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:

...

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.

We have only seen one other example so far of a feature request that could not be implemented by “simply” using basic facts from the recipe database: the ingredient type for Capability 5: Filter Recipes by Ingredients and Cuisine. We used the typeIngredient/2 facts in the ingredient_hierarchies.pl file to implement a filter for ingredient type. When you inspect the recipe_database.pl file, you will see that there are also no simple facts in the database that suggest that a recipe is vegan or spicy, for example (two restrictions that are included in the dietaryRestrction entity in the Dialogflow agent). We As for the ingredientType entity, we need to add some logic to enable the agent to conclude from the basic knowledge stored in the database about a recipe that is satisfies a dietary restriction. We will use the typeIngredient/2 predicate for this too, again.

Filtering on dietary restrictions

The basic idea to implement the logic for checking a dietary restriction is to check whether each ingredient of a recipe meets that dietary restriction. It is clear, for example, that a recipe that uses chicken, is not a vegetarian recipe. The reasoning is simple: Vegetarians do not eat any kind of meat, chicken is a kind of meat, so any recipe that uses chicken is not a vegetarian recipe. If we can retrieve this information about chicken somehow, then we can implement this logic for our agent too. When you inspect the ingredient_hierarchies.pl file, you will see that it includes facts that say exactly that. We find, for example, typeIngredient('chicken drumsticks', 'meat'). We can use these facts to conclude that various kinds of chicken and other ingredients are meat. There are no facts, however, to conclude that an ingredient fits in a vegetarian or vegan diet. Instead, you will find facts indicating that certain ingredients are non-vegetarian and non-vegan. FirstOf course, assuming that these lists of facts are complete (we give no guarantees, you might want to check that), we can then also conclude that all ingredients that are not explicitly listed as non-vegetarian should be vegetarian. Let’s first add some rules that implement this logic so that the agent can conclude that an ingredient is vegetarian, too. In the ingredient_hierarchies.pl file, at the designated location, add, for example:

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

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:

ingredientsMeetDiet([ Ingredient | Rest ], DietaryRestriction) :-

Of course, you will also need to add a base clause for this predicate with the empty list as first argument. Should this base clause succeed or fail for a dietary restriction?

Next, begin by adding some supporting predicates to the recipe_selection.pl file.

...

diet(RecipeID, DietaryRestriction) :-

In the diet rule, we need to find all the ingredients that a certain recipe has and then input them into a new function we shall create below diet, called ‘ingredientsMeetDiet’. diet should work if the list of ingredients of the inputted RecipeID fits the dietary restriction inputted DietaryRestriction.

...

DietaryRestriction

...

The ingredientsMeetDiet predicate should take a list of ingredients and check if each one meets a dietary restriction. It has a stop clause that is in the file already and will recursively check each ingredient and return ‘false’ when an ingredient does not meet the given dietary restriction. The predicate ‘typeIngredient’ can be used to check if an ingredient meets a dietary restriction. Fill in the body of the rule for ingredientsMeetDiet. 

Make an applyFilter function for it

...

Extending the logic of ingredient hierarchies

Add

...

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

...

to the ingredient hierarchy by adding ingredient type functions and type ingredient lists to include

...

lactose-free (no dairy), gluten-free

...

(no gluten), spicy

Here is an example of a typeIngredient rule:

...

We recommend using automated approaches to compile these lists.

Visuals

Nothing we ask you to do here for this capability. It’s up to you.

...