A ksana is the minimal temporal interval : within the space of a ksana one and only one ultimate event can have occurrence. There can thus be no change whatsoever within the space of a ksana — everything is at rest.
In Ultimate Event Theory every ultimate event is conceived to fill a single spot on the Locality (K0) and every such spot has the same extent, a ‘spatial’ extent which includes (at least) three dimensions and a single temporal dimension. A ksana is  the temporal interval between the ‘end’ of one ultimate event and the ‘end’ of the next one. Since there can be nothing smaller than an ultimate event, it does not make too much sense to speak of ‘ends’, or ‘beginnings’ or ‘middles’ of ultimate events, or their emplacements, but, practically speaking, it is impossible to avoid using such words. Certainly the extent of the spot occupied by an ultimate event is not zero.
The ksana is, however, considerably more extensive than the ‘vertical’ dimension of the spot occupied by an ultimate event. Physical reality is, in Ultimate Event theory, a ‘gapped’ reality and, just as an atom is apparently mainly empty space, a ksana is mainly empty time (if the term is allowed)..  Thus, when evaluating temporal intervals the ‘temporal extent’ of the ultimate events that have occurrence within this interval can, to a first approximation, be neglected. As to the actual value of a ksana in terms of seconds or nanoseconds, this remains to be determined by experiment but certainly the extent of a ksana must be at least as small as the Planck scale, 6.626 × 10–34 seconds.
A ‘full’ event-chain is a succession of bonded ultimate events within where it would not be possible to fit in any more ultimate events. So if we label the successive ultimate events of a ‘full’ event-chain, 0, 1, 2, 3……N  there will be as many ksanas in this temporal interval as there are ultimate events.
Suppose we have a full event-chain which, in its simplest form, may be just a single ultimate event repeated identically at or during each successive ksana. Such an event-chain can be imaged as a column of dots where each dot represents an ultimate event and the space in between the dots represents the gap between successive ultimate events of the chain. Thus , using the standard spacing of 2.5  this computer we have

Now, although the ‘space’ occupied by all ultimate events is fixed and  an absolute quantity (true for ‘all inertial and non-inertial frames’ if you like), the spacing between the spots where ultimate events can occur both ‘laterally’ — laterally is to be understood as including all three normal spatial dimensions — and vertically, i.e. in the temporal direction, is not  constant but variable. So, although the spots where ultimate events can occur have fixed (minuscule) dimensions, the ‘grid-distance’, the distance between the closest spots which have occurrence within the same ksana,  and so  does the temporal distance between successive ultimate events of a full event-chain. So the ksana varies in extent.  However, there is, by hypothesis,  a minimum value for both the grid-distance and the ksana. The minimal value of both is attained whenever we have a completely isolated event-chain. In practice, there is no such event-chain any more than, in traditional physics, there is a body that is completely isolated  from all other bodies in the universe. However, these minimal values can be considered to be attained for event-chains that are sufficiently ‘far away’ from all other chains. And, more significantly, these minimal values apply whenever we have a full regular event-chain considered in isolation from its event environment.
The most important point, that cannot be too strongly emphasized, is that although the number of ultimate events in an event-chain, or any continuous section of an event-chain, is absolute, the interval between successive events varies from one chain to another, though remaining constant within a single event-chain (providing it is regular). Unless stated otherwise, by ‘ksana’ I mean the interval between successive ultimate events in a ‘static’ or isolated regular event-chain. This need not cause any more trouble than the concept of intervals of time in Special Relativity where ‘time’ is understood to mean ‘proper time’, the ‘time’ of a system at rest, unless a contrary indication is given.
Thus, the ‘vertical’  spacing of events in different chains can and does differ and the minimal value will be represented by the smallest spacing available on the computer I am using. I could, for example, increase the spacing from the standard spacing to

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moment’, is not an absolute. However, unless stated otherwise, by ‘ksana’ we are to understand the duration of a ksana within a ‘static’ or isolated regular event-chain. This should not cause any more trouble than the concept of ‘time’ in Special Relativity where ‘time’ is understood to mean ‘proper time’, the ‘time’ of a system at rest, unless a contrary indication is given. However, the ‘vertical’  spacing of events in different chains can and does differ. I could, for example, increase the spacing from the standard spacing to

•           or to                     •

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S.H. 11/7/13