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

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?

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?

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

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?

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

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)

E.G. Silbury Hill Matrix

Occurs During

Overlaps in Time } {

Meets in Time

Stratigraphic Matrix – Working Diag (LRC)

Overlaps in Time

Stratigraphic Relationships in CSV

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)

“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

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?

‘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/

For Periods - Juxtaposition of Fuzzy Spatio-Temporal 4D Relations

With Thanks to Papadakis, Doerr & Plexousakis

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 Modification S17 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

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

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

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

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

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.

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