If the attribute is a boolean attribute,
this can be used to access the value.
The values taken are 'true' and 'false'.

If the attribute is an integer attribute,
this can be used to access the value.

If the attribute is a floating point attribute,
this can be used to access the value.

If the attribute is a date/time attribute,
this can be used to access the value.
time[0] contains the NX computational date
time[1] contains the NX computational time.
The time here is assumed to be in the time zone of the user.
When saved, the time is converted to UTC.

If the attribute is a string or reference attribute, then
this is a pointer to the value. The maximum length
of this string is limited by UF_ATTR_MAX_STRING_BUFSIZE

If the attribute is a reference attribute, then
this is a pointer to the reference string value.
The value may have an embedded expression with
the following syntax:
<Xm.n@exp_name> or <Xm,n@exp_name>
The X indicates that an expression is being
referenced. The m specifies the minimum field
width. If necessary, it is padded on the left to
make up the field width. The n specifies the
maximum number of digits after the decimal point of
the expression value. The decimal point can be
specified as either . or , thus either m.n or m,n
are acceptable.
This field is only used when setting a reference
value and when specifically asking for the reference
string value. UF_ATTR_cycle and UF_ATTR_read_value
will return the evaluated value, not the reference string.