CS 493/693: Distributed Systems Programming V. “Juggy” Jagannathan CSEE, West Virginia University February 07, 2005

Chapter 5: Web Services* Web Services: Concepts, Architectures and Applications G. Alonso et. al. Springer Verlag * Pictures and graphics in this presentation were provided by the authors of the book shown above.

Defining Web Services By the UDDI consortium: “self-contained, modular business applications that have open, Internet-oriented, standards-based interfaces.” By W3C: “a software application identified by a URI, whose interfaces and bindings are capable of being defined, described, and discovered as XML artifacts. A web service supports direct interactions with other software agents using XML-based messages exchanged via Internet-based protocols.” Webopedia definition: “a standardized way of integrating Web-based applications using the XML, SOPA, WSDL, and UDDI open standards over an Internet-protocol backbone. XML is used to tag the data, SOAP is used to transfer the data, WSDL is used to describe the services available, and UDDI is used for listing what services are available” More specifically: It is NOT an URL with a CGI script behind it to take in arguments and return a web page as a result – though some have characterized such a system as providing a web-based service, hence a web service.

Motivating the Need for B2B Integration Example problem  Supply chain automation – integration of multiple, independent, heterogeneous systems spanning multiple business entities

web server internal infrastructure suppliercustomer warehouse web server internal infrastructure internal procurement requests B2B interactions occur by accessing Web pages, filling Web forms, or via . Copyright Springer Verlag Berlin Heidelberg 2004 Figure 5.1.

Limitations of Conventional Middleware in B2B Integration In cross-organizational interactions, middleware has to be under the control of one of the interacting organization This is not practical in real world. No one company will agree to such a scheme. Figure 5.2

internal infrastructure supplier customer warehouse internal infrastructure internal procurement requests message broker WfMS adapter WfMS a “global” workflow is executed here the combination of message broker and adapters enables interoperability third party customer’s adapters warehouse’s adapters supplier’s adapters Copyright Springer Verlag Berlin Heidelberg 2004 Figure 5.2.

internal infrastructure supplier customer internal infrastructure customer’s adapters supplier’s adapters message broker XYZ message broker XYZ Copyright Springer Verlag Berlin Heidelberg 2004 Point-to-point integration across companies Figure 5.3.

internal infrastructure supplier warehouse middleware for supplier-customer interaction middleware for supplier-warehouse interaction middleware for supplier-XYZ interaction middleware for integrating the middleware customer another party (XYZ) yet another party (ABC) middleware for supplier-ABC interaction supplier’s adapters Copyright Springer Verlag Berlin Heidelberg 2004 Result of an absence of standardized middleware platform Figure 5.4.

Problems with conventional middleware to address cross-organizational integration In Enterprise Application Integration interactions are typically short lived – not true for cross-organizational interactions Interactions in cross-organization integration typically handled as asynchronous transactions 2 Phase commit protocols are not that useful Trust relationships become problematic

B2B integration before web services Point-to-point integration – costly due to numerous conflicting approaches (.NET, CORBA, EJB etc) EDIFACT and messaging standards WALMART was successful in implementing supply-chain inventory order system – WALMART can justify expensive systems. One-of systems, hard to implement and costly to implement  “The gap between what web provides (HTTP, XML) and what application integration requires that Web services are trying to fill.” pg. 131, Web Services book.

B2B Integration with Web Services Contributions of web services  Service-oriented architectures Addressing loosely-coupled peer-to-peer systems  Redesign of middleware protocols to support decentralized execution and multiple trust domains  Standardization

internal infrastructure supplier customer warehouse internal infrastructure internal procurement requests internal functionality made available as a service Web service interactions based on protocols redesigned for peer to peer and B2B settings languages and protocols standardized, eliminating need for many different middleware infrastructures (need only the Web services middleware) Copyright Springer Verlag Berlin Heidelberg 2004 Figure 5.5.

internal service middleware client internal service Web service Company A (provider) wide area network (Internet) internal service middleware internal service Company B (client) Copyright Springer Verlag Berlin Heidelberg 2004 Web Services and EAI Figure 5.6.

DBMS applications Web service-enabled broker sendmail application SmartQuotation SmartForecasting XYZ integrating application (contains the composition logic) assumes all back-end systems are accessible as Web services Company A (or a LAN within Company A) Copyright Springer Verlag Berlin Heidelberg 2004 Figure 5.7. Web services to integrate intra-enterprise applications

properties and semantics interfaces common base language vertical standards business protocols directories Copyright Springer Verlag Berlin Heidelberg 2004 Web service description Figure 5.8. XML WSDL WSCL, BPEL UDDI E.g. RosettaNet UDDI

middleware properties (horizontal protocols) protocol infrastructure (meta-protocols) basic and secure messaging transport Copyright Springer Verlag Berlin Heidelberg 2004 Figure 5.9. Service Interactions HTTP SOAP & WS-Security WS-Coordination WS-Transaction

Web Services composition A service that is implemented using local system resources is called “basic web service” A service that relies on other web services is labeled “composite web service.” Whether a web service is composite or basis is simply an implementation issue transparent to the “client” or “user” of the service Business Process Execution Language is one of the standards being used for composing web services.

internal service Company A (provider) Web service interface Access to internal systems internal architecture Web service client Company D (client) Web service external architectur e Company B (provider) Company C (provider) middleware Copyright Springer Verlag Berlin Heidelberg 2004 Figure Two facets of Web Services Architectures

resource manager middleware service interface integration logic resource manager middleware service interface integration logic middleware service interface integration logic other tiers Copyright Springer Verlag Berlin Heidelberg 2004 Figure Conventional Middleware Tiers

Web service interface access to internal systems conventional middleware (includes middleware services) service interface integration logic other tiers Company A (service provider) clients from other companies Conventional middleware provides lots of services (load balancing, transaction support, etc). Current Web services middleware is quite poor in this respect. Web services middleware (internal) Copyright Springer Verlag Berlin Heidelberg 2004 Figure Internal Architecture: Web services layered on top of middleware

Web service client Company A (service requester) other tiers Web service other tiers Company B (service provider) Company C (directory service provider) service descriptions 1. publish the service description 2. find 3. interact the abstraction and infrastructure provided by the registry are part of the external middleware Web services middleware (internal) Copyright Springer Verlag Berlin Heidelberg 2004 Figure External Architecture of Web Services

Web service client other tiers Web service other tiers Company A (service requester) Company B (service provider) internal middleware transaction mgmt internal middleware Company C (directory service provider) service descriptions composition engine other protocol infrastructure transaction mgmt composition engine other protocol infrastructure external middleware Copyright Springer Verlag Berlin Heidelberg 2004 Figure Web Service Architecture augmented by Peer-to-Peer protocol extensions