In computer science, the existence of an object or entity indicates that its minimum cardinality is zero. In other words, there may be no instances of the object in question. This is in contrast to the minimum cardinality of one, which requires that there be at least one instance of the object.
The concept of a minimum cardinality of zero is important in understanding the distinction between data and information. Data is a collection of facts or observations that have been recorded but have not been processed in any way. Information is data that has been organized in such a way that it can be meaningful to someone. For example, a list of birthdates might be data, but when that data is organized into a format that can be used to calculate averages and standard deviations, it becomes information.
In database theory, the minimum cardinality of an entity is often referred to as its “degree”. The degree of an entity indicates the number of attributes that must be present in order for an instance of the entity to exist. For example, a degree-2 entity would require two attributes in order for it to exist, while a degree-3 entity would require three attributes.
The Existence of an Entity Indicates That Its Minimum Cardinality Is Zero
The existence of an entity indicates that its minimum cardinality is zero. This statement is true because if an entity did not exist, then it would have no minimum cardinality.
What is an entity?
An entity is a thing or concept that can be uniquely identified. An entity could be a person, place, thing, or idea. In database design, an entity is a piece of data for which we want to store information.
What is the cardinality of an entity?
The cardinality of an entity is the number of instances of that entity that can exist in a relationship. In other words, it is the number of items in a set. The minimum cardinality is the lower limit on the number of items that can exist in a set, while the maximum cardinality is the upper limit.
What does it mean when an entity’s cardinality is zero?
An entity’s cardinality is the number of distinct values it can take on. An entity with a minimum cardinality of zero is one that can exist without any values.
For example, consider a game character who can have one or more weapons. The character itself exists independently of any weapons, so the character’s cardinality is zero. The character can have any number of weapons, up to and including zero, so the weapon’s cardinality is also zero.
In other words, the existence of an entity does not require any values; the entity can exist without values. However, an entity cannot exist without at least one value if its minimum cardinality is greater than zero.
Based on the information above, it can be concluded that the existence of an entity indicates that its minimum cardinality is zero.