XML once over lightly

1
XML- once over lightly

• Keith Beattie
• Mary Thompson
• Monte Goode
• Karlo Berket

2
Outline

• Introduction
• Namespaces
• Xpath, Xpointer, Xinclude, XLink (ksb)
• XMLSchema Schema
• A few well known schemas
• Parsing
• Java tools
• Python tools
• Authoring tools

3
eXtensible Markup Language XML

• XML structure and data expressed so that it can
  be parsed programmatically, is relatively
  human-readable, and is eXtensible
• XML Schemas not just valid XML, but conforming
  to some model

4
XML - Intro

• Subset of SGML
• Goals
• Usable over the Internet (like HTML)
• Easy to write write tools for (authoring tools,
  filters, translators, etc.)
• Compatible with SGML (apply existing tools)
• Not dependant on a DTD
• Minimum of optional features, for compatibility
• Human readable (text, not binary)
• Terseness is of minimal importance

5
XML - Definition

• Specification for creating new markup languages
  (for structured documents)
• XML does not define a set of tags you do that
• An XML document must be well-formed
  (syntactically correct)
• Tags properly nested, opened and closed, correct
  use of entities, etc.
• An XML document may optionally be validated
  against a DTD and/or a Schema.
• A DTD or Schema defines the new markup language
  (but is not required).

6
XML - Example

• lt?xml version'1.0' encoding'utf-8'?gt
• lt!DOCTYPE addressbook SYSTEM "addressbook.dtd"gt
• lt!-- ksb's addressbook --gt
• ltaddressbookgt
• ltpersongt
• ltnamegtKeith Jacksonlt/namegt
• ltphone type'moble'gt555-555-5555lt/phonegt
• ltphone type'land'gt999-999-9999lt/phonegt
• ltaddressgt1 Any Lane, Berkeley,
  94111lt/addressgt
• ltpasswordgtlt!CDATAd_at_n'tuegtltegtlt/passwordgt
  
• lt/persongt
• ltpersongt
• ltnamegtAndrew amp Lisa Wrightlt/namegt
• ltphone type'land'gt888-888-8888lt/phonegt
• ltphone type'moble'gt444-444-4444lt/phonegt
• ltaddress/gt
• lt/persongt
• lt/addressbookgt

7
DTD - Example

• lt?xml version'1.0' encoding'utf-8'?gt
• lt!-- DTD for ksb's addressbook --gt
• lt!ELEMENT addressbook (person)gt
• lt!ELEMENT person (name, phone, address,
  password?)gt
• lt!ELEMENT name (PCDATA)gt
• lt!ELEMENT phone (PCDATA)gt
• lt!ATTLIST phone type (mobleland) REQUIREDgt
• lt!ELEMENT address ANYgt
• lt!ELEMENT password ANYgt

• Limited type definition
• No hierarchy of elements
• XML Schema addresses these shortcomings

8
XML Namespaces Intro

• A means to avoid name conflicts between XML
  elements and attributes
• Elements and attributes can now have the form
  ltprefixgtltlocal namegt where ltprefixgt is the
  namespace id associated with a URI
• Since URIs define either a physical or an
  abstract resource it doesnt need to actually
  exist

9
XML Namespace URIs

• URIs have two general forms
• URL
• http//www.lbl.gov/akenti
• URN
• urnwww.lbl.govakenti
• urnuuidA941CFC3-736E-48E5-A691-C5B2FE036555
• A namespace URI is just a string with some
  guarantee of uniqueness

10
XML Namespace Example

• lt?xml version'1.0' encoding'utf-8'?gt
• lt!-- ksb's addressbook --gt
• ltksbaddressbook
• xmlnsksb'http//www.stobo.org/address
  book
• xmlnslbl'http//www.lbl.gov/addressbo
  ok
• xmlns'http//www.w3.org/addressbook'gt
• ltksbpersongt
• ltlblnamegtKeith Jacksonlt/lblnamegt
• ltphone ksbtype'moble'gt555-555-5555lt/phonegt
• ltphone ksbtype'land'gt999-999-9999lt/phonegt
• ltaddressgt1 Any Lane, Berkeley,
  94111lt/addressgt
• ltksbpasswordgtlt!CDATAd_at_n'tuemegtlt/ksbpa
  sswordgt
• lt/ksbpersongt
• lt/ksbaddressbookgt

11
Some XML syntaxes

• XPath XML Path Language -
• searches an XML document using a path-like
  string. (more on this later)
• XPointer
• an addressing scheme for individual parts of an
  XML document. think ltA NAME"foo"gt in html.
• XInclude
• include for XML documents.
• XLink
• linking syntax for XML docs. think ltA
  HREF"foo"gt in html.

12
Xpath - Syntax

• XPath does not use XML syntax but its own query
  strings
• Simple example
• ./xp.py "person/phone" lt addressbook.xml
• ltElement Node Name'phone' with 1 attributes and
  1 childrengt
• ltElement Node Name'phone' with 1 attributes and
  1 childrengt
• ltElement Node Name'phone' with 1 attributes and
  1 childrengt
• ltElement Node Name'phone' with 1 attributes and
  1 childrengt
• Not as simple example
• ./xp.py "/addressbook/personname'Keith
  Jackson'/phone_at_type'moble'/text()" lt
  addressbook.xml
• 555-555-5555

13
Xpath - Intro

• The grep (or query language) of XML
• An XPath expression is applied to an XML document
  (or DOM node) and returns one of the following
• A Collection of nodes
• A Boolean value
• A floating-point value
• A String
• Used primarily in transforms (XSLT) and XPointer

14
Xpath - Syntax

• XPath does not use XML syntax but its own query
  strings
• Simple example
• ./xp.py "person/phone" lt addressbook.xml
• ltElement Node Name'phone' with 1 attributes and
  1 childrengt
• ltElement Node Name'phone' with 1 attributes and
  1 childrengt
• ltElement Node Name'phone' with 1 attributes and
  1 childrengt
• ltElement Node Name'phone' with 1 attributes and
  1 childrengt
• Not as simple example
• ./xp.py "/addressbook/personname'Keith
  Jackson'/phone_at_type'moble'/text()" lt
  addressbook.xml
• 555-555-5555

15
Well Known XML Schemas

• XML Schema language to define other schemas
• XSLT (Extensible StyleSheet Language
  Transformation) XML-to-XML translation
• SOAP (Simple Object Access Protocol) RPC
  mechanism and serialization format (typically
  over HTTP)
• WSDL (Web Services Description Language)
  network services as endpoints operating on
  messages

16
XML Schema

• Language to define other schema
• http//www.w3.org/TR/xmlschema-0/
• Defines
• element, sequence, choice, attributes,
  complexType, simpleType
• Data types
• int, long, string, token, dateTime
• http//www.w3.org/TR/xmlschema-2/

17
Example Schema
ltxsschema xmlnsxshttp//www.w3.org/2001/XMLSch
ema" targetNamespace"http//www-stobo.org/address
book"gt ltxselement nameaddressbookgt
ltxscomplexTypegt ltxssequencegt
ltxselement nameperson typepersonTypegt
lt/xssequencegt lt/xscomplexTypegt lt/xselementgt
ltxscomplexType namepersonTypegt
ltxssequencegt ltxselement namename
typestringgt ltxselement namephone
minOccurs0 maxOccursunbounded
typephoneTypegt ltxselement nameaddress
maxOccursunbounded typestringgt
ltxselement namepassword minOccurs0gt
lt/xssequencegt lt/xscomplexTypegt
18
Example Schema (cont)
ltxssimpleType namephoneTypegt
ltxsrestriction basexsstringgt
lt/xsrestrictiongt ltxsattribute nametype
userequired ltxssimpleTypegt
ltxsrestriction basexsstringgt
ltxsenumeration valuemoble/gt
ltxsenumeration valueland/gt
lt/xsrestrictiongt lt/xssimpleTypegt
lt/xsattributegt lt/xscomplexTypegt
19
XSL XSLT

• XSL - XML Stylesheet
• a vocabulary for specifying formatting
• XSLT - XSL Transforms
• Used to map one XML schema to another
• Source tree -gt result tree

20
SOAP

• Simple Object Access Protocol
• originally intended to implement RPC
• now used for any kind of XML message
• http//www.w3.org/TR/soap12-part0,part1,part1
• Envelope
• Header, Body, Fault
• Body and Headers are defined as sequences of
  anything

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SOAP (cont)

• SOAP processing model
• assumes a distributed model where the messages go
  from a sender node through some number of
  intermediary nodes to a Ultimate receiver nodes.
• The nodes can be addressed by role names and each
  can do some processing of the message

22
WSDL

• Web Services Description Language
• http//www.w3.org/TR/wsdl12
• Describes the messages
• Operations - exchanges of messages
• PortTypes - collection of operations
• There is a binding document that describes SOAP,
  HTTP and MIME bindings

23
Resource Description Framework - RDF

• W3C Semantic Web Activity
• provides a model for metadata
• for use in knowlege representation systems
• describes the context of a document, so that
  documents can be searched for by content. -
  applies to non-text documents

24
XML Security Languages

• Define vocabularies to express
• Authentication assertions or identity
  credentials
• Authorization assertions or licenses
• Attribute assertions - attribute credentials
• Enabling secure XML messages
• Queries and Responses about security questions
• Security policies - requirements of the resource
• Security contexts - information about the user

25
XML Security Schemas

• XML Signature (W3C and IETF)
• Digital signatures for XML transactions
• XML Encryption (W3C)
• Encrypting data and representing the results in
  XML
• XKMS - key management (W3C)
• (MS, Verisign) delegate signature processing to
  a trust server on WWW (for thin or mobile clients)

26
XML Digital Signature

• Specifies XML digital signature processing rules
  and syntax
• Digital Signatures provide
• Message integrity
• Message authentication
• Signer authentication
• Signed data can be within the XML that includes
  the signature or elsewhere
• Can sign all or part of a document

27
XML Encryption

• Process for encrypting data and representing the
  result in XML
• Data can be
• arbitrary data (including XML document)
• an XML element or element content
• An XML encryption element
• contains or references the cipher data
• specifies the encryption method
• specifies key info.

28
XML Schema Reference Card

• Qualifier URN
• xs http//www.w3.org/2001/XMLSchema
• S http//www.w3.org/2002/06/soap-envelope
• xsl http//www.w3.org/1999/XSL/Format
• xslt http//www.w3.org/1999/XSL/Transform
• Xpath http//www.w3.org/TR/xpath
• dsig http//www.w3.org/2000/09/xmldsig
• xenc http//www.w3.org/2001/04/xmlenc
• xkms http//www.xkms.org/schema/xkms-2001-01-20
• saml urnoasisnamestcSAML1.0assertion
• samlp urnoasisnamestcSAML1.0protocol
• xacml urnoasisnamestcxacml1.0policy
• xacml-content urnoasisnamestcxacml1.0context

29
DOM - Document Object Model (W3C recommendation)

• DOM Structure
• Document, element, entity reference, text...
• Nodes, NodeList, NamedNodeMap
• Fundamental Interfaces
• Document
• createDocument, createAttribute, createElement,
  getElementByTagName
• NoderemoveChild
• NodeListgetNamedItem

30
DOM Parsers

• Parses the entire document into a DOM tree.
• Provide functions to examine pieces of the tree
• Provides a createDocument interface which
  generates a XML document from the DOM tree

31
Simple API for XMLSAX

• Started as a Java Event-based parser for XML
• Reports parsing events through call-backs.
• startElement(localName,qName,Attributes)
• Attributes getName, getType, getValue
• characters
• http//www.saxproject.org/ distributed through
  SourceForge

32
Parsers

• Xerces - Apache
• Java, C Perl, COM wrappers
• Does both DOM and SAX parsing
• Validates
• Java only
• IBM XML4J, Microsoft, Oracle, Netscape
• Suns JAXP (DOM and SAX)
• C
• XPAT - c (non validiating)

33
Java Tools

• J2SE (since 1.4) was JAXP1.0
• SAX and DOM interfaces
• Interface for XSLT (generic, SAX, DOM, streams)
• Java WSDP
• JAXP 1.2.2 parsers and XSLT
• JAXB schema -gt Java classes
• JAXR access to XML registries
• JAX-RPC SOAP-RPC
• SAAJ Soap with attachments

34
Java Tools

• Apache
• Xerces SAX and DOM parser
• Xalan XSLT and Xpath
• Xindice native XML database
• IBM
• XML Processing Plus Plus stream-based APIs
• XML Parser for Java
• X-IT batch processing and transformation of XML
  files

35
Python Tools

• Python Standard Library
• provides both a SAX and DOM interface
• interface to the Expat parser (Expat is a stream
  and callback based parser similar to SAX).
• - PyXML a richer set of xml tools
• fuller featured DOM implementations
• adapters to allow various parsers to use the SAX
  interface,
• XPath expression parsing and XSLT transform
  tools.
• link http//pyxml.sourceforge.net/

36
More Python Tools

• 4Suite
• even more SAX/DOM implementations
• plus XPath, XPointer,XInclude, XLink
• RDF support including an XML/RDF data
  respository and server (data access, query,
  transfomation, etc).
• link http//www.4suite.org/

37
Python Soap Support

• SOAPy - WSDL/Web Service oriented SOAP lib.
• Provides a stand-alone http-like server to run
  your soap services.
• link http//soapy.sourceforge.net/
• ZSI (Zolera Soap Infrastructure)
• offers robust support for strict typing
• conversion between native python datatypes and
  soap syntax.
• provides a stand-alone http-like server to run
  your soap services.
• link http//pywebsvcs.sourceforge.net/

38
Editing Tools

• PSGML major mode for Emacs
• Navigation, colorization, validation and other
  editing functions.
• Supports loading of DTDs, maintaining a DTD
  library, and some editing based on said.
• Done in a standard emacs-like text view.
• http//sourceforge.net/projects/psgml
• Gui XML editors
• Offers tree view of XML document with text box
  editing fields.
• Marginal utility.