The Ultimate Road Map to Chatbot Development — Part 1 (Getting Started with Language Understanding)

????Much of the progress in the Natural Language Understanding can be attributed to advancements in deep learning and NLP, and convenient access to high-end computational resources.

Being a Language Understanding company, Saarthi.

ai is building multilingual conversational agents to serve a simple motto —Diminishing the intelligence-gap between humans and conversational agents.

This series of articles aims at helping you understand the underlying elements involved in chatbot design, and the process of chatbot development, by implementing a bot in python.

OutlineHow does a Bot think?Domain IdentificationTraining Data for NLUTraining and EvaluationSetting up NLU serverHow to make NLU better?1.

How does a Bot think?For building any conversational agent, the most crucial part is understanding what the user is conveying.

Natural Language Understanding (NLU) plays an important role in this aspect.

After this, to actually build a bot, a Dialogue Framework needs to be chosen.

The flow of information through a Natural Language Understanding Engine and Dialog FrameworkWhenever a user utters queries to our conversational agent, the first task is to classify the intention of the user utterance (intent) and alongside extract out important information present in the utterance (entity).

A lot of additional tasks can be carried out in parallel, such as emotion classification (to check the mood of the user), order request classification and many more.

Once the conversational agent understands complete detail about the user utterance, it uses a Dialogue Framework to predict the actions to be carried out next.

And then, that particular action is executed (may involve database fetch or API calls) to provide the desired response back to the user.


Domain IdentificationLet us dive right into what we are eagerly waiting for…Let’s build a bot ????Highly caffeinated fingers ready to rollWe will start with a basic version of Payment Bot in Hindi.

The first step is to identify the domain of the bot.

As discussed, two important aspects of NLU are Intents and Entities.

Intents are the different categories of utterances to classify what the user could mean while conversing with the bot.

Whereas, Entities are important information present in an utterance from user.

For example, let the user utterance be —“मुझे दिल्ली के लिए एक फ्लाइट बुक करनी है।”Clearly, the user intends to book a flight and also has provided the destination which is Delhi.

Therefore, the following can be concluded.

“intent”: “book_flight”“entities”: {“destination” : “दिल्ली”}Let us narrow down our domain primarily focusing on a bot that can validate user’s mobile number, and show the current wallet balance.

There are obviously some general intents needed for every domain.

Building domain level understanding for Chatbot DevelopmentAt Saarthi.

ai, we use our chatbot development platform to train the NLU models as per the required configurations.

There is also a data tagging tool which facilitates multiple members in the Data Team to write intent utterances conveniently tagging the entities.

But, since the work is at pre-release stage, let me explain using another commonly used open-source chatbot framework ‘RasaNLU’ , to walk you through the process of building a bot.

We shall learn how to tweak some configurations in RasaNLU to make it perform better for our use case.

InstallationWe will be installing RasaNLU open-source framework for NLU training.

First make sure, your system has Anaconda setup with the latest stable version.

## create a new conda environment$ conda create -n rasanlu python==3.


1$ conda activate rasanlu$ git clone https://github.


git$ cd rasa_nlu$ pip install -r requirements.

txt$ pip install -e .

$ pip install rasa_nlu[spacy]$ python -m spacy download en_core_web_md$ python -m spacy link en_core_web_md en$ pip install rasa_nlu[tensorflow]Always prefer cloning the projects and installing from your local file system to make sure you can edit the source code according to your requirements.


Training Data for NLUPreparing training data for your chatbot usecaseAfter the NLU domain is finalized, enters the cumbersome (as any developer might think ????) task of preparing data for training the NLU.

But, once the NLU server is up and running with acceptable accuracy for classification task, a huge hindrance is avoided ????, which is usually coding the actions for the bot using any Dialogue Framework.

The training data needs to be prepared in Rasa format since we are using RasaNLU here.

Markdown (md) format is shown as an example.

Please do have a look at training data format used in Rasa.

## intent:inform- मेरा मोबाइल नंबर [9412312345](mobile) है- [70014512345](mobile)- ओ.



[2343](otp) .

## intent:show_wallet_balance- मेरा बैलेंस कितना है – मेरे पैटीएम् वॉलेट में कितनी धनराशि है.

While writing the utterances, it is a good practice to write them as an end-user of the bot.

Similarly, write the utterances for each intent present in the domain.

Since we are going to use “tensorflow embedding” pipeline of Rasa, it is important to have distinct utterances of each intent in the final training data.

Also, there must be at least 40 utterance examples to make sure we have enough test data to evaluate our model.

With these points in mind, once the dataset is finalized, CONGRATS!.????????You have overcome the initial hurdle.

Although there will be iterations on the NLU training data, for now you are all set to move towards training and evaluating the NLU.


Training and EvaluationTime to check how conversant you are!Before starting the training phase, there are few hacks that needs to be done in order to train on Hindi data.

Let us download a multi-language model from Spacy.

Then link the short-form ‘hi’ (for Hindi) to this model.

Make sure the NLU environment is activated and then use the following commands shown below.

$ python -m spacy download xx_ent_wiki_sm$ python -m spacy link xx_ent_wiki_sm hiWe need to add a config file for training our Hindi dataset on RasaNLU.

The configuration we are going to use is:Save the above lines as ‘config_tensorflow.


Move the file into rasa_nlu → sample_configs directory where all the other predefined config files are saved.

Before we proceed towards training, have a look at the token pattern and max_ngram.

Token pattern is regex defining tokens that are considered.

The default regex by Rasa ignores words with single character, which might be a problem for languages apart from English.

Hence, the token pattern is changed as shown above.

max_ngram defines the maximum number of consecutive words that can be considered together during featurization.

Generally max_ngram performs well when set to 3.

But there is an option to evaluate each and every model and finding out the best model.

Now, it’s time to train the NLU using this config file.

But before that just one last step, separate out 10% of the utterances for each intent and create another test dataset for evaluation task.

$ python -m rasa_nlu.

train –config sample_configs/config_tensorflow.

yml –data <path to your training data file> –path models –fixed_model_name nlu –project paytmbot –verboseOnce the model is successfully trained, let’s evaluate our trained model.

$ python -m rasa_nlu.

evaluate –data <path to test data set> –model models/paytmbot/nluYou might run into TclError because of the command line.

Fix it using this link.


Setting up NLU serverGreat!.????So, now we are almost done with our NLU.

All we need is to run a server locally and test some of our own utterances.

Almost done now!.Let’s get the server running.

$ python -m rasa_nlu.

server -c sample_configs/config_tensorflow.

yml –path models –port <port number>Open up the browser to check the NLU server.

localhost:<port number>/parse?q=”<example_utterance>”&project=paytmbot&model=nluYou can also use curl from terminal:$ curl -XPOST localhost:<port no>/parse -d '{"q":"<example_utterance>", "project":"paytmbot", "model":"nlu"}'6.

How to make NLU better? ????Now you might have noticed that the entity number is not that appropriate for our use case.

Because number could mean OTP, mobile number, or any other random number.

One way to classify this is by creating an external NLU layer through an API which makes duckling calls to perfectly extract phone number separately.

There are a lot of other types of entities that duckling can extract such as emails, names, distance, time and many more in multiple languages.

Even if there is no external NLU layer, there is nothing to worry about.

To complete the payment bot, we shall be using slots and validate the number entity that has been extracted to differentiate among OTP, mobile, etc.

(more on this in the next part).

Apart from using an API, there are various other tips that will help you to improve the performance of NLU.

Needless to say, the most important component is data.

If the training data for NLU is clean and contextual then the classification performs much better.

One more thing you can do is to host the NLU server on Apache.

It helps in reducing the lag after deployment.

If you are reading this part, by now you must be having a NLU server up and running in your desired port.

Congratulations!.????In the next article, we shall dive into further development of this bot using a dialog framework to design stories and train our model to predict the next action.

Hopefully, this article has allowed you to get hands-on with setting up your own NLU server and testing the accuracy of language understanding.

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Two Claps!.Three Claps!.Four Claps!.Forty ????????This article is subject to an update after the community release of our platform.

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