The requirement that an interval number be non-collapsing will be relaxed. The number system is the number system with the restriction, that intervals be non-collapsing, removed:

The number system extends the number system by allowing collapsing intervals. Each interval can be described by two intervals, and :

Parameter value is in the domain of interval if the domain constraint is satisfied:

The value of is given by *v* while the
domain is given by *d* and .
At the interval is:

- not defined if ,
- defined if , and
- potentially defined if .

The number is contained in interval
,
,
for parameter value if the interval is (potentially) defined
at and *x* lies within :

Since it is common to use the same number system as the basis for both the value and domain, there is an abbreviated syntax:

Jeff Tupper | March 1996 |