1. 6/18/2015 SDI Concepción Semantics for Spatial Data Infrastructures Werner Kuhn

2. The Economist, May 3, 2003

3. The Economist, May 17, 2003

4. Topological Operators for areas, lines, points

5. Werner KuhnSDI Concepción 5 Overlap in a GIS dialog window

6. “Where can I cross the Havel?” Road data (e.g., GDF)

8. Werner KuhnSDI Concepción 8 Composite Service plant ID 457 emission rate 29 mg/s plant location R: 3405138 H: 5760997 airport code FMO plume GML... dispersion map Create Gas Dispersion Map Get Nearest Airport Get Plant Location Input Leakage Information Get Wind Calculate Gas Dispersion Plume wind report XML...

9. Werner KuhnSDI Concepción 9 Semantic Heterogeneities Name: „prevailing_direction“ Data Type: „string“ Name: „prevailing_direction“ Data Type: XML-ComplexType Name: „wind“ Data Type: „string“ Name: „wind“ Data Type: „string“ Application Level „wind is blowing from“ points_to_compulsion  true „wind is blowing to“ points_to_compulsion  false 1. different name, same data type, same domain concept 3. same name, same data type, different or differently restricted domain concept(s) 2. same name, different data type, same domain concept

10. Werner KuhnSDI Concepción 10 Generalized Problem  Buffers, topology, navigation, and gas plume examples show problems with the semantics of geographic information describing entities (e.g., road, ferry) processes (e.g., driving, wind) relations (e.g., distance, overlap)  Context is essential for semantics Today‘s SDI separate data from operations (GML) context contained in operations is lost systems or users misinterpret data  Ontologies are supposed to provide that context Today, they don‘t They could do better How?

11. Werner KuhnSDI Concepción 11 What do we mean by Semantics ? Jaguar ReferentSymbol stands for refers to activates Concept

12. Werner KuhnSDI Concepción 12 Semantics of what ?  We are not trying to capture the meaning of natural language expressions!  We formalize the semantics of technical symbols used in GIS, databases, web services of information communities  But: information is from and for humans it derives from data through human interpretation it emerges at the user interfaces of GI technologies Thus, we need to capture meaning (cognitive semantics)

13. Medium-term research program (3-5 years) solve 3 semantic interoperability problems: e.g., road data for directions e.g., wind direction for gas plume e.g., weather services data discovery service discovery service composition

14. Werner KuhnSDI Concepción 14 Semantic Interoperability ...is the only real interoperability interoperating components share an understanding of their interfaces  today: „syntactic interoperability“ interoperating components share an interface, defined by a type signature GM_Object :: distance (geometry : GM_Object) : Distance

15. Werner KuhnSDI Concepción 15 Today: annotation ISO 19107, Spatial Schema „The operation "distance" shall return the distance between this GM_Object and another GM_Object. This distance is defined to be the greatest lower bound of the set of distances between all pairs of points that include one each from each of the two GM_Objects. A "distance" value shall be a non-negative number associated to a distance unit such as meter or standard foot. If necessary, the second geometric object shall be transformed into the same coordinate reference system as the first before the distance is calculated. If the geometric objects overlap, or touch, then their distance apart shall be zero. Some current implementations use a "negative" distance for such cases, but the approach is neither consistent between implementations, nor theoretically viable. "Distance" is one of the units of measure data types defined in ISO TS 19103. NOTE The role of the reference system in distance calculations is important. Generally, there are at least three types of distances that may be defined between points (and therefore between geometric objects): map distance, geodesic distance, and terrain distance.“

16. Werner KuhnSDI Concepción 16 Goal: axiomatization Service interfaces, requests, and responses contain symbols with undefined semantics GM_Object :: distance (geometry : GM_Object) : Distance Alexandria :: distance Stades (Syene) = 5040 1.type symbols (standing for classes of objects and literals) 2.values (standing for individual objects and literals) 3.operators (standing for methods)

17. Werner KuhnSDI Concepción 17 a philosophical discipline—a branch of philosophy that deals with the nature and the organisation of reality Science of Being (Aristotle, Metaphysics, IV, 1), asks the questions: What exists? What characterizes being? Eventually, what is being? Ontology in Philosophy

18. Werner KuhnSDI Concepción 18 Ontology in Computer Science  An ontology is an engineering artifact. It is constituted by a specific vocabulary used to describe a domain assertions on the intended meaning of the vocabulary.  Thus, an ontology describes a formal specification of a certain domain: shared understanding of a domain of interest formal and machine manipulable model of a domain “An explicit specification of a conceptualization” [Gruber93]

19. Werner KuhnSDI Concepción 19 Ontologies CAP landuse codeCAP landuse label 1Urban 1.AUrban; Residential 1.A.0.aUrban; Residential; Single family...

20. Werner KuhnSDI Concepción 20 clc: CORINE Land Cover categories

21. Werner KuhnSDI Concepción 21 Are ontologies enough?  They contain relationships between terms superclass and subclass, is_a, part_of, has_property, synonym  Their axioms are absent or in obscure and untested logical axioms  They fail to capture context activities determine semantics (e.g., driving across a river)  They are not grounded what does „artifact“ or „entity“ or „process“ mean?

22. Werner KuhnSDI Concepción 22 The underlying problem geoinformation = Spatial Reference Systems ??? interpretation

23. Werner KuhnSDI Concepción 23 Vision Users of geographic information should be able to refer thematic data to semantic reference systems, just as they refer geometric data to spatial reference systems. Software should support the  referencing and grounding process  projections to simpler semantic spaces  semantic translation among different reference systems.

24. Werner KuhnSDI Concepción 24 Semantic Reference Systems Spatial Reference System [ISO 19112] „system for identifying positions in the real world“ e.g., geodetic reference systems Temporal Reference System [ISO 19108] „basis against which time is measured“ e.g., calendars Semantic Reference System [t.b.d.] basis on which thematic data are interpreted: ‚forest‘, ‚wetland‘‚ ‚road width‘ etc. e.g., ontologies

25. Werner KuhnSDI Concepción 25 Long-term research program (5-7 years)  create methods and tools to design and use semantic reference systems for grounding (e.g. “move”) projecting (e.g. roads and ferries to edges) translating (e.g. cadastre to navigation)  based on real-world case studies transportation, emergency management, planning

26. Ferry example: Grounding

27. Werner KuhnSDI Concepción 27 Grounding in Image Schemas  Sensory-motor patterns of cognition (Johnson) container, surface, path, link, center-periphery, force...  developed through bodily experience  have internal structure  enable the perception of meaningful information from the environment (Gärdenfors)

28. Werner KuhnSDI Concepción 28 Ferry example: Semantic Projection projection

29. Werner KuhnSDI Concepción 29 Name: „prevailing_direction“ Data Type: „string“ Name: „prevailing_direction“ Data Type: XML-ComplexType Name: „wind“ Data Type: „string“ Name: „wind“ Data Type: „string“ Application Level „wind is blowing from“ points_to_compulsion  true „wind is blowing to“ points_to_compulsion  false 1. different name, same data type, same domain concept 3. same name, same data type, different or differently restricted domain concept(s) 2. same name, different data type, same domain concept Gas plume example: Translation

30. Werner KuhnSDI Concepción 30 + property A + property B + property A (range) + property B (range) Domain Concept Application Concept Semantic Reference System provides meaning (range restriction) (range restriction) + property C restricts meaning provides meaning restricts meaning

31. Werner KuhnSDI Concepción 31 Protégé Implementation

32. Werner KuhnSDI Concepción 32 Which terms can I use for an efficient keyword- based search of water level information? Problem: Semantic Heterogeneity 1 Synonyms: one concept – different terms water level, tide scale measuring gauge, control point Homonyms: one term – different concepts „water level“ – river vs. groundwater  The returned results are incomplete!  Not all returned results are relevant! Discovery

33. Werner KuhnSDI Concepción 33 Problem: Semantic Heterogeneity 2 How do I interpret the terms of a schema and formulate a query? Web Feature Services BafGELWISCHMI PegelmessungWasserstandMessungStavVody namepegelstanice wasserstand_cmhoehestav zeitpunktdatum uhrzeit gml:pointPropertystandortgml:position Retrieval  Meaning of terms used in the database schema is often ambiguous

34. Werner KuhnSDI Concepción 34 Approach: Ontological Descriptions What is the water level at point X at time Y in the Elbe River? equivalent concepts Ontological description of the query concept “water level” Query Concept Ontological description of the application concept “höhe” Application Ontology Concept based on Shared Vocabulary

35. Werner KuhnSDI Concepción 35 define query concept Request with terms of matching concepts Architecture: Ontology-Based Discovery request for shared vocabulary request with query concept request for matching concepts

36. Werner KuhnSDI Concepción 36 Architecture: Ontology-Based Retrieval Request for feature type Request for concept definitions GetFeature request

37. Werner KuhnSDI Concepción 37 Why Spatial is Special (for Semantics)  Space and time are primarily understood through processes  Semantics of symbols is not always a matter of convention physical grounding needs measurement ontologies  But human perception and social reality play an important role simplest case: geographic names and location descriptions  Need spatial reasoning at the type level  Granularity, vagueness, uncertainty and are central aspects of spatial information ...

38. Werner KuhnSDI Concepción 38 Conclusions  Spatial reference systems motivate semantic reference systems from static ontologies to computational reference systems providing referencing, projection, and translation  Semantics of spatial information poses both, general and special challenges.  Our success measures are in solving interoperability problems

39. Werner KuhnSDI Concepción 39 Some Big Challenges Grounding of ontologies („semantic datum“)  what is meant by wind direction?  what is transportation? Reasoning about processes  what does distance mean?  what does touch or overlap mean?  what is driving?  how is a gas plume determined? Improved similarity models ad hoc categories Karten bilden bei logistischen Entscheidungen der Helfer eine wichtige Grundlage: "Muss ich einen Helikopter einsetzen oder kann ich fahren?" Auch bei der Einrichtung von Hilfsstationen seien Karten und Bilder wichtig: "Wo habe ich eine ebene Fläche, die einigermaßen weit weg vom Wasser ist, die groß genug ist, um ein Zelt-Lazarett aufzubauen?“ [dpa Gespräch mit Robert Meisner, DLR, 7. Januar 2005] Formal Definition of Interoperability Automated generation of semantic annotations

40. Werner KuhnSDI Concepción 40 For more information...  MUSIL web site (Muenster Semantic Interoperability Lab): http://musil.uni-muenster.de  email to kuhn@uni-muenster.de