What Is Linked

Historical Data?

Albert Meroño-Peñuela

Rinke Hoekstra

@albertmeronyo

EKAW 2014, Linköping, Sweden 26/11/2014

Primary sources

Secondary sources

Historical Sources…

• Independence

• Reliability

• Immutability

…as RDF Graphs?

1. An IRI, once minted, should never change its intended referent.

2. Literals, by design, are constants and never change their value.

3. A relationship that holds between two resources at one time may not hold at another time.

4. RDF sources may change their state over time. That is, they may provide different RDF graphs at different times.

5. Some RDF sources may, however, be immutable snapshots of another RDF source, archiving its state at some point in time.

From http://www.w3.org/TR/rdf11-concepts/#change-over-time on RDF and change over time

…as RDF Graphs?

1. An IRI, once minted, should never change its intended referent.

2. Literals, by design, are constants and never change their value.

3. A relationship that holds between two resources at one time may not hold at another time.

4. RDF sources may change their state over time. That is, they may provide different RDF graphs at different times.

5. Some RDF sources may, however, be immutable snapshots of another RDF source, archiving its state at some point in time.

From http://www.w3.org/TR/rdf11-concepts/#change-over-time on RDF and change over time

Linked Historical Data: A Matter of

Life and Death

Dichotomy:

• Alive Web

• Dead Web

An Ontological Framework of

Historical Sources

• Problem: fundamental requirements from historians on historical sources seem flawed by design in Linked Data

• (part-of) Solution: gain understanding on the essential characteristics of historical sources

• Gain understanding = explicitly state their semantics– Persistence theories (e.g. inst. in DOLCE)

– OntoClean methodology

Persistence

• The continued or prolonged existence of

something

• Perdurantism: ordinary things have

temporal parts (i.e. persist by perduring)

• Endurantism: ordinary things are wholly

present whenever they exist (i.e. persist

by enduring)

– Can “genuinely” change over time

Persistence of Historical

Sources• Secondary sources are endurants

• Primary sources

– Same enduring properties

– Requirement: perdurance immutability (can

change but should not)

– Strong endurants (i.e. can’t change over

time)

The Identity Problem: OntoClean

If sources can change over time, how can

we guarantee that they are the same

entity?

Study of the essential characteristics of

primary and secondary sources – OntoClean

metaproperties

Metaproperties of Historical

Sources

• Rigidity (+R): a rigid property is a

property that is essential to all its

instances, i.e. ∀x φ(x) →☐φ(x)

• Non-rigid (-R), anti-rigid (~R)

• E.g. person(x), student(x)

• Primary sources = +R

• Secondary sources = ~R

Metaproperties of Historical

Sources

• Sortals (+I): classes all of whose

instances are identified in the same way

• Identity criteria of historical sources as

RDF graphs?

• Primary sources = +I

• Secondary sources carry no identity

criteria

Metaproperties of Historical

Sources

• Unity (+U): classes all of whose

individuals are wholes under the same

relation (a whole does not create

instances of its class when subdivided).

• E.g. person(x), clay(x)

• Primary sources = ~U

• Secondary sources = +U

Metaproperties of Historical

Sources

• Dependence (+D): a property is

dependent if each instance of it implies

the existence of another entity.

• E.g. student(x) → teacher(y)

• Primary sources = -D

• Secondary sources = +D

Violating Historical Source

Metaproperties• Historical graphs published in arbitrary sources

on the Web

• The AAA rule: Anyone can say Anything about Any topic– Historical graph ?g with { ?s ?p ?o } changed by

• Unauthoritative statement on a primary source:

{ ?s’ ?p’ ?o’ } with ?s’ = ?s

• Inbound links

{ ?s’ ?p’ ?o’ } with ?o’ = ?s

• Reliability? Independence?

Trusted primary sources

from digital archives

True / false answer on the existence of authoritative primary

source statements

ASK

Reliability

Trusted in-archive

IRI dereferencing services

• IRIs of the primary source remain intact

• Copy has prov:wasDerivedFrom relations

• Resolution and dereferenceability mechanisms

Independence

easy:anne-frank-diary ?

Qualified copy

Primary source RDF graph

Future Work

• Further theoretical study w/ historians

• Experimental evaluation w/ historians

– Metaproperties

• Existing historical ontologies (scarce)

• New ones

– Primary source resolution http://easy.dans.knaw.nl/

• Use cases, historical concepts

– Dutch historical censuses http://cedar-project.nl/

– Dutch book trade http://stcn.data2semantics.org/

Thank youPrimary Source Secondary Source

Dead (archived) graphs Living LOD

Strong endurant Endurant

Rigid (+R) Anti-rigid (~R)

Sortal (+I) Non-sortal (-I)

Anti-unity (~U) Unity (+U)

Independent (-D) Dependent (+D)

Dereferenceable only by archives Dereferenceable by anyone

Comments, suggestions most welcome

@albertmeronyo

https://www.cedar-project.nl/