CAA 2016 Oslo conference presentation

1. CAA 2016 - Oslo
The Matrix:
Connecting Time and Space with
archaeological research questions involving
spatio-temporal phenomena and the
conceptual relationships between them.
Keith May
@Keith_May
Historic England
University of South Wales

2. Stratigraphic data records
• A Harris Matrix primarily for recording of
context level stratigraphic relationships in the
field
• Enables all contexts to be placed on Sequence
diagrams
• But is the diagrammatic representation the
only/best way to present all the overall
stratigraphic relationships?
• Harris matrix is a tool for fieldwork recording,
what about spatio-temporal data relations
from later in analysis process?
• Is the Harris matrix diagram the best way to
preserve the stratigraphic relationships
recorded in the data?
• What is the best for re-use – especially cross-
linking and cross-searching - of data?

3. Review of Harris Relationships
• Before/After relationship
• Interfaces: can be seen to represent
Start & Finish of events
• Equals relationship?
• What does “=“ mean on the matrix?
– At the same time?
– Is the same physically?
– Occupies continuous spacetime in Past?
But not now?

4. Harris on 4D
• “A stratigraphic sequence is a diagram of
relative time: it shows all four dimensions of
the stratigraphic accumulation of a site, unlike
the two-dimensional image of the physical world of
stratified deposits seen in a section” (Brown & Harris -
Practices of archaeological stratigraphy p18)
With
thanks to
Mortimer
Wheeler

5. Review of Carver Relationships
• More concerned with presenting
the Sequencing
• and Continuity of relationships
between contexts
• More intended to represent
interpretations of the sequence
of stratigraphic units, their
groupings into features and the
relationships between those
higher order groups
• Roskams - A ‘post-excavation’
analysis tool?
• Harris matrix - an Excavation
tool?

6. Is there a division in the process from
Excavation to Post-Excavation?
• Why not enable both levels of
relationships in the process?
• Why are these separate ‘islands’
of data?
• Combine them through the
process from Excavation and
Analysis – Phase recording in
planning on site does occur
depending on
complexity/resources of sites
• Definitely the relationships are
part of the Archive Record, but
very often not easily re-useable

7. Allen Operators for Temporal Relations
• P120: occurs
before (occurs after)
• P114: is equal in time to
• P115: finishes (is finished by)
• P116: starts (is started by)
distinct because no pair of definite intervals can be related by more than one of the
relationships
exhaustive because any pair of definite intervals are described by one of the relations
qualitative (rather than quantitative) because no numeric time spans are included –
relationships are relative to each other
P117: occurs during
(includes)
P118: overlaps in time with
(is overlapped in time by)
P119: meets in time
with (is met in time by)

8. E.G. Silbury Hill Matrix
Occurs During
Overlaps in
Time }{
Meets in
Time

9. Stratigraphic Matrix – Working Diag (LRC)
Overlaps in
Time

10. Stratigraphic Relationships in CSV

11. Allen Temporal Operators & Stratigraphic relations
used in CIDOC CRM and CRMarchaeo data modelling
• P120: occurs before (occurs after)
• P114: is equal in time to
• P115: finishes (is finished by)
• P116: starts (is started by)
• P117: occurs during (includes)
• P118: overlaps in time with (is overlapped in
time by)
• P119: meets in time with (is met in time by)

12. “Meets in Time” relationship
• Interfaces at context resolution are
rarely immediately concurrent
• In a Matrix the interfaces usually
identify an hiatus or separations in
time
• Harris Interfaces between contexts
could be represented by ‘meets in
time’ relationships but with
indeterminate duration time-spans
• Some e.g. Walls or ceilings collapsed
directly on a floor
• Items buried by natural phenomena –
lava, floods, fire collapses
• ‘Meets in Time’ – more appropriate for
relationships between phases Harris 1979 – Fig2

13. Occurs During – Groups & Phases
• Contexts allocated to Groups
or Phases (specific to individual sites)
• Time-spans or Periods
allocated/interpreted for
Groups/Phases
• Group matrices will show all
contexts that “occur during”
the time-span of the Group
• Harris also distinguishes
“Periods of Deposition” from
“Periods of non-deposition” –
so can Interface hiatus occur
between phases? – more
usually meets in time?

14. ‘Overlaps in Time’ relationship
• Expresses continuity of parallel
events
• Sequences within Matrices that
overlap - but physically
separate
– E.g field boundaries
– Parts, walls, rooms, of the same
building
• Does “=“ in matrix mean equals
or possibly ‘overlaps in time’?
• Bayesian modelling uses
‘overlaps in time’ where
contexts may be sequenced in
parallel but with no direct
stratigraphic relationships.
STAR Timeline Service
Expressions of Period overlaps – see
STAR Timeline Service test client
http://perio.do/guide/

15. For Periods - Juxtaposition of
Fuzzy Spatio-Temporal 4D Relations
With Thanks to Papadakis, Doerr & Plexousakis

16. CRM archaeo
FORTH-ICS March 24, 2014
Stratigraphic Genesis
A1 Excavation Process Unit
E7 Activity
A8 Stratigraphic Unit
A3 Stratigraphic Interface
A4 Stratigraphic Genesis S10 Material Substantial
S11 Amount of Matter
AP1 produced
AP7 produced
AP9 took matter from
A5 Stratigraphic ModificationS17 Physical Genesis
AP13 has stratigraphic relation
AP8 disturbed
A2 Stratigraphic Deposit Unit
AP12 confines
E63 Beginning of Existence S18 Alteration
E18 Physical Thing
AP24 is or contains remains of
AP11 has physical relation
S22 Segment of Matter
A6 Group Declaration Event
AP16 assigned attribute to
E13 Attribute
Assignment
P141 assigned
AP10 is part of
S20 Physical Feature

17. Interfaces not sequenced (except cuts)
…Of course, archaeologists who use the Harris Matrix
recognize the unrecorded layer interfaces and these are
brought back into the analysis at a later stage, when
periods are identified (Harris, 1989, Fig. 25). It is at this
late analytic stage that the definition of a period
boundary as an interface and its specification in the
Harris Matrix as a mix of interfaces and deposits is
reconciled (Practices - Harris & Brown(s) eds, 1989, 67-
68).
“Treating the layer interface as an integral part of the
depositional context beneath it ignores the possibility
that it represents a unit of time, either because the
surface it represents was deflated by erosion, exposing
old deposits, or because the surface itself was open for
some time. The failure to record layer interfaces
potentially introduces hiatuses into the chronological
model. (Dye & Buck 2015 p85)
Dye & Buck 2015

18. Bayesian chronological model
A Bayesian chronological model comprises directly-dated events and the start and
end dates of one or more chronological phases. The start and end dates of a
chronological phase typically map directly to an archaeological context
One difference between a Bayesian chronological model
and an archaeological sequence diagram is that the
Bayesian chronological model may include relationships
that cannot be expressed by stratigraphy.
The illustration recognizes three possible relationships
between two chronological phases where one is older
than the other (Fig. 7). Only two of these relationships
can be represented stratigraphically.
Overlaps in Time relationship
“One chronological phase can be older than the other such that the end date for the
older chronological phase is the same age as the start date for the younger
chronological phase (Fig. 7, middle)”.
Meets in Time relationship

19. Spatio-temporal relationship
interrogation
Nested granularity to show
Period – Phase – Group – Context
Could enable semantic querying of
‘Which “Objects” are in contexts that
‘Occur During’ certain Phase or Period’
Dye & Buck have developed prototype
software for creating & illustrating
both stratigraphic and chronological
directed graphs. But suggest more
work needed
What are the use cases for Bayesian
Model and Harris matrix?
http://tsdye.github.io/harris-matrix
STAR semantic query browser

20. Stratigraphy in Digital Archive contents
❖ How do people record Strat?
❖ How is Harris Matrix archived?
❖ Kept as images or data?
❖ How readily able to re-use?
❖ Need a consistent format for
preservation, sharing and re-use
of the STRAT RELATIONSHIPS
❖ E.g. Data as CSV can easily
convert to RDF/XML for use by
semantic technologies e.g.
STELLAR - RDF & LOD outputs

21. Conclusions and Challenges
• More consistent standards needed for digital records of
Stratigraphic relationships if matrix data is to be re-used
effectively. – e.g. CSV - Not just images of diagrams
• Need to consider more explicit ways of expressing spatio-
temporal relations within archaeological records and
• Need new ways to visualise the complexity of the spatio-
temporal relations - extending Harris matrices
• Semantic technologies offer some possibilities, but currently it is
simpler for Temporal relations than Spatial-Temporal
• ...but representing the Granularity of the various spatio-
temporal relationships, including Stratigraphic ‘ along with other
Allen relationships, can also help in conceptualising greater
Time-Depth in the Spatio-Temporal relations in our records.

22. Acknowledgements & References
Harris, E. Principles of Archaeological Stratigraphy.
Allen, James F. Maintaining knowledge about temporal intervals.
Gavin Lucas. "The Archaeology of Time"
CIDOC CRM. http://cidoc.ics.forth.gr/
T. Dye & C. Buck - Archaeological sequence diagrams and
Bayesian chronological models
Tudhope, May, Binding, Vlachidis. "Connecting Archaeological
Data and Grey Literature via Semantic Cross Search" - Internet
Archaeology Vol 30
The Matrix - Larry & Andy Wachowski © Warner Brothers