Schema translation and data quality Sven Schade Bilateral Research Workshop: INPE and IfGI GIScience for Dynamic Environmental Sensors March, 11th, 2009

Overview of the talk My recent work Current conclusions /introduction Overview of the talk My recent work Current conclusions Relations to workshop theme Outlook

What is the motivation for my work? /recent work What is the motivation for my work? Increased demand for spatial data sharing Translations are frequently required Scientific view: Specifying intendet interpretations of data model expressions Ongoing research in using these for translation Practical view: Providing national data sets in internationally harmonised models Provide according metadata

Which problem does this work address? /recent work Which problem does this work address? Natural language descriptions of data model expressions

Which problem does this work address? /recent work Which problem does this work address? Natural language descriptions of data model expressions Use of a common language cannot be assumed Definitions include degrees of freedom Potential translations not computer-tractable Data model descriptions have to be provided in a form that permits Judgement if a translation can be performed Identification of the consequences Computer-tractable translation

What is a practical example? /recent work What is a practical example? If I: Know what the data models capture as road width , and Know about used units and measures Then I: Can infer possible translations and their effects Can provide quality metadata for translated data sets Effect: overestoimation!

What is the approach and design of research? /recent work/approach What is the approach and design of research? Semantic Reference Frame for Geospatial data Algebraic Theory for Shifting between Frames grounds Conceptual Level Implementation: Logic Program Implementation: Functional Program Formal Level Research Prototype Proof of Concept

What are the conclusions of this work? Focused on object-models of geospatial phenomena Improved support in translation on attribute level Metric and ordinal attributes Most attributes are categorical Current means can account for imprecision in: Intended interpretation Measurement Translation We only understand small parts of challenges regarding nominals But we have a good impression on current possibilities

What are the next steps? … actually that is a step back! It is easier to describe (physical) measures than complex objects. Measurement-based approach (for example inferring land cover from raw satallite imagery) First: field-models for geospatial phenomena Second: object-models for geospatial phenomena

What about an illustration? /relation to workshop theme What about an illustration? Here is the obvious one: field- and object-based Models of the Environment field-based Source: Gilberto Câmara (INPE) Requires translation (+ quality information) Provide input to Semantics i.e. clarify intended interpretations Sensors/ Sensor Web Syntax and Access (OGC: SWE)

But what about change? Geospatial Change Object Models Objects /relation to workshop theme But what about change? Geospatial Objects Change Event(s) Object Models Change of identity Basis for characterising Source: Carlos Nobre (INPE) (new?) Physical Qualities e.g. mass, length, temperature Time Continuous change Sensors

Which questions should be answered next? /outlook Which questions should be answered next? What is required to sharpen the last illustration? Do ontologies only support correct input for models of change? Should change detection use ontologies? What are the limits of computer-tractable translation? How important is the role of uncertainty modelling considering the workshop scenarios? Which types of uncertainty should be considered? Which data quality parameters are important (lineage etc.)?

/end Thank you very much! INPE and IfGI Delegation

/details Annotation

Relations between data models /details Relations between data models

User roles in ontology-driven translation /details User roles in ontology-driven translation

Activity diagram of demonstrator /details Activity diagram of demonstrator

/details GUI view

Categories of Imperfection /details Categories of Imperfection

Categories of Incompleteness /details Categories of Incompleteness