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

A N S W E R SA N S W E R S