The next thing we want to add is the capability to filter on dietary restrictions. This will require extensions to your Dialogflow agent for NLU but also require the implementation of new logic in Prolog for filtering the recipe database on these restrictions.

Dialogflow

As a first step, use the following CSV file to upload the dietaryRestiction entity:

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To make your Dialogflow agent extract this entity, you again need to add more training phrases, and annotate these phrases for the dietaryRestrction entity, and extend the addFilter intent with these phrases. You can use the test console of your agent to verify that it is able to recognize addFilter intents with dietary restrictions and extract the entity entries you just added.

Prolog and Patterns

In the previous capabilities that we implemented for filtering the recipe database, we often could simply use the facts that are part of that database to implement the filtering process (the applyFilter/4 rules). For example, for Capability 5: Filter Recipes by Ingredients and Cuisine we could use the ingredient/2 and cuisine/2 facts, and for Capability 6: Filter by Number of Ingredients & Recipe Steps, we could use time/2 for the cooking duration of a recipe and servings/2 for the number of servings. For computing the number of ingredients and recipe instructions steps, we had to do a bit more work, but these could also be computed quite straightforwardly from these basic facts.

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typeIngredient(Ingredient, 'vegetarian') :-
	not(typeIngredient(Ingredient, 'non-vegatarianvegetarian')), !.

Also add rules for the pescatarian and vegan dietary restriction. That enables our agent to handle at least three of the six dietary restrictions that we added to the dietaryRestriction entity of the Dialogflow agent. We will get back to the other three later. For now, you should assume that we can use the predicate typeIngredient/2 to check if an ingredient meets a dietary restriction. We want to implement a rule now that checks that all the ingredients in a list meet a dietary restriction, such as 'meat' or 'vegan'. You should implement an ingredientsMeetDiet/2 predicate in the recipe_selection.pl file that for any given list of ingredients checks that each one of these ingredients meets a dietary restriction. In other words, write code for the body of the recursive clause for the following rule:

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As we mentioned above, there is still information missing to implement the logic for all dietary restrictions, and also for food categories (you were already asked to add the pasta food category, but what about noodles, for example?). For the dietary restrictions, you should add typeIngredient/2 facts that can facilitate the processing of filters for lactose-free (no dairy), gluten-free (no gluten), and spicy recipes. For all three, use a simple approach that only looks at the individual ingredients that are used in a recipe. That is, for a lactose-free recipe, no dairy products should be used; for a gluten-free recipe, no products with gluten should be used; and, for a spicy recipe, the recipe should have (at least) one ingredient that is spicy (the hasIngredient/2 predicate should come to mind here). As before, we can use one fact to deduce the other, and, deduce, for example, that if an ingredient has no gluten it must be gluten-free. We can define such relations using the same type of rule as we have seen above:

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Visuals

Nothing we ask you to do here for this capability. It’s up to youYou can update the visuals based on what you think will help the user the most. Think about how you can support the implemented capability visually.

Test it Out

Try to ask your conversational agent to add dietary restrictions for, for example, vegan recipes. Try various types of restrictions to see how that works. What can you say about how consistent the logic that is defined for these restrictions is? You may want to think about how to improve that (and, if you have any ideas that you did not implement, reflect on that in your report, for example).

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