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Data Warehousing vs. Virtual Integration

Data Warehousing	Virtual Integration
crawl RDF files
store in original format
transform all files	query
query	transform only bits needed to answer query
display results

• "forward chaining"
• web search engines employ the warehousing approach
• batch processing makes sense for indexing documents, but doesn't scale well for integrating data

• "backward chaining"
• good scaling properties
• no data replication, so data fetched on demand from repositories is up to date
• systems are more complex

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