Based on the paper “Myths around Web Services” by Gustavo Alonso Web Services & Myths Around it Debashis Roy Deepa Saha

2 What is claimed? Web service is a natural evolution of conventional middleware necessary to meet the challenges of the Web and of B2B application integration. Author discusses the challenges and solutions that remain relevant regardless of how emerging standards and technologies evolve.

3 How the claim is proved? Web services are an accepted & dominant standard. Web services are the best way to implement conventional applications. Web services provide a direct link between middleware platforms of different corporations. Dynamic binding will be a common way of working with web services. All data will be in XML.

4 Outlook towards Web services A revolutionary technology  radical change in middleware, application integration & use of internet. An evolutionary step  An additional layer on top of existing middleware and EAI platforms.

5 Presentation layer Application logic layer Resource management layer Client Information system 1-tier architecture2-tier architecture Application logic layer Resource management layer Client Information system Presentation layer Middleware Application logic layer Resource management layer Information system Client Presentation layer server 3-tier architecture

6 From Middleware to Web Services Web Services & Myths Around it

7 Middleware Basic infrastucture behind distributed information system Interaction between applications across heterogeneous platforms Solution to integrating set of servers and applications under a common service interface

8 Distributed Systems Middleware Systems Programming Languages Databases Operating Systems Networking

9 Types of middleware RPC based systems  Transforms procedure calls to remote procedure calls  Foundation of web services middleware TP monitors  RPC system with transactional capabilities Object brokers  RPC system with object-oriented aspect Object monitor  TP monitors with object-oriented aspect Message-Oriented Middleware (MOM)  TP monitors with persistent message queuing feature Message brokers  MOM with message filtering and transforming capability

10 Enterprise Application Integration (EAI) Extends middleware capabilities to cope with application integration Uses application logic layers of different middleware systems as building blocks Integrates applications and enterprise data sources so that they can easily share business processes and data

11 Middleware EAI Middleware

12 Web Technologies Web browsers HTML, Java Web Server Middleware Server Databases Legacy Systems ….Intra-enterprise application integration Inter-enterprise application integration Web Technology

13 Web Services A way to expose the functionality of an information system and making it available through standard web technologies. “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” [W3C]

14 Web Services Architecture Web Services & Myths Around it

15 The two Facets of Web Services architecture Internal architecture  Web services expose internal operations to be invoked through the web  Receive requests through the web  Pass the requests to the underlying IT system External architecture  A middleware architecture which integrates different web services

16 Web service architecture comprises Internal and external architecture

17 Clients from other companies Basic architecture of a Web service implemented atop a tiered architecture Conventional Middleware

18 External architecture of Web services

19 A Quick Overview of Web Services Web Services & Myths Around it

20 Web Service Components Web service architecture has three components  Service requester  Service provider  Service registry Basic infrastructure is implemented with  UDDI  A name and directory server  WSDL  A way to describe services  SOAP  A way to communicate

21 Universal Description, Discovery and Integration A specification that defines  how to interact with a registry  What the entries on the registry look like Interaction with UDDI  Registration  Adding new service descriptions to the registry  Lookup  Queries to search for right services Types of UDDI registry  Public  Open search-engines for web services  Private  Created by companies for their own use

22 Web Services Definition Language Defines the interface to a web service  Types  XML schema describing used data types  Messages  Necessary to invoke an operation of the service  Operations  Reference to input/output message  Port type  Set of operations that conform an instance of a service  Binding  Actual protocol to be used to invoke the operations  Services and ports  References to actual location of service Types Message Port Type Operation Binding Service Abstract Part Concrete Part Port WSDL Specification

23 Simple Object Access Protocol A specification of a protocol wrapper Interaction between requester, provider and registry happen through SOAP Provides a standardized way to  Transform different protocols  Interaction mechanisms into XML documents SOAP Envelope SOAP header Header Block SOAP Body Body Block

24 Interaction among the Web service components Publish

25 The Myths Around Web Services Web Services & Myths Around it

26 Web services and standards Assumption  Most applications will speak and understand XML  All systems will support SOAP  Everybody will advertise their service in UDDI registries  All services will be described in WSDL Reality Standards no longer means globally unique in the B2B world.  Other competing B2B standards coexist  In manufacturing – Electronic Data Interchange (EDI)  In financial world – Society for World-wide Interbank Financial Telecommunication (SWIFT)

27 Web services and standards….(contd.) Fact  Web services are biased towards the protocols, representation and standards of their underlying middleware.  Web services add a new layer to the complex multi-tier architecture  Translation to and from XML  Tunneling of RPC through SOAP  Clients embedded in web servers  Alternative port types Problems  Addition of a new layer on top of the complex multi-tier system  Adds significant performance overhead  Developing, tuning, maintaining and evolving of multi-tier systems becomes more complex.

28 Web Services in Conventional Applications Conventional applications using web services  Flight reservations  Car rental  Hotel booking, etc. All of them are B2C but web services were created for B2B applications. There are some applications which can be implemented with web services but that might not be the best way  Applications that sends periodic bug reports  Applications that automatically download or install patches  Systems that use remote service to provide a functionality

29 Web Services in Conventional Applications…. (contd.) Problems  Web services are loosely coupled  Not suitable for atomic transactions among financial institutions  Trust  Can applications trust external web services?  Semantics  Web services cannot ensure that the remote application receives understandable data.

30 Direct Connectivity Across Corporate Boundaries Claim  Web services provide a direct link between middleware platforms of different corporations. Problem  The complexities of application integration and software design increase. Claim  Using RPC through SOAP is a gateway to interconnect the IT infrastructure of different companies. Reality  RPC results in a tight integration among the components and make them dependent on each other.

31 UDDI and Dynamic Binding Functionality  UDDI registries are web services’ catalogues for humans only.  Semantic interpretation of parameters and operations  Interaction between companies are regulated by contracts Software Engineering  Dynamic binding does not make sense for web services.  UDDI registry cannot do any load balancing nor any automatic redirection to a different URI in case of failure.

32 All Data will be in XML XML is a performance nightmare.  Some data types does not get along well with it.  In many cases application data need not to be in XML. XML can be used for linking heterogeneous systems.  If data format is decided, then XML becomes the syntax of SOAP only.

33 Conclusion This paper intends to give a coherent picture of  What web services are  What they contribute  Where they will be applied Web services are, at the current stage, only a natural evolutionary step from conventional application integration platforms.

34 Questions? …and may be… Answers Web Services & Myths Around it