Web Services Vagelis Hristidis FIU

9/11/20152 What is the “Transactional Web” Today: “The eye-ball Web” - the architecture of the Web is geared towards delivering information visually. Tomorrow: “The transactional Web” – the architecture of the Web geared towards intelligently exchanging information between applications.

9/11/20153 What is the “Transactional Web” “Web Services” (plural) is a blanket term representing all of the technologies that enable the “transactional web” to exist. “Web Service” (singular) is a term referring to a collection of application operations accessible over a network using Web Services technologies.

9/11/20154 Why do we need Web Services? Standard way to export functionality To implement the Semantic Web Allow agents Allow communication between applications Allow searching for available applications Examples: stock quotes, retail, b2b, libraries,…

9/11/20155 WSAH (Web Services Acronym Hell) XML SOAP WSDL UDDI WSFL DISCO PKIXKMS SAML ebXML XML-RPC XMLP XML-DIGSIG XML-ENC SOAP-SEC X-KISS CPP-CPA WSEL SOAP-RP DIME XLANG DISCO JABBER P3P DSML DAML-S XSD BPEL

9/11/20156 Roadmap Web Services Stack SOAP WSDL UDDI Web Services Composition - BPEL Issues

9/11/20157 The Web Services Stack Wire ProtocolsDescriptionDiscovery TCP/IP HTTP/SMTP/BEEP XML SOAP/XMLP SOAP Blocks XML WSDL WSDL Extensions Process Agreements Inspection Registry (UDDI) The Web Services Stack helps us understand how each of the various pieces fit into the “Big Picture”

9/11/20158 The Web Services Stack Wire Protocols Primary Role: provide a standard, flexible communications channel Secondary Role: provide a standard, flexible wire- level data representation Advantage: interoperability at the lowest level

9/11/20159 The Web Services Stack Description Primary Role: provide a standard, flexible way to describe what and how a Web service does what it does. Advantage: interoperability

9/11/ The Web Services Stack Discovery Primary Role: provide a standard, flexible way to discover where a Web service is located and where to find more information about what the Web service does (the description) Advantage: interoperability, dynamic integration

9/11/ Web Services Stack Description HTTP,IIOP, JMS, SMTP Transport XML Message SOAP WSDL UDDI Discovery Transactions Coordination WS-Security WS-Reliability Quality of Service Orchestration - BPEL4WS Business Processes Context Description Management Choreography - CDL4WS

9/11/ Roadmap Web Services Stack SOAP WSDL UDDI Web Services Composition - BPEL Issues

9/11/ SOAP SOAP stands for Simple Object Access Protocol Made up of three major parts A messaging framework An encoding standard An RPC (remote procedure call) framework It is possible to use just the messaging framework or messaging framework/encoding standard without using the RPC mechanism (though latter is where much of power lies). SOAP is based entirely on XML

9/11/ SOAP: Messaging framework Just defines a generic document type using XML This document type represents the abstraction of a message Virtually any type of message you can think of can be packaged as a SOAP message. However, doing so without RPC mechanisms takes only very small advantage of the features defined in the SOAP standard

9/11/ General (Basic) Structure SOAP Message Envelope Defines the content of the message Header (optional) Contains destination information, versioning, extensions Good place for security Body Contains payload SOAP Envelope SOAP Header SOAP Body Payload Document(s) SOAP Fault

9/11/ General (Basic) Structure SOAP Message <soap:Envelope xmlns:soap=" soap:encodingStyle=" ding/" >......

9/11/ SOAP encoding The second component of SOAP is a standard for how to represent common datatypes as SOAP types. This is knows as the encoding style. SOAP does this in a language agnostic way, much like CORBA (but not in binary form) For example, SOAP stipulates that an array of three integers be represented as: SOAP-ENC:Array SOAP-ENC:arrayType="xsd:int[3]"> 8 5 9

9/11/ SOAP RPC The third part of SOAP is an RPC mechanism that turns messages into method calls We have a generic message structure + data. It requires just a little more work to turn the message into a function call. Must be a way to represent parameters and return values, exceptions, etc.

9/11/ SOAP RPC cartoon VB application Invoice VB-Structure SOAP client SOAP Server Invoice Java-Structure Java application SOAP Message The client application thinks its making a procedure call to a remote module

9/11/ SOAP protocol bindings Question:how are SOAP messages transmitted? Answer: using existing protocols (http, SMTP, etc.) This has some obvious advantages vs. defining its own protocol Piggybacks on security model, general robustness SOAP defines bindings to different protocols that specify how SOAP is used with that protocol to send messages. http is most popular

9/11/ Roadmap Web Services Stack SOAP WSDL UDDI Web Services Composition - BPEL Issues

9/11/ Source WSDL 1.1 specification WSDL 2.0 working draft, 26 June W3C School Tutorial

9/11/ What is WSDL Web Service Description Language. An XML language used to describe and locate web services. Written in XML. Describe functionality of a web service Specify how to access the service (binding protocol, message format, and etc.) Not a W3C standard yet. Version 1.1 released March 2001 W3C Recommendation of Version 2.0 released June 2007

9/11/ Related Standards Type System: XML Schema Name space: XML namespaces Binding: SOAP, HTTP, MIME and etc.

9/11/ The Main Structure of WSDL xschema types … a set of operations communication protocols a list of binding and ports

9/11/ WSDL - Overview … Definition of data types Definition of messages Definition of port type Definition of the bindings Definition of the service

9/11/ Types define types used in message declaration XML Schema, DTD, and etc. XML Schema must be supported by any vendor of WSDL conformant products.

9/11/ <element name="tickerSymbol" type="string“ minOccur = “1” maxOccur=“10”/>

9/11/ WSDL Messages The element defines the data elements of an operation. Each messages can consist of one or more parts. The parts can be compared to the parameters of a function call in a traditional programming language.

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9/11/ WSDL Ports The element is the most important WSDL element. It defines a web service, the operations that can be performed, and the messages that are involved. The defines the connection point to a web service, an instance of. It can be compared to a function library (or a module, or a class) in a traditional programming language. Each operation can be compared to a function in a traditional programming language.

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9/11/ Operation Types The request-response type is the most common operation type, but WSDL defines four types: One-way: The operation can receive a message but will not return a response Request-response:The operation can receive a request and will return a response Solicit-response:The operation can send a request and will wait for a response Notification:The operation can send a message but will not wait for a response -- v 1.2 addition request – multiple response …

9/11/ One way and Notification Example

9/11/ Binding Binding defines how message are transmitted, and the location of the service.

9/11/ <soap:binding style ="document" transport ="

9/11/ My first service

9/11/ Roadmap Web Services Stack SOAP WSDL UDDI Web Services Composition - BPEL Issues

9/11/ WSDL and UDDI Description of web service. Discovery of web service? UDDI – yellow page.

9/11/ What is UDDI UDDI is a platform-independent framework for describing services, discovering businesses, and integrating business services by using the Internet. UDDI stands for Universal Description, Discovery and Integration UDDI is a directory for storing information about web services UDDI is a directory of web service interfaces described by WSDL or another description language

9/11/ UDDI Overview UDDI is: A Web Services API for publishing and discovering the existence of Web services A registry for managing information about Web services A coalition of organizations working together to manage UDDI registries and to further develop the Web Services API for accessing those registries.

9/11/ UDDI Overview UDDI is built around a “Yellow-pages” like data model: Business Entity Business Services Service Bindings Categories Identities TModels

9/11/ UDDI Overview TModel = “Technology Model” TModelTModel Instance Abstract metadata definition relating to some aspect of the UDDI registration Implementation specific metadata conforming to a given TModel. TModel = Abstract Class

9/11/ UDDI Overview TModels Categories & Identifiers Categorization and Identification taxonomies are TModels Categories and Identifiers are TModel Instances Keyed Referenced  Name + Value + TModel Examples: NAICS, UNSPSC, D&B # WSDL Port Types WSDL Port Types are TModels WSDL Services that are bound to a Port Type are TModel Instances WSFL Business Processes WSFL Flow Models are TModels WSFL Global Models are TModel instances TModels represent the extent of UDDI’s semantic description capabilities.

9/11/ UDDI Overview UDDI has only limited extensibility through TModels UDDI was created by IBM, Microsoft and Ariba (many companies have joined the effort) The intent was to put something together that worked.

9/11/ UDDI Overview UDDI Version 1.0 – September 2000 (in production) UDDI Version 2.0 – June 2001 UDDI Version In development UDDI will be presented to a standards body after Version 3.0

9/11/ How can UDDI be Used If the industry published an UDDI standard for flight rate checking and reservation, airlines could register their services into an UDDI directory. Travel agencies could then search the UDDI directory to find the airline's reservation interface. When the interface is found, the travel agency can communicate with the service immediately because it uses a well-defined reservation interface. (by WSDL)

9/11/ WSDL in UDDI WSDLUDDI

9/11/ WSDL in UDDI Since the service interface represents a reusable definition of a service, it is published in a UDDI registry as a tModel

9/11/ WSDL in UDDI

9/11/ Roadmap Web Services Stack SOAP WSDL UDDI Web Services Composition - BPEL Issues

9/11/ Web Services Stack Description HTTP,IIOP, JMS, SMTP Transport XML Message SOAP WSDL UDDI Discovery Transactions Coordination WS-Security WS-Reliability Quality of Service Orchestration - BPEL4WS Business Processes Context Description Management Choreography - CDL4WS

9/11/ How to leverage the full potential of Web Services Multiple invocation between two or more services All parties - Service providers and service clients SERVICE FLOW

9/11/ Web Services Meet Business Processes Web Service 1 Web Service 2 Web Service 3 Web Service 4 Web Service 5 Web Service n

9/11/ Example Problem Space Client PO Service Credit Service Inventory Service Purchase Order Credit Check Reserve Inventory Credit Response Inventory Response Invoice Consolidate Results

9/11/ Business Process Challenges Coordinate asynchronous communication between services Correlate message exchanges between parties Implement parallel processing of activities... Manipulate/transform data between partner interactions Support for long running business transactions and activities Provide consistent exception handling...

9/11/ Recent History of Business Process Standards 2000/05 XLang (Microsoft) 2001/03 BPML (Intallio et al) 2001/05 WSFL (IBM) 2001/06 BPSS (ebXML) 2002/03 BPEL4WS 1.0 (IBM, Microsoft) BPEL4WS 1.1 (OASIS) 2002/062003/01 WS-Choreography (W3C) 2003/04 WSCI (Sun et al) WSCL (HP) 2002/08 BPEL4WS 2.0 (OASIS) 2007

9/11/ Orchestration vs Choreography Orchestration An executable business process describing a flow from the perspective and under control of a single endpoint (commonly: Workflow) Choreography The observable public exchange of messages, rules of interaction and agreements between two or more business process endpoints

9/11/ Sample Business Process: Purchase Order Sample Purchase Order Purchase Order Request Purchase Order Acknowledgement Purchase Order Response Business “ A ” Business “ B ”

9/11/ From a Choreography Perspective PO Request Send PO Receive PO Ack Receive PO Response Receive PO Send PO Ack Send PO Response PO Acknowledgement PO Response Choreography – The observable public exchange of messages Public Process Business ABusiness B

9/11/ From an Orchestration Perspective Send PO Receive PO Ack Receive PO Response Transform From ERP To ERP PO Request PO Acknowledgement PO Response Orchestration – A private executable business process Private Process Business A BPEL Workflow

9/11/ Orchestration and Choreography Together Business B Business Analyst Tool Business A Send PO Receive PO Ack Receive PO Response Transform Business A BPEL Workflow PO Request PO Acknowledgement PO Response Generate BPEL Template Receive PO Send PO Ack Receive PO Response Transform Business B BPEL Workflow Two BPEL workflow templates reflecting a business agreement

9/11/ WSFL Web Service Flow Language By IBM To fit into the WS Stack naturally XML-based grammar to describe WS interactions

9/11/ Multi-party business processes Operational description  WSDL (Web Service Description Language) Composition and choreography of WS  WSFL (Web Service Flow Language)

9/11/ Flow Composition in WSFL (I) Choreograph functionalities of a collection of WS Logic of a business process Specification of the execution sequences of the functionalities of services

9/11/ Flow Composition in WSFL (II) Business tasks Control flow Data flow Activities represent units of processing. Flow of data is modeled through data links. [ WS] Activities can be mapped to the flow interface Control links define execution flow as a directed acyclic graph Activities are associated with specific typed service providers

9/11/ Global Composition in WSFL Specification of interaction pattern of a collection of WS No specification of execution sequence Interactions between service providers and service requestors Peer-to-peer interactions Hierarchical interactions A B C

9/11/ Web Services Stack Description HTTP,IIOP, JMS, SMTP Transport XML Message SOAP WSDL UDDI Discovery Transactions Coordination WS-Security WS-Reliability Quality of Service Orchestration - BPEL4WS, BPML Business Processes (WS Composition) Context Description Management Choreography - CDL4WS, WSCI

9/11/ BPML/WSCI  Complementary efforts Business Process Model Language (Orchestration) describes executable business processes private Web Services Choreography Interface describes messages between collaborating web services XML-based language for WS collaboration Public interactions and choreographies between services

9/11/ BPML XML-based meta-language Developed by Intalio, SUN, SAP, Versata, CSC, SeeBeyond ( - Business Process Management Initiative) Modeling collaborative and transactional business processes Relying on a formal model

9/11/ BPML – 5 elements Activities performance of simple or complex functions Processes types of complex activities that define its own context Contexts environment for the execution of activities Properties information exchange within a context Signals coordination of activities

9/11/ BPML key features basic activities for sending, receiving, and invoking services handles conditional, sequential, and parallel activities for Long-running processes supporting persistence supports short and long-running transactions robust exception handling mechanisms Recursive composition No automation support! Services and partners to be specified at design time

9/11/ WSCI Defines overall choreography of WS taking part in an interaction BEA Systems, BPMI.org, Commerce One, Fujitsu Limited, Intalio, IONA, Oracle Corporation, SAP AG, SeeBeyond Technology Corporation and Sun Microsystems. Uses messages No focus on the definition of executable business processes (that‘s what BPML does) Direct correspondence to WSDL Each WSCI unit of work  WSDL operation WSDL: entry points of each service WSCI: interactions among WSDL operations

9/11/ WSCI – key features (I) Support for basic activities: each activity specifies the WSDL operation involved use to define a basic request/response message use to invoke external services

9/11/ WSCI – key features (II) Support for structured activities: sequential, parallel, and conditional looping use to specify unordered actions to perform Support for business transactions and exceptions: transactional contexts can be defined in WSCI any failure in a context will result in all transactions in context being rolled back

9/11/ WSCI – concepts (I) Interface Observable behaviour of a WS in a message exchange with other WS Activities Basic unit of behaviour; either atomic or complex (composed of other activities) Processes Top-level processes and nested processes Properties Reference a value within an IF definition

9/11/ WSCI – concepts (II) Context Environment: a set of activities is executed Message correlation Structure of conversations, management of multiple conversations with the partner Exceptional behaviour Alternative patterns of behaviour; association to activities Transactional behaviour Global model Overall message exchange

9/11/ BPEL4WS- BPML BPML is a strict superset of BPEL4WS BPML and BPEL4WS share an identical set of idioms and similar syntaxes as the basis of convergence BPML provides a rich and mature language for expressing both simple and complex business processes

9/11/ BPEL4WS – BPML BPML and BPEL4WS are both block- structured languages, with the addition of nested processes in BPML BPML is based on a logical process model that can fully express concurrent, repeating, and dynamic tasks BPML builds on the foundation of WSCI for expressing public interfaces and choreographies

9/11/ BPEL4WS – BPLM/WSCI WSCI/BPML has much richer choreography support and backing by W3C working group BPEL4WS has major supporters behind it, with developer tools and documentation already available

9/11/ BPEL4WS – BPLM/WSCI

9/11/ Business Process Execution Language for Web Services Version 1.0 released by IBM, Microsoft and BEA in August 2002 Accompanied by WS-Coordination, WS-Transaction which remain unsubmitted to standards bodies Version 1.1 submitted to OASIS April 2003 XML language for describing business processes based on Web services Convergence of XLANG (Microsoft) and WSFL (IBM) Unprecendented industry consensus IBM, Microsoft, Oracle, Sun, BEA, SAP, Siebel …

9/11/ Value Proposition Portable business processes Built on top of an interoperable infrastructure of Web services Industry wide language for business processes Common skill set and language for developers Choice of process engines Standards lead to competitive offerings

9/11/ Standards Building Blocks of BPEL Description HTTP,IIOP, JMS, SMTP Transport XML Message SOAP WSDL UDDI Discovery Transactions Coordination WS-Security WS-Reliability Quality of Service Orchestration - BPEL4WS Business Processes Context Description Management Choreography - CDL4WS

9/11/ BPEL Depends on WSDL and WSDL Extensions Service Implementation Definition Service Interface Definition Service Port Binding Port types define Operations Message Type

9/11/ BPEL Scenario Structure (activities)*

9/11/ BPEL Activities Primitive Activities Structured Activities

9/11/ Partners Declare the Web services and roles used by the process Tied to WSDL of the process itself and the participating Web services by service link types Credit Service Partner 2 Inventory Service Partner 3 Partner 1 (the process) Purchase Service

9/11/ Partners in BPEL <partnerLink name=“creditChecker” serviceLinkType=“lns:creditPLT” myRole=“creditRequestor” partnerRole=“creditService”/> Purchase Process WSDL: BPEL: Purchase Process PortType:

9/11/ Variables Messages sent and received from partners Persisted for long running interactions Defined in WSDL types and messages Customer Service Process Persist Persist/ Retrieve Customer Service Persist/ Retrieve

9/11/ Variables in BPEL Purchase Process WSDL: BPEL:

9/11/ How is Data Manipulation Done? Using and, data can be copied and manipulated between variables supports XPath queries to sub-select data

9/11/ Simple Activities Receive Wait for a partner inbound message Can be the instantiator of the business process Reply Synchronous response to a receive activity Response to the inbound receive from a partner Invoke Issue a request synchronously *or* asynchronously

9/11/ Structured Activities Ordinary sequential control between activities is provided by sequence, switch, and while. Concurrency and synchronization between activities is provided by flow. Nondeterministic choice based on external events is provided by pick. The pick activity awaits the occurrence of one of a set of events and then performs the activity associated with the event that occurred

9/11/ Simple Activities Combined with Structured Activities Invoke Reply Receive

9/11/ Sample Activities in BPEL <receive partnerLink=“customer” portType=“lns:purchaseOrderPT" operation=“sendPurchaseOrder” variable=“PO” createInstance="yes" /> <invoke partnerLink=“inventoryChecker” portType=“lns:inventoryPT” operation="checkINV" inputVariable="inventoryRequest" outputVariable="inventoryResponse" /> <invoke partnerLink="creditChecker" portType=“lns:creditPT" operation="checkCRED" inputVariable="creditRequest" outputVariable="creditResponse" />... <reply partnerLink=“customer” portType=“lns:purchaseOrderPT” operation=“sendPurchaseOrder” variable=“invoice"/>

9/11/ Links – Control Flow

9/11/ Correlation Customer SendPurchase ProcessPurchaseResponse PO Correlation: POResponse Correlations: Seller AsynchPurchase AsynchPurchaseResponse initiate=yes initiate=yes pattern=out initiate=no pattern=out initiate=yes initiate=no

9/11/ Correlations in BPEL... <receive partnerLink=“Customer” portType= " SP:PurchaseOrderPT " operation= " AsynchPurchase " variable= " PO " >... <invoke partnerLink=“Customer” portType= " SP:CustomerPT " operation= “ ProcessPurchaseResponse " inputVariable= " POResponse " >...

9/11/ Scopes in BPEL Provide a shared context for subset of activities Can contain fault handlers event handlers, compensation handler variables correlation sets Can serialize concurrent access to variables ?... ?... (activities)*

9/11/ Long Running Transactions and Compensation Undo Reserve Inventory ReserveInventory CancelReserveInv InventoryService CheckCredit ChargeHoldFee CancelHoldFee CreditService Undo Charge Hold Fee

9/11/ Compensation Handlers in BPEL <invoke partnerLink= " Seller " portType= " SP:Purchasing " operation= " CancelPurchase " inputVariable="getResponse" outputVariable="getConfirmation"> <invoke partnerLink="Seller" portType="SP:Purchasing" operation="SyncPurchase" inputVariable="sendPO" outputVariable="getResponse">

9/11/ Exception Handling in BPEL catch exception Based on WSDL port defining fault can perform activities upon invocation <catch faultName="lns:cannotCompleteOrder" faultVariable="POFault"> <reply partnerLink="customer" portType="lns:purchaseOrderPT" operation="sendPurchaseOrder" variable="POFault" faultName="cannotCompleteOrder"/>

9/11/ Just Show Me How to Do it! Partner WSDL 1 Process WSDL Partner WSDL n... BPEL Scenario 1.Compile 2.Package 3.Deploy Application Server BPEL Runtime Compiled BPEL Scenario

9/11/ Tooling Requirements IDE – build your Web services WSDL authoring – model your interfaces Schema authoring – model your messages Process modeling – model your orchestration Packaging and deployment Debugging Monitoring Analyzing

9/11/ Roadmap Web Services Stack SOAP WSDL UDDI Web Services Composition - BPEL Issues

9/11/ Remember BPEL Does Not Solve “World Hunger” No data transformation No data translation No human workflow No trading partner agreements Silent on existing business protocols (ebXML, RosettaNet …) Silent on non Web service interactions (e.g. java to java)...

9/11/ But Remember: People Are Trying to Solve “World Hunger” W3C: WS-Choreography Spec: WS-Transaction Spec: WS-Coordination Spec: WS-Composite Application Framework OASIS: WS-Reliability Spec: ReliableMessaging Spec: WS-Addressing OASIS: WS-Security …

9/11/ Parting Thoughts Business process portability? Java/J2EE is portable across application servers BPEL is portable independent of Java Programming language in XML? Vendors, big and small, are busy building design times and modelers… Is BPEL in 2003/2004 J2EE in 1998? Much missing but compelling foundation

9/11/ Problems Complex long running web services. Analysis and verification Automatic composition of complex services. …

9/11/ Web Services and the Semantic Web Complementary Goals Semantic Web It’s about making links between information more intelligent. Web Services It’s about improving the way information is exchanged

9/11/ Web Services and the Semantic Web Meeting in the middle Semantic Web Provides a formal data-model for Web Services Transactional Web Provides a technology foundation for the Semantic Web

9/11/ Research topics Searching for web services Searching for sequence of web services Output of one is input to other Schema matching Trust

9/11/ References James Snell slides, IBM Andrew Siegel, UChicago Xiang Fu slides Katharina Siorpaes slides Oracle

9/11/ References V.d. Aalst, W.M.P., Dumas, M., ter Hofstede, A.H.M., Wohed, P. (2002) Pattern-based analysis of BPML (and WSCI), Cabera, F., Copeland, G., Freund, T., Klein J., Langworthy D., Orchard, D., Shewchuk, J., Storey, T. (2002) Web Service Coordination (WS-Coordination), ibm.com/developerworks/library/ws-coor/, 2002http://www- 106.ibm.com/developerworks/library/ws-coor/ Leymann, F. (2001) Web Services Flow Language (WSFL1.0), ibm.com/software/solutions/webservices/pdf/WSFL.pdf ibm.com/software/solutions/webservices/pdf/WSFL.pdf Arkin, A., (2002) Business Process Modeling Language, Arkin, A., Askary, S., Fording, S., Jekeli, W., Kawaguchi, K., Orchard, D., Pogliani, S., Riemer, K., Struble, S., Takacsi- Nagy, P., Trickovic, I., Zimek, S. (2002) Web Service Choreography Interface 1.0