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Text of ESMI-032-R1

  • 1. TF-34 and Web Services Presented at ESIF-11 Task Force 34 October 26, 2004 John Sines [email_address]

2. What is a Web Service?

  • A Web Service is
  • A web service is a software application identified by a URI, whose interface and bindings are capable of being identified, described and discovered by XML artifacts and supports direct interactions with other software application using XML based messages via Internet-based protocols.
  • (World Wide Web Consortium)

3. Intent of Web Services

  • A language and platform independent method to implement Service Oriented Architecture (SOA) using standard internet technologies
  • For application-to-application communication
  • Has little to do with HTML
  • Not limited to someone adding a hook into their web site. A web service can live anywhere on the network (Inter or Intra).
  • Entities choose to use web services for ease of implementation, conciseness of the standard, and low cost

4. Examples of Web Services

  • Southwest Airlines accesses Budget Rent-a-Car to make car reservations after making airline reservations
  • Amazon allows other companies to search and purchase items via Web Services. If you are a nutritionist you can purchase nutrition books from Amazon without leaving your nutrition web site
  • There are stock-quote services, traffic-report services, and a weather services available
  • Ideal for any Service Oriented Architecture (SOA) deployment

5. What makes up a Web Service

  • All components are based on theXMLstandard
    • SOAP:Simple Object Access Protocol
    • WSDL:Web Service Description Language
    • UDDI:Universal Description, Discovery, Integration


  • SOAP is the service messaging layer of a web service. The messages are XML based.
  • The protocol consists of three parts:
  • An envelope that defines a framework for describing what is in a message and how to process it
  • A set of encoding rules for expressing instances of application-defined datatypes
  • A convention for representing remote procedure calls and responses
  • A transport or protocol binding


  • A WSDL is an XML document that describes the functional characteristics of the services offered.
  • The WSDL describes:
  • The operations the service has available
  • The messages the service will accept
  • The protocol of the service

8. Where Web Services exist in the Standards World

  • W3C
    • XML Specifications
    • WSDL Definition Specifications
    • SOAP Specifications
    • UDDI Specifications
    • Web Services Architecture and Interoperability (WS-I) Profiles
  • Maturity of Standard
    • Introduced in 2000, and gaining momentum. Many companies are in 2 ndand 3 rdgeneration deployments
    • De-facto Standard for SOA over XML
    • Who uses them?
      • Anyone who needs interoperability between applications
  • Software and Hardware industry giants such as IBM, Sun, Dell, Microsoft, Intel are behind the standard

9. Why Web Services for ESNet?

  • Can be done in a faster and cheaper manner
    • WSDL gives widely recognized definition language to define the service messages between the GWs and the CSCEs
  • Platform and Technology neutral
  • Insulates TF-34 from the intricate underlying details of defining a protocol
  • Ease of adding new services
  • ComCARE messages are being defined as web services
  • NENA 4 Generation 1 has already developed schemas for the ALI Type Lib. The schemas are 2 weeks away from final approval

10. Reliability

  • Reliability is a concern
  • Leverage existing technologies such Clustering and Load Balancing to transparently manage reliability
  • Techniques have been established to ensure that the messages get to their endpoints
  • Heartbeat mechanism can still be implemented

11. Security

  • Security concerns are the same as connection oriented architecture
  • Web Service over HTTP or HTTPS can be as secure as any website
    • SSL, Basic Auth, NTLM, Passport, custom
  • Relies on security capabilities of the transport layer
  • Security best practices are being recommended. People who specialize have put an a great amount of effort in developing the best practices documents.

12. Pros and Cons of Web services for ESNet

  • Pros
    • Faster definition and deployment. Reduced deployment cost for PSAPs, service providers, and ESMI intergrades
    • Clarity of the Standard
    • Ease of implementation with off the shelf technologies
      • Can use Microsofts .NET or Javas J2EE (IBM Web Spear, BEA Web Logic, etc.)
      • Leverage Application Server Technology
      • Leverage Load Balancer Technology
    • A number of runtime management and support tools available
    • A number of production/development tools available (many more than SIP). In the .NET development environment, development of web services is completely wizard driven
    • Allows for extensibility in protocol
    • Allows for a more scalable architecture
    • Seamless fail-over with the use of Load Balancers and Clustering- Connections are acquiesced on every call to a service
    • Leverage existing NENA XML schemas
    • Ease of integration of ComCARE work
    • Allows for easy market entryfor new data service providers
    • Affords PSAPs highest degree of flexibility for adding new services
    • Supports distributed Service Registry's which dynamically show which services are available for use

13. Pros and Cons of Web services for ESNet (Continued)

  • Pros (Contd)
    • SOA supports the creation ofSecurity Services which incorporates authentication, certification, andencryption through std.PKI and other security practices
    • Supports 'Virtual Security Gateways' which model a physical security gateway, but are more flexible to extend, consolidate, and upgrade
    • Each endpoint can be both a 'Client' and a 'Server' - this allows PSAPs to not only ask for information, but to also provide information easily
    • Web-Services can be added as extensions to existing hub-and-spoke system design toenable service-enabled applications to interoperate
    • Connectionless model only connects when datais needed - allows for messaging efficiency
    • Overall message overhead is reduced
    • Presence services can be implemented to ensure the application is available when needed (Heartbeats can still be implemented)
    • Web-based connectionsare fast - since these areno different thanany otherIP-based connection (on the order of milliseconds)
  • Cons
    • The web services standards may evolve
    • Overhead in initiating a connection
    • Matching requirements - individual customer requirements are possible but need to be carefully managed among all customers
    • Availability - no architecture is perfect - many of the same dedicated 'guaranteed' data delivery infrastructure can be leveraged to assure increased availability in a Web-Services model

14. Pros and Cons of Hub and Spoke/Connection Oriented Architecture

  • Pros
    • Few connection establishments means less overhead
    • Software exception is thrown if there is a problem with a TCP/IP socket
    • Hub-and-spoke Enterprise Integration Architecture(EAI) is the most popular of traditional EAI models - been around for a while
    • Hub-and-spoke EAI's provide physical congestion control points to the PSAPs
    • Hub-and-spoke EAI's provide physical congestion control points to the PSAPs
    • Affords CESE client a certain amount of autonomy by virtue of RG hiding rem