1 Michael Klein [email protected] Verlesung Informationssysteme: Neuere Konzepte Web Services

1

Michael [email protected]

http://www.michaelklein.net/nki

Verlesung“Informationssysteme: Neuere Konzepte”

Web Services

2 Vorlesung “Informationssysteme: Neuere Konzepte”, Teil I, Michael Klein 2

Übungsblätter

Zunächst: Besprechung der 3 Übungsblätter

3

Michael [email protected]

http://www.michaelklein.net/nki

Verlesung“Informationssysteme: Neuere Konzepte”

Web Services

(Folien teilweise auf englisch)


Szenario (1)

Telefon-anschluss?

Telefongesellschaft

Auftrag


Szenario (2)Tele

fongese

llsch

aft

Auftrag

Reservierung der Nummer

Eintrag Telefonbuch

Einkauf Endgeräte

Versand Endgeräte

Eintrag?

Einzug Anschlussgebühr

en

Anschlussverfügbar?

ja

nein

nein

ja

ok

Entschuldigungs-schreiben

Prob

Geschäftsprozess


Dienstorientierte Architektur

Geschäftsprozess

Funktionalität A

Dienst-geber 1

Funktionalität A

Dienst-geber 2

Funktionalität A

Dienst-geber 3

Funktionalität A‘

Dienst-geber 5

Funktionalität B‘

Nutzung von Funktionalität externer Entitäten über Dienste

Funktionalität kann evtl. kostengünstig ausgelagert werden.


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


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)


General Process: the „Service Triangle“

Repository

Requestor(Client)

Provider(Server)

1. describe offer

2. publish

3. describe request

4. search For

5. match

6. select7. configure

8. invoke 9. execute

10. transfer results


Service Description Language

ServiceRequests

ServiceRequests

Service Provider

ServiceProvider

ServiceProvider

ServiceProvider

ServiceProvider

ServiceDesc

ServiceDesc

ServiceDesc

ServiceDesc

ServiceDesc

?Which provider is appropriate? (matching)How to invoke it? (binding, configuration)

11

Web Services

WSDL, SOAP, UDDI


What is a Web Service?

Web Service

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

xml xml


Task of the Technologies

Repository

Requestor(Client)

Provider(Server)

1. describe offer

2. publish

3. describe request

4. search For

5. match

6. select7. configure

8. invoke 9. execute

10. transfer results

WSDLWSDL

UDDI

SOAP

automatic prematching based on categories manual matching and selecting static binding


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


Web Service Stack

Communication

Description Discovery

TCP/IP

HTTP

XML

SOAP

XML

WSDL

WSDL Extensions

UDDI

Semantics

Task: provide a standard, flexible communications channel

Task: provide a standard, flexible way to describe what and how a Web service does what it does.

Task: provide a standard, flexible way to discover where a Web service is located .

XML

16

WSDL

Building Blocks


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)


WSDL 1.2 Components as UML Diagram

service = publiclycallable functionality

operation = function thatprocesses an input

messageand returns an output message

message = collection ofinformation that can be exchanged via network

CONCRETE

ABSTRACTservice

port

0..*

port type

operation message

part

0..*

0..*

input

output

fault

0..1

0..1

0..1

*

*

*

* 1binding1*has has

element : type


Types

defines important datatypes primitive types from XML schema complex types buildable via <complexType>-Tag

<types> <schema targetNamespace="http://example.com/stockquote.xsd" xmlns="http://www.w3.org/2000/10/XMLSchema"> <element name="TradePriceRequest"> <complexType> <all> <element name="tickerSymbol" type="string"/> </all> </complexType> </element> <element name="TradePrice"> <complexType> <all> <element name="price" type="float"/> </all> </complexType> </element> </schema> </types>


Messages

<message name="GetLastTradePriceInput"> <part name="body" element="xsd1:TradePriceRequest"/> </message> <message name="GetLastTradePriceOutput"> <part name="body" element="xsd1:TradePrice"/> </message>

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


Operation and PortType

<portType name= "StockQuotePortType"> <operation name = "GetLastTradePrice"> <input message = "tns:GetLastTradePriceInput"/> <output message = "tns:GetLastTradePriceOutput"/> </operation></portType>

Operation is abstract functionality that receives an input messages processes it send set an output

and fault messages

PortType groups operations to interfaces


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


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

<binding name="StockQuoteBinding„ type="tns:StockQuotePortType"> <soap:binding style= "document" transport= "http://schemas.xmlsoap.org/soap/http"/> <operation name= "GetLastTradePrice"> <soap:operation soapAction=“http://example.com/GetLastTradePrice"/> <input> <soap:body use= "literal"/> </input> <output> <soap:body use= "literal"/> </output> </operation> </soap:binding></binding>


Port and Service

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

<service name="StockQuoteService"> <port name="StockQuotePort" binding="tns:StockQuoteBinding"> <soap:address location="http://example.com/stockquote"/> </port></service>


Components of WSDL 1.2 – Summary

CONCRETE

ABSTRACTservice

port

0..*

port type

operation message

part

0..*

0..*

input

output

fault

0..1

0..1

0..1

*

*

*

* 1binding1*has has

element : type


Renamings in WSDL 2.0

Port

PortType

Message

Part

WSDL 1.2 WSDL 2.0

Endpoint

Interface

no special tag. Directly definedby xs:element and xs:complexType

no special tag. Directly definedby xs:sequence and xs:element


Example for Changes in WSDL 2.0

<types> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema“

targetNamespace="http://…/schemas/resSvc.xsd“>

<xs:element name="checkAvailability“ type="tCheckAvailability"/> <xs:complexType name="tCheckAvailability"> <xs:sequence> <xs:element name="checkInDate" type="xs:date"/> <xs:element name="checkOutDate" type="xs:date"/> <xs:element name="roomType" type="xs:string"/> </xs:sequence> </xs:complexType> <xs:element name="checkAvailabilityResponse" type="xs:double"/> <xs:element name="invalidDataError" type="xs:string"/> </xs:schema> </types>

Message

Part

28

WSDL

Discovery


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 r’s 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


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


Type based Matcher

Service

ir_1

…ir_n

or_1

…or_m

Service

io_1

…io_k

oo_1

…oo_l

Request r Offer o

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


Problems with WSDL Matching

Service

incomingmessages

outgoingmessages

Message oriented service description

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

33

WSDL

Tools and Extensions


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) IBM’s Websphere Graphical WSDL editors like CapeClear WSDL generators (“right-click on method”) WSDL validators …


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


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


Web Service Composition – BPEL4WS

servicerequestor

serviceprovider

subprovider 1

subprovider 2

subprovider 3

WSDL BPEL4WS

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”)


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

39

Ausblick:

Semantic Web Services



Geschäftsprozess

Funktionalität A

Dienst-geber 1

Funktionalität A

Dienst-geber 2

Funktionalität A

Dienst-geber 3

Funktionalität A‘

Dienst-geber 5

Funktionalität B‘

Nutzung von Funktionalität externer Entitäten über Dienste

Dynamische Dienstbindung


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


Ansätze

ALLGEMEIN:Von 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.


Gemeinsames Vokabular

Grundsätzlicher Ansatz:Rechnerverständlichkeit benötigt gemeinsames Vokabular

Einsatz von Ontologien

Location

Room Buildingwithin

room2.14:Room room335:Room geb50.34:Buildingwithin

Schema

Instanzen


Typen von Dienstbeschreibungen

Dienst

eingehendeNachrichten

abgehende Nachrichten

1. Reinnachrichtenbasierte Dienstbeschreibung(z.B. WSDL)

Dienst

Zustände vor Dienstausführun

g

Zustände nach Dienstausführun

g

2. GetrenntNachrichten-/Zustandsbasierte Dienstbeschreibung(z.B. OWL-S)

Dienst

3. Rein Zustandsorientierte Dienstbeschreibung(z.B. DSD)

konfigurierbare Zustände vor

Dienstausführung

konfigurierbare Zustände nach

Dienstausführung

Zustand

Information


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

46

ZUSAMMENFASSUNG


Zusammenfassung


WSDLSOAP

UDDI

Semantische Dienstbeschreibung

Dynamische Dienstbindung

Dienstverzeichnis

Web Service

abstrakte vs. konkrete Dienstbeschreibung

Vergleich vonWSDL-Beschreibungen

rein zustandsorientierteDienstbeschreibungBPEL4WS

message-operation-port-service


Thank youfor your attention!

Documents

1 Michael Klein [email protected] Verlesung Informationssysteme: Neuere Konzepte Web Services