
```
<presentation
   name = 'put here the instance name'
   maxConstraintArity = 'put here the greatest constraint arity'
   minViolatedConstraints = 'the minimum number of violated constraints'
   nbSolutions = 'put here the number of solutions'
   solution = 'put here a solution'
   type = 'CSP'>
   format = 'XCSP 2.1'
 Put here the description of the instance
</presentation>

```

Only the attribute format is mandatory (all other attributes are optional as they mainly provide human-readable information). It must be given the value 'XCSP 2.1' for the current format. The attribute name must be a valid identifier (or the special value '?'). The attribute maxConstraintArity is of type integer and denotes the greatest arity of all constraints involved in the instance. The attribute minViolatedConstraints can be given an integer value denoting the minimum number of constraints that are violated by any full instantiation of the variables, an expression of the form 'at most k' with k being a positive integer or '?'. The attribute nbSolutions can be given an integer value denoting the total number of solutions of the instance, an expression of the form 'at least k' with k being a positive integer or '?'.

For example,
- nbSolutions = '0' indicates that the instance is unsatisfiable,
- nbSolutions = '3' indicates that the instance has exactly 3 solutions,
- nbSolutions = 'at least 1' indicates that the instance has at least 1 solution (and, hence, is satisfiable),
- nbSolutions = '?' indicates that it is unknown whether or not the instance is satisfiable, The attribute solution indicates a solution if one exists and has been found.

The type attribute indicates the kind of problem described by this instance. It should be set to 'CSP' for a constraint satisfaction problem, 'QCSP' for a quantified CSP and 'WCSP' for a weighted CSP. For compatibility with the XCSP
2.0 format, this attribute is optional for CSP instances (but it is strongly advised to use it). It is mandatory for other types of instances (QCSP, WCSP,...).

Remark that the optional attribute maxSatisfiableConstraints, although still authorized, is deprecated. We encourage to use minViolatedConstraints instead.

## 3.2 Domains

The XML element called <domains> admits an attribute which is called nbDomains and contains some occurrences (at least, one) of an element called
<domain>, each one being associated with at least one variable of the instance.