Chapter 2: Basic Standards for Web Services Service-Oriented Computing: Semantics, Processes, Agents – Munindar P. Singh and Michael N. Huhns, Wiley, 2005

Chapter 22Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 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)

Chapter 23Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Standards for Web Services

Chapter 24Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Markup and Metadata History None, e.g., CSV 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 Generally, comprehensible (easier debugging), though verbose and arcane

Chapter 25Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns XML Basics and Namespaces <arbitrary:toptag xmlns=" xmlns:arbitrary=" xmlns:random=" Optional text also known as PCDATA

Chapter 26Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns XML Schema Grammar (data definition language) for specifying valid documents Uses same syntax as regular XML documents: verbose and difficult to read Provides local scoping of subelement names Incorporates namespaces Types Primitive (built-in): string, integer, float, date, … simpleType constructors: list, union Restrictions: intervals, lengths, enumerations, regex patterns, Flexible ordering of elements Key and referential integrity constraints

Chapter 27Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Web Services: Basic Architecture Service Broker Service Provider Service Requestor Bind or invoke (SOAP) Find or discover (UDDI) Publish or announce (WSDL) Registry; well-known Not well-known

Chapter 28Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 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

Chapter 29Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Describing a Service Name e.g., GetTemperature Types of Input Parameters e.g., (String, String) Types of Output Parameters e.g., Integer

Chapter 210Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 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

Chapter 211Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Ex. SOAP Request POST /temp HTTP/1.1 Host: Content-Type: text/xml; charset="utf-8" Content-Length: xxx SOAPAction: " <env:Envelope xmlns:env=" env:encodingStyle=" Honolulu now

Chapter 212Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Ex. SOAP Response HTTP/ OK Content-Type: text/xml; charset="utf-8" Content-Length: xxx SOAPAction: " <env:Envelope xmlns:env=" env:encodingStyle=" 30

Chapter 213Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 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

Chapter 214Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns WSDL Data Model

Chapter 215Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 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

Chapter 216Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 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 services behavior businessEntities: describes the specifications of multiple tModels

Chapter 217Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Yellow, Green, and White Pages in UDDI

Chapter 218Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Data Model for UDDI

Chapter 219Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns WSDL UDDI

Chapter 220Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Chapter 2 Summary The main triad of Web services standards Bring together well-known ideas SOAP: object access and messaging WSDL: based on CORBA IDL UDDI: based on directories Provide necessary functionality for interoperation Are complicated in their details Meant for tool vendors rather than programmers Increasingly hidden by tools