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CSG Mini-Workshop: Web Services
Justin Tilton
instructional media + magic, inc.
As presented at the
Common Solutions Group Meeting
May 9, 2002
Chicago, Illinois
JA-SIG Workshop Series
Overview
• Data
XML
• Validation
Schema
• Transport
SOAP
• Security
SAML
• Description
WSDL
• Directory
UDDI
• Transformation
XSLT
Data:
XML Overview
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XML is for structuring data [1]
• Structured data includes things like:
• spreadsheets, address books,
configuration parameters, financial
transactions, and technical drawings
• XML is a set of rules for designing
text formats that let you structure
your data.
• XML is not a programming language,
and you don't have to be a
programmer to use it or learn it
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XML is for structuring data [2]
• XML makes it easier for a computer
to generate data, read data, and
ensure that the data structure is
unambiguous
• XML avoids common pitfalls in
language design:
• it is extensible
• it is platform-independent
• and it supports internationalization and
localization
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XML is a family of technologies [1]
• XML 1.0 is the specification that defines
what "tags" and "attributes" are
• Xlink describes a standard way to add
hyperlinks to an XML file
• XPointer and XFragments are syntaxes in
development for pointing to parts of an
XML document
• XSL is the advanced language for
expressing style sheets. It is based on XSLT
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XML is a family of technologies [2]
•
XSLT is a transformation language used for
rearranging, adding and deleting tags and
attributes
•
XPath is a language for navigating in an XML
document
•
XML Schemas help developers to precisely define
the structures of their own XML-based formats.
•
XQuery provides flexible query facilities to extract
data from real and virtual documents on the Web
•
XML Signatures provide integrity, message
authentication, and signer authentication services
for an XML document
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XML is new, but not that new
• Development of XML started in 1996 and
has been a W3C Recommendation since
February 1998
• Before XML there was SGML, developed in
the early '80s, and widely used for large
documentation projects
• The development of HTML started in 1990.
• The designers of XML simply took the best
parts of SGML, guided by the experience
with HTML, and produced something very
powerful
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HTML and XHTML
• The successor to HTML is XHTML
• XHTML has almost all of the same elements
as HTML, but the syntax has been changed
slightly to conform to the rules of XML
• XHTML allows "<p>", but not "<r>" since <p> is
defined in XHTML and <r> is not
• XHTML says that "<p>" stands for "paragraph",
and not for "price", "person", or anything else
• Emerging applications such as uPortal are using
XHTML to output content to browsers
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XML has namespaces
• To eliminate name confusion when
combining documents, XML provides a
namespace mechanism
• XSL and RDF are good examples of XMLbased formats that use namespaces
• XML Schema is designed to support
modularity by defining XML document
structures, making it easy to combine two
schemas to produce a merged document
structure.
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XML is license-free
• XML is license-free, platformindependent and well-supported
• A large and growing community of
tools and engineers experienced in
the technology
• Since XML is license-free, you can
build your own software around it
without fees
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An example of XML [element]
<?xml version="1.0"?>
<breakfast_menu>
<food>
<name>Belgian Waffles</name>
<price>
<amount>5.95</amount>
<currency>US Dollars</currency>
</price>
<description>two of our famous Belgian Waffles with
plenty of real maple syrup</description>
<calories>650</calories>
</food>
<food>
<name>Strawberry Belgian Waffles</name>
<price>
<amount>7.95</amount>
<currency>US Dollars</currency>
</price>
<description>light Belgian waffles covered with
strawberries and whipped cream</description>
<calories>900</calories>
</food>
</breakfast_menu>
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An example of XML [attribute]
<?xml version="1.0"?>
<breakfast_menu>
<food>
<name>Belgian Waffles</name>
<price currency="US Dollars">5.95</price>
<description>two of our famous Belgian Waffles with
plenty of real maple syrup</description>
<calories>650</calories>
</food>
<food>
<name>Strawberry Belgian Waffles</name>
<price currency="US Dollars">7.95</price>
<description>light Belgian waffles covered with
strawberries and whipped cream</description>
<calories>900</calories>
</food>
</breakfast_menu>
Validation:
XML Schema Overview
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What is an XML Schema?
• XML Schema is an XML based
alternative to Document Type
Definition (DTD)
• The purpose of an XML Schema is to
define the legal building blocks of an
XML document, just like a DTD.
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An XML Schema defines:
• Elements and attributes that can appear in
a document
• Simple child-parent element relationships
• The sequence in which the child elements
can appear
• The number of child elements
• Whether an element is empty or can
include text
• Data types for elements and attributes
• Default values for elements and attributes
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XML Schemas replacing DTDs
• We think that very soon XML
Schemas will be used in most Web
applications as a replacement for
DTDs. Here are some reasons:
• XML Schemas are richer than DTDs
• XML Schemas are written in XML
• XML Schemas support data types
• XML Schemas support namespaces
• XML Schemas are extensible to future
additions
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XML Schema & Data Types
• With data type support it is easier to:
• Describe permissible document content
• Validate the correctness of data
• Work with data from a database
• Define data facets (restrictions on data)
• Define data patterns (data formats)
• Convert data between different data
types
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Why Schema is important
• A well-formed XML document is a
document that conforms to the XML
syntax rules
• Even if documents are Well-Formed
they can still contain errors, and
those errors can have serious
consequences.
• With XML Schemas, most of these
errors can be caught by your
validating software.
XML Schema: Practical
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The simplest element definition
• A schema specifies a set of valid toplevel elements.
• In the simplest case, we can define an
element to describe a name of the city:
Schema:
<xsd:element name="city" type="xsd:string"/>
Document:
<city>Washington</city>
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Another element definition
• A schema specifies a set of valid top-level
elements.
• Complex types can define elements with children:
Schema:
<xsd:element name="note">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="to" type="xsd:string"/>
<xsd:element name="from" type="xsd:string"/>
<xsd:element name="heading" type="xsd:string"/>
<xsd:element name="body" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
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Another element definition
• A schema specifies a set of valid toplevel elements.
• Complex types can define elements with
children:
Document:
<note>
<to>Sam</to>
<from>Jack</from>
<heading>Your presentation</heading>
<body>Please update section II</body>
</note>
Transport:
SOAP Overview
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What is SOAP?
• SOAP is an XML based protocol to let
software components and
applications communicate using
standard Internet HTTP
• SOAP stands for Simple Object
Access Protocol
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SOAP is:
• A communication protocol
• For communication between applications
• A format for sending messages
• Designed to communicate via internet
• Platform independent
• Language independent
• Based on XML
• Simple and extensible
• Remote procedure call protocol
• SOAP will be developed as a W3C standard
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Why SOAP?
• SOAP is Transport Protocol independent
• Transport protocol chosen according to network
architecture and type of exchange
• Real time over the internet might use HTTP,
where a batch processing application might use
SMTP
• SOAP provides a way to communicate
between applications running on different
operating systems, with different
technologies and different programming
languages
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SOAP was Proposed
• UserLand, Ariba, Commerce One,
Compaq, Developmentor, HP, IBM,
IONA, Lotus, Microsoft, and SAP
proposed SOAP to W3C, in May 2000
• The ebXML Plenary voted on 16
February 2001 to use SOAP 1.1 and
SOAP With Attachments as part of
the ebXML transport specification
• Anyone using the transport portion of
ebXML will therefore be using SOAP
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SOAP Building Blocks
• A SOAP message is an ordinary XML
document.
• The XML document contains the
following XML elements:
• A SOAP envelope, that defines the
content of the message
• A SOAP header (optional), that contains
header information such as credentials
• A SOAP body, that contains request and
response information
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Syntax Rules
• A SOAP message:
• Must be encoded using XML
• Must have a SOAP envelope
• Can have a SOAP header
• Must have a SOAP body
• Must use the SOAP envelope namespaces
• Must use the SOAP encoding namespace
• Must NOT contain a DTD reference
• Must NOT contain XML processing instructions
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SOAP Request Example
<soap:Envelope>
<soap:Body>
<GetPrice>
<Item>Apples</Item>
</GetPrice>
</soap:Body>
</soap:Envelope>
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SOAP Template
<soap:Envelope
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/“
soap:encodingStyle=
"http://schemas.xmlsoap.org/soap/encoding/">
<soap:Header>…</soap:Header>
<soap:Body>…</soap:Body>
<soap:Fault>…</soap:Fault>
</soap:Envelope>
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The Envelope Element
• The <Envelope> element must be
the root element of a SOAP message
• It defines the XML document as a
SOAP message.
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The Header Element
• The <Header> element can contain
additional, application specific
information about the SOAP message
• For example, the Header element can
contain information about the language
and currency values used in the SOAP
message
• Optionally, the header can carry
authorization & authentication
information
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The Body Element
• The <Body> must be present in a
SOAP message
• It contains the actual SOAP message
or “payload”
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A SOAP Example [1]
• The SOAP request:
<soap:Envelope>
<soap:Body>
<xmlns:m="http://www.stock.org/stock" />
<m:GetStockPrice>
<m:StockName>IBM</m:StockName>
</m:GetStockPrice>
</soap:Body>
</soap:Envelope>
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A SOAP Example [2]
• The SOAP response:
<soap:Envelope>
<soap:Body>
<xmlns:m="http://www.stock.org/stock" />
<m:GetStockPriceResponse>
<m:Price>34.5</m:Price>
</m:GetStockPriceResponse>
</soap:Body>
</soap:Envelope>
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SAML Assertion
<SAML>
<AssertionID>
http://www.bizexchange.test/assertion/AE0221
</AssertionID>
<Issuer>
URN:dns-date:www.bizexchange.test:2001-01-03:19283
</Issuer>
<Conditions>
<Audience>
http://www.bizexchange.test/rule_book.html
</Audience>
</Conditions>
<Subject>
<Account>Alice</Account>
</Subject>
<Resources>
<string>http://www.elsevier.com/Journal_X/</string>
<string>https://www.SantaMariaUniversity.edu/SIS/</string>
</Resources>
</SAML>
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Building web services
• Web services architecture overview
Web service
requestor
3
bind
4
2
find
UDDI Service
look up web service
call
Call Web Service
Retrieve WSDL
Definition
1
publish
Register Web Service
(at development time)
Web service
provider
WSDL
Document
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WSDL
• Web Services Description Language
• Language describing what services are
available and how they can be accessed
• Messages being sent
• End-points for message processing
• WSDL makes it easy for client
applications to use a web sevice
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WSDL
• WSDL document structure
<definitions>
root element
<types/>
data type definitions
<message/>
abstract message definitions
<portType/>
set of abstract operations
<binding/>
protocols for a portType
<service>
grouping of related ports
<port/>
</service>
</definitions>
network address for a binding
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UDDI
• Universal Description, Discovery and
Integration
• A web services registry system
• White pages – general information
• Yellow pages – service classifications
• Green pages – operation rules
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UDDI: Registry organization
businessEntity
keyedReference
tModelKey
keyName
keyValue
businessKey
name
URL
description
contacts
businessServices
identifierBag
categoryBag
contact
phone
address
e-mail
businessService
keyedReference
tModelKey
keyName
keyValue
serviceKey
tModelKey
name
description
bindingTemplates
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UDDI: SOAP API
• Registry API
• Find methods
• Inquiry API
• Save methods
• find_business
• save_business
• find_service
• save_service
• find_binding
• save_binding
• find_tModel
• save_tModel
• Get methods
• Delete methods
• get_businessDetail
• delete_business
• get_serviceDetail
• delete_service
• get_bindingDetail
• delete_binding
• get_tModelDetail
• delete_tModel
The Meteor Channel:
an example of Web services
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Meteor in a nutshell…
Lender
XML
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Diagram of Meteor Concept
Web Services
HTML
Student
Meteor
XML
Access Provider
Data Provider
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As implemented ...
Web Services
Meteor
Secure HTML
Standard
Browser
Secure XML
uPortal
Meteor
SOAP
Meteor
SOAP
Database
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Data from multiple sources, locations
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Meteor Channel in the uPortal
The End
Justin Tilton
[email protected]