NU EECS 317 - Semistructured Data Extensible Markup Language Document Type Definitions (35 pages)

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Semistructured Data Extensible Markup Language Document Type Definitions



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Semistructured Data Extensible Markup Language Document Type Definitions

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Pages:
35
School:
Northwestern University
Course:
Eecs 317 - Data Management & Information Processing

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XML Semistructured Data Extensible Markup Language Document Type Definitions 1 Semistructured Data Another data model based on trees Motivation flexible representation of data Often data comes from multiple sources with differences in notation meaning etc Motivation sharing of documents among systems and databases 2 The InformationIntegration Problem Related data exists in many places and could in principle work together But different databases differ in 1 Model relational object oriented 2 Schema normalized unnormalized 3 Terminology are consultants employees Retirees Subcontractors 4 Conventions meters versus feet 3 Example Every bar has a database One may use a relational DBMS another keeps the menu in an MS Word document One stores the phones of distributors another does not One distinguishes ales from other beers another doesn t One counts beer inventory by bottles another by cases 4 Two Approaches to Integration 1 Warehousing Make copies of the data sources at a central site and transform it to a common schema Reconstruct data daily weekly but do not try to keep it more up to date than that 2 Mediation Create a view of all sources as if they were integrated Answer a view query by translating it to terminology of the sources and querying them 5 Warehouse Diagram Warehouse Wrapper Wrapper Source 1 Source 2 6 A Mediator Result User query Mediator Query Result Result Query Wrapper Quer y Result Source 1 Wrapper Query Result Source 2 7 Graphs of Semistructured Data Nodes objects Labels on arcs attributes relationships Atomic values at leaf nodes nodes with no arcs out Flexibility no restriction on Labels out of a node 8 Example Data Graph Notice a new kind of data root beer bar beer manf name servedAt manf A B name Bud Miller name addr Joe s Maple prize year 1995 award Gold The beer object for Bud The bar object for Joe s Bar 9 XML XML Extensible Markup Language While HTML uses tags for formatting e g italic XML uses tags for semantics e g this is an address Key



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