11/14/08Andrew Frank1 Time and Process in GIS: What can ontology contribute? Andrew U. Frank...

11/14/08Andrew Frank 1

Time and Process in GIS:What can ontology contribute?

Andrew U. FrankGeoinformationTU [email protected]

mailto:[email protected]


Dynamic GIS:

The current GIS maintain static views of the world.

The user want to understand how the world evolves in time (e.g. “Global Change” discussion).

The users are interested in computational models of geographic

space and the processes in it.

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GIS should be Computational Models:Current GIS are static data collections,

described by static ontologies.

The new GIS must combine data

withprocesses

to model the dynamic reality!

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Ontological challenge for dynamic, temporal GIS:Current ontologies describe the static

structure of the world.Not included are the processes and their

semantics.

A dynamic GIS must be described with an ontology that contains objects and operations!

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Structure of talk:

1. What is an Ontology? 2. The multi-tier system of ontologies3. Add operations to ontology to capture

processes4. How to describe ontologies with

operations5. More uses for ontology: create graphical

user interface from the ontology6. Conclusions: Paradigm change is

necessary!

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Goal of talk

1. Include operations in the ontology2. The ontology (with operations) is more

useful, e.g. a user interface can be derived

3. More useful ontology will find more use and produce more benefits!

The challenge is, to find methods to describe ontologies with operations!

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Ontology today

Ontology in information science is defined as “an explicit formal specification of the terms in the domain and relations among them”.

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Ontology captures structure

Structure of the data is represented in • is_a relations• part_of relations• Instance relations

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Two critical observations:

1. a static view: no process, no operations, nothing changes;

2. it is very difficult:imagine how difficult it is to describe the structure of a dish (e.g. apple pie) in contrast to the recipe (a description of a process)

Overview


My Goal:

I need an ontology to understand the practical difficulties in the use of Geographic Information:–vagueness, error, resolution–spatial and temporal data–differences in semantics hindering interoperability

In all cases, operations are key to understanding!


My approach to ontology must be comprehensive:I am interested in the whole of human

interaction with the world, not only the verbal, propositional and mostly conscious part classical philosophy concentrates on.

We cannot avoid to consider the human living in the world and moving about with his body and feelings if we want to produce useful Geographic Information.


Conscious vs. non-conscious mental operationsI have the suspicion, that • Operations as necessary conditions for

classifications are mostly non-conscious

• Object and object classification are mostly conscious

This explains perhaps the focus on nouns and taxonomy in classical ontology and logic.


Terminological difficulties:

Many discussions are caused by misunderstandings and differences in the use of words.

For example, the notion ‘ontology’, but also ‘reality’, ‘think’

and even more difficult:‘is’, ‘exists’, ‘that is not the way the world is’.

Modelization – for example using UML – is confused by different notions of ‘exist’.


Verbal vs. pictorial expression of problems:Much conceptualization is already done

when words are used to describe the reality.

I use here pictures to connect my presentation more directly with your bodily experience; I work on the integration of feelings in the ontology.


Why a multi-tier ontology?

Most efforts to structure ontologies strive for maximum generality.

They propose a single set of rules applicable to everything.e.g. Aristotle's categories, mereology

Our experiments show that no single proposed ontology covers all areas important in a GIS.


Multiple tiers to integrate different approachesEach tier follows its own logic. Much what others have discovered about

ontology is extremely useful,but proposals are contradictory in detail.

A multi-tier approach separates different suggestions in different tiers and integrates them.

This approach is comparable to Constructivism (Heinz von Foerster, Cybernetics).


Overview of the tiers

0. The physical environment1. Observations of the environment and activities2.The reality of objects

a. Objects and actionsb. Generalizations: classes and operations

3a. Subjective Reality3b. Social reality

Legal realityCommunication

1 .. 3 are rather epistemologies, projected ontologies or e-ontologies.


Tier 0: Physical environment

Only part which is truly an ontology, the world as it is, without the presence of cognitive agents.

There is little we know about this!


Assume a field construction of worldPhysical properties for every point in

space and time:f (x,y,z,t) = a

Not all functions are continuous,but space and time is assumed continuous.

Physical laws (laws of nature) can be expressed as differential equations in properties of points.

Many properties are determined; not all of these are observable (or known) to us!


Tier 1: Observation of physical environment by agentsObservations for every point in space

yield a quantitative value.obs (x,y,z, obs-type) = value

Differentiation between environment and observing agent,properties of the environment and observation

Connections to tier 0: observation functions and activities of agents


Tier 1: Activities change the environmentAgents can act on the environment and

effect change in it. The change in the environment can be

observed.

There are two linked feedback loop (morphism)Physical activity – observed changeBody feeling of activity – sensory activity(Schmidt: Selective – Contingent)


Observations types:

Point observations – values for material properties, local motion, forces, temperature etc.

Synchronous observations of many (usually regularly located) points.Example: vision(philosophers would call observation types “categories”).


A Landscape


What was shown?

3 types of observations:wave energy in 3 frequency bands

for each observation type, 2.1 million observations in a regular grid (central perspective from a point)

Neither my sensor, nor the representation contains any hint of mountains, trees, buildings etc.Did you see any?


Tier 2: The Reality of Objects

People have a strong tendency to form objects which maintain identity in time.Objects are formed to maintain invariant properties in time.

Object formation reduces bulk of representation and leads to economic reasoning:From many point observations we deduce a single object with properties related to the point observations.


Connection to tier 1: Objects form areas of uniform observation valuesAreas of uniform value for an observation

are merged to objects.Uniformity in values of observation can be in

- same color- same speed or direction of movement- same material

Objects are constructed to have identity and continue in time.This reduces the load on memory enormously.


Lifestyles of Objects

Object continue in time.Objects are created and destroyed.Living things are born and die.Some objects can be suspended.

There are rules of what operations are applicable to certain types of objects.

Damir Medak (TU Wien) and Kathleen Hornsby (U Maine)


A Table Top


Granularity

The observations where made with a certain resolution.

Objects are formed from observations – sometimes the resolution is reduced, because less granularity is sufficient for the task at hand.Examples: Noodle dish is resolved into single noodles only when you are eating it.

And what to do with the sauce?


Object formation (2)

Philosophers talk a lot about natural kinds

living objects, animals or plants.

These are easy,but there are other cases – very natural

as well:


Objects as uniform areas

Objects form partition of space (and time).

Multiple ways of subdividing space:Different observations or combinations of observations

Different spatial, temporal or observation granularity.

Typically problems result from objects formed from different observations.


Actions

Actions- complex sequences of (physical) activities which change the environment.

- cause the values of properties of objects to change

Philosophers could use the Hegelian terms Voraussetzung (observation of environment abstracted to object properties) and Setzung (actions).


Connections from tier 2 to tier 1:

The actions change properties in some spatial-temporal region.

The property values of objects are the integration of the observable property values for spatial regions.


Tier 2b: Generalization to types

From many similar physical objects, we form objects types (classes).

Similar actions are generalized to operations.

Objects must have properties to permit actions.

Object types are classes of objects which have the necessary properties for operation.

Gibson used the term ‘affordances’ for the properties of objects which link them to operations.


Tier 3a: Subjective Reality- Individual cognitive agents

Individual internal realityFeelings are subjectively realSituations as complex associations of

objects are assessed with the corresponding feelings.


Individual differences in observationAgents use observation methods which

are limited and subject to error.Object formation can vary

(e.g. effects of granularity)

and is influenced by the task at hand (context).

The beliefs agents from about the world resulting from observations

vary, even if two agents observe the same reality.


Memory consists of assessed situationsSituations are assessed with respect to feelings.Memory is assessed situations of objects and

relations.

Feelings are bodily and cognitively real, at the limit between conscious and unconscious (Gerhard Roth).

Conscious Generalizations:Histories: Situations and Emotions (past)Plans: Desired situations and potential actions

(future)


Reflection

We observe the actions of other and assume similar causes (invisible feelings).

Socialization is a process at a hierarchically slower pace than observation-action.

Connection to fixed point semantics of denotational semantics.


Connection between tier 2 and 3:Reflection and Fixpoint:

Individual agents assume that other agents decide and act following similar patterns than they themselves.

Hierarchy of processes:- observations – operations- Objects – actions

- Object types – action types (algebraic operations)

- Histories – Plans (reflections)


Tier 3b: Social reality

Much what we consider part of reality is only a social convention.

Most important are the conventions in language:(applies to natural language or expert slang)

Names of thingsObjects are named,

individual names like ‘Stella’, ‘John’, etc.

or classes, like ‘plate’, ‘fork’ , dog


Institutional objects

Abstract objects are formed, to facilitate social interactions:Money, Parcels..

John Searle:An object X counts as Y in the context of C


Example: Money

This is ‘legal tender’, but physically only printed paper.

Social convention: can be used to buy things.

Rules for physical objects apply to the paper,other rules apply to the ‘legal tender’

For example: temporal extend of physical object and ‘legal tender’ is not the same.


Example: Communication

It is an obvious fact, that we can communicate.

Communication is based on the exchange of physical signs in the environment.

Communication is not always perfect.What are the rules?


An Example:Communication with Maps:A map-making agent explores an

environment,Draws a map,Map using agent uses map to navigate.


Connection between tier 3a and 3b:Social processes externalize in

symbolic form the individual socialization:

Cultural Reality


Why Formalization:Limitations of human abilitiesOur abilities for logical analysis of

complex situations is limited.Typical problems:

Levels of generalizations confuse us,Polysemous words trick us into false, seemingly logical conclusions,

Confusion between instances (tokens) and types.


Formalization with Tools

Formal tools are urgently needed.The effort reported here is designed for

implementation (and is in large parts implemented).

We have constructed simulations with multiple, cognitive and communicating agents.


Ontology languages 1: UML

Informal, but extensive use:Uniform Modeling Language (UML) – limited by lack of formal definition – no conclusions drawn or consistency checked automatically.

Tools (graphical editors) for UML are available:Nice, easy to use, flexible – but no formal background, therefore no fixed semantics, not much can be checked for consistency!

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Ontology languages 2: Description logicsconsists of • A set of unitary predicates denote

concept names• A set of binary relations, which denote

role names• Recursive constructors to form more

complex constructs from the concepts and roles.

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Many variants of Description Logics:Various DL with different levels of

expressive power and computational complexity, depending which constructors are included:–union and intersections of concepts–negation of concepts–value (universal) restriction–existential restriction

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Actual languages:

The Web Ontology Language OWL (the culmination from a sequence of KL-ONE (1985).... DAML, OIL, DAML+OIL).

A compromise between expressive power and tractability of logical deductions (goal: consistent theory!)

Practically: very limited and difficult to use.

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Example “Person - Gender”:<rdf:RDF

xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"

xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"

xmlns:owl="http://www.w3.org/2002/07/owl#"

xmlns="http://localhost:8080/OWLBuergerInformation.owl#"

xml:base="http://localhost:8080/OWLBuergerInformation.owl">

<owl:Ontology rdf:about=""/>

<owl:Class rdf:ID="Gender"/>

<owl:Class rdf:ID="Person"/>

<owl:Class rdf:ID="Woman">

<rdfs:subClassOf rdf:resource="#Person"/>

<owl:equivalentClass>

<owl:Restriction>

<owl:onProperty rdf:resource="#Gender"/>

<owl:hasValue rdf:resource="#female" rdf:type="#Gender"/>

</owl:Restriction>

</owl:equivalentClass>

</owl:Class>

<owl:ObjectProperty rdf:ID="gender"

rdf:type="http://www.w3.org/2002/07/owl#FunctionalProperty">

<rdfs:range rdf:resource="#Gender"/>

<rdfs:domain rdf:resource="#Person"/>

</owl:ObjectProperty>

<owl:DatatypeProperty rdf:ID="name"


<rdfs:range rdf:resource="http://www.w3.org/2001/XMLSchema#string"/>


</owl:DatatypeProperty>

<owl:DatatypeProperty rdf:ID="firstname"


<rdfs:range rdf:resource="http://www.w3.org/2001/XMLSchema#string"/>


</owl:DatatypeProperty>

<Person rdf:ID="STilgner" firstname="Susanne" name="Tilgner">

<Gender rdf:resource="#female"/>

</Person>

</rdf:RDF>

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Ontology editors, e.g. Protege

Ontology editor based on description logic.Produces ontologies in different output

languages (e.g. OWL-Light).Very difficult to use, very time consuming.

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Example: definition of pizza

Gives list of incredients (structure) but not the process of baking one!

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Extend ontology descriptions with time, change, processWhy is this difficult?1. First order logic is essentially static,

adding time - adds confusing bulk to expression:

move (P, A, B, T) :-is_at (P, A, T1) & is_at (P, B, T2) & before

(T1, T) & after (T2, T)

- frame problem:need to state what does not change to allow logical inference

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First order logic:

Difficult to represent change and process in first order logic

(complicated temporal logics would be needed)

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Ontologies with operations is an object-oriented ontology!In an object orientation view the world

consists ofobjects with operations!

The object-oriented research in software engineering concentrates uses an algebraic approach to model object classes and operations applicable to the objects.

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ExampleDogs are Animals and breath:class Animals a where

breath :: a -> StateChange World

class Animals => Dogs d wherebark :: d -> StateChange Worldeat :: d -> f -> StateChange World

Used: Monads from Category Theory

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Programming with inheritance:

The is_a relation does not translate directly to the operations.

class Numbers n where

division :: n -> n -> n

instance Numbers Rational

instance Numbers Int

Int is subset of Rational

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2nd Problem: Contravariance of Functions

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Solution

Parametric polymorphism, as shown in the above example, where

class Numbers n where ...has a parameter n.

The usual ad-hoc polymorphism of current programming languages (C++, Java) is not theoretically clean.

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Formalization (2): Second order languageSpatio-temporal models:

Change is caused by actions, operations.

The formal language must treat operations as ‘first class objects’ – i.e. the formal language must be second order.First order = variables only for individualsSecond order = variables for operations


Formalization (3): Practical tool

Functional programming language:Haskell (download from www.haskell.org)

Strongly typedLazyPure functional

(i.e. mathematically clean,no unknown assumptions)

Executable – result can be tested

http://www.haskell.org/


Conclusions

Integration of many ideas about ontologies in a multi-tier framework.

Conceptualization is influenced by task; this creates the data fusion problem.


Conclusions (2)

Formalization is crucial to achieve integration of different concepts (as necessary for data fusion),otherwise the complexity overwhelms!

Processes are linking the tiers. Formalization must have operations.


Conclusions (3): connections between tiers:The connections between the tiers are different:

Tier 0 – Tier 1: observation of point properties of the environment, activities change properties

Tier 1 – Tier 2: Areas of Uniform properties aggregated to

objectsSequences of connected activities

aggregated to actionsTier 2 – Tier 2b:

generalization to object types and action typesTier 2 - Tier 3a – feelings, assessment of situations

(associations of objects and actions)Tier 2 and 3a – Tier 3b –

X counts as Y in the context ZSocialization (hierarchy of processes)


Conclusions (4): Closed loop semantics The symbolic realm for which we have to

give the semantics must be connected to reality by two paths:

From reality to symbols (perception, conceptualization, etc.)

From symbols through decisions to actions

If the loop is closed, the semantics is defined by perception-action (compare to “affordance”)


Formalization of ontology:

Describe operations as algebras of object classes.

Describe the perception and the action as an algebra.

Construct linkages as morphism (structure preserving mappings)

In the context of this algebra (and this ontology)

- data quality- information contentcan be measured.


Process is fundamental!

Classical ontologies are verbal and focus on objects. They suffer from internal contradictions.

Only a process oriented ontology can integrate the different tiers of reality.

11/14/08Andrew Frank1 Time and Process in GIS: What can ontology contribute? Andrew U. Frank...

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