why on Earth
do we need
spatial semantics?
Femke Reitsma
Institute of Geography
School of Geosciences
University of Edinburgh
http://www.nesc.ac.uk/esi/themes/theme_04
outline
• what are spatial semantics?
• why do we need semantics?
• what’s special about spatial semantics?
• what is this eSI theme thing all about?
why on Earth
do we need
spatial semantics?
spatial vs. geographic
spatial
geographic
why on Earth
do we need
spatial semantics?
language components
• vocabulary + grammar = language
• natural language
- large and growing vocabulary
- poorly defined grammar
- very expressive
• formal language
- limited vocabulary
- well defined grammar
- formal semantics
syntax and semantics
• Syntax – defines how symbols can be combined
• Semantics – provides the meaning of syntactically
valid collections of symbols
http://headrush.typepad.com/creating_passionate_users/2005/12/have_you_update.html
the mouse tickled the
elephant with a feather
semantic heterogeneity
• different words have the same or similar meaning
munro
mountain
Ben Nevis
semantic heterogeneity
• the same words have different meaning
pants
why on Earth
do we need formal
spatial semantics?
formal languages
• mathematical/algebraic based specifications
(many different logics and formalisms)
•
•
•
•
concise
unambiguous
can verify
limited vocabulary
why on Earth
do we need formal
spatial semantics?
semantics of spatial information
Australia has begun talks with Indonesia and Nauru over the fate of 85 asylum
seekers rescued from the Indian Ocean, the government said on Saturday
as media reported that the group would be sent back to Sri Lanka.
Reuters Friday, February 23, 2007; 11:08 PM
metadata
semantics
metadata
semantics
metadata
semantics
feature semantics
geographic knowledge semantics
• knowledge about how to use geographic information (GI)
• knowledge about GI operations and methods
• human or physical geography
All of the above is a bit ho hum…
• Unique about spatial information are
spatial relationships
…..Geometric & Topological relationships
spatial relation
semantics
latent geosemantics
<x,y,z,t, {a1,a2,…an}>
Spatial relations
classes (features?)
instances
properties
outline
• what are spatial semantics?
• why do we need formal semantics?
• what’s special about spatial semantics?
• what is this eSI theme thing about?
formalising semantics
• gives us…
- ability to reason – e.g. to infer
- unambiguous statements
• practically …
- ensures that different implementations are
the same (i.e. interoperability)
- it supports increased automation of
processes by enabling machine reasoning
good syntax ≠ good semantics
“::=” - may be composed of
“|” - or
K. Slonneger and B. L. Kurtz. Formal Syntax and Semantics of Programming Languages: A Laboratory Based Approach. Addison-Wesley, 1995.
good syntax ≠ good semantics
This grammar allows:
“the bird sang a song”
“the elephant played a tune on his pipe”
But also:
“the pipe sang the bird by an elephant”
formalise in an ontology
• allows us to describe our domain
of interest (e.g. ice creams)
• forces unambiguous statements
• supports reasoning
what are ontologies
a shared vocabulary plus a specification
(characterization) of its intended meaning
(Guarino 1998 )
collection of symbols
meaning of symbols
i.e. semantics
why do we need ontologies?
to help us and computers
deal with semantic heterogeneity
•
•
•
•
information integration
clear specifications of conceptualizations
knowledge discovery, utility, and sharing
interoperability
reasoning with spatial semantics
N
A
near
B
C
far
a bit of formal semantics goes a long way…
I want some
gumboots!
Gumboots
- red band
Wellington Boot Ontology
Properties: – made of rubber
Synonyms: – willy, wellie,
topboot, gumboot
Wellies
some spatial semantics go even further…
Lochs in the Highlands
the meaning of in
Lochs in the Highlands
• axiomatic specification
e.g. “transitive” or “reflexive”?
• converse relations
e.g. “contains” or “has”
• synonyms
e.g. “inside”
• mapping onto geometric operations
a little more complex…
Temporal reasoning – March 7 – 9th
Spatial reasoning – near the trail of interest
e.g. from W3C geo incubator group: http://www.w3.org/2005/Incubator/geo/charter
a little more scientific…
atmospheric model
Constant a = 4.567
Constant b = 2
Constant c = 56
outline
• what are spatial semantics?
• why do we need formal semantics?
• what’s special about spatial semantics?
• what is this eSI theme thing about?
what’s special about spatial?
Tobler’s first law of geography:
“everything is related to everything else, but
near things are more related than distant things”
Tobler, W. R. 1970. A computer movie simulating urban growth
in the Detroit region. Economic Geography 46: 234–40.
spatial autocorrelation
….and spatio-temporal autocorrelation,
or process autocorrelation??
spatial anisotropy
• isotropic plane:
• geographic plane:
spatial anisotropy
scale selection
That's another thing we've learned from your Nation," said Mein Herr, "mapmaking. But we've carried it much further than you. What do you consider the
largest map that would be really useful?"
"About six inches to the mile."
""Only six inches!"exclaimed Mein Herr. "We very soon got to six yards to the mile.
Then we tried a hundred yards to the mile. And then came the grandest idea of all!
We actually made a map of the country, on the scale of a mile to the mile!"
"Have you used it much?" I enquired.
"It has never been spread out, yet," said Mein Herr: "the farmers objected: they
said it would cover the whole country, and shut out the sunlight! So we now use
the country itself, as its own map, and I assure you it does nearly as well.”
Lewis Carroll’s ‘Sylvie and Bruno Concluded’
scale matters
scale interdependence
emergent global structure
spatial boundaries
• MAUP
vs.
spatial boundaries
• system/environment
boundaries
• system/environment
The Bretherton diagram
Source: Earth Systems Science Overview: a program for global change, NASA 1986
spatial relationships?
•Direction
(B is NE of A)
B
•Distance
(B is far from or 5 km from A)
•Topological Relationships
(B is disjoint from A)
A
qualitative spatial + temporal reasoning
• represent and reason about temporal and
spatial knowledge
what is where
where is what
when is x where it is ?
how long was it there?
when did x occur?
what is next to a?
How are x and y
spatially and temporally
related?
outline
• what are spatial semantics?
• why do we need formal semantics?
• what’s special about spatial semantics?
• what is this eSI theme thing about?
eSI theme
Spatial Semantics for Automating
Geographic Information Processes
what are we doing?
• bringing scientific visitors to eSI
• initiating research and collaboration
• running a series of workshops
http://www.nesc.ac.uk/esi/themes/theme_04
research focus
Fundamental issues of composition and integration of
spatial data sets (i.e. harmonisation), geographic knowledge
and model components
Australia has begun talks with Indonesia and Nauru over the fate of 85 asylum
seekers rescued from the Indian Ocean, the government said on Saturday
as media reported that the group would be sent back to Sri Lanka.
Reuters Friday, February 23, 2007; 11:08 PM
eScience
• getting the fundamentals right leads to eScience
• need for a cyberinfrastructure or eScience
framework for geoscience research that recognises
spatial semantics
Stolen from: http://www.newgrantinfo.com/2006_Newsletters/2006_JuneEuro.htm
thank you