23. April 1998

First Agile Meeting 1998 1

Aspects of Interoperability

Specifications For Interoperability:Formalising Spatial Relations 'In', 'Auf' and 'An'

and

the Corresponding Image Schemata ‘Container’, ‘Surface’ and 'Link’

Andrew U. FrankDept. of Geoinformation Technical University Viennafrank@geoinfo.tuwien.ac.at

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First Agile Meeting 1998 2

Overview

InteroperabilityWhat are interoperability research questions?Semantics as the main problemCase study: spatial relationsResearch methodology

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Interoperability

Interoperability means ‘working together’, e.g., languages.

Not a new topic for GIScooperation between agencies dealing with space is a

must; they currently work together.

Interoperability is facilitated by human intervention.

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Interoperability by data exchange

Previous discussion:data exchange(with extensive discussion of format changes and standardization)

Disadvantage of data exchange: updates are not propagated

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Technical Solution

Access over the net to the ‘live’ database of another agency.

Made possible by oubiquous net access Technically a communication is established

between client and server.Two programs – running usually on different

machines – cooperate in solving a GIS problem. Exchange of requests and answers:

language to formulate both:SQL extensions for spatial data (for requests)interpretation of the data delivered

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Metaphor for Interoperable GIS

connect an appliance to the power network

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Superficial level of observation

the plug matches the outletInteroperability = matching interface?Issue: Standardization of Plugs

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Standards needed for Interoperability

Plugs must be standardized, but their specification is arbitrary, as demonstrated by the variety of plugs one encounters in the world.

Standardization of plugs is an important question; but not a research issue!

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Interoperability means co-operation

The interface must allow the exchange between systems.

Expectation and offer must meet.Expectation of appliance:

110 Volt, AC 60 HzExpectation of power supplier:

resistance of 100 Ohm (draws max. 1.1 A)The standardization of these values is not a

research issue; other values were possible.

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What has science contributed?

A theory of electric power;the interface is described in terms of physical

measures;electric tension, measured in Voltelectric force, resistance

scales of measurement with the corresponding units.

Interoperability requires abstract description of interfaces:

without a specification of 110 V and the corresponding measurement methods user interfaces would become interoperable only through testing.

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Need:

Formal semantics, for example for measured values in geography and social sciences:

Description of an observable quantity, Measurement methodUnit values

Repeatable abstract description which can be compared between cooperating partners.

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Interoperability research

Mostly not research questions, but questions of standardization;

not in need of academic contributions.

Quality requirements for ResearchInteroperability standardization requires clean

solutions from the research community:Comprehensive,ConsistentConsent

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Problem for Geographic Information:

GIS interoperability requires the exchange of Geographic Information.

Description of information means description of semantics.

Two major issues, closely related:What do data describe – semantics of dataHow to describe data – meta data

Deep issue (and not novel): What does a word mean?

A rose by any other name, would smell as sweet.

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Definition of Semantics:

“The West Peak is 1140 ft high”How should I interpret this sentence? What should I do?

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Description of Semantics

Natural language is ambiguous and depends on human interpretation, which varies between people.

Interoperability was a problem before computers !

Formal Language descriptions requiredNatural language must be translated into a formal

language, which can be translated in computer codealternative:

write code directly, which then becomes the (unreadable) formal definition.

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Requirements for the Language:

assess expressive power and precision of definition of semantics:

computationally completedescriptive, not proceduralreferentially transparentstrongly typedobject oriented, polymorphichigher order functions

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Restricted user community

Reduced answer for GIS:Exchange of semantics in a limited user

community. Address restricted problems:Need restriction of problem size to tackle it.For GIS we need not approach the problem of

full natural language understanding:“I like boxing” or “Time flies like an arrow”.

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For GIS needed: Semantics of spatial relationsTo capture semantics means to formalize.

Example: 9-intersection

Examples:Egenhofer: topology, cardinal directions and distances, configuration of points –

How to approach the other spatial relations, as expressed in natural languages.

(This is a topic worked on since 1986, the ‘Las Navas’ meeting, and carried through several NCGIA and Varenius initiatives, starting with I2.)

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Case study: in, auf, an

Consider relations with respect to movement of objects;

Selected ontology: table top space, blocks and similar objects (fruit, bowl…)

Similar relations for geography have been studied with the same methods.

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Converse of 'auf' blocks object of movement:

'Auf' blocks the movement of the supporting object.

It cannot be moved unless the object 'auf' it is removed.

x 'auf' y (in scene) => blocked (move y in scene)Teller und Gläser sind auf dem Tisch. Wir müssen den

Tisch zuerst abräumen, bevor wir ihn auf die andere Seite des Zimmers bringen können.

Plates and glasses are on the table. We have to remove all objects from the table, before we can move it to the other side of the room.

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'In', 'an': Invariance under movement of relatum

These relations are invariant under movement. If x is 'in' y and y is moved, then x is still 'in' y

(and the same for 'an').x 'in' y (in scene) => x 'in' y (in move y in scene) = True

x 'an' y (in scene) => x 'an' y (in move y in scene) = True

These rules will not be expressed explicitly, as they are subsumed by the 'stable world property' (nothing changes unless specifically indicated).

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'In', 'an': block movement of object

'In' and 'an' create a link between the object and the relatum which resists movement.

x 'in' y (in scene) => blocked (horizontal move x in scene)

Der Apfel kann nicht aus der Schale rollen, aber du kannst ihn dir herausheben.

The apple cannot roll out of the bowl, but you can take it out (lift it out).

x 'in' y and 'closed' y (in scene) => blocked (move x in scene)

Du mußt die Büchse öffnen, dann kannst du die Würfel herausnehmen.

You must open the box. Then you can take out the dice.

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'In' blocks target of movement

An object cannot be moved to a target if this is already in another object. This is justified by situations as:

x 'in' y (in scene) => blocked (move z into x (in scene))

Du mußt den Beutel zuerst aus der Tasche nehmen, bevor du die Münze hineingeben kannst.

You must take the purse out of the pocket to put the coin in.

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Undoes a Previous Relation of Object: 'auf''Auf' does not restrict the movement of the object:

x 'auf' y (in scene) => move x in scene

Du kannst das gelbe Buch nehmen, es liegt auf dem Tisch.You can take the yellow book, it is on top of the table.

A previously established relation becomes false and a new relation is established:

scene2 = move x Rel y (scene1)

a Auf z (in scene1) = True

a Auf z (in scene2) = False

a Rel y (in scene2) = True

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'An' presupposes a physical connection between the object and the relatum..Movement is restricted unless the link is broken.

x 'an' y (in scene) => blocked (move x)

Ich habe das Papier auf das Buch gelegt, jetzt klebt es daran. Wenn du das Papier mitnehmen willst, mußt du es sorgfältig lösen.

I have put the paper on (auf) the book, now it is glued on (an). If you want to take it with you, then you have to carefully remove it.

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Research Methodology

Linguistic style researchRestrict to particular language

Select example sentences: demonstrate an existing language mechanism

(neither the only one, nor all of them; completeness is usually not achievable

Investigate entailments: what follows from a sentence;what can be concluded normally.

Often a need to investigate small stories

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Specific research method

Restrict to a particular environment e.g. table top space

investigate a group of preposition with respect to a (few) operations;

restrict domain of application to very restricted area;

assume polysemy to identify single relations.

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Method to formalize

Algebra: The operations are functionsRelations

Use category theory to achieve a coherent formalization (specifically Allegories)

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What are the primitives

Formal suggestions from mathematical allegory theory

Cognitive science research suggest image schemata

There is a hypothesis that there are a small number of fundamental concepts, which are widely used (also metaphorically) .

Most of them are spatial.The theory of experientialism gives a base for

meaning.

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Partial List of Image Schemata

Container Balance Full-Empty IterationCompulsion

Blockage Counterforce Process SurfaceRestraint

Remove Enablement Attraction Matching Part-Whole

Mass-Count Path Link Collection ContactCentre-Periphery Cycle Splitting

MergingObject Scale Near-Far Superimposition

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Conclusions

Interoperability is limited by semantics.How to understand the data exchanged?Need for formal methods to describe at least

subsets of terminology for limited user groups.

Demonstrated a case study, how semantics of spatial preposition (for table top space, but with the same method also for geographic space) can be captured.

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GIPSIE Project

EU project (DG III: Information Technology)to promote Open GIS within the GI industryto bring European Issues into the OGC processto contribute with research to the Open GIS

standards