Content
- Is Dublin Core enough?
- Information integration issues
- CIDOC CRM
Thinking about Dublin Core
Dublin Core: a sample
Consider the case (shorthand notation for DC)
dc:title=Pietà
dc:creator=Michelangelo
dc:date=1499
dc:subject=Madonna
dc:subject=Christ
or:
dc:title=Madonna del cardellino
dc:creator=Raffaello
dc:date=1505
dc:subject=Madonna
dc:subject=Child
The implicit meaning is:
- both “Michelangelo” and
“Raffaello” are (better: an instsnce of the class) artist
- a particular artifact (the Pietà, for
example) has been made by Michelangelo, is
dated 1499, and has subject
“Madonna” and “Christ”
- the second one (the painting) has been made
by Raffaello, is dated 1505, and has
subject “Madonna” and
“Child”
Dublin Core: some limitations
We specify some properties of an object
We can add controlled vocabularies to be sure that we
specify correct terms for creator or
subject, but only humans can:
-
check the consistency between
dc:creator and dc:date as no
artifact can be made by an artist after her/his death,
o before her/his birth date (plus, let us say, 10
years?)
- having found an artifact, search for artifacts
made in the same period, or by artists which
were living and active in the same period
- find artifacts (for example portraits) which are
imaginary portraits, because:
- the scene is imaginary, or
- subjects never existed because they are
mythological, or
- subjects were not existing at the time of life of
the artist or in the same time themselves (for
example the famous painting School of Athens
by Raffaello)
These are typical examples of spatio-temporal
reasoning
Information integration
Information Integration
-
Standard vocabularies
-
- definition difficult and time
consuming
- once defined, standards don't adapt well
- people don't implement standards
correctly anyway
-
Common schema
-
- in principle the simplest way
-
different schemas, different cultural
traditions
-
failure!
-
Metadata level
-
- a typical example: Dublin Core
- the number of metadata vocabularies will
continue to grow (M. Doerr)
-
doubtful metadata vocabularies can exploit
the full richness of possible
associations
Metadata vs ontology
A base for understanding
-
Core metadata
-
- intended for integration
- created, edited, viewed by humans
-
human factors play a primary role
-
Core ontology
-
- underlying formal model for tools that
integrate source data and perform a variety of
extended functions
- higher levels of complexity are
tolerable
-
completeness and logical
correctness are the driving forces
- base for deriving knowledge
CIDOC-CRM is a formal ontology which can be used
to perform reasoning.
Motivations for CIDOC CRM
-
Reality of semantic interoperability is
frustrating:
- many standards
- many proprietary metadata
- many proprietary data structures
- many terminology systems
-
Core systems like Dublin Core represent a
common denominator by far too small to fulfil
advanced requirements
-
Overstretching of semantics in order to
capture complex semantics leads to further loss of
meaning, even though most of the contents encoded
in the various structures seems to be pretty well
comprehensive to common sense
(
quoted from M. Doerr)
CIDOC-CRM
CIDOC CRM is ...
For information about the CIDOC CRM and related
work please visit the corresponding
CIDOC CRM website (new site: http://new.cidoc-crm.org/).
The CRM is also available as ISO 21127.
- A collaboration with the International
Council of Museums
- An ontology of 81 classes and 132
properties for culture and more
- With the capacity to explain many (meta)data
formats
- Serving as:
-
intellectual guide to create schemata,
formats, profiles
- A language for analysis of existing sources for
integration "Identify elements with common
meaning"
-
Transportation format for data integration
/ migration / Internet
Role of CIDOC
CIDOC CRM terminology (partial)
-
class: identified by numbers preceded by the
letter "E"
-
subclass: specialization of another class (its
superclass)
-
superclass: generalization of one or more
other classes (its subclasses)
-
multiple inheritance: a class may have more
than one immediate superclass
-
property: identified by numbers preceded by
the letter "P" (define relationship between
two classes)
-
subproperty: specialization of another
property (its superproperty)
-
superproperty: a generalization of one or more
other properties (its subproperties)
- …
Working Document 6.2.2
CIDOC CRM terminology (partial)
-
intension (of a class or property): its
intended meaning
-
extension (of a class): the set of real life
instances belonging to the class that fulfil the
criteria of its intension (with the "Open World
Assumption")
-
Open World Assumption: information stored is
incomplete relative to the universe of discourse they
intend to describe
Properties can have properties, such as in the
case of an Activity (E7) carried out
(P14) by an Actor (E39).
- Example: the painting of the Sistine Chapel (E7)
was carried out by (P14.1) Michelangelo Buonarroti (E21)
in the role of master craftsman (E55) (we will be back to this example)
- (Note that E21 Person is a subclass of E39
Actor)
CIDOC CRM: reasoning about spatial information
Explanation
CIDOC CRM: reasoning about temporal information
Explanation
CIDOC CRM: termini ante quem post quem
A sample
Epitaphios GE34604
Formal description using CIDOC-CRM
Epitaphios GE34604 (Entity Iconographic Object)
is identified by
TA 959a (entity Object Identifier)
GE 34604 (entity Object Identifier)
preferred identifier is
GE 34604 (entity Object Identifier)
has type
ecclesiastical embroidery
liturgical cloth
current owner
Museum Benaki (Legal Body)
has type
private museum
has contact points
<Ifigenia Dionissiadu> ifi@benaki.gr (entity Contact Point)
Koumbari Street 1, Athens (entity Address)
...
(1998 Martin Doerr and Ifigenia Dionissiadou)
RDF+OWL are fit for the job!
<?xml version="1.0" encoding="ISO-8859-7"?>
<rdf:RDF xml:lang="en"
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
xmlns:crm="cd://#" xml:base="//">
<crm:E84.Information_Carrier rdf:about="Epitaphios GE34604">
<crm:P2F.has_type>
<crm:E55.Type rdf:about="ecclesiastical embroidery">
</crm:E55.Type>
</crm:P2F.has_type>
<crm:P2F.has_type>
<crm:E55.Type rdf:about="liturgical cloth">
</crm:E55.Type>
</crm:P2F.has_type>
<crm:P52F.has_current_owner>
<crm:E40.Legal_Body rdf:about="Museum Benaki">
</crm:E40.Legal_Body>
</crm:P52F.has_current_owner>
<crm:P55F.has_current_location>
<crm:E53.Place rdf:about="drawer 8 / case 27 / room 6 / floor sub 1 / new wing">
<crm:P2F.has_type>
<crm:E55.Type rdf:about="drawer">
</crm:E55.Type>
...
- just a serialization format for metadata: ensures
interoperability across SW tools
- OWL meets and exceeds current CRM needs: a number of
reasoners available
As a collection of triples
Still in machine domain! Albeit simpler to read, such visualization is still not friendly to humans
(rdf:#type is a shorthand for: http://www.w3.org/1999/02/22-rdf-syntax-ns#type)
| subject (or resource) |
predicate (or property) |
value (or object) |
| Epitaphios GE34604 |
rdf:#type |
cidoc:#E84.Information_Carrier |
| ecclesiastical embroidery |
rdf:#type |
cidoc:#E55.Type |
| Epitaphios GE34604 |
cidoc:#P2F.hastype |
ecclesiastical embroidery |
| liturgical cloth |
rdf:#type |
cidoc:#E55.Type |
| Epitaphios GE34604 |
cidoc:#P2F.hastype |
liturgical cloth |
| Museum Benaki |
rdf:#type |
cidoc:#E40.Legal_Body |
| Epitaphios GE34604 |
cidoc:#P52F.has_current_owner |
Museum Benaki |
| Creation of Epitaphios GE34604 |
rdf:#type |
cidoc:#E12.Production_Event |
| handwork |
rdf:#type |
cidoc:#E55.Type |
| Creation of Epitaphios GE34604 |
cidoc:#P2F.has_type |
handwork |
| none |
rdf:#type |
cidoc:#E52.Time-Span |
| none |
cidoc:#P81F.ongoing_throughout |
"1682"@en |
| none |
cidoc:#P82F.at_some_time_within |
"1682"@en |
| Creation of Epitaphios GE34604 |
cidoc:#P4F.has_time-span |
none |
| Istanbul |
rdf:#type |
cidoc:#E53.Place |
| Creation of Epitaphios GE34604 |
cidoc:#P7F.took_place_at |
Istanbul |
| Epitaphios GE34604 |
cidoc:#P108B.was_produced_by |
Creation of Epitaphios GE34604 |
| ... |
... |
... |
A graph visualization
A graph visualization(2)
An example in OWL
-
The statement
-
The painting of the Sistine Chapel was carried out by
Michelangelo Buonarroti
-
Abstracting from the statement
-
- The painting of the Sistine Chapel (the subject)
is an (instance of) activity
- carried out by is a predicate
- Michelangelo Buonarroti is an (instance of)
Person
-
In OWL (conceptually)
-
the paintingOfSistineChapel (E7.Activity) was
carried_out_by (P14F) MichelangeloBuonarroti
(E21.Person)
-
In OWL (graphically)
-
-
In OWL (XML Syntax)
-
-
Terrific!
- but suitable for machines,
harmful for human beings!
Conclusion
- La rappresentazione della conoscenza è essenziale per una elaborazione automatica delle informazioni esistenti sul
web
- Le
tecnologie del Semantic Web (RDF, RDFS, OWL) consentono di
rappresentare,
esportare e
condividere la conoscenza in maniera interoperabile
