Issue 294: E55 Type relations
Posted by Martin on 28/12/2015
I wish you all a Happy New Year!
Please see this document to discuss properties of E55 Type
for archaeological reasoning
Posted by Øyvind on 6/1/2016
This was an interesting read. I have a question:
I do not understand the logic of the last paragraph in page 2. First they talk about
 “a specific time period in which and only in which objects of a given type have been created”
and then they go on to talk about
 no finds from other periods.
 is much weaker than  but is seems to me that  is still used as evidence for . I do not argue that is wrong to use it as evidence (there are never proofs in heritage based research of this kind) but I fail to see how it can be seen as a closed world assumption — that is pretty strong.
I think it is a good choice to model it as an implicit restriction, though; the modelling looks fine. It is more the use of “closed world” I wonder about.
As for the choice between modelling of periods as timespans or periods I think this feeds well into the discussion we have on space-time modelling and this document will be useful for the discussions in Prato.
Posted by Wolfgang Schmidle on 6/1/2016
Co-author here. Yes, we use  as evidence for , and if new evidence is unearthed, the "restricted" statement may turn out to be false.
The "closed world assumption" was only meant as an analogy. We do not argue that a "Restriction" statement in the sense of a bounding box can be inferred from the given "appears in" and "typical for" statements. (Maybe one should also distinguish between the knowledge of the archaeologist and the — possibly incomplete — list of actual "appears in" and "typical for" statements.) Instead, it probably needs to be an explicit new statement, and the inferred statement in Figure 3 should probably have a different name that doesn't suggest anything but an inferred statement.
The point of the Restriction being a timespan rather than a period was, I think, that the sum of periods may not automatically be a period itself. In particular, it may not be identical to the "production of the Paukenfibel" period. However, in Figure 3 we assume that there is at least no temporal gap inbetween. And timespan means more or less the same as spacetime volume here since the area in the example is always the same.
By the way, we have a similar problem in our gazetteer, where we need to express the fact that a given region is part of the union of three other regions.
Posted by Martin on 6/1/2016
My opinion to your questions:
Is it more precise to model the sum of periods as a timespan or a period itsself?
It is more precise to model it as a period, in case this period has a common unity criterion.
It is equally more precise to model it as a spacetime volume, but RDF has no construct to describe that
an STV is exactly the sum of a set of components. The same holds for periods.
How should a hiatus be expressed then? So the stopped and later on picked up
usage of the same object. As a second timespan / period attached to the appearance of an object?
I think it needs a negative property. To be discussed with Carlo Meghini.
• Relation of Types and objects that refer to that type: Is it important to have at least
one object for a “appears in” assignment to refer to.
Well, yes for capturing the argument. If the object is described, the "appears in" could be inferred.
I think a "restricted to" would be a good property. It is more than the sum of "appears in". It requires
an argument of having sufficiently dense observation at other times and sites, or historical sources.
Posted by Øyvind on 7/1/2016
Thank you, Wolfgang! This makes sense to me.
The criteria for what is a period have to be decided by the experts. Yet, I think it is pretty clear that the Renaissance Augustus is a different period from the one in antiquity. Connected, but different.