UH COSC 3480 - Semistructured Data Extensible Markup Language Document Type Definitions (30 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:
30
School:
University of Houston
Course:
Cosc 3480 - Design of File Database System

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Jeff Ullman Introduction to XML XML Semistructured Data Extensible Markup Language Document Type Definitions 1 Jeff Ullman Introduction to XML Semistructured Data Another data model based on trees Motivation flexible representation of data o Often data comes from multiple sources with differences in notation meaning etc Motivation sharing of documents among systems and databases 2 Jeff Ullman Introduction to XML 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 o Labels out of a node o Number of successors with a given label 3 Jeff Ullman Introduction to XML Example Data Graph Notice a new kind of data root beer bar beer manf name servedAt manf A B name Bud M lob name addr Joe s Maple prize year 1995 award Gold The beer object for Bud The bar object for Joe s Bar 4 Jeff Ullman Introduction to XML 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 idea create tag sets for a domain e g genomics and translate all data into properly tagged XML documents 5 Jeff Ullman Introduction to XML Well Formed and Valid XML Well Formed XML allows you to invent your own tags o Similar to labels in semistructured data Valid XML involves a DTD Document Type Definition a grammar for tags 6 Jeff Ullman Introduction to XML Well Formed XML Start the document with a declaration surrounded by xml Normal declaration is xml version 1 0 standalone yes o Standalone no DTD provided Balance of document is a root tag surrounding nested tags 7 Jeff Ullman Introduction to XML Tags Tags as in HTML are normally matched pairs as FOO FOO Tags may be nested arbitrarily XML tags are case sensitive 8 Jeff Ullman Introduction to XML Example Well Formed XML xml version 1 0 standalone yes A NAME subobject BARS BAR NAME Joe s Bar NAME BEER NAME Bud NAME PRICE 2 50 PRICE BEER BEER NAME Miller NAME A BEER PRICE 3



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