Standards for Web Services: Semantics, Processes, and Agents Overview

1. Chapter 2:Basic Standards for Web Services Service-Oriented Computing: Semantics, Processes, Agents– Munindar P. Singh and Michael N. Huhns, Wiley, 2005 Annotated by Juggy Jagannathan in this color

2. Highlights of this Chapter • eXtensible Markup Language (XML) • Simple Object Access Protocol (SOAP) • Web Services Description Language (WSDL) • Directory Services • Universal Description, Discovery, and Integration (UDDI) Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

3. Standards for Web Services Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

4. XML Web Service Foundation Open and with broad industry support • Publish, Find, Use Services • UDDI • Service Interactions • SOAP • Universal Data Format • XML • Description Language • WSDL • Ubiquitous Communications • TCP/IP, HTTP, SMTP, SIP, Reliable messaging • Security (authentication and authorization) • WS-Security, SAML Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

5. Markup History • None • Ad hoc tags • SGML (Standard Generalized Markup L): complex, few reliable tools • HTML (HyperText ML): simple, unprincipled, mixes structure and display • XML (eXtensible ML): simple, yet extensible subset of SGML to capture new vocabularies • Machine processible • Comprehensible to people: easier debugging Check out: http://www.w3schools.com/default.asp For some tutorial on XML-related technologies Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

6. XML Basics and Namespaces <?xml version="1.0"?> <!– not part of the document per se --> <arbitrary:toptag xmlns=“http://one.default.namespace/if-needed” xmlns:arbitrary=“http://wherever.it.might.be/arbit-ns”       xmlns:random=“http://another.one/random-ns”>      <arbitrary:atag attr1=“v1” attr2=“v2”> Optional text also known as PCDATA <arbitrary:btag attr1=“v1” attr2=“v2” /> </arbitrary:atag> <random:simple_tag/> <random:atag attr3=“v3”/> <!– compare with arbitrary:atag above --> </arbitrary:toptag> </arbitrary:toptag> Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

7. XML Schema Appendix A has some examples • A data definition language for XML: defines a notion of schema validity • Same syntax as regular XML documents • Local scoping of subelement names • Incorporates namespaces • Types • Primitive (built-in): string, ID, IDREF, integer, float, date, … • simpleType constructors: list, union • Restrictions: intervals, lengths, enumerations, regex patterns, • Flexible ordering of elements • Key and referential integrity constraints Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

8. Web Services: Basic Architecture Service Broker Registry; well-known Publish or announce (WSDL) Find or discover (UDDI) Service Provider Service Requestor Bind or invoke (SOAP) Not well-known Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

9. Basic Profile (BP 1.0) • The Web Services Interoperability Organization (WS-I) has specified the following Basic Profile version 1.0: • SOAP 1.1 • HTTP 1.1 • XML 1.0 • XML Schema Parts 1 and 2 • UDDI Version 2 • WSDL 1.1 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

10. Describing a Service • Namee.g., GetTemperature • Types of Input Parameterse.g., (String, String) • Types of Output Parameterse.g., Integer Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

11. Interactions Via Methods Via Messages CatalogService() invoke catalog Purchasing() confirmation # invoke Order() Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

12. SOAP (Simple Object Access Protocol) • Used to exchange messages via HTTP, SMTP, and SIP (Session Initiation Protocol for Internet telephony) • Originally designed for remote-procedure calls (RPC) • Works through firewalls on port 80 • Character-based, so easy to encrypt/decrypt and thus easy to secure • Inefficient due to character, not binary, data and large headers • Does not describe bidirectional or n-party interaction Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

13. Ex. SOAP Request POST /temp HTTP/1.1 Host: www.socweather.com Content-Type: text/xml; charset="utf-8" Content-Length: xxx SOAPAction: "http://www.socweather.com/temp" <!-- The above are HTTP headers --> <?xml version=“1.0”?> <env:Envelope xmlns:env="http://schemas.xmlsoap.org/soap/envelope/" env:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"/> <env:Body> <m:GetTemp xmlns:m="http://www.socweather.com/temp.xsd"> <m:City>Honolulu</m:City> <m:When>now</m:When> </m:GetTemp> </env:Body> </env:Envelope> Message sent to this URL Define the namespace for the message Get me the temp in Honolulu now Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

14. Ex. SOAP Response HTTP/1.1 200 OK Content-Type: text/xml; charset="utf-8" Content-Length: xxx SOAPAction: "http://www.socweather.com/temp" <?xml version=“1.0”?> <env:Envelope xmlns:env="http://schemas.xmlsoap.org/soap/envelope/" env:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"/> <env:Body> <m:GetTempResponse xmlns:m="http://www.socweather.com/temp.xsd"> <m:DegreesCelsius>30</m:DegreesCelsius> </m:GetTempResponse> </env:Body> </env:Envelope> Syntax for encoding response Temp is 30o Celsius Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

15. WSDL: Web Services Description Language • Describes a programmatic interface to a Web service, including • Definitions of data types • Input and output message formats • The operations provided by the service • Network addresses • Protocol bindings Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

16. Concepts • Operation: Equivalent to a method • Message: Typed data that can be IN, OUT or INOUT • Type: Typed data using XML Schema • Port Type: Like a class or like Java interface – a collection of operations • Binding: A mechanism to invoke operations – how do I invoke this method? • Port: a reference to where an operation may be invoked • Service: a collection of ports (classes) Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

17. WSDL Data Model Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

18. WSDL Example: 1 <?xml version="1.0"?> <!-- the root element, wsdl:definitions, defines a set of --> <!-- related services --> <wsdl:definitions name="Temperature" targetNamespace="http://www.socweather.com/schema" xmlns:ts="http://www.socweather.com/TempSvc.wsdl" xmlns:tsxsd="http://schemas.socweather.com/TempSvc.xsd" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"> Namespace for temperature service Schema for temperature service Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

19. WSDL Example: 2 <!-- wsdl:types encapsulates schema definitions of --> <!-- communication types; here using xsd --> <wsdl:types> <!-- all type declarations are expressed in xsd --> <xsd:schema targetNamespace="http://namespaces.socweather.com" xmlns:xsd="http://www.w3.org/1999/XMLSchema"> <!-- xsd def: GetTemp [City string, When string] --> <xsd:element name="GetTemp"> <xsd:complexType> <xsd:sequence> <xsd:element name="City" type="string"/> <xsd:element name="When" type="string"/> </xsd:sequence> </xsd:complexType> </xsd:element> Structure for GetTemp message as a schema definition Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

20. WSDL Example: 3 <!-- xsd def: GetTempResponse [DegreesCelsius integer] --> <xsd:element name="GetTempResponse"> <xsd:complexType> <xsd:all> <xsd:element name="DegreesCelsius" type="integer"/> </xsd:all> </xsd:complexType> </xsd:element> <!-- xsd def: GetTempFault [errorMessage string] --> <xsd:element name="GetTempFault"> <xsd:complexType> <xsd:all> <xsd:element name="errorMessage" type="string"/> </xsd:all> </xsd:complexType> </xsd:element> </xsd:schema> </wsdl:types> Structure for GetTempResponse message as a schema definition Structure for handling faults Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

21. WSDL Example: 4 <!-- wsdl:message elements describe potential transactions --> <!-- Most messages, as here, have only one part. Multiple --> <!-- parts provide a way to aggregate complex messages --> <!-- request GetTempRequest is of type GetTemp --> <wsdl:message name="GetTempRequest"> <wsdl:part name="body" element="tsxsd:GetTemp"/> </wsdl:message> <!-- response GetTempResponse is of type GetTempResponse --> <wsdl:message name="GetTempResponse"> <wsdl:part name="body" element="tsxsd:GetTempResponse"/> </wsdl:message> <!-- wsdl:portType describes messages in an operation --> <wsdl:portType name="GetTempPortType"> <!-- wsdl:operation describes the entire protocol from --> <!-- input to output or fault --> <wsdl:operation name="GetTemp"> <!-- The order of input and output is significant; input --> <!-- preceding output indicates the request-response --> <!-- operation type --> <wsdl:input message="ts:GetTempRequest"/> <wsdl:output message="ts:GetTempResponse"/> <wsdl:fault message="ts:GetTempFault"/> </wsdl:operation> </wsdl:portType> GetTempRequest Message GetTempResponse Message PortType Operations with messages Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

22. WSDL Example: 5 Document Style as opposed to RPC-style <!-- wsdl:binding states a serialization protocol for --> <!-- this service --> <wsdl:binding name="TempSvcSoapBinding" type="ts:GetTempPortType"> <!-- leverage off soap:binding document style --> <soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http"/> <!-- semi-opaque container of network transport details --> <!-- classed by soap:binding above @@@ --> <wsdl:operation name="GetTemp"> <soap:operation soapAction="http://www.socweather.com/TempSvc"/> <!-- further specify that the messages in the --> <!-- wsdl:operation "GetTemp" use SOAP? @@@ --> <wsdl:input> <soap:body use="literal" namespace="http://schemas.socweather.com/TempSvc.xsd"/> </wsdl:input> <wsdl:output> <soap:body use="literal" namespace="http://schemas.socweather.com/TempSvc.xsd"/> </wsdl:output> <wsdl:fault> <soap:body use="literal" namespace="http://schemas.socweather.com/TempSvc.xsd"/> </wsdl:fault> </wsdl:operation> </wsdl:binding> Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

23. WSDL Example: 6 <!-- wsdl:service names a new service "TemperatureService" --> <wsdl:service name="TemperatureService"> <wsdl:documentation>socweather.com temperature service </wsdl:documentation> <!-- connect it to the binding "TempSvcSoapBinding" above --> <wsdl:port name="GetTempPort" binding="ts:TempSvcSoapBinding"> <!-- give the binding a network address --> <soap:address location="http://www.socweather.com/TempSvc"/> </wsdl:port> </wsdl:service> </wsdl:definitions> Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

24. Directory Services • Support discovery: enable applications, agents, Web service providers, Web service requestors, people, objects, and procedures to locate each other • White pages – entries found by name • Yellow pages – entries found by characteristics and capabilities • A basic directory might be a simple database (passive) or a broker/facilitator (active, that provides alerts and recruits participants) • UDDI – both white pages and yellow pages, but passive Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

25. UDDI: Universal Description, Discovery, and Integration • UDDI is a Web service that is based on SOAP and XML • UDDI registers • tModels: technical descriptions of a service’s behavior • businessEntities: describes the specifications of multiple tModels Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

26. Yellow, Green, and White Pages in UDDI Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

27. Core Data Structures for UDDI Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

28. UML Model for Business Entity in a UDDI Registry Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

29. WSDL  UDDI Correspondence Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

30. An Inquiry to a UDDI Registry <?xml version="1.0" encoding="UTF-8"?> <find_business xmlns="urn:uddi-org:api_v3"> <findQualifiers> <findQualifier> uddi:uddi.org:findqualifier:exactmatch </findQualifier> </findQualifiers> <!--find information about all businesses with the exact name "WeatherService Inc." --> <name>WeatherService Inc.</name> </find_business> Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

31. Response from a UDDI Registry <?xml version="1.0" encoding="UTF-8"?> <businessList> <businessInfos> <businessInfo businessKey="...KO..."> <name>WeatherService, Inc.</name> <serviceInfos> <serviceInfo serviceKey="...KN..." businessKey="...K1..."> <name>Temperature Service</name> </serviceInfo> </serviceInfos> </businessInfo> </businessInfos> </businessList> Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

32. Chapter 2 Summary • The main triad of Web services standards • Bring together well-known ideas • Provide necessary functionality for interoperation • Are complicated in their details • Meant for tool vendors rather than programmers • Increasingly hidden by tools Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns