SIS code: 
Kristýna Klesnilová, Jan Cuřín

NPFL123 – Dialogue Systems


This course is a detailed introduction into the architecture of spoken dialogue systems, voice assistants and conversational systems (chatbots). We will introduce the main components of dialogue systems (speech recognition, language understanding, dialogue management, language generation and speech synthesis) and show alternative approaches to their implementation.

The lab sessions will be dedicated to implementing a simple dialogue system and selected components (via weekly homework assignments). We will use Python and a version of our Dialmonkey framework for this.

Logistics (spring 2024)

Schedule change

Since Ondrej is away on March 20, the lecture on March 20 is CANCELLED.

And since we need to go through 12 lectures and have only 12 weeks (due to 1 and 8 May falling on Wednesdays), we'll rearrange the schedule this way:

  • 13 March: 2 lectures -- 4. Language understanding & 5. Dialogue state tracking
    • we’ll finish around 6:50pm, so it'll be a bit longer
  • 20 March: CANCELLED
  • 27 March: 1 lecture (6. Dialogue policies) + HW4 & HW5
    • this might take slightly longer
    • HW deadlines will be spaced apart
  • 3 April: 1 lecture (7. Neural policies & NLG) + HW6 & HW7
    • usual length, it’s actually best to do these two HW together


The course will be taught in English, but we're happy to explain in Czech, too.

Time & Place

In-person lectures and labs take place in the Malá Strana building.

  • Lectures: Wed 15:40, room S5 (2nd floor)
  • Labs: Wed 17:20, room S5 (2nd floor)

In addition, we plan to stream both lectures and lab instruction over Zoom and make the recordings available on Youtube (under a private link, on request). We'll do our best to provide a useful experience.

  • Zoom meeting ID: 981 1966 7454
  • Password is the SIS code of this course (capitalized)

There's also a Slack workspace you can use to discuss assignments and get news about the course. Invite links will be sent out to all enrolled students by the start of the semester. Please contact us by email if you want to join and haven't got an invite yet.

Passing the course

To pass this course, you will need to take an exam and do lab homeworks. There's a 60% points minimum for the exam and 50% for the homeworks to pass the course. See more details here.

Topics covered

Dialogue systems schema
  • Dialogue system types & formats (open/closed domain, task/chat-oriented)
  • Data for dialogue systems
  • Dialogue systems evaluation
  • What happens in a dialogue (linguistic background)
  • Dialogue system components
    • speech recognition
    • language understanding, dialogue state tracking
    • dialogue management
    • language generation
    • speech synthesis
  • Voice assistants & question answering
  • Dialogue authoring tools (IBM Watson Assistant/Google Assistant/Amazon Alexa)
  • Open-domain/chitchat chatbots


PDFs with lecture slides will appear here shortly before each lecture (more details on each lecture are on a separate tab). You can also check out last year's lecture slides.

1. Introduction Slides Domain selection Questions

2. What happens in a dialogue? Slides Dataset exploration Questions

3. Data & Evaluation Slides Rule-based Natural Language Understanding Questions

4. Natural Language Understanding Slides Questions Statistical Natural Language Understanding

5. Neural NLU + State Tracking Slides Questions Belief State Tracking

6. Dialogue Policy (non-neural) Slides Dialogue Policy Questions

7. Neural policies & Natural Language Generation Slides API/Backend Calls Questions

8. Dialogue Tooling Slides Template NLG Questions

9. Voice Assistants & Question Answering Slides Service Integration Questions


A list of recommended literature is on a separate tab.


1. Introduction

 21 February Slides Domain selection Questions

  • What are dialogue systems
  • Common usage areas
  • Task-oriented vs. non-task oriented systems
  • Closed domain, multi-domain, open domain
  • System vs. user initiative in dialogue
  • Standard dialogue systems components

2. What happens in a dialogue?

 28 February Slides Dataset exploration Questions

  • Dialogue turns
  • Utterances as acts, pragmatics
  • Grounding, grounding signals
  • Deixis
  • Conversational maxims
  • Prediction and adaptation

3. Data & Evaluation

 6 March Slides Rule-based Natural Language Understanding Questions

  • How to get data for building dialogue systems
  • Available corpora/datasets
  • Annotation
  • Data splits
  • Evaluation metrics -- subjective & objective, intrinsic & extrinsic
  • Significance checks

4. Natural Language Understanding

 13 March Slides Questions Statistical Natural Language Understanding

  • What needs to be handled to understand the user
  • How to represent meaning: grammars, frames, graphs, dialogue acts (“shallow parsing”)
  • Rule-based NLU
  • Basics of machine learning, discriminative & generative classifiers
  • Classification-based NLU (features, logistic regression, SVM)
  • Sequence tagging (HMM, MEMM, CRF)

5. Neural NLU + State Tracking

 13 March Slides Questions Belief State Tracking

  • Some basics about neural networks
  • How to use neural networks for NLU: neural classifiers and sequence taggers
  • Handling speech recognition noise
  • What is dialogue state, what is belief state, and what they're good for
  • Dialogue as a Markov decision process (MDP)
  • Dialogue trackers: generative and discriminative
  • Static and dynamic trackers

6. Dialogue Policy (non-neural)

 27 March Slides Dialogue Policy Questions

  • What's a dialogue policy -- how to choose the next action
  • Finite-state, frame-based, and rule-based policies
  • Reinforcement learning basics
  • Value and policy optimization (SARSA, Q-learning, REINFORCE)
  • Mapping to POMPDs (partially observable MDPs)
  • Summary space (making it tractable)
  • User simulation

7. Neural policies & Natural Language Generation

 3 April Slides API/Backend Calls Questions

  • Deep reinforcement learning
  • Deep Q-Networks, Policy Networks
  • Natural language generation
  • Sentence planning & Surface realization
  • Templates
  • Rule-based approaches
  • Neural: seq2seq, RNNs, Transformers

8. Dialogue Tooling

 10 April Slides Template NLG Questions

  • What are the standard tools for building dialogue systems on various platforms
  • IBM Watson, Google Dialogflow, Alexa Skills Kit
  • How to define intents, slots, and values
  • How to build your own basic dialogues

9. Voice Assistants & Question Answering

 17 April Slides Service Integration Questions

  • What are voice assistants
  • Where, how and how much are they used
  • What are their features and limitations
  • What is question answering
  • Basic question answering techniques
  • Knowledge graphs

Homework Assignments

There will be 12 homework assignments, each for a maximum of 10 points. Please see details on grading and deadlines on a separate tab. Note that there's a 50% minimum requirement to pass the course.

Assignments should be submitted via Git – see instructions on a separate tab. Please take special care about naming your Git branches and files the way they're given in the assignments. If our automatic checks don't find your files, you'll lose points!

You should run automatic checks before submitting -- have a look at Code that crashes during the automatic checks will not get any points. You may fail the checks and still get full points, or ace the checks and get no points (especially if your code games the checks). Note that you should update your checkout since the code for the assignments might be changed during the semester.

All deadlines are 23:59:59 CET/CEST.


1. Domain selection

2. Dataset exploration

3. Rule-based Natural Language Understanding

4. Statistical Natural Language Understanding

5. Belief State Tracking

6. Dialogue Policy

7. API/Backend Calls

8. Template NLG

9. Service Integration

1. Domain selection

 Presented: 21 February, Deadline: 8 March

You will be building a task-oriented dialogue system in (some of) the homeworks for this course. Your first task is to choose a domain and imagine how your system will look like and work like. Since you might later find that you don't like the domain, you are now required to pick two, so you have more/better ideas later and can choose only one of them for building the system.


The required steps for this homework are:

  1. Pick two domains of your liking that are suitable for building a task-oriented dialogue system. Think of a reasonable backend (see below).

  2. Write 5 example system-user dialogues for both domains, which are at least 5+5 turns long (5 sentences for both user and system). This will make sure that your domain is interesting enough. You do not necessarily have to use English here (but it's easier if we understand the language you're using -- ask us if unsure, Czech & Slovak are perfectly fine).

  3. Create a flowchart for your two domains, with labels such as “ask about phone number”, “reply with phone number”, “something else” etc. It should cover all of your example dialogues. You can use e.g. Mermaid to do this, but the format is not important. Feel free to draw this by hand and take a photo, as long as it's legible.

    • It's OK (even better) if your example dialogues don't go all in a straight line (e.g. some of them might loop or go back to the start).

Files to commit

Please stick to the file naming conventions -- you will lose points if you don't!

  • hw1/ with short commentary on both domains (ca. 10-15 sentences) -- what they are, what features you'd like to include, what will be the backend.

  • hw1/examples-<domain1>.txt, hw1/examples-<domain2>.txt -- 5 example dialogues for each of the domains (as described above). Use a short domain name, best with just letters and underscores.

    • Please use UTF-8 encoding for these files.
  • hw1/flowchart-<domain1>.{pdf,jpg,png}, hw1/flowchart-<domain2>.{pdf,jpg,png} -- the flowcharts for each of the domains, as described above.

See the instructions on submission via Git -- create a branch and a merge request with your changes. Make sure to name your branch hw1 so we can find it easily.


You may choose any domain you like, be it tourist information, information about culture events/traffic, news, scheduling/agenda, task completion etc. You can take inspiration from stuff presented in the first lecture, or you may choose your own topic.

Since your domain will likely need to be connected to some backend database, you might want to make use of some external public APIs -- feel free to choose under one of these links:

You can of course choose anything else you like as your backend, e.g. portions of Wikidata/DBPedia or other world knowledge DBs, or even a handwritten “toy” database of a meaningful size, which you'll need to write to be able to test your system.

2. Dataset exploration

 Presented: 28 February, Deadline: 15 March

The task in this lab is to explore dialogue datasets and find out more about them. Your job will thus be to write a script that computes some basic statistics about datasets, and then try to interpret the script's results.


  1. Take a look at the Dialog bAbI Tasks Data 1-6 dataset. Read the description of the data format in the readme.txt file. You'll be working with Tasks 5 and 6 (containing full generated dialogues and DSTC2 data). Use the training sets for Task 5 and Task 6.

  2. Write a script that will read all turns in the data and separate the user and system utterances in the training set.

    • Make the script ignore any search results lines in the data (they don't contain a tab character).
    • If the script finds a turn where the user is silent (the user turn contains only <SILENCE>), it should concatenate the system response from this turn to the previous turn. Note that this may happen on multiple consecutive turns, and the script should join all of these together into one system response.
      • If <SILENCE> is the first word in the dialogue, just delete it.
    • For tokenization, you should use the word_tokenize function from the nltk package.
  3. Implement a routine that will compute the following statistics for both bAbI tasks for system and user turns (separately, i.e., 4 sets of statistics altogether):

    • data length (total number of dialogues, turns, words)
    • mean and standard deviations for individual dialogue lengths (number of turns in a dialogue, number of words in a turn)
    • vocabulary size
    • Shannon entropy and bigram conditional entropy, i.e. entropy conditioned on 1 preceding word (see lecture 2 slides)

    Commit this file as hw2/

  4. Along with your script, submit also a dump of the results. The results should be formatted as JSON file with the following structure:

        "dialogues_total": XXX,
        "turns_total": XXX,
        "words_total": XXX,
        "mean_dialogue_turns": XXX,
        "stddev_dialogue_turns": XXX,
        "mean_dialogue_words_per_turn": XXX,
        "stddev_dialogue_words_per_turn": XXX,
        "vocab_size": XXX,
        "entropy": XXX
        "cond_entropy": XXX
    "task5_system": ...
    "task6_user": ...
    "task6_system": ...

(Create a dict and use json.dump for this.) Commit the json file as hw2/results.json.

  1. Add your own comments, comparing the results between the two bAbI Tasks. 3-5 sentences is enough, but try to explain why you think the vocabulary and entropy numbers are different.

    Put your comments in Markdown as hw2/

Files to commit

There are empty files ready for you in the repo the right places, you just need to fill them with information.

Just to sum up, the files are:

  • hw2/ -- your data analysis script
  • hw2/results.json -- JSON results of the analysis
  • hw2/ -- your comments

Create a branch and a merge request containing (changes to) all requested files. Please keep the filenames and directory structure.


  • Don't worry too much about the exact numbers you get, slight variations in implementation may cause them to change. We won't penalize it if you don't get the exact same numbers as us, the main point is that your implementation should be reasonable (and you shouldn't be off by orders of magnitude).

  • Don't worry about system api_calls, just treat them as a normal system turn.

3. Rule-based Natural Language Understanding

 Presented: 6 March, Deadline: 28 March (extended!)

In this assignment, you will design a dialogue system component for Natural Language Understanding in a specific domain. For completing it, you will use our prepared Dialmonkey dialogue framework (which is the base of your Gitlab repository), so you can test the outcome directly.

Language understanding means converting user utterances (such as “I'm looking for a Chinese restaurant in the city center”) into some formal representation used by the dialogue manager. We'll use dialogue acts as our representation – so the example sentence would convert to something like inform(food=Chinese,area=centre) or find_restaurant(food=Chinese,area="city center"), depending on how you define the intents, slots and values within the dialogue acts for your own domain.

Note: We're not thinking about how to reply just yet! The only thing we're concerned with is representing user inputs in our domain with reasonable intents, slots, and values.


  1. Make yourself familiar with the Dialmonkey-npfl123 repository you cloned for the homeworks. Read the README and look around a bit to get familiar with the code. Have a look at the 101 Jupyter notebook to see some examples.

  2. Recall the domains you picked in the first homework assignment and choose one of them. If you've changed your mind in the meantime, you can even pick a different domain.

  3. Think of the set of dialogue acts suitable to describe this domain, i.e., list all intents, slots and values that will be needed (some slots may have open sets of values, e.g. “restaurant name”, “artist name”, “address” etc.). List them, give a description and examples in Markdown under hw3/

  4. Create a component in the dialogue system (as Python code) that:

    • inherits from dialmonkey.component.Component
    • is placed under dialmonkey.nlu.rule_<your-domain>
    • implements a rule-based NLU for your domain -- i.e., given user utterance, finds its intent, slots and values
    • yields Dialogue Act items you designed in step 3 (as DA objects).

    Please only use the core Python libraries and those listed in requirements.txt. If you have a good reason to use a different library from PyPi, let us know and we can discuss adding it into the requirements (but this will be global for everyone).

  5. Create a YAML config file for your domain in the conf directory. You can use the sample_conf.yaml file or nlu_test.yaml as a starting point. These files are almost identical, just have a look at the I/O setup if you're interested. Note that instead of a policy and NLG components, a system with this config will simply reply with the NLU result.

  6. Write at least 15 distinct utterances that demonstrate the functionality of your class (a tab-separated file with input + corresponding NLU result, one-per-line). Make sure your NLU gives you the same results. The test utterances can (but don't have to) be taken over from the example dialogues you wrote earlier for your domain. Save them as hw3/examples.tsv.

Files to include in your merge request

There will be empty files ready for you in the right place, just rename them according to your domain (e.g. change <your_domain> to restaurant, bus etc.) and fill them with the required content.

  • Lists of intents, slots and values in hw3/
  • Your NLU component in dialmonkey/nlu/rule_<your_domain>.py
  • Your configuration file in conf/nlu_<your_domain>.yaml
  • Example test utterances & outputs in hw3/examples.tsv

Create a branch and a merge request containing (changes to) all requested files. Please keep the filenames and directory structure.


Use regular expressions or keyword matching to find the intents and slot values (based on the value, you'll know which slot it belongs to).

If you haven't ever used regular expressions, have a look some tutorials:

Note that you might later need to improve your NLU to handle contextual requests, but you don't need to worry about this now. For instance, the system may ask What time do you want to leave? and the user replies just 7pm. From just 7pm (without the preceding question), you don't know if that's a departure or arrival time. Once you have your dialogue policy ready and know how the system questions look like (which will be the 6th homework), you'll be able to look at the last system question and disambiguate. For now, you can keep these queries ambiguous (e.g. just mark the slot as “time”).

4. Statistical Natural Language Understanding

 Presented: 27 March, Deadline: 12 April

In this assignment, you will build and evaluate a statistical Natural Language Understanding component on the DSTC2 restaurant information data. For completing it, you will use the Dialmonkey framework in your code checkout so you can test the outcome directly.


  1. Locate the data in your Dialmonkey-NPFL123 repository in data/hw4/. This is what we'll work with for this assignment.

  2. Implement a script that trains statistical models to predict DAs. We'll use classifiers here. Your approach shouldn't be to predict the whole DA as a single classifier, rather you should classify the correct value for each intent-slot pair where applicable (e.g. inform(food) has multiple possible values) and classify a binary 0-1 for each intent-slot pair that can't have different values (e.g. request(price) or bye() ).

    Don't forget that for the multi-value slots, you'll need a “null” value too. Have a look at examples here to get a better idea.

    You can use any kind of statistical classifier you like (e.g. logistic regression, SVM, neural network), with any library of your choice (e.g. Scikit-Learn, Tensorflow, Pytorch ).

    Using binary classifiers for everything may be an option too (especially if you use neural networks with shared layers), but the number of outputs will be rather high, hence the recommendation for multi-class classifiers. Note that we can't do slot tagging here, as the individual words in the texts aren't tagged with slot values.

  3. Train this model on the training set. You can use the development set for parameter tuning. Using dialmonkey.DA.parse_cambridge_da() should help you get the desired DA values out of the textual representation. Do not look at the test set at this point!

  4. Evaluate your model on the test set and report the overall precision, recall and F1 over dialogue act items (triples of intent-slot-value).

    Use the script provided in dialmonkey.evaluation.eval_nlu. You can run it directly from the console like this:

    ./dialmonkey/evaluation/ -r data/hw4/dstc2-nlu-test.json -p hw4/predicted.txt

    The script expects reference JSON in the same format as your data here, and a system output with one DA per line. You can have a look at conf/nlu_test.yaml to see how to get one-per-line DA output.

    For the purpose of our evaluation script F1 computation, non-null values count as positives, null values count as negatives. Whether they're true or false depends on whether they're correctly predicted.

  5. Implement a module in Dialmonkey that will load your NLU model and work with inputs in the restaurant domain. Create a copy of the nlu_test.yaml config file to work with your new NLU.

Files to include in your merge request

  • Your statistical NLU module as dialmonkey/nlu/ and your trained model. The filename for the model will depend on your implementation, it just needs to be loaded automatically for your model to work. Preferrably store in the same directory, but it could be anywhere else if needed. If the file is too big for Git (>10MB), share it using a cloud service (e.g. CESNET OwnCloud) and make your NLU module download it automatically in __init__().
  • Your YAML config file under conf/nlu_dstc.yaml.
  • Your training script as hw4/
  • Your predicted output as hw4/predicted.txt and a short evaluation report under hw4/ (including your F1 scores).

Important implementation notes

Note 1: Please do not use any Python libraries other than the ones in requirements.txt, plus the following ones: torch (Pytorch), tensorflow, pytorch-lightning, torchtext, transformers (Huggingface). Note that scikit-learn is included already. If you need any others, please let us know beforehand.

Note 2: Please make sure that your code doesn't take more than a minute to load + classify the first 20 entries in the test data. For the sake of model storage, it's better to choose a smaller one, especially if you choose to play with pretrained language models.

Note 3: And this one is for all further assignments -- Do not use absolute file paths in your solution! You may want to try out os.path.dirname(__file__), which gets you the directory of the current source file. If you need to use slashes in a (relative!) path, use either os.path.join instead, or use forward slashes and a pathlib.Path object (simply create it using filename = Path(filename)). This will handle the slashes properly both on Windows and Linux. Note that we're mainly checking on Linux, so any backslashes in file paths will break our workflow and we may deduce points.


  • Start playing with the classifier separately, only integrate it into Dialmonkey after you've trained a model and can load it.

  • If you have never used a machine learning tool, have a look at the Scikit-Learn tutorial. It contains most of what you'll need to finish this exercise.

  • You'll need to convert your texts into something your classifier understands (i.e., some input numerical features). You can probably do very well with just “bag-of-words” as input features to the classifier -- that means that you'll have a binary indicator for each word from the training data (e.g. word “restaurant”). The feature for the word “restaurant” will be 1 if the word “restaurant” appears in the sentence, 0 if it doesn't. You can also try using the same type of features for bigrams. Have a look at the DictVectorizer class in Scikit-Learn. You may also want to consider CountVectorizer, which could speed up things even more.

  • For Scikit-Learn, you can use pickle to store your trained models. If you want to pickle classes, use the dill library instead (since pickle can't do that).

  • To easily load JSON files, you can use the SimpleJSONInput class.

  • You better don't use the naive Bayes classifier, it doesn't work well on this data – basically anything else works better (you won't lose any points if you use naive Bayes, just don't expect good performance).

5. Belief State Tracking

 Presented: 27 March, Deadline: 26 April (extended)

This week, you will build a simple probabilistic dialogue/belief state tracker to work with NLU for both your own domain of choice (3rd assignment) and DSTC2 (4th assignment).


  1. Implement a dialogue state tracker that works with the dial.state structure (it's a dict) and fills it with a probability distribution of values over each slot (assume slots are independent), updated during the dialogue after each turn. Don't forget None is a valid value, meaning “we don't know/user didn't say anything about this”.

    At the beginning of the dialogue, each slot should be initialized with the distribution {None: 1.0}.

    The update rule for a slot, say food, should go like this:

    • Take all mentions of food in the current NLU, with their probabilities. Say you got Chinese with a probability of 0.7 and Italian with a probability of 0.2. This means None has a probability of 0.1.
    • Use the probability of None to multiply current values with it (e.g. if the distribution was {'Chinese': 0.2, None: 0.8}, it should be changed to {'Chinese': 0.02, None: 0.08}.
    • Now add the non-null values with their respective probabilities from the NLU. This should result in {'Chinese': 0.72, 'Italian': 0.2, None: 0.08}.

    To make sure your tracker works with either NLU system, simply use whatever is in dial.nlu as the input. Make sure both your NLU systems fill in the dial.nlu structure -- feel free to edit your NLU systems' code.

    Note that you should be using probability estimates in your statistical NLU from the 4th assignment now (for your rule-based NLU on own domain from the 3rd assignment, just assume a probability of 1 if your patterns match).

    Set a threshold for low-probability NLU outputs that you'll ignore in the tracker (good choice is 0.01-0.05), so that the outputs are not too messy.

  2. Create new configuration files both for your own rule-based domain and for DSTC2, which include NLU and the tracker. In addition, use dialmonkey.policy.dummy.ReplyWithState as the output (so the system's response is now the current dialogue state).

    You can use conf/dst_test.yaml as a starting point (just put in your NLU and tracker).

  3. Run your NLU + tracker over your NLU examples from 3rd assignment and the first 20 lines from the DSTC2 development data (file data/hw4/dstc2-nlu-dev.json ) from the 4th assignment data and save the outputs to a text file for both. You can use Dialmonkey's file input settings for this.

    Treat the examples as a single dialogue, even though such a “dialogue” doesn't make any logical sense. Your tracker should be able to handle it.


  • You can have a look at an example dialogue with commentary for the update rule in a separate file (it's basically the same stuff as above, just more detailed).

  • Remember that all this is just about slots, not intents – do not consider intents as part of the state. You generally don't need to track past intents, just the current intent from NLU is enough to guide the system.

  • If your statistical NLU is built as classifiers for intent-slot pairs (as foreseen by default in HW4), you can just use the probabilities coming from the inform intent for the given slot. The best way would be to add up "positive" intents such as inform or confirm and discount negative ones, such as deny, but we don't require you to do this as part of the assignment.

Files to include in your merge request

  • Your tracker code under dialmonkey/dst/
  • Your updated configuration files for both domains under conf/dst_<my-domain>.yaml and conf/dst_dstc.yaml.
  • Your text files with the outputs into hw5/outputs_<my-domain>.txt and hw5/outputs_dstc.txt.

6. Dialogue Policy

 Presented: 3 April, Deadline: 6 May (with HW7!)

This week, you will build a rule-based policy for your domain.


  1. Implement a rule-based policy that uses the current NLU intent (or intents, coming from your NLU) and the dialogue state (coming from your tracker) to produce system action dialogue acts. You can use just the most probable value for each slot, assuming its probability is higher than a given threshold (e.g. 0.7). Since your NLU is rule-based, the actual value of the threshold doesn't matter much (should be >0): you'll likely have zero or one value with a probability of 1, the rest with a probability zero.

    The policy should:

    • Check the current intent(s) and split the action according to that
    • Given the intent, check that the state contains all necessary slots to respond:
      • if it does, fill in a response system DA into the dial.action field.
      • if it doesn't, fill in a system DA requesting more information into the dial.action field.

    You can use the flowcharts you built in HW1 to guide the policy's decisions (but it's fine if you don't stick to them).

    You can skip any API queries and hardcode the responses at first (you will build the actual backend in HW7), or you can build the two assignments together.

  2. Save the policy under dialmonkey.policy.rule_<your_domain> and create a configuration file for your own domain that will include it.

  3. In your new configuration file, include dialmonkey.policy.dummy.ReplyWithSystemAction as the last step -- this replaces dialmonkey.policy.dummy.ReplyWithState you used previously (don't worry that you have two things from the policy package in your pipeline).

  4. Check that your policy returns reasonable system actions for each of your NLU test utterances, if you treat each utterance as a start of a separate new dialogue (it's OK if it's not exactly what is meant, the utterances will be taken out of context).

    Run your policy over your NLU test utterances, each taken as a start of a separate dialogue, and save the outputs to a text file. You can either do this by hand, or you may consider creating a script that creates an instance of ConversationHandler and uses handler.run_dialogue() -- see the 101 Jupyter notebook. Outputs can be saved to a file using dialmonkey.output.text.FileOutput.

Files to include in your repository

  • Your policy (dialmonkey/policy/rule_<your_domain>.py) and your updated configuration file (conf/act_<your_domain>.yaml).
  • The outputs of your policy on your NLU test utterances as hw6/outputs.txt.

Note: If you're submitting together with HW7, make just a single merge request, with a branch labelled hw7, but include all the files required for both assignments.

Note 2: To make testing smooth, please merge your HW3 merge request into master & merge that into your submission MR for HW6/HW7. This will make your NLU examples file available for us, so we see not just the output but also the corresponding inputs in the repository.


  • Note that we're not creating natural language responses just yet, just the system action DAs.

  • Your policy will most probably be a long bunch of if-then-else statements. Don't worry about it. You may want to structure the file a bit so it's not a huge long function though -- e.g., add the handling of different request types into separate functions, if it's not just 1 line.

  • You may want to complete this homework together with the next one, which will be about backend integration. That's why the deadline is in 3 weeks, not 2.

7. API/Backend Calls

 Presented: 3 April, Deadline: 7 May (with HW6)

This week is basically a continuation of the last one -- filling in the blank API call placeholders you created last time. If you want to, you can complete the 6th and 7th homework at the same time (the deadline is the same).


  1. Implement all API/backend queries you need for the policy you implemented in the last homework assignment. The implementation can be directly inside dialmonkey.policy.rule_<your_domain>, or you can create a sub-package (a subdirectory, where you put the main policy inside and any auxiliary stuff into other files in the same directory).

    It depends on your domain if the implementation will be external API queries (preferrable) or some kind of internal database (e.g. a CSV table). In case you implement a local database, please add at least 10 different entries (let us know if you think this doesn't make sense for your domain).

  2. Test your policy with outputs on at least 3 of the test dialogues you created in the 1st homework assignment. You can of course make alterations if your policy doesn't behave exactly as you imagined the first time. If you changed your domain, you can draft 3 dialogues of 5+ turns.

    Also, don't worry that the output is just dialogue acts at the moment.

Files to include in your repository

  • Commit your policy (dialmonkey/policy/rule_<your_domain>.py), updated with API calls.
  • Put logs of your test dialogues as hw7/outputs.txt (with user inputs and system output acts).

Note: if you're submitting together with HW6, make just a single merge request, with a branch labelled hw7, but include all the files required for both assignments.

Implementation notes

For hw7/outputs.txt, please make the format like this:

U: Hello, how are you?
S: hello()&request(area)
U: Thank you, goodbye!
S: bye()

U: Hello, I need a cheap restaurant
S: hello()&confirm(price=cheap)&request(area)

Make all lines start with U: and S: marking the user and system turns, with system turns consisting of dialogue acts (in Cambridge or Dialmonkey format). Put an empty line between different dialogues.

Update: There's now a class called DialogueLogOutput, which will sort out the format for you. Just use it as your output stream (see the README on how to do that). Note that you'll need to update from upstream to be able to use that class in your code!


  • If you want to access an external API using Python, check out the requests library. It makes it easy to call external APIs using JSON. You can get the result with just a few lines of code.

8. Template NLG

 Presented: 10 April, Deadline: 13 May

In this homework assignment, you will complete the text-based dialogue system for your domain by creating a template-based NLG component.


  1. Implement a template-based NLG with the following features:

    • The NLG system is (mostly) generic and can load templates for your domain from a JSON or YAML file (only one of these formats is fine!), showing a DA -> template mapping.

    • The NLG system is able to prioritize a mapping for a specific value -- e.g. inform(price=cheap) -> “You'll save money here.” should get priority over inform(price={price}) -> “This place is {price}.”

    • The NLG system is able to put together partial templates (by concatenating), so you can get a result for e.g. inform(price=cheap,rating=3) even if you only have templates defined for inform(price={price}) and inform(rating={rating}), not the specific slot combination. So if you have templates inform(price={price}) -> “The place is {price}.” and inform(rating={rating}) -> “The place is rated {rating} stars.”, your output for inform(price=cheap,rating=3) should be “The place is cheap. The place is rated 3 stars.”

      This doesn't need to search for best coverage, just take anything that fits, such as templates for single slots if you don't find the correct combination.

    • The system is able to produce multiple variations for certain outputs, e.g. bye() -> Goodbye. or Thanks, bye!

  2. Create templates that cover your domain well.

  3. Save your NLG system under dialmonkey.nlg.templates_<your-domain> and add it into your conf/text_<your-domain>.yaml configuration file.

  4. Test your NLG system with the test dialogues you used in the previous assignment.

Implementation instructions

Make sure your template NLG is really domain-general. We're going to test it on a different domain from yours! You can have specific additions for your domain in there, just make sure it'll work reasonably well with any slot names.

Access to template file: In your NLG class, include a constructor method with this signature: def __init__(self, config). Call super().__init__(config) as the first thing inside this constructor method. Include a def load_templates(self, filename) function which loads your templates and call it in the constructor (note this method will be called in our tests!).

You can pass the filename to the constructor (inside config) via the YAML config file, e.g. you add:

    - dialmonkey.nlg.templates_<your-domain>:
        templates_file: dialmonkey/nlg/templates_<your-domain>.<yaml|json>

And you can use config['templates_file'] in the constructor to get the file path.

Paths warning (repeat): If you need slashes in the path, use forward slashes and a pathlib.Path object (simply create it using filename = Path(filename)), it will handle the slashes properly both on Windows and Linux. Do not use absolute paths! You may want to try out os.path.dirname(__file__), which gets you the directory of the current source file.

Templates format: Use a dict where keys are DAs (either in native triple style, or Cambridge style) and values are lists of templates (variants), with slot placeholders marked using curly braces. Example YAML:

- This place is cheap.

- This place is {price}.

- Goodbye.
- Thanks, bye!

Example JSON:

"inform(price=cheap)": [
    "This place is cheap."

"inform(price={price})": [
    "This place is {price}."

"bye()": [
    "Thanks, bye!"

Setting the reply: Call dial.set_system_response(text) where text is your NLG output, so the system actually uses your NLG to respond. Remove ReplyWithSystemAction (used in HW6 & HW7) from your config file, it's no longer needed :-).

Files to include in your merge request

  • Your NLG implementation in dialmonkey/nlg/templates_<your-domain>.py
  • Your templates file in dialmonkey/nlg/templates_<your-domain>.<yaml|json>
  • A full configuration file for your domain, which includes the NLG system, under conf/text_<your-domain>.yaml
  • Logs of the test dialogues from HW7, now with NLG output, in hw8/outputs.txt

9. Service Integration

 Presented: 17 April, Deadline: 20 May

In this homework, you will integrate the chatbot for your domain into an online assistant of your choice (Google/Alexa/Facebook/Telegram). Telegram is the “default”, but you can choose whichever you like.


  1. Choose a service that you want to use for this homework. We prepared some instructions for Google Dialogflow, Alexa Skills, Facebook Messenger, and Telegram. but can also use the IBM Watson Assistant as shown in the lecture by Honza. Note that Dialogflow and Alexa are unfortunately not available for Czech.

  2. Implement the frontend on your selected platform. You can either carry over intents, slots & values from your NLU directly into Dialogflow/Alexa/Watson, or you can work with free text and run the NLU in the backend. For Messenger and Telegram, that's the only option (but their frontend basically comes for free).

  3. Implement a backend that will connect to your frontend – handle its calls and route them to your dialogue system in Dialmonkey (either with NLU already processed, or with free text as input). You can use the get_response method in dialmonkey.conversation_handler.ConversationHandler to control the system outside of the console. Don't forget to save context in between requests. However, you can assume for simplicity that the bot will always have just one dialogue, i.e. you do not have to care about parallel conversations.

  4. Link your frontend to your backend (see Hints below).

Detailed instructions

Amazon Alexa
  • Alexa allows you to run NLU directly in your backend but it's a bit tricky -- the only way to get free text is to use the SearchQuery built-in slot. You can set up an intent where the only part of the utterance is this slot.

  • For implementing backend, you can use the Flask-Ask package as a base. You can have a look at an Alexa Skill Ondrej made for inspiration (not many docs, though, sorry).

  • Set your backend address under “Endpoint” (left menu).

Google Dialogflow
  • To make use of you NLU, you can make use of the Default fallback intent which gets triggered whenever no other intent is recognized.
  • For backend implementation, you can use Flask-Assistant.
  • Set your backend address under “Webhooks” for the individual intents (under the “Fulfillment” menu of each intent). If you want to get free text of the requests, have a look at this snippet.
Facebook Messenger

For Messenger, you need to perform several steps, however, it allows you to work with textual inputs directly. In general, you can follow the tutorial. Here are the important steps you need to complete:

  • Implement a webserver using Flask. It might be a good idea to start from the example implementation (feel free to reuse it).
    See the tutorial here for other options.
  • You need to implement GET method handler for verification and POST method handler to receive message and send the reply. You can also use pymessenger, though the code isn't maintained.
  • Set up your webserver on a public URL.
  • The verification step requires two tokens -- a verification token (an arbitrary string that you choose) and an access token (which you'll get from Facebook).
  • Visit the dev page. Create an account, add a Messenger app and create a sample Facebook page (in the “App page” category).
  • Link the page to your app (under “Messenger” – “Settings”) and obtain the access token for use in your webserver (generate & save into your code).
  • Add a callback URL pointing to your webserver and the verification token (the one you chose).

Telegram also allows direct text input. There's also a handy Python-Telegram-Bot library that has a webserver built in.

  • You need to get a telegram bot API token from the BotFather -- it's pretty straightforward, you talk to this “one bot to rule them all”, ask it for /newbot and it'll guide you through the process. You can find more info on their documentation page.
  • With the use of your API token, you need to create the telegram bot using Python-Telegram-Bot. These examples should be a good way of starting it. There's even a tutorial. In general, you'll need to implement a command handler that'll pass on the message from Telegram to your system. No web server is necessary, Python-Telegram-Bot has one built in.
  • Start up your bot and you can talk to it on Telegram.

Files to include in your merge request

  • Commit your frontend export into hw9/:
    • In Alexa, go to “JSON Editor” in the left menu and copy out the contents into a file intent_schema.json.
    • In Dialogflow, go to your agent settings (cogged wheel next your agent/skill/app name on the top left), then select the “Export & Import” tab and choose “Export as ZIP”. Please commit the resulting subdirectory structure, not the ZIP file.
    • Nothing is required for Messenger and Telegram at this point.
  • Commit your bot server code into hw9/ This code will probably import a lot from Dialmonkey and require it to be installed -- that's expected.
    • Make sure that python hw9/ will run the bot with the default settings. Use if __name__ == '__main__' for that, so we can import your code for tests.
    • Include a function called reply_<google|alexa|facebook|telegram> that replies to a message (depending on the service) or calls a function that does that (passing on whatever parameters are needed on the given platform). This corresponds to:
      • Google: A Flask-Assistant function with the decorator @assist.action('Default fallback intent')
      • Alexa: A Flask-Ask function with the decorator @ask.intent('YourDefaultIntent')
      • Facebook: The webhook function with the Flask decorator @app.route('/', methods=['POST'])
      • Telegram: A function set as Python-Telegram-Bot MessageHandler for default text messages (this is the function called echo in the tutorial)
    • In case you reimplement your intents for Google/Alexa, you may skip implementing this function (since it would decompose into many different functions). We'll check manually 🙂.
  • Add a short README telling us how to run your bot. You don't need to commit any API tokens (we can get our own for testing), but let us know in the readme where to add the token.


  • To test out your backend, you can run your server on your own machine and use ngrok for testing purposes. Ngrok will tunnel a port on your machine and expose it publicly over HTTPS.
  • Alternatively, you could think about deploying your server on a PaaS site. Here's a list of a few that feature a free tier. (This is entirely optional and untested by us. We tested Heroku but that's no longer free.)
  • To import dialmonkey.* in your solution so that you can easily use your own modules, there are essentially two ways:
    • You can make an editable install of your Dialmonkey-npfl123 checkout directory -- within your virtualenv/conda environment, simply go to your checkout directory and run:
pip install -e .

That way, you can make imports from all the Dialmonkey packages from anywhere.

  • Alternatively, you can add the .. directory into hw9/'s sys.path. This is essentially what we're doing with the automatic tests. Use relative paths for the import, like this:
import os, sys
sys.path.append(os.path.abspath(os.path.join(os.path.dirname(__file__), '..')))

Homework Submission Instructions

All homework assignments will be submitted using a Git repository on MFF GitLab.

We provide an easy recipe to set up your repository below:

Creating the repository

  1. Log into your MFF gitlab account. Your username and password should be the same as in the CAS, see this.
  2. You'll have a project repository created for you under the teaching/NPFL123/2024 group. The project name will be the same as your CAS username. If you don't see any repository, it might be the first time you've ever logged on to Gitlab. In that case, Ondřej first needs to run a script that creates the repository for you (please let him know on Slack). In any case, you can explore everything in the base repository. Your own repo will be derived from this one.
  3. Clone your repository.
  4. Change into the cloned directory and run
git remote show origin

You should see these two lines:

* remote origin
  Fetch URL:
  Push  URL:

  1. Add the base repository (with our code, for everyone) as your upstream:
git remote add upstream
  1. You're all set!

Submitting the homework assignment

  1. Make sure you're on your master branch
git checkout master
  1. Checkout a new branch -- make sure to name it hwX (e.g. “hw4” or “hw11”) so our automatic checks can find it later!
git checkout -b hwX
  1. Solve the assignment :)

  2. Add new files and commit your changes -- make sure to name your files as required, or you won't pass our automatic checks!

git add hwX/
git commit -am "commit message"
  1. Push to your origin remote repository:
git push origin hwX
  1. Create a Merge request in the web interface. Make sure you create the merge request into the master branch in your own forked repository (not into the upstream).

     Merge requests -> New merge request
Merge request
  1. Wait a bit till we check your solution, then enjoy your points :)!
  2. Once approved, merge your changes into your master branch – you might need them for further homeworks.

Updating from the base repository

You might need to update from the upstream base repository every once in a while (most probably before you start implementing each assignment). We'll let you know when we make changes to the base repo.

To upgrade from upstream, do the following:

  1. Make sure you're on your master branch
git checkout master
  1. Fetch the changes
git fetch upstream master
  1. Apply the diff
git merge upstream/master master

Exam Question Pool

The exam will have 10 questions, mostly from this pool. Each counts for 10 points. We reserve the right to make slight alterations or use variants of the same questions. Note that all of them are covered by the lectures, and they cover most of the lecture content. In general, none of them requires you to memorize formulas, but you should know the main ideas and principles. See the Grading tab for details on grading.


  • What's the difference between task-oriented and non-task-oriented systems?
  • Describe the difference between closed-domain, multi-domain, and open-doman systems.
  • Describe the difference between user-initiative, mixed-initiative, and system-initiative systems.

Linguistics of Dialogue

  • What are turn taking cues/hints in a dialogue? Name a few examples.
  • Explain the main idea of the speech acts theory.
  • What is grounding in dialogue?
  • Give some examples of grounding signals in dialogue.
  • What is deixis? Give some examples of deictic expressions.
  • What is coreference and how is it used in dialogue?
  • What does Shannon entropy and conditional entropy measure? No need to give the formula, just the principle.
  • What is entrainment/adaptation/alignment in dialogue?

Data & Evaluation

  • What are the typical options for collecting dialogue data?
  • How does Wizard-of-Oz data collection work?
  • What is corpus annotation, what is inter-annotator agreement?
  • What is the difference between intrinsic and extrinsic evaluation?
  • What is the difference between subjective and objective evaluation?
  • What are the main extrinsic evaluation techniques for task-oriented dialogue systems?
  • What are some evaluation metrics for non-task-oriented systems (chatbots)?
  • What's the main metric for evaluating ASR systems?
  • What's the main metric for NLU (both slots and intents)?
  • Explain an NLG evaluation metric of your choice.
  • Why do you need to check for statistical significance (when evaluating an NLP experiment and comparing systems)?
  • Why do you need to evaluate on a separate test set?

Natural Language Understanding

  • What are some alternative semantic representations of utterances, in addition to dialogue acts?
  • Describe language understanding as classification and language understanding as sequence tagging.
  • How do you deal with conflicting slots or intents in classification-based NLU?
  • What is delexicalization and why is it helpful in NLU?
  • Describe one of the approaches to slot tagging as sequence tagging.
  • What is the IOB/BIO format for slot tagging?
  • What is the label bias problem?
  • How can an NLU system deal with noisy ASR output? Propose an example solution.

Neural NLU & Dialogue State Tracking

  • Describe a neural architecture for NLU.
  • What is the dialogue state and what does it contain?
  • What is an ontology in task-oriented dialogue systems?
  • Describe the task of a dialogue state tracker.
  • What's a partially observable Markov decision process?
  • Describe a viable architecture for a belief tracker.
  • What is the difference between dialogue state and belief state?
  • What's the difference between a static and a dynamic state tracker?

Dialogue Policies

  • What are the non-statistical approaches to dialogue management/action selection?
  • Why is reinforcement learning preferred over supervised learning for training dialogue managers?
  • Describe the main idea of reinforcement learning (agent, environment, states, rewards).
  • What are deterministic and stochastic policies in dialogue management?
  • What's a value function in a reinforcement learning scenario?
  • What's the difference between actor and critic methods in reinforcement learning?
  • What's the difference between model-based and model-free approaches in RL?
  • What are the main optimization approaches in reinforcement learning?
  • Why do you typically need a user simulator to train a reinforcement learning dialogue policy?

Neural Policies & Natural Language Generation

  • How do you involve neural networks in reinforcement learning (describe a Q network or a policy network)?
  • What are the main steps of a traditional NLG pipeline – describe at least 2.
  • Describe one approach to NLG of your choice.
  • Describe how template-based NLG works.
  • What are some problems you need to deal with in template-based NLG?
  • Describe a possible neural networks based NLG architecture.

Dialogue Tooling

  • What is a dialogue flow/tree?
  • What are intents and entities/slots?
  • How can you improve a chatbot in production?
  • What is the containment rate (in the context of using dialogue systems in call centers)?
  • What is retrieval-augmented generation?

Voice assistants & Question Answering

  • What is a smart speaker made of and how does it work?
  • Briefly describe a viable approach to question answering.
  • What is document retrieval and how is it used in question answering?
  • What is a knowledge graph?

Automatic Speech Recognition

  • What is a speech activity detector?
  • Describe the main components of an ASR pipeline system.
  • How do input features for an ASR model look like?
  • What is the function of the acoustic model in a pipeline ASR system?
  • What's the function of a decoder/language model in a pipeline ASR system?
  • Describe the architecture of an end-to-end neural ASR system.

Text-to-speech Synthesis

  • How do humans produce sounds of speech?
  • What's the difference between a vowel and a consonant?
  • What is F0 and what are formants?
  • What is a spectrogram?
  • What are main distinguishing characteristics of consonants?
  • What is a phoneme?
  • What are the main distinguishing characteristics of different vowel phonemes (both how they're produced and perceived)?
  • What are the main approaches to grapheme-to-phoneme conversion in TTS?
  • Describe the main idea of concatenative speech synthesis.
  • Describe the main ideas of statistical parametric speech synthesis.
  • How can you use neural networks in speech synthesis?


  • What are the three main approaches to building chatbots?
  • How does the Turing test work? Does it have any weaknesses?
  • What are some techniques rule-based chatbots use to convince their users that they're human-like?
  • Describe how a retrieval-based chatbot works.
  • How can you use neural networks for chatbots? Does that have any problems?
  • Describe a possible architecture of an ensemble chatbot.

Course Grading

To pass this course, you will need to:

  1. Take an exam (a written test covering important lecture content).
  2. Do lab homeworks (various dialogue system implementation tasks).

Exam test

  • There will be a written exam test at the end of the semester.
  • There will be 10 questions, we expect 2-3 sentences as an answer, with a maximum of 10 points per question.
  • To pass the course, you need to get at least 50% of the total points from the test.
  • We plan to publish a list of possible questions beforehand.

In case the pandemic does not get better by the exam period, there will be a remote alternative for the exam (an essay with a discussion).

Homework assignments

  • There will be 12 homework assignments, introduced every week, starting on the 2nd week of the semester.
  • You will submit the homework assignments into a private Gitlab repository (where we will be given access).
  • For each assignment, you will get a maximum of 10 points.
  • All assignments will have a fixed deadline.
  • If you submit the assignment after the deadline, you will get:
    • up to 50% of the maximum points if it is less than 2 weeks after the deadline;
    • 0 points if it is more than 2 weeks after the deadline.
  • Once we check the submitted assignments, you will see the points you got and the comments from us as comments on your merge requests on Gitlab.
  • You need to get at least 50% of the total assignments points to pass the course.
    • You can take the exam even if you don't have 50% yet (esp. due to potential delays in grading), but you'll need to get the required points eventually.


The final grade for the course will be a combination of your exam score and your homework assignment score, weighted 3:1 (i.e. the exam accounts for 75% of the grade, the assignments for 25%).


  • Grade 1: >=87% of the weighted combination
  • Grade 2: >=74% of the weighted combination
  • Grade 3: >=60% of the weighted combination
  • An overall score of less than 60% means you did not pass.

In any case, you need >50% of points from the test and >50% of points from the homeworks to pass. If you get less than 50% from either, even if you get more than 60% overall, you will not pass.

No cheating

  • Cheating is strictly prohibited and any student found cheating will be punished. The punishment can involve failing the whole course, or, in grave cases, being expelled from the faculty.
  • Discussing homework assignments with your classmates is OK. Sharing code is not OK (unless explicitly allowed); by default, you must complete the assignments yourself.
  • All students involved in cheating will be punished. E.g. if you share your assignment with a friend, both you and your friend will be punished.

Recommended Reading

You should pass the course just by following the lectures, but here are some hints on further reading. There's nothing ideal on the topic as this is a very active research area, but some of these should give you a broader overview.

Basic (good but very brief, available online):

More detailed (very good, available as e-book from our library):

Further reading:

  • Janarthanam: Hands-On Chatbots and Conversational UI Development. Packt 2017.
    • practical guide on developing dialogue systems for current platforms, virtually no theory
  • Gao et al.: Neural Approaches to Conversational AI. arXiv:1809.08267
    • an advanced, good overview of the latest neural approaches in dialogue systems
  • McTear et al.: The Conversational Interface: Talking to Smart Devices. Springer 2016.
    • practical, for current platforms, more advanced and more theory than Janarthanam
  • Jokinen & McTear: Spoken dialogue systems. Morgan & Claypool 2010.
    • good but slightly outdated, some systems very specific to particular research projects
  • Rieser & Lemon: Reinforcement learning for adaptive dialogue systems. Springer 2011.
    • advanced, slightly outdated, project-specific
  • Lemon & Pietquin: Data-Driven Methods for Adaptive Spoken Dialogue Systems. Springer 2012.
    • ditto
  • Skantze: Error Handling in Spoken Dialogue Systems. PhD Thesis 2007, Chap. 2.
    • good introduction into dialogue systems in general, albeit slightly dated
  • McTear: Spoken Dialogue Technology. Springer 2004.
    • good but dated
  • Psutka et al.: Mluvíme s počítačem česky. Academia 2006.
    • virtually the only book in Czech, good for ASR but dated, not a lot about other parts of dialogue systems