Software from Components. Part II Architectural Systems Web Services

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1 Software from Components Part II Architectural Systems Web Services

2 2 Content Web Services SOAP WSDL BPEL

3 3 Obligatory Reading ISC, Chapter 2.4 W.M.P. Van der Aalst. Don't go with the flow: Web services composition standards exposed. IEEE Intelligent Systems, Jan/Feb P. Wohed, W.M.P. Van der Aalst, M. Dumas, A. ter Hofstede. Analysis of Web Service Composition Languages: The Case of BPEL.

4 4 Literature YAWL

5 Web Services and Architecture Systems Architecture systems may have different forms of architectural languages: 5 Topology-based (Unicon, ACME, Darwin) Coordination schemes (CoSy) Imperative scripts (Darwin) Web Service Systems and Languages (WSS) are a form of architectural system They separate programming-in-the-small from programming-in-thelarge (2-level programming) Components encapsulate the service knowledge The architectural level (orchestration, aggregation, composition) treats the big picture However, WSS have an imperative architectural language

6 Keyword: Service Accounts Coop. Amazon.com Billing Servicearchitecture Order processing UPS Citybank 6 Delivery Creditability check Payment

7 Reuse of (some) Services Accounts Web Agregate Order acceptance Billing Storage Packing Paket service Checking Amazon.com Billing Order processing Bank 7 Delivey Creditability check Payment

8 8 Web Services: basic concept Operation/Process Data Standards required!

9 9 Service-Oriented Architectures (SOA) Future webservice architectures will be SOA SOA are based on traders Services will be offered Services will be searched and discovered Services will be downloaded Services will be executed

10 10 Description Framework Revolution Judgments Vision Evolution Exists Judgment Approaches Components of Web Services

11 XML Data Exchange + W3C Recommendation (standard) + Easy syntax for hierarchical structured documents Widely spread, accepted - No semantics - Not compact / low performance - Ongoing standardizations Data: XML-document Approach Components of Web Services 11 Exists XML Message Description

12 12 XML Example <treatment> <patient insurer= nr= /> <doctor city = HD nr= 4321 /> <service> <mkey>1234-a</mkey> <date> </date> <diagnosis>no complications. </diagnosis> </service> </treatment>

13 13 XML Types and Regular Expressions Type Regular Expression ARRAY OF X (X)* RECORD X, Y,..., Z (X, Y,..., Z) UNION X, Y,..., Z (X Y... Z)

14 14 Example: Simple XML Schema types <simpletype name= mkey base= string > <pattern value= [0-9]+(-[A-Z]+)? /> </simpletype> <simpletype name= insurer base= integer > <precision value= 7 /> </simpletype> <simpletype name= mydate base= date > <mininclusive value= /> <maxexclusive value= /> </simpletype>

15 15 Example: Complex XML Schema types <complextype name= treatment > <element name= patient type= patient /> <choice> <element ref= doctor /> <element ref= hospital /> </choice> <element ref= service maxoccurs= unboanded /> </complextype>

16 16 Example: XML Schema Attributes <complextype name= patient content= empty > <attribute ref = insurer use= required /> <attribute name= nr use= required > <simpletype base= integer > <precision value= 10 /> </simpletype> </attribute> <attribute name= since type= mydate /> </complextype>

17 17 Question Why do people like XML? It is wordy Slow Ugly...

18 18 The Sumerian Law on Readability Every language that is not readable by humans will vanish

19 19 SOAP, An XML-based Interaction Protocol Body Header Envelope Simple Object Access Protocol (SOAP) defines the message format

20 SOAP An XML-Based RPC Message contains target address and an envelope with name space, encoding attributes and Header (fixed format) contains Authentication (Sender, Receiver), Transactions, Error handling information, Routing information Body contains user data (free format) Transport is transparent, predefine channels: HTTP (with back channel, de facto standard) SMTP (Simple Mail Transport Protocol) TCP (with back channel) 20

21 Example: SOAP Header Message Header POST /TreatmentAdmin HTTP/1.1 HTTP HOST: Content-Type: text/xml Charset= utf-8 Content-Length: nnnn SOAPaction: <SOAP-ENV:Envelop xmlns:soap-env= SOAP-ENV:Encoding= /encoding > <SOAP-ENV:Header> <a:authentication xmlns:a= > SOAP Envelop </a:authentication> </SOAP-ENV:Header> <SOAP-ENV:Body> </SOAP-ENV:Body> </SOAP-ENV:Envelop> 21

22 Example: SOAP Body <SOAP-ENV:Body> <m:addtreatment xmlns:a= <treatment> <patient insurer= nr= /> <doctor city = HD nr= 4321 /> <service> <mkey>1234-a</mkey> <date> </date> <diagnosis>no complications. </diagnosis> </service> XML Data 22 </treatment> </SOAP-ENV:Body>

23 SOAP Interaction Protocol + W3C Recommendation (standard) + Implements RPC - Untyped user data, types to encode in the message - Interpretation of SOAP messages required - High overhead / low performance - Ongoing standardizations Approach Components of Web Services W3C Web Services Activity WS Architecture WG XML Protocol WG (SOAP) WS Description WG (WSDL WS Coordination Group Exists SOAP Messaging Exists XML Message Description 23 Exists HTTP, FTP, IIOP, MQ,... Network

24 The Interface Concept of Web Services

25 25 Service Interface XML input / output Operation Web Service Interface Web Services Description Language (WSDL) defines a service interface

26 26 WSDL Components and Their Interfaces A WSDL Interface is a set of ports Functions with types of parameter and results in XML Schema Event ports Plays a similar role as ports of a UML component <<WebService>>

27 27 Advantages WSDL abstracts from underlying Protocol (http, SOAP, mime, IIOP, etc.) Component model Advantage: Mapping to CORBA, EJB, DCOM,.NET are available Contrary to all component models seen so far, WSDL unifies call and event ports And abstracts from the underlying component model, introducing the component model as a secret

28 WDSL Specification Structure Types In XML schema or another typing language Messages The data that is communicated Operation An interface of the service, with input and output, fault parameters Port type A named set of operations (as in UML) Binding A mapping of the port to underlying component models, e.g., http, soap, or mime Service 28 A set of related ports

29 WSDL XSD Types <wsdl:types> <XMLSchema:schema [target name space definitions]> <XMLSchema:element name= addtreatment > <XMLSchema:complextype> <XMLSchema:sequence> <s:element minoccurs="1" maxoccurs="1" name="parameter" nillable="true" type="a:treatment"/> </XMLSchema:sequence> </XMLSchema:complextype> </XMLSchema:element> <XMLSchema:element name= addtreatmentresponse > <XMLSchema:complextype> <XMLSchema:sequence> <s:element minoccurs="1" maxoccurs="1" name= result" nillable="true" type="xmlschema:bool"/> </XMLSchema:sequence> </XMLSchema:complextype> </XMLSchema:element> <XMLSchema:complextype name= treatment > </XMLSchema:complextype> </XMLSchema:schema> 29

30 30 Operations in Port Types Event or message based: Notification: data-out port. One-way: data-in port. Call-based Request-Response: procedure port. Solicit-Response: send, then receive (caller port)

31 31 Example: WSDL <wsdl:definitions [name space definitions]> <wsdl:types> </wsdl:types> <wsdl:message name= addtreatmentsoapin > <part name= parameters element= addtreatment /> </wsdl:message> <wsdl:message name= addtreatmentsoapout > <part name= parameters element= addtreatmentresponse /> </wsdl:message> <wsdl:porttype name= TreatmentAdminSOAP > <wsdl:operation name= addtreatment > <wsdl:input message= addtreatmentsoapin /> <wsdl:output message= addtreatmentsoapout /> </wsdl:operation> </wsdl:porttype> <binding [binding to SOAP / HTTP Protocols] </wsdl:definitions> Actual interface

32 32 Example: Binding WSDL to SOAP <wsdl:binding name= livetoken type= Token > <soap:binding style= document transport= > <operation name= GetLastPrice > <soap:operation soapaction= > <input> <soap:body use= literal > </input> <output> <soap:body use= literal > </output> </operation> <wsdl:binding>

33 WSDL Service Interface + W3C Recommendation (standard) + Imitates Interface Definition Languages Part of BPEL (see later) - No inheritance on WSDL - No standard mapping to data in programming languages - No web service as parameters/results Approach Components of Web Services Exists WSDL Service Description Exists SOAP Messaging Exists XML Message Description 33 Exists HTTP, FTP, IIOP, MQ,... Network

34 34 Offer and Find Services Standardized publishing, advertisement Extended name server, describing interface and properties XML Descriptor White Page: Address Yellow Page: Semantics (based on standard taxonomy) Green Page: Technical specification of service Logically central, physically distributed data base Universal Description, Discovery and Integration (UDDI) defines service properties

35 UDDI White Page Registered (and other) names Service Description Contact person (name, s, ) Telephone/fax number Web site Yellow Pages Service category Type of industry Type av products/services Geographic localization 35 Green Pages Offered service Documentation, description Principles cooperation realization WSDL WSDL

36 Offer and Find Services +Required and approached - No W3C Recommendation (standard) - No search strategies - No no trader or market place Approach Components of Web Services Evolution UDDI Service Discovery Evolution UDDI Service Publication Exists WSDL Service Description Exists SOAP Messaging Exists XML Message Description 36 Exists HTTP, FTP, IIOP, MQ,... Network

37 Business Processes on the Web with BPEL

38 38 Business Process How to define a business process on the web There are many languages proposed today: WSFL, WSCL, WSCI, XLANG, WSEL, UML, WSUI, WSXL, BPML IBM & Microsoft: BPEL, BPEL4WS OASIS: WS BPEL Business Process

39 39 Ingredients... BPEL is an architectural language for web services Based on workflow languages Mixing control and data flow operators BPEL is a composition language Composing web services, using their ports Relying on messages (events) and calls BPEL builds on WSDL For service interface descriptions BPEL adds connections (partner link types)

40 40 Side Stepping: Which Operational Specifications Exist? Data flow graphs Data flows through operations Activity diagrams: data flows through actions Control-flow graphs Nodes are control-flow operations that start other operations on a state Mixed approaches Cyclic data-flow graphs (also called static-single assignment graphs, SSA) Cycles are marked by phi-nodes that contain control-flow guards Statecharts: events trigger state transitions Petri nets: tokens mark control and data-flow Workflow languages: mix control and data-flow

41 41 Workflow Languages A workflow language specifies control and data flow over a set of operations The operations need not be executed automatically, but can be performed by humans The workflow runs in parallel, because it must model the business process of a company Workflows are nearer to Colored Petri Nets than to Statecharts Examples: ARIS system for SAP FlowMark (IBM) Lotus Domino (IBM) YAWL (van der Aalst, Einhoven): based on Colored Petri Nets

42 42 Typical Operations in Workflow Languages AND-split: all XOR-split: 1 of n OR-split: m of n AND-join: all of n XOR-join: 1 of n OR-join: m of n

43 43 What are Workflow Engines? Workflow engines are interpreters of workflows They maintain the parallelism in a workflow and synchronize all processes Usually, they also support for interactive applications Undo Transactions with rollback and commit Compensation (in case of error) They are, for web services and component systems, composition engines that execute a composition program

44 44 BPEL Made Simple BPEL is a activity-diagram like language, with parallelism and transactions with different kind of join and split operators with ports and connections BPEL can be edited graphically, and has an XML abstract syntax To create a web service, becomes a similar activity as editing an UML activity diagram or Petri Net

45 45 BPEL Specification Structure Process definition Header with namespace declarations Variables: global variables of the process PartnerLink declarations: interface declaration with whom is the process connected? Partners: actual partners of the communication Correlation sets: Which instance of a process is talking to which other instance? Fault handler: What happens in the case of an exception? Compensation handler: compensation actions Event handler: what happens in case of a certain event? A (structured) main operation e.g., sequence or flow

46 46 WSDL Definitions as a Basis BPEL uses WSDL definitions to define types, message types, and port types WSDL definitions can be without binding Bindings can be added when the BPEL process is deployed That increases reuse of the process This achieves component model transparency (independence of the underlying component model) BPEL adds partner link types (connector types) which are typed connections

47 A Simple Pizza Order  <process name= OrderPizza suppressjoinfailure= yes xmlns= pns= > <partnerlinks> <partnerlink name= PizzaService partnerlinktype= pns:orderchannel myrole= PizzaOrderer > </partnerlinks>  <variables> <variable name= input messagetype= PizzaOrder /> <variable name= output messagetype= PizzaDelivery /> </variables> <faulthandlers>... </faulthandlers> <sequence name= body > <invoke name= order partnerlink= PizzaService porttype= PizzaOrder operation= body variable= output > <receive name= acknowledgement partnerlink= PizzaService porttype= Pizza operation= body variable= input > </sequence> </process> 47 Connector

48 48 Flow Operations are Workflow Graphs The <flow> operation is structured as a workflow graphs The names of messages, ports, partner links help to span up the graph <flow> executes its sequences in parallel <links> can synchronize parallel tasks <flow> <links><link> name= A </link> </links> <link>name= B </link> <sequence>..<invoke> <target name= A >..</sequence> <sequence>...<target name = B >...</sequence> </flow> A B

49 49 Other Operations Structured control-flow sequence switch while flow pick (XOR join) terminate compensate scope assign

50 50 BPEL Tools Collaxa designer People work on the translation of Colored Petri Nets and UML activity diagrams from and to BPEL CPN have good formal features (see PUM) and can be used for deadlock checking, etc. YAWL is such a nice language, see the work of [van der Aalst]

51 Business Process Approach Components of Web Services Vision BPEL BPML WSCI Workflow Evolution UDDI Service Discovery Evolution UDDI Service Publication Exists WSDL Service Description Exists SOAP Messaging Exists XML Message Description 51 Exists HTTP, FTP, IIOP, MQ,... Network

52 52 Trust and Security Integrity: intact, unchanged Confidentiality: cryptification policy Authentication: proof of identity Authorization: access to execute certain services Non-Repudiation: waranty on failior Legal Rights: copy rights, reselling rights, Privacy: handling personal data

53 Trust and Security WS-Security Components of Web Services Evolution Vision BPEL BPML WSCI Work Flow Evolution UDDI Service Discovery Evolution Exists Exists UDDI WSDL SOAP Service Publication Service Description Messaging Security Exists XML Message Description 53 Exists HTTP, FTP, IIOP, MQ,... Network

54 54 Technical Conclusion Defined with XML Web Services minimum WS-Security BPEL BPML UDDI UDDI WSDL SOAP XML WSCI HTTP, FTP, IIOP, MQ,...

55 55 Problems of Classical Component Systems Different basic communication of the systems, Corba components cannot talk directly with COM components etc. Adaptation on technical level necessary Not full remote transparency Dependence on the component model

56 Web Services Component Model Transparency Language adaptation: XML Schema + WSDL Remote transparency: SOAP (+ HTTP) Component model transparency (EJB, COM+, CORBA, CCM, Beans, etc...) Remote Client Java EJB WSDL Local Client C CCM WSDL Server C++ COM+ WSDL 56 SOAP (HTTP) Remote SOAP (HTTP) Local

57 Evaluation of Web Services as composition system

58 58 Component Model Mechanisms for secrets and transparency: very good Location, language, component model transparency Communication protocol transparency Generic BPEL Web Services (without bound WSDL ports)

59 59 Composition Technique Mechanisms for connection Protocol transparency allows for flexible connections WSDL binding is flexible Mechanisms for aspect separation Mechanisms for Meta-modeling Used Scalability: Better Changes of protocol possible Changes of distribution easy Changes of workflow easy

60 60 Composition Language BPEL workflows are a nice composition language Not yet full exchangeability of connector types But graphic support for workflow specifications Metacomposition fully supported The generation of a BPEL script is easy, because it is XML based Environments as Collaxa will generate workflow from other specifications Generic workflow architectures will be possible

61 Web Services - Component Model Secrets Development environments Types Distribution Business services Contracts Binding points 61 Infrastructure Versioning Parameterization

62 Web Services Composition Technique and Language Adaptation Connection Product quality Extensibility Software process Aspect Separation Metacomposition 62 Scalability

63 63 Web Services as Composition Systems Component Model Composition Technique Contents: Completely hidden Binding points: WSDL ports Adaptation: well supported Automatic transactions, recovery Several types of connectors BPEL is a workflow language Composition Language

64 64 So Far: Blackbox Composition Standard middleware CORBA, DCOM Implicit middleware EJB Architecture systems Web services Composition Filters

65 The Ladder of Component and Composition Systems Aspect Systems Aspect Separation Aspect/J View Systems Composition Operators Composition Filters Hyperslices Software Composition Systems Composition Language Invasive Composition Metaclass Composition Piccola Architecture Systems Classical Component Systems Architecture as Aspect Standard Components Darwin ACME.NET CORBA Beans EJB Object-Oriented Systems Objects as Run-Time Components C++ Java Modular Systems Modules as Compile- Modula Ada Time Components

66 66 The Second Part of the Course (After Easter): Greybox Composition Generic programming Generic program elements Home-made connectors View-based programming Formal foundations (lambda N, pi-calculus) Record calculi, Scala Hyperspace programming Aspect-oriented development Aspect-oriented programming Aspect-oriented design Dynamic aspect-oriented programming (EAOP) Invasive software composition

67 67 Novel Forms of Composition Uniform composition Generic component models Active document composition Architectural styles for active documents and web systems Roundtrip engineering and composition

68 Some Abbreviations ebxml: Electronic Business XML UDDI: Universal Description, Discovery and Integration OAG: Open Applications Group OASIS: Organization for the Advancement of Structured Information Standards SOAP: Simple Object Access Protocol HTTP: Hypertext Transfer Protocol tpaml: Trading Partner Agreement Markup Language UML: Unified Modeling Language UN/CEFACT: United Nations Centre for the Facilitation of Procedures and Practices in Administration, Commerce and Transport WSFL: Web Services Flow Language WSDL: Web Services Description Language WSIL: Web Services Inspection Language WSXL: Web Services Experience Language WSCL: Web Services Conversation Language WSUI: Web Services User Interface WSML: Web Services Meta Language WSCM: (Web Services Component Model) Numer omdöpt till WSIA WSIA: Web Services for Interactive Applications WSEL: Web Services Endpoint Language 68

69 Some URL

70 The End Many slides inherited from Stig Berild's talk on the Nordic Conference on Web Services, Nov. 2002 Prof.

70 70 The End Many slides inherited from Stig Berild's talk on the Nordic Conference on Web Services, Nov Prof. Welf Löwe, Web Service Competence Center (WSCC), Växjö University:

7. Web Services and Service-Oriented Architectures

7. Web Services and Service-Oriented Architectures Prof. Dr. Uwe Aßmann Technische Universität Dresden Institut für Software- und Multimediatechnik http://st.inf.tu-dresden.de Version 10-0.2, June 15,