[Crm-sig] ISSUE 240: Start/End vs Period of Existence

martin martin at ics.forth.gr
Sat Apr 19 21:38:08 EEST 2014


Hi Vladimir,

Good initiative, but a lot of these things have been discussed in length in
CRM-SIG, and recently we have entered a discussion about start events of 
periods.
I'll point you to respective literature, please have a look at that.

Please do not propose too many things at a time, it makes it difficult 
to manage
the issue.

In continuation of Stephen: Yes, it is intentional that states that can 
only be
acquired by explicit events, such as ownership, membership etc., are 
described
by these events. This is to ensure monotonicity under increase of 
incomplete,
but consistent knowledge. True life-long observation is extremely rare, 
therefore
most such states are concluded from events. If this is the case, these 
should be
documented, and not the states. The states should be deductions, and any 
user
of the CRM is free to introduce such deductions.

"Modeling such Periods of Existence is significantly more economical 
than modeling with Start/End events. "

This is no argument. Firstly, the size of all metadata together are a 
negligible fraction of image
data we keep. Secondly, these events are the hooks for other, distinct, 
historically relevant
information. Birth and death have quite different contexts and actors 
involved.

Not all periods can have start or end events. Simply, because the event 
itself has
a duration as a fact of physics, and this creates and infinite 
recursion. To define properties
is easy. What we need is an understanding of the semantics of "starting 
something".
Is there an concept of cause or occasion? How does a start event behave 
in space-time?

See in particular:

 1. Doerr, M., Kritsotaki, A., & Stead, S. (2005). Thesauri of
    historical periods - A proposal for standardization. /In Proceedings
    CIDOC '05 Conference/, Zagreb, Croatia, 24-27 May.
 2. Doerr, M., Kritsotaki, A., & Stead, S. (2004). Which Period is it? A
    Methodology to Create Thesauri of Historical Periods. /Computer
    Applications and Quantitative Methods in Archaeology Conference,
    CAA2004/, Prato, Italy, 13-17 April.

"momentary events" are a fiction of computer science. A basic 
requirement for the CRM is that it is
scale-invariant. There is no smallest granularity for events we could 
easily point to.

You write:
"HOWEVER, there is no standard way to state the "Period of 
use/existence/activity of something", such as: - period of use of an 
Identifier (Appellation, Title), Type - life of a Person - floruit of a 
Person"

Use of an identifier and the floruit of a person is explicitly modelled 
in FRBRoo v2.0.

The problem with states, such as "period of use" is the open world 
semantics:
What is actually observed knowledge, and what is inference? This distinction
is the "soul" of the CRM. See the CRM Sci extension just publioshed on 
the CRM site
for a definition of states. Expecting your comments.

See also Doerr, M., & Hiebel, G.H (2013). CRMgeo: Linking the CIDOC CRM 
to GeoSPARQL through a Spatiotemporal Refinement. 
2013.TR435_CRMgeo_CIDOC_CRM_GeoSPARQL.pdf 
<http://www.ics.forth.gr/tech-reports/2013/2013.TR435_CRMgeo_CIDOC_CRM_GeoSPARQL.pdf>.

Finally, events and temporal knowledge is fuzzy. Allen relationships 
have only temporal
meaning, they are accidental.

See also:
Doerr, M., Plexousakis, D., Kopaka, K., & Bekiari, 
Ch. (2004). Supporting Chronological Reasoning in Archaeology. /In 
Computer Applications and Quantitative Methods in Archaeology 
Conference, CAA2004/, (pp. 13-17).

For dealing with fuzzy boundaries.

Indeed, life of a person is one of the candidates for a period with 
start/end events, but,
is it a "Period" or just the spacetime volume of the person?

best,

martin



On 19/4/2014 4:39 ??, Stephen Stead wrote:
> Vladimir
> I am not trying to answer all your points but I have a couple of comments
> that may address several of them.
> In general we have taken the design approach of not modelling condition
> states as they tend to lead to monotonicity problems when combining
> different data streams. As far as I can remember a parallel effort by a
> different research group did try that approach and ran into so many problems
> with their model that the development effort was abandoned. However, not
> before we had harmonised the constructs they had with the CRM.
> Our contention is that it is always better to calculate at query time what
> the current state of knowledge indicates is the period that a state existed.
>
> We also consider it axiomatic that no event is "momentary": all temporal
> events have duration.
> HTH
> Rgds
> SdS
>
>
> Stephen Stead
> Tel +44 20 8668 3075
> Mob +44 7802 755 013
> E-mail steads at paveprime.com
> LinkedIn Profile http://uk.linkedin.com/in/steads
>
>
> -----Original Message-----
> From: Crm-sig [mailto:crm-sig-bounces at ics.forth.gr] On Behalf Of Vladimir
> Alexiev
> Sent: 19 April 2014 12:00
> To: 'crm-sig'
> Subject: [Crm-sig] ISSUE 240: Start/End vs Period of Existence
>
> Hi!
>
> (An issue that arose at public-esw-thes at w3.org under subject Re: TGN place
> types (broader/narrower spanning ConceptSchemes) and was discussed to some
> extent between me and Richard Light)
>
> There are many "dual" Events in CRM that indicate the Start/End of
> something:
> - Beginning/End of Existence
> - Birth/Death of a person
> - Identifier Assignment with props assigned/deassigned
> - Acquisition with props transferred from/to
> - Transfer of Custody with props from/to
> - Production/Destruction (not completely dual)
> - Part Addition/Removal
> - Formation/Dissolution of a group
> - agent Joining/Leaving a group
>
> There are also events that indicate Start, without a corresponding End
> event:
> - Creation (End is not appropriate, since conceptual things are forever)
> - Type Assignment (IMHO should also have "type deassigned", just like
> Identifier Assignment)
>
> HOWEVER, there is no standard way to state the "Period of
> use/existence/activity of something", such as:
> - period of use of an Identifier (Appellation, Title), Type
> - life of a Person
> - floruit of a Person
> - period of group membership or profession of a Person (e.g. reign) One
> would have to model them as Event/Activity in which the concerned entity
> participated, with some P2_has_type.
>
> We also need to relate the start/end events to the period of existence.
> P116_starts and P115_finishes almost fit the bill, though they bind only one
> of the endpoints.
> E.g. P115: "allows the ending point for a E2 Temporal Entity to be situated
> by reference to the ending point of another temporal entity of longer
> duration".
> P115 makes no relation between the starting points. But Death is *the* end
> of Life, so *both* points of Death must be strongly related to the ending
> point of Life.
> - We could introduce sub-properties:
>    P216 really starts (really started by): "an E2 Temporal Entity (e.g.
> Birth) is considered to be "momentary", and is the start of a longer E2
> Temporal Entity (e.g. Life)"
>    P215 really finishes (really finished by): "an E2 Temporal Entity (e.g.
> Death) is considered to be "momentary", and is the finish (end) of a longer
> E2 Temporal Entity (e.g. Life)"
> - These should be subproperties not only of starts/finishes, but also of
> forms_part_of :
>    P216_really_starts rdfs:subPropertyOf P116_starts, P9i_forms_part_of.
>    P215_really_finishes rdfs:subPropertyOf P115_finishes,
> crm:P9i_forms_part_of.
> (This is optional, we could just use P116 and P115)
>
> Finally, we need some rules to relate the 4 time-points (P82a, P81a, P81b,
> P82b) of the Start/End events to those of the Existence period.
> I'm not sure what the rules should be... One approach could be that:
> - Start/End are considered "momentary" events, thus have only 2 points
> (P81a=P82a, P82b=P81b)
> - these points correlate to Existence as follows: Start.P82a=Existence.P82a,
> Start.P82b=Existence.P81a, End.P82a=Existence.P81b, End.P82b=Existence.P82b.
> Maybe this is a bit naïve, since:
> - "momentary" is a relative term. Birth could be described as a minute
> event, usually is described as an  the "expected" inequalities
> P82a<=P81a<=P81b<=P82b do not always hold, see
>    Deducing event chronology in a cultural heritage documentation system
> (Holmen & Ore, CAA 2009)
>
> Modeling such Periods of Existence is significantly more economical than
> modeling with Start/End events.
> So I think this is a new important shortcut pattern: one event (e.g. Life)
> being the shortcut expression of two events (Birth/Death).
> I expect the classical objection will be raised, that Life is not used often
> in cataloging practice.
> But if there's enough interest to have explicit classes for Birth/Death, how
> can there be not enough interest to have specific class for Life?
>
> In the attached Turtle file I've defined a couple of extension classes (Life
> and Membership) and given some examples.
> Note that Joining/Leaving are longcuts of Membership, which itself is a
> longcut of P107_has_current_or_former_member.
> So it's interesting that we've discovered an expression at intermediate
> level of detail between super-detailed (Joining/Leaving) and undetailed
> (P107)
>
> I give an example of a king whose reign finishes with his life (descension
> coincides with Death).
> It would be interesting to try to model Picasso's creative periods with this
> machinery, e.g. see http://en.wikipedia.org/wiki/Picasso
> http://en.wikipedia.org/wiki/Picasso%27s_Blue_Period
>
> Cheers! Vladimir
>
>
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> Crm-sig at ics.forth.gr
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>


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