1. Overview of Web Services and Service Oriented Architecture (SOA)
Vijayan Sugumaran
School of Business Administration
Oakland University
Rochester, MI 48309

2. Background Build a distributed computing platform for the Web
Applications are encapsulated, loosely coupled Web “components” that can bind dynamically to each other
Easily find these components and integrate them to meet specific requirements
Plug-and-Play
Buy and integrate code into your system
Subscribe to necessary services

3. What are Web Services? New breed of Web application
Self-contained, self-describing, modular applications that can be published, located, and invoked across the Web
Perform functions, which can be anything from simple requests to complicated business processes
Once a Web service is deployed, other applications (and other Web services) can discover and invoke the deployed service

4. Web Services Promise
Web Services connect computers and devices with each other using the Internet to exchange data and combine data in new ways.
The key to Web Services is on-the-fly software creation through the use of loosely coupled, reusable software components.
Software can be delivered and paid for as streams of services as opposed to packaged products.
Business services can be completely decentralized and distributed over the Internet.
The dynamic enterprise and dynamic value chains become achievable and may be even mandatory.

5. Attributes of Web-Services
Web-based Protocols : Web-services based on HTTP are designed to work over the public internet. The use of HTTP for transport means these protocols can traverse firewalls, and can work in a heterogeneous environment.
Interoperability : SOAP defines a common standard that allows differing systems to interoperate. E.g., the tooling allows Visual Basic clients to access Java server components and vice versa.
XML-based : The Extensible Markup Language is a standard framework for creating machine-readable documents.
Fremantle et al. 2002, Enterprise Services, CACM. Oct

6. Web Services Technologies
Web Services technology and underlying standards are being rapidly developed
Introduction of ebXML for Web Service has generated lot of interest in the B2B market.
To provide services, the interface of the service should be described with a standard language.
The contents of services should be registered with a registry, shared on the Web.
A service repository is a distributed directory of services and has functions for searching and registering.

7. Web Services Technologies (continued)
In the service registry, information about service’s location and usage are included.
A particular user could use one or more of the services at run time to accomplish a particular task.
Standards are needed to perform the integration function

8. Designing Web Services
Enable universal interoperability
Enable (Internet scale) dynamic binding
Support service oriented architecture (SOA)
Efficiently support both open (Web) and more constrained environments
Based on standards. Pervasive support is critical
Minimal amount of required infrastructure should be assumed
Very low level application integration expected

9. Web Services Standards
UDDI provides a mechanism for clients to find web services. A UDDI registry is similar to a CORBA trader, or it can be thought of as a DNS service for business applications.
WSDL defines services as collections of network endpoints or ports. A port is defined by associating a network address with a binding; a collection of ports define a service.
SOAP is a message layout specification that defines a uniform way of passing XML-encoded data. In also defines a way to bind to HTTP as the underlying communication protocol. SOAP is basically a technology to allow for “RPC over the web”.

10. Web services technology stack
Collection of Web Services standards has been put together and categorized into different levels depending upon their function
Divided into four levels: protocol, description, interaction and security
Helps us to understand the purpose of the standards and their underlying assumptions that might be required
Example: interaction level (CS-WS) presupposes process description level (BPEL4WS), and focuses on exchange of messages based on the order of sequence described in the process description level

11. Web Services Stack (Turner et al., 2003)

12. Web Services: How They Work?
SOAP Messages
Requestor
(http transport)
SOAP Client
Web Service Provider
Components required
Software which needs to be exposed as a Web service
A SOAP Server (Apache Axis, SOAP::Lite, etc.)
HTTP Server (if HTTP is used as the transport level protocol)
SOAP Client (Apache Axis, SOAP::Lite etc.)
From S. Chandrasekaran’s Talk

13. Simple Web Service Invocation
Service Requestor
Remote
Web Service
Repository
(Web Sites) 2
Manual
Web Service
Lookup
HTTP GET 3
WSDL File
Write
Client Code 1
Remote
Web service 4
SOAP Request
Invoke Web
Service
Publish Web
Service 5
SOAP Response
WSDL - Web Service Description
SOAP - Web Service Message Protocol
From S. Chandrasekaran’s Talk

14. Web Service Description
Why describe Web services?
A service requestor needs to analyze a service for his requirements
A Web service needs to provide the following information
the operations it supports
the transport and messaging protocols on which it supports those operations
the network endpoint of the Web service
Languages such as WSDL, DAML-S, RDF can be used for describing Web services
WSDL – describes the syntactic information of a service
DAML-S and RDF – describe the syntactic as well as the semantic information
From S. Chandrasekaran’s Talk

15. SOAP-Simple Object Access Protocol
Simple lightweight protocol for exchanging XML data over the Web
Envelop for transmitting messages, guidelines for encoding data, rules for representing remote procedure calls (RPCs)
SOAP message structure – an XML element with two child elements
Header – security, routing, proper handling of message
Body – actual message to be transmitted
Also defines a model that dictates how recipients should process SOAP messages
The message model also includes actors, which indicates who should process the message

16. Web Service Message Protocol - SOAP
SOAP is an XML Messaging Protocol
that allows software running on disparate operating systems, running in different environments to
make Remote Procedure Calls (RPC).
Header
Body

17. WSDL – Web Services Description Language
Describes the programmatic interface of a web service – similar to IDL
Two parts of WSDL description:
Application-level (abstract interface)
Vocabulary, Message, and Interaction
data type definitions, operations supported by the service, input/output message formats
Specific protocol-dependent details
network address, protocol bindings, etc.
what communication protocol to use
how to accomplish individual service interactions
where to terminate communication
A port element describes a single end point as a combination of a binding and a network address
A service element groups a set of related ports

18. Web Service Description (WSDL)
Abstract
Description
Concrete
Description
From S. Chandrasekaran’s Talk

19. UDDI – Universal Description, Discovery, and Integration
Mechanism to register and locate web services
Interaction with UDDI accomplished via a set of pre-defined SOAP interfaces
Web services register two types of information within UDDI:
tModel (technical model)
Abstract service protocols that describe a particular web service’s behavior
businessEntity
Describes the service implementation
Refers to multiple tModels and provides descriptions about the behavior of the collection of tModels

20. UDDI (Universal Description, Discovery and Integration)
UDDI serves as a “Business and services” registry and are essential for dynamic usage of Web services
UDDI APIs
Publication API - Authenticated set of operations that allow organizations to publish businesses, services, service type specifications
Inquiry API - Non authenticated public set of operations that allows users to extract information out of the UDDI registry.
From S. Chandrasekaran’s Talk

21. From S. Chandrasekaran’s Talk
UDDI
UDDI classifies businesses and services according to standard taxonomies
Why Classification ?
Searches based on keywords alone, could return a large set of hits for a particular search
Classification of services and businesses allows to perform better searches
Registry Data
White Pages
Yellow Pages
Green Pages
ServiceType Registrations
From S. Chandrasekaran’s Talk

22. From S. Chandrasekaran’s Talk
UDDI
White Pages
contains business name, text description, contact info and other related info.
Yellow Pages
contains classification information about the business entity and types of the services the entity offers.
e.g. a business entity could have itself classified as a sports equipment manufacturer and also as a skateboard manufacturer.
Green Pages
contains information about how to invoke the offered services.
If a business entity were to offer its catalog online, its Green
pages entry would have a reference to its catalog URL
From S. Chandrasekaran’s Talk

23. From S. Chandrasekaran’s Talk
UDDI
Service Types
Reusable, abstract definitions of services ( ~ abstract part of WSDL)
that are defined by industry groups and standard bodies.
These reusable abstractions are referred to as “Technology Models”
The UDDI data structure corresponding to this is called “TModels”
TModels
Any abstract concept can be registered within UDDI as a TModel.
e.g. If you define a new WSDL port type, you can define a TModel that represents the port type within the UDDI
From S. Chandrasekaran’s Talk

24. Business Registrations
How UDDI Works ?
Marketplaces, search engines, and business apps query the registry to discover services at other companies 4. 1.
SW companies, standards bodies, and programmers populate the registry with
descriptions of different types of services
Business Registrations
Businesses populate the registry with
descriptions of the services they support 2.
UDDI Business Registry
Business uses this data to facilitate easier integration with each other over the Web 5.
Service Type
Registrations 3.
UBR assigns a programmatically unique identifier to each service and business registration
Source :

25. Service Oriented Architecture and Related Challenges

26. Current Business Trends
How can, new value be created by leveraging existing technology investments?
How can technology help reconfigure operational processes and improve flexibility through business process outsourcing?
How can companies move from one-channel, single business unit solutions to cross-enterprise, multi-channel solutions?
How can the inside-out process perspective (customer management, supply chain) be balanced with an outside-in services view

27. Service Oriented Architecture (SOA)
SOA - structure of the system
Includes software components, externally visible properties of those components, relationships among them, and constraints on their use
The underlying foundation for designing and developing SOA is the emerging field of Web Services
Enables different software components to be integrated without having to develop these components from scratch - no hassle of custom coding

28. Services Aspect of Web-Services
Modular : Service Components are useful in themselves, reusable, and it is possible to compose them into larger components.
Available : Services are available to systems that wish to use them. Services must be exposed outside of the particular paradigm or system they are available in.
Described : Services have a machine-readable description that can be used to identify the interface of the service, and its location and access information.
Implementation-independent : The service interface must be available in a way that is independent of the ultimate implementation.
Published : Service descriptions are made available in a repository where users can find the service and use the description to access the service.
Fremantle et al. 2002, Enterprise Services , CACM. Oct

29. Putting it Together Web Services (SOAP, UDDI, WSDL)
Data exchange between two programs in XML format
Operate on syntactic level : Web services infrastructure do not access data content.
Web Service
Requestor
UDDI
repository
Provider
Invoke
through
SOAP
Discover
or access
WSDL
Register

30. Web Services Invocation
Invocation Model
One way invocation
Request/Reply invocation
Solicit/Response invocation
Invoked Entity (Service Provider)
Publishes WSDL operation with input and output message
Invoker (Service Requester) : No concept
Especially not a “subroutine” call a la RPC with appropriate stack operations or stub generation

31. WS-Based Development Standards organizations Three stakeholders
Wide Web Consortium (W3C)
Organization for the Advancement of Structured Information Systems (OASIS)
Web Services Industry body (WS-I)
Microsoft, IBM, BEA, Sun Micro Systems, SAP, Oracle and Hewlett-Packard
Three stakeholders
service provider
service consumer
Web Services Standards Organizations
Several challenges exist in integrating Web Services into E-commerce applications

32. WS Based Application Development Issues
Identifying and analyzing the challenges that exist for each of these stakeholders
Presents a framework that organizes and inter-relates the challenges in an easily understandable manner
The framework is intended to help both the service consumers and providers in improving their expectations and quality regarding Web Services

33. Concerns with SOA-based Application Development
Automate individual applications based on cross-organizational, heterogeneous software components
Coordination of a set of Web Services working toward a common goal
Web services performance needs to be optimized
Quality of service parameters as well as service level agreements
Monitoring and controlling of Web Services

34. Standards Organizations
Stakeholders
WS Providers
WS Consumers WS
Integrators
&
Publishers
Web
Service
Vendors
Application
Assemblers
End
Users
Standards Organizations
W3C
OASIS
WS-I
Others

35. Challenges in WS Integration
Important issues with adoption of web services
insufficient standardization
low acceptance of service consumers
critical mass of available useful services
Need a framework for studying web services adoption
technical and non-technical issues associated with web services deployment
These two dimensions have to be investigated for all the major stakeholders
web service providers, web service consumers, and standards organizations

36. Web Services Providers
Identifying new web services requirements, design, implementation, testing, eliciting customer feedback
Web services development strategy, architecture standards, and design requirements
Service provider specific processes such as metering, accounting, and billing
Service delivery overhead
Coordination function is critical because business transactions usually follow a contractually defined, fixed pattern

37. Web Service Providers (contd.)
Support for versioning management
Quality of Service (QoS) policy
Service Level Agreements (SLAs), legally binding contracts that establish bounds on various QoS metrics
Unpredictable workloads and high peak-to-average ratios in workload intensity
Implementing priority-based admission control mechanisms

38. Web Service Consumers Application Assemblers and End Users
Difficulty in identifying relevant web services and integrating them to generate a cohesive application
Manually search for web services, typically by completing a web form to search a repository
Dealing with web services that evolve over time
For discontinued services application should automatically search for the next best fit and seamlessly integrate it

39. Web Service Consumers Service Integrators face a number of issues:
Efficiency - web services execution must be very efficient
Expressiveness - B2B interactions are complex, requires expressive set of supported integration concepts
Security - interactions must be secured to prevent attacks of all types, and non-repudiation must be provided for reliable record keeping
Reliability - remote and distributed communication must be reliable, and messages must be sent exactly once to ensure dependable interactions
Manageability - inter-enterprise communication changes frequently, requiring easily manageable technology

40. WS Standards Organizations
Business process dynamics and nonfunctional properties of service-enabled processes are poorly addressed
Current standards do not put forth a methodology to assist designers in building web services on top of legacy assets
Specifications to support creating robust service compositions
Standards-based definition of an interoperability communication protocol

41. WS Standards Organizations
Mechanisms for service description, discovery, and composition and a basic set of quality of service protocols
Design guidelines, including:
large granularity of messages
asynchronous messaging,
bi-directionality of services,
endpoint discovery, service agents,
request pipeline
context and content-based routing

42. Overall Challenges Framework
Web Services
Suppliers
Web Services
Consumers
Web Services
Registry
Web Services
Standards Organizations

43. Web Services Supplier Technical Challenges
Service description and profile
WS accessibility, and documentation
Architecture standards & infrastructure
Design Requirements
Web services evolution
Managerial Challenges
Pricing & Quality of Service commitments
Identifying new services
Customer feedback and support
Partnerships with third party providers
Demand management and Liability

44. Web Services Consumer Technical Challenges
Search and identification of relevant WS
Customization and integration
Validation and testing
Technology, domain & task characteristics
Tools, infrastructure and metrics
Managerial Challenges
WS utilization strategy
Promoting WS, training and education
Resource allocation and support
Incentives and rewards
Partnership management and Security

45. WS Standards Organizations
Technical Challenges
Service description, publishing & invocation
WS technology stack components
Modeling web services
Architectures for WS applications
Specifications for all aspects of WS
Managerial Challenges
Future directions for WS research & practice
WS implementation guidelines
Vendor cooperation for common standards
Open standards and interoperability
Consistency between standards

46. Summary
Mass market for web services are slow to materialize and businesses are slow to adopt web services technology
Web services based development warrants a shift in paradigm, and managers are ill equipped to assess the advantages and disadvantages
Myriad of challenges faced in adopting web services haven’t been thoroughly explored
Challenges framework for studying the adoption and diffusion of web services from the stakeholders’ perspective
Managerial challenges have to be investigated using relationships between web service producers and consumers