Categories of Vocabulary Compatibility
Dmitry Lenkov
Oracle
Interoperability
Ability of two or more parties to
• Exchange information about metadata
• Establish metadata equivalency
• Exchange and understand metadata (or data about asset)
• Exchange data (information) or provide service (car delivery)
• Delivery protocols
• Messaging protocols
• Content – syntax and semantics
Interoperability layers
Metadata interoperability
Fundamental for accessing data and services on the Internet
• Relationships between multiple descriptions in terms of
Interoperable (common semantics) vocabularies
• Single query meaning over descriptions expressed in multiple descriptive formats (vocabularies)
• Communities of interest based on a set of interoperable vocabularies
Topic Topic subscriptionsubscription
generategenerateSubscriptioSubscription metadatan metadata valid?valid?validatevalidate
confirmconfirm
validatevalidate
validatevalidate
storestore
InfoInfo
valid?valid?valid?valid? generategenerate Info Info metadatmetadat
aa
validatevalidate requestrequestvalid?valid?
deliverdeliver Use and / or distributeUse and / or distribute InfoInfo
yesyes
yesyes
yesyes
nono
nono
nono
nono
SourceSource DestinationDestination
yesyes
Data / Metadata exchange
Interoperability Challenges
Explosion of Standards and Standard Organizations
• Dozens of standard organizations and standards
• No coordination
• No consistency
High cost of multi-end, multi-standard interoperability
• Development
• Testing
• Maintenance
• Vertical - on the deployment platform
• Horizontal - on multiple client/server/peer systems
Interoperability dependencies
Interoperability categories
Language level• SQL, XML schema and query languages, ontologies
• Each language provides means to build vocabularies with
• Syntax to communicate data and
• Form queries about data
Compatibility of vocabularies• Within one language – same XML schema
• Across languages – DM schema to XML
• Levels of compatibility – equality, equivalence, comparability
Entity / Data / Asset
Entity• Generic term to items such as
• Cars, applications, books, scientific articles
Entity can be data• Online book, document, Information item
• Digital asset
• Car, DVD with music or film
Entity can be non-digital asset
Entity has associated metadata in one or more vocabularies
Distinction between description, query, and filter is purely functional
Metadata / Data Metadata is data about an asset or data
• It is a set of statements about an asset in one or more vocabularies
• If an asset is data (information), these vocabularies usually are different from vocabularies expressing data
Metadata can be of three kinds:• Description – specifics of an asset or data
• Query – short term expression of interest
• Filter (subscription) – long term expression of interest
•
Vocabularies Vocabulary
• Set of terms representing classes of entities, or instances
• Includes data types model, if any Taxonomy
• Set of relations between classes of entities
• Relations - Subsumption, instantiation, equivalence
• Is a vocabulary with non-empty taxonomy and a set of constraints in the associated constraint language
Ontology
Data and Metadata Hierarchy
Entity (asset)
Descriptions / QueriesVocabulary
Descriptions / QueriesVocabulary
describe
describe
for
for
describe
data/metadata
data/metadata
Vocabulary Equivalence - Example
Example: Equal vocabularies (A & B)• Same terms, same data type model, same taxonomy
• Is it enough to say that they are equal? – NO!
Evaluate vocabulary metadata• Is the same vocabulary C used for A’s and B’s metadata?
• Yes, evaluate A’s and B’s metadata – same constraints, conversion (XSLT: A to B), set of synonyms, etc. - ?
• Recursion – apply the process to A’s & B’s metadata vocabularies
No, different vocabularies - for A’s & B’s metadata
Vocabulary Equivalence
Vocabularies A and B are equivalent if• A’s and B’s metadata are specified in the same vocabulary C and
• A’s and B’s metadata specify same set of constraints and/or a conversion (XSLT A to B, taxonomy mapping, etc.) and/or a set of synonyms, etc.
else if for A’s and B’s metadata vocabularies C and D correspondingly are used and
Vocabularies C and D are equivalent and
•
•
• A’s and B’s metadata satisfy condition
Comparable vocabularies
Vocabularies with equivalent subsets• How to deal with it
• Default values or instances
• Optional fields and partial evaluation
Examples• Vocabulary evolution and versioning
• Independent creation for the same purpose and the same semantics
Mediation vs. Pear-to-pear
Mediation• There is a set of (standard) vocabularies supported by a mediator
• Vocabularies of all communicating parties should be equivalent to one or more vocabularies in the mediator set
Pear-to-pear• Vocabulary equivalence is on a pear-to-pear basis
• Greater effort for each pear
• Higher degree of flexibility, independence, and trust
AQ&Q U E S T I O N SQ U E S T I O N S
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