ELEC3609 Week 6 XML

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ELEC3609 Week 6 XML

• XML is a language for creating other languages!
• XML lets you define schemas for tag-based
  languages (markup language)
• XML allows you to extend any existing language
  (schema) with your own tags (ergo, eXtensible)
• Examples of XML schemas
• financial transactions (stock transactions)
• business documents (purchase order, invoice)
• remote procedure calls (SOAP)
• configuration files (security, server properties)

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World Wide Web Consortium (W3C)http//www.w3c.org
/
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XML Working Group

• W3C formed XML Working Group 1996 with these
  design goals
• XML shall be straightforwardly usable over the
  Internet
• XML shall support a wide variety of applications
• XML shall be compatible with SGML
• It shall be easy to write programs which process
  XML documents
• The number of optional features in XML is to be
  kept to the absolute minimum, ideally zero
• XML documents should be human-legible and
  reasonably clear
• The XML design should be prepared quickly
• The design of XML shall be formal and concise
• XML documents shall be easy to create
• Terseness in XML markup is of minimal importance

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XML History

• XML 1.0 became a standard (W3C recommendation) on
  10 February 1998
• effort grew out of experience with SGML
• cooperation between various W3C member
  organizations (including Microsoft, Sun, IBM, HP,
  Adobe)
• XML 1.1 became a standard (W3C recommendation) on
  4 February 2004
• less rigid constraints on names
• addresses issues involving character sets

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Application Integration
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Application Integration
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Application Integration
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Platform-Independent Services

• In the past, functionality was exposed to remote
  clients via various remote object standards
• COM/DCOM
• CORBA
• Java RMI
• Using these remote objects required a significant
  investment in a platform
• Web Services provide a new way to expose
  functionality
• use XML and XML data types for transport
• work with any platform
• provide a bridge to existing business services

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XML 1.1
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XML Declaration
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DOCTYPE
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Elements
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Element
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Attributes
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Attributes

• Name
• Must start with letter or underscore and can
  contain only letters, numbers, hyphens, periods,
  and underscores
• Value
• Can be of several types, but is almost always a
  string
• Must be quoted
• title"Lecture 2
• match'item"baseball bat"'
• Cannot contain lt or (by itself)
• PCDATA
• Text that appears as the content of an element

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Entities
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CDATA
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Comments
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Processing Instructions
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Event-Based Parsing
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Parsing

• In linguistics, to divide language into small
  components that can be analyzed. For example,
  parsing this sentence would involve dividing it
  into words and phrases and identifying the type
  of each component (e.g., verb, adjective, or
  noun)
• For XML, parsing means reading an XML document,
  identifying the various components, and making it
  available to an application

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Grammars in Backus-Naur Form

• In order to parse a document, you need to be able
  to specify exactly what it contains
• XML specification does this for XML using a
  grammar in Backus-Naur Form (BNF)
• A grammar describes a language through a series
  of rules
• A rule describes how to produce a something
  (e.g., a start tag) by assembling characters and
  other non-terminal symbols
• Made up of
• non-terminal symbols
• terminal symbols (data that is taken literally)

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Arithmetic
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A grammar for XML
where Name is one or more characters excluding gt
and CharData is zero or more characters excluding
lt.
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Tokenizing and Recognizing

• Tokenizing Creates tokens from the character
  stream
• Element name, equal sign, start tag
• Recognizing Understands the syntax of the
  document and checks for orrectness
• Builds a syntax tree

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recursive descent parsing

• XML's grammar works well with a parsing technique
  known as recursive descent parsing. Basically
• You write a function that is responsible for
  parsing every non-terminal in the grammar
• You assume that the document matches the grammar
• The correct alternation in a rule can be
  determined by examining a few tell-tale starting
  characters
• You recursively parse the document, calling each
  non-terminal parsing function as dictated by the
  grammar
• Use exception handling to handle errors when they
  occur deep in the recursive call tree