Question: What is the definition of a person swimming?
About the article "Human swimming", section "Abstract".

Candidate passages:
Here is the definition of "person" data element as defined in the www.w3c.org Friend of a Friend specification *:Although most people do have an intuitive understanding of what a person is, the definition has much room for improvement.
The first problem is that the definition is circular.
Note that this definition really does not help most readers and needs to be clarified.
Here is the definition of the "Person" Data Element in the Global Justice XML Data Model 3.0 *:Note that once again the definition is still circular.
Person should not reference itself.
The definition should use terms other than person to describe what a person is.
Here is a more precise but shorter definition of a person:Note that it uses the word "individual" to state that this is an instance of a class of things called human being.
Technically you might use "homo sapiens" in your definition, but more people are familiar with the term "human being" than "homo sapiens," so commonly used terms, if they are still precise, are always preferred.
Sometimes your system may have cultural norms and assumptions in the definitions.
For example if your "Person" data element tracked characters in a science fiction series that included aliens you may need a more general term other than "human being". 
Most organizations use the UN’s definition of youth which is a person between the ages of 15 to 24, but some organizations expand that definition to 30. 
Linguists have also been involved in this field in attempts to change misconceptions about language.
One common example is the definition of nouns.
Traditionally a noun is defined as a "person, place, or thing".
While this definition captures much of what nouns are it does not incorporate all possible definitions and uses.
For example, mental concepts such as "belief" or "idea" are also nouns but do not neatly fit the traditional definition.
This can be especially difficult for children to understand.
A more comprehensive definition seeks to describe nouns through their features and uses.
However this definition requires the teacher to have greater knowledge of English syntax. 
Swimming lessons is the process of learning to swim.
In most countries there is a definition of a number of swimming levels that is reached in the process of the curriculum.
The respective certificates of swimming tests are required for further training in aquatic abilities.
Many countries have defined a minimum swimming level that children should reach by the end of primary education, in most cases with the help of school swimming classes being part of the normal curriculum.
Children are often given swimming lessons, which serve to develop swimming technique and confidence.
Children generally do not swim independently until 4 years of age. 
An "intensional definition", also called a "coactive" definition, specifies the necessary and sufficient conditions for a thing being a member of a specific set.
Any definition that attempts to set out the essence of something, such as that by genus and differentia, is an intensional definition.
An "extensional definition", also called a "denotative" definition, of a concept or term specifies its "extension".
It is a list naming every object that is a member of a specific set.
Thus, the "seven deadly sins" can be defined "intensionally" as those singled out by Pope Gregory I as particularly destructive of the life of grace and charity within a person, thus creating the threat of eternal damnation.
An "extensional" definition would be a list of the seven.
In contrast, while an intensional definition of "Prime Minister" might be "the most senior minister of a cabinet in the executive branch of government in a parliamentary system", an extensional definition is not possible since it is not known who future prime ministers will be.
One important form of the extensional definition is "ostensive definition".
This gives the meaning of a term by pointing, in the case of an individual, to the thing itself, or in the case of a class, to examples of the right kind.
So you can explain who "Alice" (an individual) is by pointing her out to me; or what a "rabbit" (a class) is by pointing at several and expecting me to 'catch on'.
The process of ostensive definition itself was critically appraised by Ludwig Wittgenstein.
An "enumerative definition" of a concept or term is an "extensional definition" that gives an explicit and exhaustive listing of all the objects that fall under the concept or term in question.
Enumerative definitions are only possible for finite sets and only practical for relatively small sets.