Sws lecture4-handouts

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Sws lecture4-handouts

Sws lecture4-handouts

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STI Innsbruck
STI InnsbruckSTI Innsbruck
Education

Sws lecture4-handouts

Sws lecture4-handouts

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4/9/2018 1 1 © Copyright 2010   Dieter Fensel and Srdjan Komazec, updated by Anna Fensel in 2016‐2018 Semantic Web Services SS 2018 Web services Anna Fensel 09.04.2018 2 Where are we? # Title 1 Introduction 2 Web Science + + Cathy O’Neil’s talk: “Weapons of Math Destruction” 3 Service Science 4 Web services 5 Web2.0 services 6 Semantic Web 7 Semantic Web Service Stack (WSMO, WSML, WSMX) 8 OWL-S and the others 9 Semantic Services as a Part of the Future Internet and Big Data Technology 10 Lightweight Annotations 11 Linked Services 12 Applications 13 Mobile Services
4/9/2018 2 3 Outline • Motivation • Technical solution – SOAP protocol and related specifications – WSDL interface definition language – Additional related specifications • Illustration by a larger example • Possible Extensions • Summary • References 4 MOTIVATION
4/9/2018 3 5 Motivation: “What is a Web Service?” https://www.youtube.com/watch?v=u80uPzhFYvc 6 Motivation SOA • Service-Oriented Architecture • For large-scale distributed computing • For interoperability within and among enterprises • Business-oriented services – Coarse-grained service interfaces – Improves evolvability, manageability • Needs a suitable set of technologies
4/9/2018 4 7 Motivation Solutions needed to implement SOA lifecycle • SOA is a programming style • An SOA application is a composition of services • A ‘service’ is a building block/unit of an SOA • Service encapsulates a business process • A Service Provider registers services • Service consumption involves Find- Bind-Execute pattern • Questions – How to specify data involved in the process? – How to specify the way to access a service functionality? – How to communicate to services? – Can we use some existing solutions? Service Registry Service Consumer Service Provider Register Find Bind Execute SOA Elements 8 Motivation Web Services • Technology for SOA • Client-server messaging approach – With predefined Message exchange patterns – Independent of network protocols • Application-specific interfaces – Similar to RPC, CORBA • Most data in XML – Descriptions in XML Schema
4/9/2018 5 9 Motivation RPC vs. Web Services • Remote Procedure Calls • Aim to hide the network – Distributed system looks like a local system – Some calls happen to go over the network • But network is important – Latency, bandwidth – Reliability – connection, nodes • RPC is harmful 10 Motivation Why is RPC considered harmful? • Introduces semantics of a synchronous, blocking invocation – SOA needs a more flexible implementation technology • Usage of statically typed interfaces – Late binding is one of the premises of SOA • Restrictive, inflexible and does not provide the required level of abstraction – Implicit introduction of the behavior which characterizes unified memory space solutions • Hinders resolution of the interoperability issues – Harder to adapt • An appropriate SOA underlying technology needs to shift from the single-machine-centric vision towards the network-centric vision
4/9/2018 6 11 Motivation CORBA vs. Web Services • CORBA = Distributed Objects – Encourages fine-grained design • Much more advanced than RPC • High barrier to entry – Caused by binary protocols, high core complexity • Initial big interoperability problems – Due to the above, and incomplete specifications 12 TECHNICAL SOLUTION WEB SERVICE SPECIFICATION AND PROTOCOL STACK
4/9/2018 7 13 Position in the Communication Architecture: TCP/IP vs. OSI Model See: http://www.tcpipguide.com/free/t_TCPIPArchitectureandtheTCPIPModel-2.htm 14 Web Service Stack Overview Service Transport Service Messaging Service Description Service Discovery - Registry of Web Services - UDDI - Describes the public interface to a specific Web Service - WSDL - XML-based message encoding - XML-RPC, SOAP - Message transportation - HTTP, SMTP, FTP, BEEP Web Service Specification and Protocol Stack Service‐based Processes - Compositions of Web Services - WS-BPEL
4/9/2018 8 15 SOAP Overview • née Simple Object Access Protocol – In fact, simple messaging protocol • Current version: 1.2 @ W3C Recommendation 2007 • Message structure • Processing model • Protocol bindings 16 SOAP Messages • XML Envelope • Body – Application payload – Faults • Headers – Metadata, processing instructions – May be marked as mandatory – Possibly targeted at intermediaries
4/9/2018 9 17 SOAP Message Example <soap:Envelope namespaces…> <soap:Header> <wsa:MessageID> unique ID </wsa:MessageID> <wsa:ReplyTo> endpoint </wsa:ReplyTo> </soap:Header> <soap:Body> <bank:BalanceRequest> data </bank:BalanceRequest> </soap:Body> </soap:Envelope> 18 SOAP Message Envelope Body Header
4/9/2018 10 19 SOAP Processing Model • Processing a message 1. Selecting headers targeted at me – The current intermediary or ultimate receiver 2. Checking for understanding – Do I understand all that is targeted at me and marked as mandatory? 3. Processing everything in some order 20 SOAP Mandatory Headers • mustUnderstand="true" – The recipient must understand them – Implies agreement to act in accordance to the spec – Non-mandatory headers can be ignored • This mechanism enables gracious evolution – If a new feature can be ignored, its introduction won't harm older nodes – If a new feature must be understood, its introduction will be discovered early by older nodes, without unexpected behavior
4/9/2018 11 21 SOAP Protocol Bindings • Transporting the message over a network • Addressing – What an endpoint address looks like • Serialization – How to put the XML message in on-the-wire bits and bytes • Connection – How to send the bits to the endpoint 22 SOAP HTTP Binding • Addressing: URIs • Serialization: HTTP message body – Media type application/soap+xml • Connection: TCP • Possibly Web-friendly – SOAP 1.1 only used HTTP POST
4/9/2018 12 23 SOAP MEPs • Message Exchange Patterns • Request-Response – Input message followed by output or fault • SOAP-Response – Request without SOAP (e.g. HTTP GET) – SOAP output or fault 24 SOAP Summary • Still pretty simple • Extremely extensible • HTTP binding for easy communication • The value of SOAP: XML and Processing Model
4/9/2018 13 25 SOAP Attachments • XML is nice, but… not binary • XOP: XML-binary Optimized Packaging – Binary data in XML logically in the tree – On serialization, it is outside, raw, efficient • MIME multipart message • MTOM: XOP for SOAP – Message Transfer Optimization Mechanism – Extends SOAP HTTP binding 26 WS-Addressing • Simple routing protocol • Endpoint References for addressing – With parameters or metadata in addition to the service address • Message headers for routing & correlation – Many headers use endpoint references
4/9/2018 14 27 WSA Msg Info Headers • To – let the middleware deliver the message • From, ReplyTo, FaultTo – channels back • MessageID, RelatesTo – simple correlation • Action – semantics implied by the message <S:Header> <wsa:MessageID> unique ID </wsa:MessageID> <wsa:ReplyTo> endpoint </wsa:ReplyTo> <wsa:To> address </wsa:To> <wsa:Action> URI </wsa:Action> </S:Header> 28 WSDL Overview • Web Service Description Language – Interface Definition Language (IDL) for Web Services • Current version: 2.0 @ W3C Recommendation 2007 – Version 1.1 still in widespread use • Interface – reusable, abstract – Operations with MEPs • Binding – reusable, concrete • Service implements an interface – Endpoints use bindings
4/9/2018 15 29 WSDL Component Structure service service service 30 WSDL Component Structure service service service endpoint endpoint
4/9/2018 16 31 WSDL Component Structure service service service endpoint endpoint interface interface interface 32 WSDL Component Structure service service service endpoint endpoint interface interface interface fault fault operation operation operation fault
4/9/2018 17 33 WSDL Component Structure service service service endpoint endpoint interface interface interface fault fault operation operation operation fault interface interface binding 34 WSDL Component Structure service service service endpoint endpoint interface interface interface fault fault operation operation operation fault interface interface binding fault fault operation operation operation fault
4/9/2018 18 35 WSDL Component Structure interface fault fault operation operation operation fault 36 WSDL Component Structure interface fault fault operation operation operation fault msg ref msg ref message ref msg ref msg ref fault ref
4/9/2018 19 37 WSDL Component Structure interface fault fault operation operation operation fault msg ref msg ref message ref msg ref msg ref fault ref types 38 WSDL Component Structure interface fault fault operation operation operation fault msg ref msg ref message ref msg ref msg ref fault ref types fault fault operation operation element declaration type definition
4/9/2018 20 39 WSDL Component Structure interface fault fault operation operation operation fault msg ref msg ref message ref msg ref msg ref fault ref types fault fault operation operation element declaration type definition 40 WSDL Interface • Design of application interface – Possibly extending other interfaces • Operations – Message exchange pattern (MEP) – Input/output messages, faults – Referencing XML elements defined in types • Faults – Used and reused by operations
4/9/2018 21 41 WSDL Interface Example <interface name=“Banking”> <operation name=“transfer” pattern=“http://www.w3.org/2004/08/wsdl/in-out”> <input element=“Transfer”/> <output element=“Balance”/> <outfault ref=“InvalidBankAccount”/> <outfault ref=“InsufficientFunds”/> </operation> <operation name=“balance” safe=“true” pattern=“http://www.w3.org/2004/08/wsdl/in-out”> <input element=“BalanceRequest”/> <output element=“Balance”/> <outfault ref=“InvalidBankAccount”/> </operation> <fault name=“InvalidBankAccount” element=“InvalidAccountInfo” /> <fault name=“InsufficientFunds” element=“InsufficentFundsInfo” /> </interface> 42 WSDL Predefined MEPs Invocation: In-only In-out Out-only Out-in Messaging: Robust in-only In-optional-out Robust out-only Out-optional-in core additional, not formal standard
4/9/2018 22 43 WSDL Invocation MEPs • In-only: a single input message – No faults • In-out: a single input message, a single output message – A fault may replace output message • Out-only and Out-in mirror images of the above 44 WSDL Messaging MEPs • Robust in-only: a single input message – May trigger a fault • In-optional-out: a single input message, possibly an output message – Either message may trigger a fault • Robust out-only, Out-optional-in mirrored
4/9/2018 23 45 WSDL Bindings • Networking details necessary for accessing the service • Copies interface structure • SOAP and HTTP bindings provided 46 WSDL Bindings • SOAP binding: – XML message in SOAP envelope – Transport using a SOAP protocol binding (HTTP) • HTTP binding: – Web-friendly – XML message in payload, or as parameters in the URI
4/9/2018 24 47 WSDL Service • A logical node of the application • One interface • Multiple alternate endpoints • Endpoints may have different bindings – E.g. SOAP over HTTP for a public endpoint, and SOAP over JMS for the intranet 48 WSDL Service Example <service name=“HypoTirol” interface=“Banking”> <endpoint name=“visible” binding=“HTTP” address=“http://ht.at/bankingSvc” /> <endpoint name=“tls” binding=“SecureHTTP” address=“https://ht.at/bankingSvc” /> </service>
4/9/2018 25 49 WSDL Summary • Concrete service • Abstract and reusable Interface • Network binding • WSDL does not imply implementation – CORBA IDL requires objects • Exchange of XML business documents • Extensible in many ways 50 UDDI • Universal Description, Discovery and Integration • A Web service registry API specification – Business-oriented service publication, discovery (initially limited search capabilities) – Itself has Web service interface – Useful for intranet registries • A failed public service
4/9/2018 26 51 UDDI Structure • Business entity – Organization information, contact • Business Service – A group of related services • Binding Template – Information on how to access the service • tModel (technical model) – Any kind of specification, e.g. WSDL – Also for classification, categorization 52 WS-Policy Overview • Non of the previous solutions is addressing the non-functional aspects in the context of Web Services – e.g., a Web Service can be accessed only if a particular security constrains (like secure channel communication) hold • WS-Policy is an XML-based set of specifications to advertise and specify service-related non-functional metadata – Security, Quality of service, Privacy, Transactional policies • WS-Policy main specifications – WS-Policy Framework • Provides model and syntax to describe and communicate policies – WS-Policy Assertions • Defines a common set of policy assertions for Web services – WS-Policy Attachments • General-purpose mechanisms for associating such policies with the subjects to which they apply • Capability vs. requirement policy
4/9/2018 27 53 WS-Policy A Policy • Policy is a collection of policy alternatives (OR) – Auth tokens: Kerberos OR X509 • Policy alternative is a collection of policy assertions (AND) – Auth token AND secure channel • Policy assertions specify – traditional policies that will ultimately manifest on the wire (authentication scheme, transport protocol selection), and – critical to proper service selection and usage (privacy policy, QoS characteristics). • Two "operators" (XML tags) are used to make statements about policy combinations: – wsp:ExactlyOne - asserts that only one child node must be satisfied. – wsp:All - asserts that all child nodes must be satisfied. • The intersection is a new policy that complies with both their requirements/capabilities 54 WS-Policy An Example of the Security Policy <wsp:Policy> <wsp:ExactlyOne> <wsse:SecurityToken> <wsse:TokenType>wsse:Kerberosv5TGT </wsse:TokenType> </wsse:SecurityToken> <wsse:SecurityToken> <wsse:TokenType>wsse:X509v3 </wsse:TokenType> </wsse:SecurityToken> </wsp:ExactlyOne> </wsp:Policy>
4/9/2018 28 55 WS-BPEL Overview • WS-BPEL is an orchestration executable language for specifying interactions with Web Service – Defines an interoperable integration model for Web Service-based processes. – Describes high-level state transition interactions of a process. • The language supports following basic facilities: – Message exchanges, – Property-based message correlation mechanism, – XML and WSDL typed variables, – Structured programming-language concepts such as if-then-else, while, sequence, and flow, – Scoping system to allow encapsulation of logic with local-variables, fault-, compensation- and event- handlers, – Serialized scopes to control concurrent access to variables, – Language plug-in model which allows expression writing in the language such as XPath 56 WS-BPEL WS-BPEL v2.0 MetaModel Model taken from http://www.ebpml.org
4/9/2018 29 57 WS-BPEL Main elements • Process – Root element for a WS-BPEL process specification • Variable – Holding messages that constitute a part of the state of a business process. • Activity – Perform the process logic. – Basic vs. structured activities. • PartnerLink – Models peer-to-peer conversational partner relationships. • Catch – Scope-based custom fault-handling activities. • Correlation – Used to differentiate instances of the business processes. – The declaration of correlation relies on declarative properties of messages. • onEvent – Scope-based concurrent answering to events – onEvent vs, onAlarm 58 WS-BPEL An Example Example figures and WSBPEL specification taken from OASIS standard Web Services Business Process Execution Language Version 2.0, 11 April 2007
4/9/2018 30 59 WS-BPEL An Example <process name="purchaseOrderProcess" targetNamespace=http://example.com/ws-bp/purchase xmlns=http://docs.oasis-open.org/wsbpel/2.0/process/executable xmlns:lns="http://manufacturing.org/wsdl/purchase"> <partnerLinks> <partnerLink name="purchasing” partnerLinkType="lns:invoicingLT” myRole="invoiceRequester" partnerRole="invoiceService" /> <partnerLink name="shipping" partnerLinkType="lns:shippingLT” myRole="shippingRequester" partnerRole="shippingService" /> <partnerLink name="scheduling” partnerLinkType="lns:schedulingLT” partnerRole="schedulingService" /> </partnerLinks> <variables> <variable name="PO" messageType="lns:POMessage" /> <variable name="Invoice" messageType="lns:InvMessage" /> <variable name="shippingRequest"messageType="lns:shippingRequestMessage" /> <variable name="shippingInfo"messageType="lns:shippingInfoMessage" /> <variable name="shippingSchedule"messageType="lns:scheduleMessage" /> </variables> <faultHandlers> <catch faultName="lns:cannotCompleteOrder"faultVariable="POFault" faultMessageType="lns:orderFaultType”> <reply partnerLink="purchasing"portType="lns:purchaseOrderPT" operation="sendPurchaseOrder" variable="POFault" faultName="cannotCompleteOrder" /> </catch> </faultHandlers> … 60 WS-BPEL An Example … <sequence> <receive partnerLink="purchasing" portType="lns:purchaseOrderPT” operation="sendPurchaseOrder" variable="PO" createInstance="yes”> </receive> <flow> <links> <link name="ship-to-invoice" /> <link name="ship-to-scheduling" /> </links> <sequence> <assign> <copy> <from>$PO.customerInfo</from> <to>$shippingRequest.customerInfo</to> </copy> </assign> <invoke partnerLink="shipping" portType="lns:shippingPT" operation="requestShipping" inputVariable="shippingRequest" outputVariable="shippingInfo"> <sources> <source linkName="ship-to-invoice" /> </sources> </invoke> <receive partnerLink="shipping” portType="lns:shippingCallbackPT" operation="sendSchedule" variable="shippingSchedule”> <sources> <source linkName="ship-to-scheduling" /> </sources> </receive> </sequence> …
4/9/2018 31 61 WS-BPEL An Example … <sequence> <invoke partnerLink="invoicing” portType="lns:computePricePT" operation="initiatePriceCalculation” inputVariable="PO”> </invoke> <invoke partnerLink="invoicing" portType="lns:computePricePT" operation="sendShippingPrice" inputVariable="shippingInfo”> <targets><target linkName="ship-to-invoice" /></targets> </invoke> <receive partnerLink="invoicing” portType="lns:invoiceCallbackPT” operation="sendInvoice" variable="Invoice" /> </sequence> <sequence> <invoke partnerLink="scheduling” portType="lns:schedulingPT” operation="requestProductionScheduling” inputVariable="PO"> </invoke> <invoke partnerLink="scheduling” portType="lns:schedulingPT” operation="sendShippingSchedule” inputVariable="shippingSchedule”> <targets><target linkName="ship-to-scheduling" /></targets> </invoke> </sequence> </flow> <reply partnerLink="purchasing" portType="lns:purchaseOrderPT” operation=”sendPurchaseOrder" variable="Invoice”> </reply> </sequence> </process> 62 The Rest of the Specs • Security: authentication, encryption • Reliable messaging – “Get the message there or tell me” • Transactions: ACID, Compensating • WS-BPEL: Scripting Web Services • Interoperability: WS-I Basic Profile • … and still more
4/9/2018 32 63 ILLUSTRATION BY A LARGER EXAMPLE 64 Virtual Travel Agency
4/9/2018 33 65 Blue Hotel WSDL (1) <?xml version="1.0" encoding="utf-8" ?> <description xmlns="http://www.w3.org/ns/wsdl" targetNamespace= "http://www.bluehotel.com/wsdl/BlueHotelService" xmlns:tns= "http://www.bluehotel.com/wsdl/BlueHotelService" xmlns:bhns= "http://www.bluehotel.com/schemas/BlueHotelService" xmlns:wsoap= "http://www.w3.org/ns/wsdl/soap" xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:wsdlx= "http://www.w3.org/ns/wsdl-extensions"> <documentation> This document describes the Blue Hotel Web service. </documentation> 66 Blue Hotel WSDL (2) <types> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.bluehotel.com/schemas/BlueHotelService" xmlns="http://www.bluehotel.com/schemas/BlueHotelService"> <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="tCheckAvailabilityResponse"/> <xs:complexType name="tCheckAvailabilityResponse"> <xs:sequence> <xs:element name="roomType" type="xs:string"/> <xs:element name="rateType" type="xs:string"/> <xs:element name="rate" type="xs:double"/> </xs:sequence> </xs:complexType> <xs:element name="invalidDataError" type="xs:string"/> </xs:schema> </types>
4/9/2018 34 67 Blue Hotel WSDL (3) <interface name = "BlueServiceInterface" > <fault name = "invalidDataFault" element = "bhns:invalidDataError"/> <operation name="opCheckAvailability" pattern="http://www.w3.org/ns/wsdl/in-out" style="http://www.w3.org/ns/wsdl/style/iri" wsdlx:safe = "true"> <input messageLabel="In" element="bhns:checkAvailability" /> <output messageLabel="Out" element="bhns:checkAvailabilityResponse" /> <outfault ref="tns:invalidDataFault" messageLabel="Out"/> </operation> </interface> 68 Blue Hotel WSDL (4) <binding name="BlueServiceSOAPBinding" interface="tns:BlueServiceInterface" wsoap:protocol= "http://www.w3.org/2003/05/soap/bindings/HTTP/" type="http://www.w3.org/ns/wsdl/soap"> <fault ref="tns:invalidDataFault" wsoap:code="soap:Sender"/> <operation ref="tns:opCheckAvailability" wsoap:mep= "http://www.w3.org/2003/05/soap/mep/soap-response"/> </binding> <service name="BlueService" interface="tns:BlueServiceInterface"> <endpoint name="reservationEndpoint" binding="tns:BlueServiceSOAPBinding" address="http://www.bluehotel.com/BlueService"/> </service> </description>
4/9/2018 35 69 Blue Hotel UDDI Binding Template <bindingTemplate bindingKey= "uuid:36F1B765-BDB3-4837-828D-8284301E5A2A" serviceKey= "uuid:40E6D5A8-3E16-4f01-99DA-035229685A40"> <description xml:lang="en"> SOAP binding for Blue Hotel service </description> <accessPoint URLType="http"> http://www.bluehotel.com/hotel:80/soap </accessPoint> <tModelInstanceDetails> <tModelInstanceInfo tModelKey= "uuid:AE1B645F-CF2F-491f-811A-4868705F5904"/> </tModelInstanceDetails> </bindingTemplate> 70 Blue Hotel UDDI tModel <tModel tModelKey= "uddi:WE1B6Q5F-CF2F-491f-811A-4868705F5904" operator="http://www.bluehotel.com/hotel" authorizedName="George Blue"> <name>BlueHotelInterface Port Type</name> <description> An interface for the Blue Hotel service </description> <overviewDoc><overviewURL> http://www.bluehotel.com/services/ BlueHotelService.wsdl </overviewURL></overviewDoc> </tModel>
4/9/2018 36 71 Blue Hotel SOAP Request POST /InStock HTTP/1.1 Host: www.example.org Content-Type: application/soap+xml; charset=utf-8 Content-Length: nnn <?xml version="1.0"?> <soap:Envelope soap:encodingStyle= "http://www.w3.org/2001/12/soap-encoding" xmlns:soap="http://www.w3.org/2001/12/soap-envelope"> <soap:Body xmlns:bhns= "http://www.bluehotel.com/wsdl/BlueHotelService"> <bhns:checkAvailability> <bhns:checkInDate>2009-03-24</bhns:checkInDate> <bhns:checkOutDate>2009-03-30</bhns:checkOutDate> <bhns:roomType>Single</bhns:roomType> </bhns:checkAvailability> </soap:Body> </soap:Envelope> 72 Blue Hotel SOAP Response HTTP/1.1 200 OK Content-Type: application/soap+xml; charset=utf-8 Content-Length: nnn <?xml version="1.0"?> <soap:Envelope soap:encodingStyle= "http://www.w3.org/2001/12/soap-encoding" xmlns:soap="http://www.w3.org/2001/12/soap-envelope"> <soap:Body xmlns:bhns= "http://www.bluehotel.com/wsdl/BlueHotelService"> <bhns:checkAvailabilityResponse> <bhns:roomType>Single</bhns:roomType> <bhns:rateType>Discount</bhns:rateType> <bhns:rate>150.50</bhns:rate> </bhns:checkAvailabilityResponse> </soap:Body> </soap:Envelope>
4/9/2018 37 73 SUMMARY 74 Web Services Summary • Technology for service-oriented systems • Core: protocol + IDL (SOAP + WSDL) • Many extension specifications • Messaging paradigm – Sometimes RPC • Biggest benefit: XML – Vendor-neutral, platform-independent – Interoperable – Easy to begin and play with – But hidden in the frameworks • Unless you're a developer of the framework
4/9/2018 38 75 Possible Extensions • Semantic Web Services, Linked Services – Automating the use of Web services – Using semantic technologies • RESTful services – Real Web services – Integrated with the Web • Microservices – Small services – Domain-driven design and virtualisation 76 References • Mandatory reading: – G. Alonso, F. Casati, H. Kuno, V. Machiraju, 2004. Web Services, Concepts Architectures and Applications. Springer Verlag ISBN 3-540-44008-9. – WSDL http://w3.org/TR/wsdl20 – SOAP http://w3.org/TR/soap12 – UDDI http://uddi.xml.org/
4/9/2018 39 77 References • Further reading: – O’Reilly books: 2002 2007 2015 – XOP http://w3.org/TR/xop10 – MTOM http://w3.org/TR/soap12-mtom – WS-Addressing http://w3.org/TR/ws-addr-core – WS-Policy http://w3.org/TR/ws-policy – WS-BPEL http://docs.oasis-open.org/wsbpel/2.0/OS/wsbpel-v2.0-OS.html – OASIS http://oasis-open.org/ – W3C http://w3.org/ 78 References • Wikipedia links: – http://en.wikipedia.org/wiki/Web_Services – http://en.wikipedia.org/wiki/Web_Services_Description_Language – http://en.wikipedia.org/wiki/SOAP – http://en.wikipedia.org/wiki/Universal_Description_Discovery_and_Integratio n – http://en.wikipedia.org/wiki/Business_Process_Execution_Language – http://en.wikipedia.org/wiki/WS-Addressing – http://en.wikipedia.org/wiki/XML-binary_Optimized_Packaging – http://en.wikipedia.org/wiki/WS-Policy – http://en.wikipedia.org/wiki/Web_services_protocol_stack • YouTube links (SOAP, WSDL, etc. implementation in Eclipse): – https://www.youtube.com/watch?v=mKjvKPlb1rA&list=PLqq- 6Pq4lTTZTYpk_1DOowOGWJMIH5T39 (SOAP Web Service Basics at Java Brains channel)
4/9/2018 40 79 Next Lecture # Title 1 Introduction 2 Web Science + + Cathy O’Neil’s talk: “Weapons of Math Destruction” 3 Service Science 4 Web services 5 Web2.0 services 6 Semantic Web 7 Semantic Web Service Stack (WSMO, WSML, WSMX) 8 OWL-S and the others 9 Semantic Services as a Part of the Future Internet and Big Data Technology 10 Lightweight Annotations 11 Linked Services 12 Applications 13 Mobile Services 80 Questions?

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Sws lecture4-handouts

  • 1. 4/9/2018 1 1 © Copyright 2010   Dieter Fensel and Srdjan Komazec, updated by Anna Fensel in 2016‐2018 Semantic Web Services SS 2018 Web services Anna Fensel 09.04.2018 2 Where are we? # Title 1 Introduction 2 Web Science + + Cathy O’Neil’s talk: “Weapons of Math Destruction” 3 Service Science 4 Web services 5 Web2.0 services 6 Semantic Web 7 Semantic Web Service Stack (WSMO, WSML, WSMX) 8 OWL-S and the others 9 Semantic Services as a Part of the Future Internet and Big Data Technology 10 Lightweight Annotations 11 Linked Services 12 Applications 13 Mobile Services
  • 2. 4/9/2018 2 3 Outline • Motivation • Technical solution – SOAP protocol and related specifications – WSDL interface definition language – Additional related specifications • Illustration by a larger example • Possible Extensions • Summary • References 4 MOTIVATION
  • 3. 4/9/2018 3 5 Motivation: “What is a Web Service?” https://www.youtube.com/watch?v=u80uPzhFYvc 6 Motivation SOA • Service-Oriented Architecture • For large-scale distributed computing • For interoperability within and among enterprises • Business-oriented services – Coarse-grained service interfaces – Improves evolvability, manageability • Needs a suitable set of technologies
  • 4. 4/9/2018 4 7 Motivation Solutions needed to implement SOA lifecycle • SOA is a programming style • An SOA application is a composition of services • A ‘service’ is a building block/unit of an SOA • Service encapsulates a business process • A Service Provider registers services • Service consumption involves Find- Bind-Execute pattern • Questions – How to specify data involved in the process? – How to specify the way to access a service functionality? – How to communicate to services? – Can we use some existing solutions? Service Registry Service Consumer Service Provider Register Find Bind Execute SOA Elements 8 Motivation Web Services • Technology for SOA • Client-server messaging approach – With predefined Message exchange patterns – Independent of network protocols • Application-specific interfaces – Similar to RPC, CORBA • Most data in XML – Descriptions in XML Schema
  • 5. 4/9/2018 5 9 Motivation RPC vs. Web Services • Remote Procedure Calls • Aim to hide the network – Distributed system looks like a local system – Some calls happen to go over the network • But network is important – Latency, bandwidth – Reliability – connection, nodes • RPC is harmful 10 Motivation Why is RPC considered harmful? • Introduces semantics of a synchronous, blocking invocation – SOA needs a more flexible implementation technology • Usage of statically typed interfaces – Late binding is one of the premises of SOA • Restrictive, inflexible and does not provide the required level of abstraction – Implicit introduction of the behavior which characterizes unified memory space solutions • Hinders resolution of the interoperability issues – Harder to adapt • An appropriate SOA underlying technology needs to shift from the single-machine-centric vision towards the network-centric vision
  • 6. 4/9/2018 6 11 Motivation CORBA vs. Web Services • CORBA = Distributed Objects – Encourages fine-grained design • Much more advanced than RPC • High barrier to entry – Caused by binary protocols, high core complexity • Initial big interoperability problems – Due to the above, and incomplete specifications 12 TECHNICAL SOLUTION WEB SERVICE SPECIFICATION AND PROTOCOL STACK
  • 7. 4/9/2018 7 13 Position in the Communication Architecture: TCP/IP vs. OSI Model See: http://www.tcpipguide.com/free/t_TCPIPArchitectureandtheTCPIPModel-2.htm 14 Web Service Stack Overview Service Transport Service Messaging Service Description Service Discovery - Registry of Web Services - UDDI - Describes the public interface to a specific Web Service - WSDL - XML-based message encoding - XML-RPC, SOAP - Message transportation - HTTP, SMTP, FTP, BEEP Web Service Specification and Protocol Stack Service‐based Processes - Compositions of Web Services - WS-BPEL
  • 8. 4/9/2018 8 15 SOAP Overview • née Simple Object Access Protocol – In fact, simple messaging protocol • Current version: 1.2 @ W3C Recommendation 2007 • Message structure • Processing model • Protocol bindings 16 SOAP Messages • XML Envelope • Body – Application payload – Faults • Headers – Metadata, processing instructions – May be marked as mandatory – Possibly targeted at intermediaries
  • 9. 4/9/2018 9 17 SOAP Message Example <soap:Envelope namespaces…> <soap:Header> <wsa:MessageID> unique ID </wsa:MessageID> <wsa:ReplyTo> endpoint </wsa:ReplyTo> </soap:Header> <soap:Body> <bank:BalanceRequest> data </bank:BalanceRequest> </soap:Body> </soap:Envelope> 18 SOAP Message Envelope Body Header
  • 10. 4/9/2018 10 19 SOAP Processing Model • Processing a message 1. Selecting headers targeted at me – The current intermediary or ultimate receiver 2. Checking for understanding – Do I understand all that is targeted at me and marked as mandatory? 3. Processing everything in some order 20 SOAP Mandatory Headers • mustUnderstand="true" – The recipient must understand them – Implies agreement to act in accordance to the spec – Non-mandatory headers can be ignored • This mechanism enables gracious evolution – If a new feature can be ignored, its introduction won't harm older nodes – If a new feature must be understood, its introduction will be discovered early by older nodes, without unexpected behavior
  • 11. 4/9/2018 11 21 SOAP Protocol Bindings • Transporting the message over a network • Addressing – What an endpoint address looks like • Serialization – How to put the XML message in on-the-wire bits and bytes • Connection – How to send the bits to the endpoint 22 SOAP HTTP Binding • Addressing: URIs • Serialization: HTTP message body – Media type application/soap+xml • Connection: TCP • Possibly Web-friendly – SOAP 1.1 only used HTTP POST
  • 12. 4/9/2018 12 23 SOAP MEPs • Message Exchange Patterns • Request-Response – Input message followed by output or fault • SOAP-Response – Request without SOAP (e.g. HTTP GET) – SOAP output or fault 24 SOAP Summary • Still pretty simple • Extremely extensible • HTTP binding for easy communication • The value of SOAP: XML and Processing Model
  • 13. 4/9/2018 13 25 SOAP Attachments • XML is nice, but… not binary • XOP: XML-binary Optimized Packaging – Binary data in XML logically in the tree – On serialization, it is outside, raw, efficient • MIME multipart message • MTOM: XOP for SOAP – Message Transfer Optimization Mechanism – Extends SOAP HTTP binding 26 WS-Addressing • Simple routing protocol • Endpoint References for addressing – With parameters or metadata in addition to the service address • Message headers for routing & correlation – Many headers use endpoint references
  • 14. 4/9/2018 14 27 WSA Msg Info Headers • To – let the middleware deliver the message • From, ReplyTo, FaultTo – channels back • MessageID, RelatesTo – simple correlation • Action – semantics implied by the message <S:Header> <wsa:MessageID> unique ID </wsa:MessageID> <wsa:ReplyTo> endpoint </wsa:ReplyTo> <wsa:To> address </wsa:To> <wsa:Action> URI </wsa:Action> </S:Header> 28 WSDL Overview • Web Service Description Language – Interface Definition Language (IDL) for Web Services • Current version: 2.0 @ W3C Recommendation 2007 – Version 1.1 still in widespread use • Interface – reusable, abstract – Operations with MEPs • Binding – reusable, concrete • Service implements an interface – Endpoints use bindings
  • 19. 4/9/2018 19 37 WSDL Component Structure interface fault fault operation operation operation fault msg ref msg ref message ref msg ref msg ref fault ref types 38 WSDL Component Structure interface fault fault operation operation operation fault msg ref msg ref message ref msg ref msg ref fault ref types fault fault operation operation element declaration type definition
  • 20. 4/9/2018 20 39 WSDL Component Structure interface fault fault operation operation operation fault msg ref msg ref message ref msg ref msg ref fault ref types fault fault operation operation element declaration type definition 40 WSDL Interface • Design of application interface – Possibly extending other interfaces • Operations – Message exchange pattern (MEP) – Input/output messages, faults – Referencing XML elements defined in types • Faults – Used and reused by operations
  • 21. 4/9/2018 21 41 WSDL Interface Example <interface name=“Banking”> <operation name=“transfer” pattern=“http://www.w3.org/2004/08/wsdl/in-out”> <input element=“Transfer”/> <output element=“Balance”/> <outfault ref=“InvalidBankAccount”/> <outfault ref=“InsufficientFunds”/> </operation> <operation name=“balance” safe=“true” pattern=“http://www.w3.org/2004/08/wsdl/in-out”> <input element=“BalanceRequest”/> <output element=“Balance”/> <outfault ref=“InvalidBankAccount”/> </operation> <fault name=“InvalidBankAccount” element=“InvalidAccountInfo” /> <fault name=“InsufficientFunds” element=“InsufficentFundsInfo” /> </interface> 42 WSDL Predefined MEPs Invocation: In-only In-out Out-only Out-in Messaging: Robust in-only In-optional-out Robust out-only Out-optional-in core additional, not formal standard
  • 22. 4/9/2018 22 43 WSDL Invocation MEPs • In-only: a single input message – No faults • In-out: a single input message, a single output message – A fault may replace output message • Out-only and Out-in mirror images of the above 44 WSDL Messaging MEPs • Robust in-only: a single input message – May trigger a fault • In-optional-out: a single input message, possibly an output message – Either message may trigger a fault • Robust out-only, Out-optional-in mirrored
  • 23. 4/9/2018 23 45 WSDL Bindings • Networking details necessary for accessing the service • Copies interface structure • SOAP and HTTP bindings provided 46 WSDL Bindings • SOAP binding: – XML message in SOAP envelope – Transport using a SOAP protocol binding (HTTP) • HTTP binding: – Web-friendly – XML message in payload, or as parameters in the URI
  • 24. 4/9/2018 24 47 WSDL Service • A logical node of the application • One interface • Multiple alternate endpoints • Endpoints may have different bindings – E.g. SOAP over HTTP for a public endpoint, and SOAP over JMS for the intranet 48 WSDL Service Example <service name=“HypoTirol” interface=“Banking”> <endpoint name=“visible” binding=“HTTP” address=“http://ht.at/bankingSvc” /> <endpoint name=“tls” binding=“SecureHTTP” address=“https://ht.at/bankingSvc” /> </service>
  • 25. 4/9/2018 25 49 WSDL Summary • Concrete service • Abstract and reusable Interface • Network binding • WSDL does not imply implementation – CORBA IDL requires objects • Exchange of XML business documents • Extensible in many ways 50 UDDI • Universal Description, Discovery and Integration • A Web service registry API specification – Business-oriented service publication, discovery (initially limited search capabilities) – Itself has Web service interface – Useful for intranet registries • A failed public service
  • 26. 4/9/2018 26 51 UDDI Structure • Business entity – Organization information, contact • Business Service – A group of related services • Binding Template – Information on how to access the service • tModel (technical model) – Any kind of specification, e.g. WSDL – Also for classification, categorization 52 WS-Policy Overview • Non of the previous solutions is addressing the non-functional aspects in the context of Web Services – e.g., a Web Service can be accessed only if a particular security constrains (like secure channel communication) hold • WS-Policy is an XML-based set of specifications to advertise and specify service-related non-functional metadata – Security, Quality of service, Privacy, Transactional policies • WS-Policy main specifications – WS-Policy Framework • Provides model and syntax to describe and communicate policies – WS-Policy Assertions • Defines a common set of policy assertions for Web services – WS-Policy Attachments • General-purpose mechanisms for associating such policies with the subjects to which they apply • Capability vs. requirement policy
  • 27. 4/9/2018 27 53 WS-Policy A Policy • Policy is a collection of policy alternatives (OR) – Auth tokens: Kerberos OR X509 • Policy alternative is a collection of policy assertions (AND) – Auth token AND secure channel • Policy assertions specify – traditional policies that will ultimately manifest on the wire (authentication scheme, transport protocol selection), and – critical to proper service selection and usage (privacy policy, QoS characteristics). • Two "operators" (XML tags) are used to make statements about policy combinations: – wsp:ExactlyOne - asserts that only one child node must be satisfied. – wsp:All - asserts that all child nodes must be satisfied. • The intersection is a new policy that complies with both their requirements/capabilities 54 WS-Policy An Example of the Security Policy <wsp:Policy> <wsp:ExactlyOne> <wsse:SecurityToken> <wsse:TokenType>wsse:Kerberosv5TGT </wsse:TokenType> </wsse:SecurityToken> <wsse:SecurityToken> <wsse:TokenType>wsse:X509v3 </wsse:TokenType> </wsse:SecurityToken> </wsp:ExactlyOne> </wsp:Policy>
  • 28. 4/9/2018 28 55 WS-BPEL Overview • WS-BPEL is an orchestration executable language for specifying interactions with Web Service – Defines an interoperable integration model for Web Service-based processes. – Describes high-level state transition interactions of a process. • The language supports following basic facilities: – Message exchanges, – Property-based message correlation mechanism, – XML and WSDL typed variables, – Structured programming-language concepts such as if-then-else, while, sequence, and flow, – Scoping system to allow encapsulation of logic with local-variables, fault-, compensation- and event- handlers, – Serialized scopes to control concurrent access to variables, – Language plug-in model which allows expression writing in the language such as XPath 56 WS-BPEL WS-BPEL v2.0 MetaModel Model taken from http://www.ebpml.org
  • 29. 4/9/2018 29 57 WS-BPEL Main elements • Process – Root element for a WS-BPEL process specification • Variable – Holding messages that constitute a part of the state of a business process. • Activity – Perform the process logic. – Basic vs. structured activities. • PartnerLink – Models peer-to-peer conversational partner relationships. • Catch – Scope-based custom fault-handling activities. • Correlation – Used to differentiate instances of the business processes. – The declaration of correlation relies on declarative properties of messages. • onEvent – Scope-based concurrent answering to events – onEvent vs, onAlarm 58 WS-BPEL An Example Example figures and WSBPEL specification taken from OASIS standard Web Services Business Process Execution Language Version 2.0, 11 April 2007
  • 30. 4/9/2018 30 59 WS-BPEL An Example <process name="purchaseOrderProcess" targetNamespace=http://example.com/ws-bp/purchase xmlns=http://docs.oasis-open.org/wsbpel/2.0/process/executable xmlns:lns="http://manufacturing.org/wsdl/purchase"> <partnerLinks> <partnerLink name="purchasing” partnerLinkType="lns:invoicingLT” myRole="invoiceRequester" partnerRole="invoiceService" /> <partnerLink name="shipping" partnerLinkType="lns:shippingLT” myRole="shippingRequester" partnerRole="shippingService" /> <partnerLink name="scheduling” partnerLinkType="lns:schedulingLT” partnerRole="schedulingService" /> </partnerLinks> <variables> <variable name="PO" messageType="lns:POMessage" /> <variable name="Invoice" messageType="lns:InvMessage" /> <variable name="shippingRequest"messageType="lns:shippingRequestMessage" /> <variable name="shippingInfo"messageType="lns:shippingInfoMessage" /> <variable name="shippingSchedule"messageType="lns:scheduleMessage" /> </variables> <faultHandlers> <catch faultName="lns:cannotCompleteOrder"faultVariable="POFault" faultMessageType="lns:orderFaultType”> <reply partnerLink="purchasing"portType="lns:purchaseOrderPT" operation="sendPurchaseOrder" variable="POFault" faultName="cannotCompleteOrder" /> </catch> </faultHandlers> … 60 WS-BPEL An Example … <sequence> <receive partnerLink="purchasing" portType="lns:purchaseOrderPT” operation="sendPurchaseOrder" variable="PO" createInstance="yes”> </receive> <flow> <links> <link name="ship-to-invoice" /> <link name="ship-to-scheduling" /> </links> <sequence> <assign> <copy> <from>$PO.customerInfo</from> <to>$shippingRequest.customerInfo</to> </copy> </assign> <invoke partnerLink="shipping" portType="lns:shippingPT" operation="requestShipping" inputVariable="shippingRequest" outputVariable="shippingInfo"> <sources> <source linkName="ship-to-invoice" /> </sources> </invoke> <receive partnerLink="shipping” portType="lns:shippingCallbackPT" operation="sendSchedule" variable="shippingSchedule”> <sources> <source linkName="ship-to-scheduling" /> </sources> </receive> </sequence> …
  • 31. 4/9/2018 31 61 WS-BPEL An Example … <sequence> <invoke partnerLink="invoicing” portType="lns:computePricePT" operation="initiatePriceCalculation” inputVariable="PO”> </invoke> <invoke partnerLink="invoicing" portType="lns:computePricePT" operation="sendShippingPrice" inputVariable="shippingInfo”> <targets><target linkName="ship-to-invoice" /></targets> </invoke> <receive partnerLink="invoicing” portType="lns:invoiceCallbackPT” operation="sendInvoice" variable="Invoice" /> </sequence> <sequence> <invoke partnerLink="scheduling” portType="lns:schedulingPT” operation="requestProductionScheduling” inputVariable="PO"> </invoke> <invoke partnerLink="scheduling” portType="lns:schedulingPT” operation="sendShippingSchedule” inputVariable="shippingSchedule”> <targets><target linkName="ship-to-scheduling" /></targets> </invoke> </sequence> </flow> <reply partnerLink="purchasing" portType="lns:purchaseOrderPT” operation=”sendPurchaseOrder" variable="Invoice”> </reply> </sequence> </process> 62 The Rest of the Specs • Security: authentication, encryption • Reliable messaging – “Get the message there or tell me” • Transactions: ACID, Compensating • WS-BPEL: Scripting Web Services • Interoperability: WS-I Basic Profile • … and still more
  • 32. 4/9/2018 32 63 ILLUSTRATION BY A LARGER EXAMPLE 64 Virtual Travel Agency
  • 33. 4/9/2018 33 65 Blue Hotel WSDL (1) <?xml version="1.0" encoding="utf-8" ?> <description xmlns="http://www.w3.org/ns/wsdl" targetNamespace= "http://www.bluehotel.com/wsdl/BlueHotelService" xmlns:tns= "http://www.bluehotel.com/wsdl/BlueHotelService" xmlns:bhns= "http://www.bluehotel.com/schemas/BlueHotelService" xmlns:wsoap= "http://www.w3.org/ns/wsdl/soap" xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:wsdlx= "http://www.w3.org/ns/wsdl-extensions"> <documentation> This document describes the Blue Hotel Web service. </documentation> 66 Blue Hotel WSDL (2) <types> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.bluehotel.com/schemas/BlueHotelService" xmlns="http://www.bluehotel.com/schemas/BlueHotelService"> <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="tCheckAvailabilityResponse"/> <xs:complexType name="tCheckAvailabilityResponse"> <xs:sequence> <xs:element name="roomType" type="xs:string"/> <xs:element name="rateType" type="xs:string"/> <xs:element name="rate" type="xs:double"/> </xs:sequence> </xs:complexType> <xs:element name="invalidDataError" type="xs:string"/> </xs:schema> </types>
  • 34. 4/9/2018 34 67 Blue Hotel WSDL (3) <interface name = "BlueServiceInterface" > <fault name = "invalidDataFault" element = "bhns:invalidDataError"/> <operation name="opCheckAvailability" pattern="http://www.w3.org/ns/wsdl/in-out" style="http://www.w3.org/ns/wsdl/style/iri" wsdlx:safe = "true"> <input messageLabel="In" element="bhns:checkAvailability" /> <output messageLabel="Out" element="bhns:checkAvailabilityResponse" /> <outfault ref="tns:invalidDataFault" messageLabel="Out"/> </operation> </interface> 68 Blue Hotel WSDL (4) <binding name="BlueServiceSOAPBinding" interface="tns:BlueServiceInterface" wsoap:protocol= "http://www.w3.org/2003/05/soap/bindings/HTTP/" type="http://www.w3.org/ns/wsdl/soap"> <fault ref="tns:invalidDataFault" wsoap:code="soap:Sender"/> <operation ref="tns:opCheckAvailability" wsoap:mep= "http://www.w3.org/2003/05/soap/mep/soap-response"/> </binding> <service name="BlueService" interface="tns:BlueServiceInterface"> <endpoint name="reservationEndpoint" binding="tns:BlueServiceSOAPBinding" address="http://www.bluehotel.com/BlueService"/> </service> </description>
  • 35. 4/9/2018 35 69 Blue Hotel UDDI Binding Template <bindingTemplate bindingKey= "uuid:36F1B765-BDB3-4837-828D-8284301E5A2A" serviceKey= "uuid:40E6D5A8-3E16-4f01-99DA-035229685A40"> <description xml:lang="en"> SOAP binding for Blue Hotel service </description> <accessPoint URLType="http"> http://www.bluehotel.com/hotel:80/soap </accessPoint> <tModelInstanceDetails> <tModelInstanceInfo tModelKey= "uuid:AE1B645F-CF2F-491f-811A-4868705F5904"/> </tModelInstanceDetails> </bindingTemplate> 70 Blue Hotel UDDI tModel <tModel tModelKey= "uddi:WE1B6Q5F-CF2F-491f-811A-4868705F5904" operator="http://www.bluehotel.com/hotel" authorizedName="George Blue"> <name>BlueHotelInterface Port Type</name> <description> An interface for the Blue Hotel service </description> <overviewDoc><overviewURL> http://www.bluehotel.com/services/ BlueHotelService.wsdl </overviewURL></overviewDoc> </tModel>
  • 36. 4/9/2018 36 71 Blue Hotel SOAP Request POST /InStock HTTP/1.1 Host: www.example.org Content-Type: application/soap+xml; charset=utf-8 Content-Length: nnn <?xml version="1.0"?> <soap:Envelope soap:encodingStyle= "http://www.w3.org/2001/12/soap-encoding" xmlns:soap="http://www.w3.org/2001/12/soap-envelope"> <soap:Body xmlns:bhns= "http://www.bluehotel.com/wsdl/BlueHotelService"> <bhns:checkAvailability> <bhns:checkInDate>2009-03-24</bhns:checkInDate> <bhns:checkOutDate>2009-03-30</bhns:checkOutDate> <bhns:roomType>Single</bhns:roomType> </bhns:checkAvailability> </soap:Body> </soap:Envelope> 72 Blue Hotel SOAP Response HTTP/1.1 200 OK Content-Type: application/soap+xml; charset=utf-8 Content-Length: nnn <?xml version="1.0"?> <soap:Envelope soap:encodingStyle= "http://www.w3.org/2001/12/soap-encoding" xmlns:soap="http://www.w3.org/2001/12/soap-envelope"> <soap:Body xmlns:bhns= "http://www.bluehotel.com/wsdl/BlueHotelService"> <bhns:checkAvailabilityResponse> <bhns:roomType>Single</bhns:roomType> <bhns:rateType>Discount</bhns:rateType> <bhns:rate>150.50</bhns:rate> </bhns:checkAvailabilityResponse> </soap:Body> </soap:Envelope>
  • 37. 4/9/2018 37 73 SUMMARY 74 Web Services Summary • Technology for service-oriented systems • Core: protocol + IDL (SOAP + WSDL) • Many extension specifications • Messaging paradigm – Sometimes RPC • Biggest benefit: XML – Vendor-neutral, platform-independent – Interoperable – Easy to begin and play with – But hidden in the frameworks • Unless you're a developer of the framework
  • 38. 4/9/2018 38 75 Possible Extensions • Semantic Web Services, Linked Services – Automating the use of Web services – Using semantic technologies • RESTful services – Real Web services – Integrated with the Web • Microservices – Small services – Domain-driven design and virtualisation 76 References • Mandatory reading: – G. Alonso, F. Casati, H. Kuno, V. Machiraju, 2004. Web Services, Concepts Architectures and Applications. Springer Verlag ISBN 3-540-44008-9. – WSDL http://w3.org/TR/wsdl20 – SOAP http://w3.org/TR/soap12 – UDDI http://uddi.xml.org/
  • 39. 4/9/2018 39 77 References • Further reading: – O’Reilly books: 2002 2007 2015 – XOP http://w3.org/TR/xop10 – MTOM http://w3.org/TR/soap12-mtom – WS-Addressing http://w3.org/TR/ws-addr-core – WS-Policy http://w3.org/TR/ws-policy – WS-BPEL http://docs.oasis-open.org/wsbpel/2.0/OS/wsbpel-v2.0-OS.html – OASIS http://oasis-open.org/ – W3C http://w3.org/ 78 References • Wikipedia links: – http://en.wikipedia.org/wiki/Web_Services – http://en.wikipedia.org/wiki/Web_Services_Description_Language – http://en.wikipedia.org/wiki/SOAP – http://en.wikipedia.org/wiki/Universal_Description_Discovery_and_Integratio n – http://en.wikipedia.org/wiki/Business_Process_Execution_Language – http://en.wikipedia.org/wiki/WS-Addressing – http://en.wikipedia.org/wiki/XML-binary_Optimized_Packaging – http://en.wikipedia.org/wiki/WS-Policy – http://en.wikipedia.org/wiki/Web_services_protocol_stack • YouTube links (SOAP, WSDL, etc. implementation in Eclipse): – https://www.youtube.com/watch?v=mKjvKPlb1rA&list=PLqq- 6Pq4lTTZTYpk_1DOowOGWJMIH5T39 (SOAP Web Service Basics at Java Brains channel)
  • 40. 4/9/2018 40 79 Next Lecture # Title 1 Introduction 2 Web Science + + Cathy O’Neil’s talk: “Weapons of Math Destruction” 3 Service Science 4 Web services 5 Web2.0 services 6 Semantic Web 7 Semantic Web Service Stack (WSMO, WSML, WSMX) 8 OWL-S and the others 9 Semantic Services as a Part of the Future Internet and Big Data Technology 10 Lightweight Annotations 11 Linked Services 12 Applications 13 Mobile Services 80 Questions?