Change - Semantic Gap

Created on March 13, 2013, 9 a.m. by Hevok & updated on March 18, 2013, 8:15 p.m. by Hevok

In general the Interoperability of Metadata should be achieved by the use of Ontologies. ¶
The Problem is among heterogeneous Metadata there is a Semantic Gap. This Semantic Gap can be bridged with the Help of Ontologies. The Problem of the Semantic Gap means the different Ontologies can be applied to represent identical Knowledge. The Problem is how can one find out that these different Ontologies really mean the same Thing or describe the same Thing. ¶
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Even considering a small wWorld with three bBricks in an initial sState and one wants to bring this bBricks into a final sState in the same wWorld, where all of these bBricks stand one of Top of each other. ¶
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One can model this with some Objects (Block A, B and C as well as a Table and a hand that is able to grab these Objects). Then one has several Relations, for example there is the on Relation that says a bBlock stands on top of another block. There is a clear Relation that means if we have a bBlock in the heand we clear it. The bBlock is hold with the holding Relation. Lastly one cnan ask whether the hHand is empty or not. With this modeling one is able to bring the wWorld from its initial sState to the final sState of the wWorld. ¶
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This is however not the only way to model this. Another aApproach is with less oObjects, namely one Block A, B and C. So here we do not need the tTable nor the hHand, but therefore we have other kind of rRelations. In addition to the on, clear, holding and handEmpty Relation there is instead of defining a tTable a Relation that a Block X stands on a tTable (which is other true or not true). ¶
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To model this in kind of a representational Tree one has Entity and Relation Classes. There one has Entity Table, bBlock and hHand. Belonging to them there is a tTable T, Blocks A, B and C as well as hHand H. The Relations can be binary, unary or even have no aArguments like handEmpy which gives back a bBoolean (True or False). The World can also be described with the help of Axioms where one says if X stands on Y and Y stands on Z than X is above Z for eExample. ¶
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In the other model one has only one tType of Entity, namely bBlock which contains Block A, B and C. There are also Relations with an additional unary Relation onTable. ¶
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The problem is that one has two different mModels, but from the tTree rRepresentation they are quite similar. We can identify in these trees which has the same Meaning or does represent the same as in the other tree. So one can define Mappings. One has to do this because one wants to find out whether this two Models really denote the same. To bridge this we need an Ontology rRepresentation that is able to map one mModel into another Model. One has to understand this Model. ¶
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The Semantic Web is based on Interoperability of Metadata ¶
Among heterogeneous Metadata there is a Semantic Gap that can be bridged with the help of Ontologies ¶
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- Problem of the Semantic Gap: ¶
+ different Ontologies can be applied to represent identical Knowledge. ¶
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Let's Model a wWorld: ¶
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- Models: ¶
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Objects Relations Objects Relations ¶
block A on(X,Y) block A on(X,Y) ¶
block B clear(X,Y) block B clear(X) ¶
block C holding(X) block C onTable(X) ¶
table T handEmpty holding(X) ¶
hand H handEmpty ¶
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- Axiom: on(X,Y) ⋀ on(Y,Z) → above(X,Y) ¶
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behind the Model there is an Ontology ¶