Verlesung%20

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VerlesungInformationssysteme Neuere Konzepte
Web Services
Michael Klein kleinm_at_ipd.uni-karlsruhe.de http//w
ww.michaelklein.net/nki
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Übungsblätter

• Zunächst
• Besprechung der 3 Übungsblätter

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VerlesungInformationssysteme Neuere Konzepte
Web Services
Michael Klein kleinm_at_ipd.uni-karlsruhe.de http//w
ww.michaelklein.net/nki
(Folien teilweise auf englisch)
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Szenario (1)
Telefongesellschaft
Telefon- anschluss?
Auftrag
5
Szenario (2)
Anschluss verfügbar?
nein
ja
Geschäftsprozess
Reservierung der Nummer
ja
Auftrag
Eintrag Telefonbuch
Eintrag?
Telefongesellschaft
nein
ok
Einkauf Endgeräte
Versand Endgeräte
Prob
Einzug Anschlussgebühren
Entschuldigungs-schreiben
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Dienstorientierte Architektur
Geschäftsprozess

• Nutzung von Funktionalität externer Entitäten
  über Dienste

Funktionalität A
Funktionalität B
Dienst- geber 3
Dienst- geber 5
Funktionalität A
Dienst- geber 1
Funktionalität A
Dienst- geber 2
? Funktionalität kann evtl. kostengünstig
ausgelagert werden.
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Service Oriented Computing

• Network not as collection of documents but as a
  collection of functionality
• Applications and business processes use
  functionality of other entities
• especially interesting
• in mobile networks with limited capabilities
• in the internet large companies, many services ?
  outsourcing
• Integration of distributed functionality across
  organizational and network boundaries

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Characteristics of SOC

• Characteristics
• Functionality is hidden behind an interface
• Offered functionality is publicly described
• Service public functionality that can be
  published, discovered, and executed across the
  network(client-server paradigm)

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General Process the Service Triangle
9. execute
Requestor (Client)
Provider (Server)
3. describe request
1. describe offer
5. match
Repository
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Service Description Language
Service Requests
Service Requests
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Web Services

• WSDL, SOAP, UDDI

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What is a Web Service?
Web Service
xml
xml

• Web Service
• service that Accessible through the internet
• consumes and produces xml documents
• is uniquely identified by an uri
• Based on three main technologies
• WSDL Web Service Description Language
• SOAP Simple Object Access Protocoll
• UDDI Universal Description, Discovery and
  Integration

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Task of the Technologies
9. execute
Requestor (Client)
Provider (Server)
SOAP
3. describe request
1. describe offer
WSDL
WSDL
5. match
Repository
UDDI

• automatic prematching based on categories
• manual matching and selecting
• static binding

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WSDL, SOAP, and UDDI

• WSDL
• to describe the functionality of a service
• helps to find an appropriate service
• helps to invoke a found service correctly
• UDDI
• directory service
• is itself a service
• helps to get an overview of the services in the
  repository
• only helpful in case of very many services
• SOAP
• communication protocol between service requestor
  and provider
• helps to transfer simple (atomic) and complex
  (composite) data
• ? All based on XML

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Web Service Stack
Communication
Description
Discovery
SOAP
Semantics
XML
WSDL Extensions
UDDI
HTTP
WSDL
XML
TCP/IP
XML
Task provide a standard, flexible way to
discover where a Web service is located .
Task provide a standard, flexible way to
describe what and how a Web service does what it
does.
Task provide a standard, flexible
communications channel
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WSDL

• Building Blocks

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History of WSDL
NASSL SDL/SCL
2000 Microsoft, IBM and Ariba jointly issue WSDL
1.0
2001 A dozen companies submit WSDL 1.1 as W3C
Note
2002 W3C publishes WSDL 1.2 as Working Draft
2003 WSDL is separated into three parts core,
messages, bindings
2004 WSDL 2.0 (mainly renamings)
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WSDL 1.2 Components as UML Diagram
service publicly callable functionality
ABSTRACT
message collection of information that can be
exchanged via network
CONCRETE
operation function that processes an input
message and returns an output message
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Types

• defines important datatypes
• primitive types from XML schema
• complex types buildable via ltcomplexTypegt-Tag

lttypesgt ltschema targetNamespace"http//example
.com/stockquote.xsd" xmlns"http//www.w3.o
rg/2000/10/XMLSchema"gt ltelement
name"TradePriceRequest"gt ltcomplexTypegt
ltallgt ltelement
name"tickerSymbol" type"string"/gt
lt/allgt lt/complexTypegt lt/elementgt
ltelement name"TradePrice"gt
ltcomplexTypegt ltallgt
ltelement name"price" type"float"/gt
lt/allgt lt/complexTypegt lt/elementgt
lt/schemagt lt/typesgt
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Messages

• combines types to abstract messages
• smallest interchangeable units
• unidirectional
• built up from parts

ltmessage name"GetLastTradePriceInput"gt ltpart
name"body" element"xsd1TradePriceRequest"/gt
lt/messagegt ltmessage name"GetLastTradePriceOutpu
t"gt ltpart name"body" element"xsd1TradePrice"
/gt lt/messagegt
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Operation and PortType

• Operation is abstract functionality that
• receives an input messages
• processes it
• send set an output and fault messages
• PortType groups operations to interfaces

ltportType name "StockQuotePortType"gt
ltoperation name "GetLastTradePrice"gt
ltinput message "tnsGetLastTradePriceInput"/gt
ltoutput message "tnsGetLastTradePriceO
utput"/gt lt/operationgtlt/portTypegt
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Operation Types

• One-way operationsinput only
• Request-Responseinput, then output(default)
• Solicit-Responseoutput, then input
• Notificationoutput only

client
server
client
server
client
server
client
server
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Binding

• Connects abstract PortTypes with concrete Ports
• Defines concrete message syntax
• Defines concrete communication protocol details
• Most important protocol SOAP
• Simpler protocols like HTTP GET/POST possible

ltbinding name"StockQuoteBinding
type"tnsStockQuotePortType"gt ltsoapbinding
style "document" transport
"http//schemas.xmlsoap.org/soap/http"/gt
ltoperation name "GetLastTradePrice"gt
ltsoapoperation soapActionhttp//example.com/Get
LastTradePrice"/gt ltinputgt
ltsoapbody use "literal"/gt lt/inputgt
ltoutputgt ltsoapbody use
"literal"/gt lt/outputgt
lt/operationgt lt/soapbindinggtlt/bindinggt
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Port and Service

• Port specifies a concrete address of a binding
• Service is a collection of such ports

ltservice name"StockQuoteService"gt ltport
name"StockQuotePort" binding"tnsStockQuoteBindi
ng"gt ltsoapaddress
location"http//example.com/stockquote"/gt
lt/portgtlt/servicegt
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Components of WSDL 1.2 Summary
ABSTRACT
CONCRETE
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Renamings in WSDL 2.0
WSDL 1.2
WSDL 2.0
Port
Endpoint
PortType
Interface
Message
no special tag. Directly defined by xselement
and xscomplexType
Part
no special tag. Directly defined by xssequence
and xselement
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Example for Changes in WSDL 2.0
lttypesgt ltxsschema xmlnsxs"http//www.w3.org/2
001/XMLSchema targetNamespace"http///sche
mas/resSvc.xsdgt ltxselement
name"checkAvailability type"tCheckAvailability"
/gt ltxscomplexType name"tCheckAvailab
ility"gt ltxssequencegt
ltxselement name"checkInDate"
type"xsdate"/gt ltxselement
name"checkOutDate" type"xsdate"/gt
ltxselement name"roomType"
type"xsstring"/gt
lt/xssequencegt lt/xscomplexTypegt
ltxselement name"checkAvailabil
ityResponse" type"xsdouble"/gt
ltxselement name"invalidDataError"
type"xsstring"/gt lt/xsschemagt lt/typesgt
Message
Part
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WSDL

• Discovery

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Matching

• Task
• Given a service description for a requested
  service r and a service description of an offered
  service o. Question Is o suitable to fulfill
  rs needs? To what degree?
• Idea
• Matcher compares o and r and calculates matching
  value in 0,1
• 0.0 o is not suitable at all
• 1.0 o is perfectly suitable
• intermediate values o is suitable to the given
  degree

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Matching WSDL Descriptions Approaches

• (1) Keyword based Search
• Request r is set of keywords.
• ? Matching value is only a hint
• ? Manual postprocessing and selection necessary
• (2) Type based Matchers
• Check whether input message of request provides
  more information than input message of offer
• Check whether output message of request wants
  less information than output message of offer
• wants less
• each type in the request has to appear in the
  offer
• types of the offer have to be a subtype of the
  desired types in the request

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Type based Matcher
Request r
Offer o
ir_1
io_1
or_1
oo_1
Service
Service




ir_n
io_k
or_m
oo_l

• For each or_i in r Is there a oo_j in o with
  oo_j subtypeof or_i
• For each io_i in o Is there a ir_j in r with
  ir_j subtypeof io_i

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Problems with WSDL Matching
Message oriented service description
incomingmessages
outgoingmessages
Service

• Problems
• Not really new. Already in CORBA, DCOM, EJB,
  ebXML,
• ? No advantage to pure interface description
• Semantics not clearFunctionality has to be
  guessed from flow of information
• ? What does a service, that requests a String
  and outputs an Integer?
• ? automatic selection difficult
• Strict message compatibilityIf messages between
  provider and requestor do not match, the service
  cannot be used

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WSDL

• Tools and Extensions

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Tools for WSDL

• Integration in Programming Languages
• Microsoft .NET
• Sun Java Web Service Development Pack
• XML Processing, SOAP Binding, XML Registry
• Web Services Toolkit (WSTK) von IBM
• Plugins for Eclipse (WSDL Viewer, WSDL Validator,
  )
• SOAP for Perl
• NuSOAP SOAP Toolkit for PHP
• Tools / Server Components for WSDL
• Axis (SOAP Server)
• IBMs Websphere
• Graphical WSDL editors like CapeClear
• WSDL generators (right-click on method)
• WSDL validators

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WSDL in Practice Early Adopters

• amazon.com
• Amazon E-Commerce Service
• Everything but really buy
• ItemLookup, ItemSearch, SimilarityLookup
• CartAdd, CartClear, CartCreate, CartGet,
  CartModify
• Service requestors need to registers first
• Intended usage including Amazon in own web sites
• ebay.com
• eBay SOAP API
• Offer Items, Place Bids, Search for articles
• google.com

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WS- Language Extension for WSDL

• WS-PolicyFor including non-functional
  requirements/assertions in WSDL descriptions
• WS-Resource Framework (WSRF)For describing
  resources and states on the service provider.
• WS-Security (WSS)For securing the usage of web
  services
• WS-CoordinationFor enhancing WSDL descriptions
  by protocols to coordinate the actions of several
  participants. Example WS-AtomicTransaction

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Web Service Composition BPEL4WS
subprovider 1
service requestor
service provider
subprovider 2
subprovider 3
BPEL4WS
WSDL

• BPEL4WS Business Process Execution Language
  for Web Services
• Specification of the Orchestration, i.e. the
  coordination between main service and its
  subservice providers.
• Developed by Microsoft (XLANG) and IBM (WSFL)

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Evaluation of WSDL

• Advantages
• Easy to understand
• Widely accepted
• Rich tool support
• good integration in programming languages
• many extensions
• important early adopters
• upcoming standard for description
• Disadvantages
• Low semantics
• primitive matchers
• not usable for automatic service selection
• designed for static service binding

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AusblickSemantic Web Services
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Dienstorientierte Architektur
Geschäftsprozess

• Nutzung von Funktionalität externer Entitäten
  über Dienste

• Dynamische Dienstbindung

Funktionalität A
Funktionalität B
Dienst- geber 3
Dienst- geber 5
Funktionalität A
Dienst- geber 1
Funktionalität A
Dienst- geber 2
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Dynamic Service Binding

• Dynamic Service Binding
• Advantages
• robust
• context-aware
• network independent
• Most important task automation
• ? Complete process should be automatic
• Important
• Semantic Service Description Language

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Ansätze

• ALLGEMEINVon syntaktischer zu semantischer
  Dienstbeschreibung
• Einigung auf ein gemeinsames Vokabular ?
  Ontologie
• Nicht mehr Drucker/Printer/prt/lpt1, sondern
  PRINTER
• Zusätzlich Beschreibung der Zustandsänderung
  durch den Dienst
• Welcher Zustand muss vor Dienstausführung gelten?
• Welcher Zustand gilt nach erfolgreicher
  Dienstausführung?
• Getrennte Anfrage- und Angebotsbeschreibungen
• Anfrager kann Präferenzen in die Anfrage
  integrieren
• Was muss, was soll, was darf, was könnte etc.

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Gemeinsames Vokabular

• Grundsätzlicher Ansatz
• Rechnerverständlichkeit benötigt gemeinsames
  Vokabular
• ? Einsatz von Ontologien

Location
Schema
Room
Building
within
Instanzen
room2.14Room
room335Room
geb50.34Building
within
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Typen von Dienstbeschreibungen
eingehende Nachrichten
abgehende Nachrichten
1. Rein nachrichtenbasierte Dienstbeschreibung (z
.B. WSDL)
Dienst
Zustand
Information
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Vorteile

• Vorteile eines gemeinsamen Vokabulars
• Keine unterschiedliche Benennung des gleichen
  Sachverhalts
• ? Beschreibung ist eindeutig
• ? Computer kann Vergleich selbstständig
  durchführen
• Allerdings auch Einigungsaufwand
• Vorteile von rein zustandsorientierten
  Beschreibungen
• Keine explizite Beschreibung von Nachrichten
• ? Einfluss der ausgetauschten Information auf
  Zustände klar definiert
• ? Dienst können passen, obwohl Informationsfluss
  unterschiedlich

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ZUSAMMENFASSUNG
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Zusammenfassung
UDDI
Dienstorientierte Architektur
Web Service
SOAP
WSDL
message-operation-port-service
Semantische Dienstbeschreibung
Vergleich von WSDL-Beschreibungen
abstrakte vs. konkrete Dienstbeschreibung
Dienstverzeichnis
rein zustandsorientierte Dienstbeschreibung
Dynamische Dienstbindung
BPEL4WS
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Thank you for your attention!