Relations of objects ​

Objects themselves already contain a large amount of information about the subject area. But objects in the world do not exist on their own, they are somehow related to each other, they interact in some way. Important, useful, or interesting statements about what is happening in the world are built as phrases about several objects, about their relationships. To reflect such information in ontological models, relationships between objects are included.

Actually, the first example of a relationship we have already considered. Object categorization is a relationship that connects an individual with a category or a narrower category with a broader category. We agreed to designate the relationship of categorization with the pronoun "this", so that any categorization relationship looks like a triplet:

S this O, where S - an individual or category, and O is always a category.

This triplet is read as "Object S belongs to category O."

But with the help of a triplet (Semantic triple), any relationship between two objects can be expressed:

S P O

In the expressed relationship triplet:

• S (first element) is called the "subject" of the relationship
• P (second element) is called the "predicate" (actually the relationship)
• O (third element) is called the "object" of the relationship

Here we encounter synonymy - since we call "objects" in our course everything that our thinking distinguishes in the world. To avoid confusion, when referring to the "object" as what is in the third place in the triplet, we will call "everything that our thinking distinguishes in the world" (individuals and categories) - "entities."

In linguistics, subject, predicate, and object are familiar to you from school - subject, predicate, and object in a sentence in natural language (for example, in Russian). It is from linguistics that these terms have come into ontological modeling, as a triplet resembles a phrase in natural language.

Examples of relationships as phrases in Russian, while maintaining the structure of triplets:

Mom washes the window.

The cook holds a knife.

Carrots are boiling in a pot.

Predicates used in relationships are universal. We can change entities, describing the same relationship but between other entities:

Anna washes her grandson.

Ivan Ivanovich holds a hammer.

Meat is boiling in soup.

It is also possible to interchange the subject and object while preserving the meaning of the relationship, but changing the predicate:

The window is being washed by mom.

The pot is being used to cook carrots.

If we want to build more quality and formal models, we need to use entities (objects) in relationships that we have already learned to distinguish and name, and also agree on naming rules for predicates.

For individuals and categories as subjects and objects in triplets, we will use our previous agreements, and for predicates, we will agree to use phrases with a lowercase verb, without quotes, but with spaces replaced by underscores (the relationship "this" for categorization will remain an exception for now). For example, like this:

"Anna Petrovna Imyarekova" washes "Petr Sergeevich Borisov"

"bought by me on 25.02.2023 kilograms of meat" is_boiling_in my five-liter blue saucepan

Above are examples of relationships between two individuals, and these relationships, like the individuals themselves, exist at a certain time in a certain place in space.

Note that relationships between two categories are created to reflect completely different interactions and relationships that do not literally coincide with the relationships between the individuals in these categories, although they are somewhat similar. Relationships between categories make sense of statements about the connections of all objects in one category with objects of another, real or potential:

"Grandmother" helps_to_care_for "Grandson"

"Pot" is_used_for_cooking "Meat"

Compare these relationships with the ones above.

Relationships between individuals and categories are currently limited in our model to the categorization relationship "this". We will further clarify the understanding of the categorization relationship, while relationships between individuals and categories are rarely encountered in relatively exotic models. However, an example of such exoticism will be seen below.

Remember that in the ontology of our course, as far as we have constructed it, any individual X is the subject of the categorization relationship

X - this "Individual physical object"

And any category Y is the subject of the categorization relationship

Y - this "Category"

Explicitly recording these relationships in the model is not meaningless. We tried to introduce and observe the naming agreement, but in real projects, this is not always possible, and drawing conclusions about categorization based on the name takes time, so sometimes it is more convenient to explicitly specify the category. Such a relationship, essentially just a statement that the object is singled out in the world, is called a "declaration of an object".

One more remark - of course, relationships are also distinguished based on the role (or roles) for which the model is being made. Even if the entities are clearly linked to the practices of some role, some relationships between them may be invisible or uninteresting from that role.