What is extensional techniques?

Extensional techniques refer to methods used in various fields, such as mathematics and computer science, to analyze or represent objects by their observable properties or behaviors rather than their internal structures. These techniques emphasize the importance of external characteristics and outcomes, allowing for a focus on how entities interact with each other and their environments. In programming, for example, extensional techniques can be used in functional programming to reason about functions based on their input-output behavior rather than their implementation details.