The Utility of XML

1
The Utility of XML
Martin Doerr
Center for Cultural Informatics
Institute of Computer Science
Foundation for Research and Technology - Hellas
Heraklion, May 25, 2001
2
XML is

• XML is a compromise between databases and free
  texts
• It takes the better from both sides without being
  perfect on either side.
• It is readable. It allows to disambiguate
  meaning.
• It is simple.
• It is rich enough to open a new systems paradigm.

3
What is a Document ?

• A composite statement a unit relating known
  facts, items and categories with new knowledge -
  linguistic or by other media.
• It has an inner logic the pure rendered
  knowledge, independent from language and form.
• It has a meaningful structure The sequence,
  arrangement or linking used to render the inner
  logic.
• It has a presentation Structure and style to
  assist perception and impression

4
A document
5
The statements.

• Diego Velasquez is Spanish.
• Diego Velasquez lived 1599-1660.
• Diego Velasquez painted Juan de Pareja.
• Juan de Pareja is a painting.
• Juan de Pareja has dimension 81,3X69,9cm
• Juan de Pareja is Moorish.
• Juan de Pareja is a painter.
• Philipp IV sent Velazquez to Italy.
• ..

6
Another document
7
Whats Wrong with HTML

• If written properly, normal HTML may reflect
  document presentation, but it cannot adequately
  represent the semantics structure of data

Artifact Title
Artist Name
ltBgtMONET, ClaudeltBgtltBRgt Haystacks at Chailly at
SunriseltBRgt 1865ltBRgt Oil on canvasltBRgt 30 x 60 cm
(11 7/8 x 23 3/4 in.)ltBRgt San Diego Museum of Art
ltBRgt ltPgt ltIMG SRChttp//192.41.13.240/artchive/

m/monet/hayricks.jpggt
Date
Dimensions
Material
Image Reference
Museum
8
User Problems/ Design Reasons

• Preserving info units who said that /
  self-contained
• Entering data
• what can I say,
• what should I say,
• how can I say it.
• Rendering data how to tell my child, the
  public
• Accessing data querying, mediation
• Reusing data transmission to other
  environments, merging, evolution of local system,
  preservation for future use.

9
In Technical Terms

• Transformation under preservation of meaning
• Correct adaptation of presentation without
  knowing meaning
• Packaging information for presentation 1
  document
• Sequencing categories for data input.
• Interpretation of intended meaning - searching
• Automatic relating of common meaning merging
  of different statements

10
Whats wrong with

• Free texts Clear packaging, rendering for one
  target, not machine processable (poor querying,
  categories uncomprehensive), poorly reusable, no
  help to enter data, transform data..
• HTML Solves platform-independence of
  presentation, weak connection between meaning and
  presentation structure not far better than free
  text.
• Databases Clear logical structure,
  categorization, machine processable, excellent
  querying, difficult presentation, transformation,
  merging, evolution, no information units
• XML Clear packaging, logical structure, machine
  processable if correctly used, clear separation
  and relation of meaningful structure and
  presentation.
• Helpful to enter data, easy to extend,
  transform, present. Can be queried, structure not
  independent from user view.

11
XML and databases

• Databases
• Schema first Prior to data, complete,
  inflexible analysis of all categories and their
  relations.
• Table structures indexes prepared, excellent
  consistency enforcement.
• XML
• Data first structure explanatory, can come
  second, need not be formalized, extensible,
  DTDs can be combined
• semi-structured flexible, but reduced guarantee
  if a question can be answered, reduced
  consistency enforcement.
• Embedded schema each instance carries the
  schema it uses
• querying by parsing without index structures
  ideal transport format.

12
Data First, Embedded Schema

• This document carries the interpretation with it.
  It is readable without knowledge of the schema.

ltARTISTgt ltNAMEgtltFIRSTgtClaudelt/FIRSTgtltLASTgtMonet
lt/LASTgtlt/NAMEgt ltARTWORKgt ltARTIFACTgt
ltTITLEgtHaystacks at Chailly at
Sunriselt/TITLEgt ltDATEgt1865lt/DATEgt
ltMATERIALgtOil on canvaslt/MATERIALgt
ltDIM Metriccmgt
ltHEIGHTgt30lt/HEIGHTgtltWIDTHgt60lt/WIDTHgtlt/DIMgt
ltDIM Metricingt
ltHEIGHTgt11 7/8lt/HEIGHTgtltWIDTHgt23
3/4lt/WIDTHgtlt/DIMgt ltLOCATIONgtSan
Diego Museum of Artlt/LOCATIONgt
ltIMAGE Filehttp//192.41.13.240/artchive/m/monet
/hayricks.jpg/gt lt/ARTIFACTgt
lt/ARTWORKgt lt/ARTISTgt
13
Whats important

• Data first delayed analysis, preserves data.
• Embedded schema facilitates data transport,
  readable in the future.
• Separation of semantics and presentation
  enables information reuse.
• Guides and controls data entry
• Same meaning can be encoded in multiple formats
• DTD design depends on purpose Transport,
  presentation, data entry

14
Useful Applications

• Prescription for documentation / input
• Data transfer between systems (middle ware)
• Document bases with full query access.
• Combine database with XML documents
  mission-critical data in tables and DTD, rich
  extensible structures in DTD only.
• Create data for long-term use even machine
  readable from paper!
• Create information sets for multiple presentation

15
Final Remark

• How to encode meaning without structure
  ambiguities
• gt use RDF/ RDFS
• How to standardize meaning of element types
  (tags) ?
• gt use ontologies e.g. formulated in RDFS!