| 1. |
- Broekstra, Jeen, et al.
(författare)
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Enabling Knowledge Representation on the Web by Extending RDF Schema
- 2001
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Recently, there has been a wide interest in using ontologies on the Web. As a basis for this, RDF Schema (RDFS) provides means to dene vocabulary, structure and constraints for expressing metadata about Web resources. However, formal semantics are not provided, and the expressivity of it is not enough for full-fledged ontological modeling and reasoning.In this paper, we will show how RDFS can be extended in such a way that a full knowledge representation (KR) language can be expressed in it, thus enriching it with the required additional expressivity and the semantics of this language. We do this by describing the ontology language OIL as an extension of RDFS. An important advantage of our approach is a maximal backward compatability with RDFS: any meta-data in OIL format can still be partially interpreted by any RDFS-only-processor.The OIL extension of RDFS has been carefully engineered so that such a partial interpretation of OIL meta-data is still correct under the intended semantics of RDFS: simply ignoring the OIL specic portions of an OIL document yields a correct RDF(S) document whose intended RDFS semantics is precisely a subset of the semantics of the full OIL statements. In this way, our approach ensures maximal sharing of meta-data on the Web: even partial interpretation of meta-data by less semantically aware processors will yield a correct partial interpretation of the meta- data. We conclude that our method of extending is equally applicable to other KR formalisms.
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| 2. |
- Hedborg, Fredrik, et al.
(författare)
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Evidence for hypoxia-induced neuronal-to-chromaffin metaplasia in neuroblastoma
- 2003
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Ingår i: The FASEB Journal. - : Wiley. - 0892-6638 .- 1530-6860. ; 17, s. 598-
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Tidskriftsartikel (refereegranskat)abstract
- We present evidence that in neuroblastoma, a pediatric malignancy of embryonal sympathetic origin, hypoxia, underlies a phenotypic switch from a primitive neuronal to a chromaffin cell type. This conclusion is based on morphological and molecular data on 116 clinical tumors and is supported by data on the phenotypic effects of hypoxia on neuroblastoma cell lines when studied in monolayer culture and as tumor xenografts. In the clinical material, extensive chromaffin features were seen in regions of chronic tumor hypoxia. This was the exclusive form of intra-tumoral maturation of stroma-poor tumors and was also seen in stroma-rich tumors, either exclusively or in combination with ganglion-like cells. In neuroblastoma cell lines, hypoxia induced changes in gene expression associated with the chromaffin features observed in vivo. We therefore propose tumor hypoxia as a major cue determining phenotype in sympathetic tumors of neuroblastic origin. Because it appears to be reversible upon reoxygenation in monolayer culture, we suggest the term metaplasia for the phenomenon.
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| 3. |
- Klein, Michel, et al.
(författare)
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The Relation between Ontologies and XML Schemas
- 2001
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Support in the exchange of data, information, and knowledge is becoming a key issue in current computer technology. Ontologies may play a major role in supporting the information exchange processes, as they provide a shared and common understanding of a domain. However, it is still an important question how ontologies can be applied fruitfully to online resources. Therefore, we will investigate the relation between ontology representation languages and document structure techniques (schemas) on the web. We will do this by giving a detailed comparison of OIL, a proposal for expressing ontologies in the Web, with XML Schema, a proposed standard for describing the structure and semantics of XML based documents. We will argue that these two refer to different levels of abstraction, but that, in several cases, it can be advantageous to base a document schema on an ontology. Lastly, we will show how this can be done by providing an translation procedure from an OIL ontology to a specific XML Schema. This will result in a schema that can be used to capture instances of the ontology.
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