Skill Structure

Exploring the foundational components of a basic Mycroft Skill.

Video Tutorial: Anatomy of a Skill

If we now navigate to our new Skill, we can see that it is made up of a number of files and folders.

$ ls -l
total 20
drwxr-xr-x 3 kris kris 4096 Oct  8 22:21 dialog
-rw-r--r-- 1 kris kris  299 Oct  8 22:21 __init__.py
-rw-r--r-- 1 kris kris 9482 Oct  8 22:21 LICENSE
-rw-r--r-- 1 kris kris  283 Oct  8 22:21 README.md
-rw-r--r-- 1 kris kris  642 Oct  8 22:21 settingsmeta.yaml
drwxr-xr-x 3 kris kris 4096 Oct  8 22:21 vocab

We will look at each of these in turn.

vocab, dialog, and locale directories

The dialog, vocab, and locale directories contain subdirectories for each spoken language the skill supports. The subdirectories are named using the IETF language tag for the language. For example, Brazilian Portugues is 'pt-br', German is 'de-de', and Australian English is 'en-au'.

By default, your new Skill contains one subdirectory for United States English - 'en-us'. If more languages were supported, then there would be additional language directories.

$ ls -l dialog
total 4
drwxr-xr-x 2 kris kris 4096 Oct  8 22:21 en-us

Dialog Directory

There will be one file in the language subdirectory (ie. en-us) for each type of dialog the Skill will use. Currently this will contain all of the phrases you input when creating the Skill.

$ ls -l dialog/en-us
total 4
-rw-r--r-- 1 kris kris 10 Oct  8 22:21 first.dialog

When instructed to use a particular dialog, Mycroft will choose one of these lines at random. This is closer to natural speech. That is, many similar phrases mean the same thing.

For example, how do you say 'goodbye' to someone?

• Bye for now

• See you round

• Catch you later

• Goodbye

• See ya!

Vocab Directory

Each Skill defines one or more Intents. Intents are defined in the vocab directory. The vocab directory is organized by language, just like the dialog directory.

We will learn about Intents in more detail shortly. For now, we can see that within the vocab directory you may find multiple types of files:

• .intent files used for defining Padatious Intents

• .voc files define keywords primarily used in Adapt Intents

• .entity files define a named entity also used in Adapt Intents

In our current example we might see something like:

$ ls -l vocab/en-us
total 4
-rw-r--r-- 1 kris kris 23 Oct  8 22:21 first.intent

This .intent file will contain all of the sample utterances we provided when creating the Skill.

Locale Directory

This directory is a newer addition to Mycroft and combines dialog and vocab into a single directory. This was requested by the Community to reduce the complexity of a Skills structure, particularly for smaller Skills. Any of the standard file types that we've looked at so far will be treated the same if they are contained in the dialog, vocab, or locale directories.

This also includes the regex directory that you will learn about later in the tutorial.

__init__.py

The __init__.py file is where most of the Skill is defined using Python code. We will learn more about the contents of this file in the next section.

Let's take a look:

Importing libraries

from adapt.intent import IntentBuilder
from mycroft import MycroftSkill, intent_handler

This section of code imports the required libraries. Some libraries will be required on every Skill, and your skill may need to import additional libraries.

Class definition

The class definition extends the MycroftSkill class:

class HelloWorldSkill(MycroftSkill):

The class should be named logically, for example "TimeSkill", "WeatherSkill", "NewsSkill", "IPaddressSkill". If you would like guidance on what to call your Skill, please join the ~skills Channel on Mycroft Chat.

Inside the class, methods are then defined.

__init__()

This method is the constructor. It is called when the Skill is first constructed. It is often used to declare state variables or perform setup actions, however it cannot utilise MycroftSkill methods as the class does not yet exist. You don't have to include the constructor.

An example __init__ method might be:

def __init__(self):
    super().__init__()
    self.already_said_hello = False
    self.be_friendly = True

initialize()

Perform any final setup needed for the skill here. This function is invoked after the skill is fully constructed and registered with the system. Intents will be registered and Skill settings will be available.

def initialize(self):
    my_setting = self.settings.get('my_setting')

Intent handlers

Previously the initialize function was used to register intents, however our new @intent_handler decorator is a cleaner way to achieve this. We will learn all about the different Intents shortly. You may also see the @intent_file_handler decorator used in Skills. This has been deprecated and you can now replace any instance of this with the simpler @intent_handler decorator.

In our current HelloWorldSkill we can see two different styles.

1. An Adapt handler, triggered by a keyword defined in a ThankYouKeyword.voc file.

   @intent_handler(IntentBuilder('ThankYouIntent').require('ThankYouKeyword'))
   def handle_thank_you_intent(self, message):
       self.speak_dialog("welcome")

2. A Padatious intent handler, triggered using a list of sample phrases.

   @intent_handler('HowAreYou.intent')
   def handle_how_are_you_intent(self, message):
    self.speak_dialog("how.are.you")

In both cases, the function receives two parameters:

• self - a reference to the HelloWorldSkill object itself

• message - an incoming message from the messagebus.

Both intents call the self.speak_dialog() method, passing the name of a dialog file to it. In this case welcome.dialog and how.are.you.dialog.

stop()

You will usually also have a stop() method.

This tells Mycroft what your Skill should do if a stop intent is detected.

def stop(self):
    pass

In the above code block, the pass statement is used as a placeholder; it doesn't actually have any function. However, if the Skill had any active functionality, the stop() method would terminate the functionality, leaving the Skill in a known good state.

create_skill()

The final code block in our Skill is the create_skill function that returns our new Skill:

def create_skill():
    return HelloWorldSkill()

This is required by Mycroft and is responsible for actually creating an instance of your Skill that Mycroft can load.

Please note that this function is not scoped within your Skills class. It should not be indented to the same level as the methods discussed above.

LICENSE

This file contains the full text of the license your Skill is being distributed under. It is not required for the Skill to work, however all Skills submitted to the Marketplace must be released under an appropriate open source license.

README.md

The README file contains human readable information about your Skill. The information in this file is used to generate the Skills entry in the Marketplace. More information about this file, can be found in the Marketplace Submission section.

settingsmeta.yaml

This file defines the settings that will be available to a User through their account on Home.Mycroft.ai.

Jump to Skill Settings for more information on this file and handling of Skill settings.

What have we learned

You have now successfully created a new Skill and have an understanding of the basic components that make up a Mycroft Skill.