### 3.7.66. Core

Denotes that a global constraint is an important constraint. In fact many constraints can been seen as variations or extensions around one of the following notions:

Both, the $\mathrm{𝚎𝚕𝚎𝚖𝚎𝚗𝚝}$ and the $\mathrm{𝚊𝚕𝚕𝚍𝚒𝚏𝚏𝚎𝚛𝚎𝚗𝚝}$ constraints, are the most commonly used global constraints. Many core global constraints can be seen as an extension of the $\mathrm{𝚊𝚕𝚕𝚍𝚒𝚏𝚏𝚎𝚛𝚎𝚗𝚝}$$\left(〈{x}_{1},{x}_{2},\cdots ,{x}_{n}〉\right)$ constraint along one of the two following lines: