a set of user expressions that satisfy the transition by compiling into regular expressions. These expressions can be formed using the below constructs, which are all arbitrarily nestable and concatenable:


'hello there'

directly match the user utterance "hello there"


'{hello there, hi}'

matches if the utterance contains any term inside {}, in this case "hello there", "hi", "hi hello there", and "oh hi bob" all match


'<bob, hi>'

matches as long as the utterance contains all terms inside <>, in this case, "hi bob" and "oh bob hi" both would match, but not "hi"


i am -bad

prepend - to negate the next term in the expression. The example will match any expression starting with "i am" where "bad" does NOT follow. Note that the scope of the negation extends to the end of the utterance due to limitations in regex.

Flexible sequence

'(hi, bob, how, you)'

matches as long as the utterance contains all terms inside (), and the terms are ordered properly within the utterance. Matches in the example include "hi bob how are you", but not "how are you bob"

Inflexible sequence

'[how, are, you]'

matches an exact sequence of terms with no words inserted between terms. The only utterance matching the example is "how are you"

Regular expression

'/[A-Z a-z]+/'

substrings within // define a python regex


'[{hi, hello} (how /is|was/ weekend)]'

would match "hi how was your weekend", "oh hello, so how is the weekend going", ...

Variable assignment

'i am %f={good, bad}'

using %var= will assign variable var to the next term in the expression. The variable will persist until overwritten, and can be referenced in future NLU or NLG expressions. The example would match either "i am good" or "i am bad", and assigns variable "f" to either "good" or "bad" depending on what the user said.

Variable reference

why are you $f today

using $ references a previously assigned variable. If no such variable exists, the expression as a whole returns with no match. The example would match "why are you good today" if f="good", but would not match if f="bad"

If NLU debugging gets tricky

For a precise understanding of the NLU expressions you produce, you can view the compiled python regex like so:

print(dialogue_manager.graph().arc(source, target).re)

And then debug at (make sure to switch to python regexes)

Knowledge base and ontology

The Knowledge Base and Ontology are optional components of the dialogue manager that allow you to write more generalizable transitions.

The Knowledge Base and Ontology are modeled as a unified (single) directed graph. You specify the knowledge and ontology elements you need by updating the database.json file.

The Knowledge Base is defined as a list of predicates, where a predicate is stored as a list [subject, relation, object].

'predicates': [
    ['dog', 'sound', 'bark'],
    ['bark', 'quality', 'annoying'],
    ['scarlett johansson', 'plays', 'black widow']

The Ontology is defined as a mapping between categories and a list of elements of that category. The category string must always begin with the ampersand symbol: &.

'ontology': {
    '&feeling': ['sad', 'happy', 'angry'],
    '&animal': ['dog', 'cat', 'bird']

Taking these two structures together, the final database.json for this example would look like the following:

'predicates': [
        ['dog', 'sound', 'bark'],
        ['bark', 'quality', 'annoying'],
        ['scarlett johansson', 'plays', 'black widow']
'ontology': {
        '&feeling': ['sad', 'happy', 'angry'],
        '&animal': ['dog', 'cat', 'bird']

Ontology reference

'i am &feeling'

Using a prepended & references a node in the ontology. Any subtype of the referenced node can be matched in the expression.

Knowledge base reference

'a dog can #dog:sound#'

substrings encapsulated within ## reference a set of nodes in the knowledge graph. The set is created by starting at the node defined before the initial :, then traversing arcs labeled by each subsequent term following :. In this case, all nodes related to "dog" by a "sound" arc are valid matches. For example, the utterances "a dog can bark" and "a dog can growl" might be matched if "bark" and "growl" were present in the knowledge graph.

'a dog is #dog:sound:quality#'

knowledge base expressions can chain multiple predicates together. suppose the predicates sound(dog, bark) and quality(bark, annoying) were present in the knowledge base. The expression would match "a dog is annoying"

'black widow is played by #black widow:/plays#'

using / reverses the direction of a knowledge graph relation. If plays(scarlett johansson, black widow) is present in the KB, then the above expression matches "black widow is played by scarlett johansson"

'a %a=&animal, can #$a:sound#'

knowledge graph expressions can be built using veriable references. Together with ontology reference, highly generalizable expressions can be written. Given an appropriately constructed KB and ontology, this example might match "a cow can moo", "a dog can bark", and everything in between.

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