To understand the problem, we must define the differences/heterogeneities between metadata.\nHeterogeneities that interfere with interoperability: \nStructural (model-related): \n element definition conflicts\n naming: models elements representing same element given different name\n Identification: If they have an id, having different one (sometimes no id, only name exists)\n Constraints: datatype for example.\n Domain Representation\n Abstraction level: domain representation conflicts, entities arranged into different generalization hierarchies, or distributed into different model elements\n Multidimensional correspondences: Conflict in the multiple relationships drawn up.\n Meta-level discrepancy: information with in different elements (like naming)\n Domain coverage: one model has data x, the other does not.\nSemantic: (language differences in schema)\n Domain conflicts: different expressiveness of languages\n Terminological: naming: synonyms and homonyms\n Scaling/Unit Conflicts: different measurement units\n Representation: format of date value for example\n\n
Metadata MappingPresentation By Vladimir Bukhin on Oct 8th
Contents• Metadata interoperability goals.• Deﬁnition of Metadata.• Metadata Building Blocks.• Heterogeneities with metadata .• Interoperability Solutions.• Metadata Mapping.• Conclusion.
MetadataInteroperability Goals• Metadata interoperability: • Systems and applications can work with or use metadata across system boundaries.• Requirements: • Machines need to communicate to exchange metadata. • Machines must be able to read/process the data received. • Machines + humans must be able to interpret the metadata correctly.
What is Metadata• Metadata: • “the sum total of what one can say about any information object at any level of aggregation, in a machine understandable representation.”• Information Object: • “anything that can be addressed and manipulated by a human or a system as a discrete entity.”
Metadata Building Blocks - Deﬁne Schemes, meta-meta-model, UML, XML, SQL DLL. - Deﬁnes how attribute like ‘title’ will be semantically presented. - Element Deﬁnitions. - Content Rules. - Descriptive Metadata elements
Interoperability Solutions• Agreement on a certain model: • Accredited institution like W3C or ISO. • Consensus, Standard, or assurance of uniform implementation.• Agreement on meta-model: • Schema is deﬁned by the same language (standard model with different implementations)• Reconciliation of structural and semantic heterogeneities: • Mapping schema languages to others’ language. • Instance transformation (changing meta attributes to correspond)
Metadata Mapping Maintaining representations Start Find relationships and heterogeneitiesMetadata transformation. Formal Declaration of Answer queries over mapping relationships metadata sources.
Conclusion• Mapping suggested over Standards. • Standards require licensing, software tools, personnel costs. • Mapping has high discovery cost.
Bibliography• Haslhofer, Bernhard and Wolfgang Klas. 2010. A survey of techniques for achieving metadata interoperability. ACM Comput. Surv. 42, 2, Article 7 (February 2010), 37 pages.