'NET Web Services and CORBA A Conflict of Interests

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.NET Web Services and CORBAA Conflict of
Interests?

• Chris Lafikes

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Presentation Overview

• Distributed Applications Overview
• CORBA Architecture
• CORBA Example (Air Traffic Control System)
• Web Services Architecture
• Web Services Example
• Comparison
• Conclusion
• Web Service Tech Demo
• Questions

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Distributed Architecture Overview

• What is a Distributed System?
• A collection of independent computers that
  appears to its users as a single
• coherent system.
• Why use a distributed system?
• Save development cost by integrating (not
  redesigning) legacy components.
• Some tasks more suited to certain platforms

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Distributed Architecture Overview

• Non-Function Requirement
• Scalability - Ability of a system to accommodate
  growth.
• Measurement How well your system performs as
  the system load becomes larger.
• Quality of Service (QOS)

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Distributed Architecture Overview

• Non-Function Requirement
• Openness - How easy it is to extend or modify
  the system.
• Measurement Well defined set of interfaces that
  are vendor independent.

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Distributed Architecture Overview

• Non-Function Requirement
• Heterogeneity - Ability of the system to
  accommodate for variety in its component
  structure.
• Development Language
• Operating System
• Hardware Platform
• Network
• Example .NET Architecture.

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Distributed Architecture Overview

• Transparency - Ability to hide the distribution
  of the system from the user.

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Distributed Architecture Overview

• Transparency
• Access Hide how a resource is being accessed.
• Location Hide were a resource
• is located.

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Distributed Architecture Overview

• Non-Functional Attributes Summary

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CORBA Architecture

• CORBA (Common Object Request Broker Architecture)
  
• Set of standards defined by the OMG (Object
  Management Group)
• Middleware Layer for Distributed Objects
• Open, vendor-independent architecture
• Tightly Coupled Client/Server

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CORBA Architecture

• ORB (Object Request Broker) - Facilitates
  communication between the requestor (client) and
  the object implementation (server).
• Marshal and unmarshal the request and response
  data
• Distributes and Resolves Object References
• Provide Network Services.
• Result Location and Access Transparency

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CORBA Architecture
Standard ORB Provided Services
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CORBA Architecture

• IDL (Interface Definition Language)
• Language Independent Contract
• Used to create client and server stubs
• Stubs Proxies that hide the network details
  from the client
• Result Platform and Language Independence

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CORBA Architecture
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CORBA Architecture

• Communication between ORBs
• GIOP - General Inter-ORB Protocol
• IIOP - Internet Inter-ORB Protocol

Result Distributed System Across Multiple
Network Segments
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CORBA Architecture

• CORBA Advantages
• Object-Oriented
• Location/Access Transparency
• Language Independence
• Hardware Independence
• OS Independence
• Rich Set of Services

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CORBA Architecture

• CORBA Disadvantages
• Loosely Defined Standards
• Poor ORB interoperability
• Proprietary Extensions
• Firewall Traversal
• Thick Clients

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CORBA Example

• Air Traffic Control System
• Number of Legacy Components
• High Availability Requirement (2.6 minutes
  downtime per year)
• Soft Real Time Scheduling
• Multiple delivery mechanisms(P2P, Multicast,
  Events, Request/Response)

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CORBA Example

• Mission Critical Requirements
• Replication
• Consistency
• Availability

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CORBA Example

• Air Traffic Control Communication
• Events Updated Flight Plans
• Reliable Multicast - Aircraft Status
• Un-Relable Mutlicast Real Time Radar Data
• Point to Point Command and Control

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CORBA Example
ATC System Diagram
Data Logging and Analysis
Data Generators
Controllers and Viewers
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CORBA Example
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CORBA Example

• Evolutionary Design Slow upgrade
• Interface packages
• Flight Plan
• Sub-System Tracking
• Sector Plans

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CORBA Example

• Integration Issues
• Required Services not Defined
• Availability Management
• Data Replication
• No Real Time Scheduling Standard.
• Proprietary Vendor Solution Used
• ORB Portability

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Web Services Architecture

• XML Based
• Message Passing Service
• Standard IT Protocols
• Loosely-Coupled

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Web Services Architecture
Find Service
Describe Service
Package Data, Provide Common Typing System
Data encoded as XML
Sends XML Messages
Web Services Protocol Stack
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Web Services Architecture

• XML Extensible Markup Language
• Similar to HTML but with user defined tags and
  attributes

Attribute
Element
Namespace
Sample XML Document
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Web Services Architecture

• XML Advantage
• Easy To Parse
• Readability Debugging
• Industry Standard
• XML Disadvantages
• Readability Security Risk
• Size

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Web Services Architecture

• XML Schema - XML document used to describe the
  data types an a XML document.

Data Type
Variable Name
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Web Services Architecture

• XML Schema Advantages
• Parser Reusability
• Data Abstraction
• Language Independent
• Layered Architecture

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Web Services Example

• SOAP Simple Object Access Protocol
• Message Enveloping Protocol used to send and
  Receive XML documents.
• Interoperability - Cross-Platform Data Types
• Defined through a XML Schema

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Web Services Architecture

• XML Soap Document Structure.
• Envelope Mandatory root element that packages
  the message.
• Header Extra supplemental information such as
  Authentication and Routing.
• Body Mandatory element containing the data to
  be sent and decoded.

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Web Services Architecture
Example Soap Document
XML Encoding
Envelope
Header
Body
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Web Services Architecture

• Soap Fault Contains details related to errors
  in the processing and sending.
• Router didnt understand header info.
• Error occurred at service while processing data

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Web Services Architecture

• Soap Advantages
• Web Standard Protocol
• Designed for Simplicity
• Soap Disadvantages
• No Advanced Features
• Standard is a bit broad.

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Web Services Architecture

• WSDL Web service Description Language
• Describes how to use a Service in Term of
• Endpoint Information
• Messages
• Operations
• Data Types
• Transport
• Used to Create Proxy Files

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Web Services Architecture

• WSDL Key Elements
• Types
• Messages
• PortType
• Binding
• Service Elements

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Web Services Architecture

• WSDL Types
• Describes the Data Types used by the Service

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Web Services Architecture

• WSDL Messages
• Describes the Messages Used by the Service

Defined in the Types Section
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Web Services Architecture

• WSDL Port Type
• List of Operations and their Supported Types

Defined in the Messages Section
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Web Services Architecture

• WSDL Binding
• Defines Transport Protocol and Message
  Definitions.

Messages will use SOAP as the Transport Protocol
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Web Services Architecture

• WSDL Service
• Defines endpoint for the Service

Service Endpoint Location
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Web Services Architecture

• WSDL Advantages
• Very Flexible Layered Approach
• Descriptive
• Disadvantages
• Complex Hard to read and write.

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Web Services Architecture

• UDDI Universal Description, Discovery, and
  Integration.
• Global Registry to Publish Web Services
• Search through Web Browser or API
• Replicated
• Web Link
• http//test.uddi.microsoft.com

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Web Services Architecture

• UDDI
• Three Main Structures
• businessEntity
• businessService
• TModel

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Web Services Architecture

• UDDI businessEntity
• Hold Information Related to your business
• Physical Address
• E-mail
• Phone Number

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Web Services Architecture

• UDDI businessService
• Information about the Services Provided
• Service Name
• GUID
• Service Description
• Access Point (URL)

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Web Services Architecture

• UDDI tModel (Type Model)
• A classification for the Service
• Name
• Description
• Classification
• WSDL Document

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Web Services Architecture

• UDDI Advantages
• Global Federated Directory
• Search Features (API or Browser)
• Disadvantages
• Structurally Complicated
• Not really used.

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Web Services Example

• Johnson Controls Metasys Building Management
  System.
• Automate Building Systems and Management
• Gathers historical Data

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Web Services Example

• Supervisory Controller Used to Monitor and
  Control subsystems
• Ventilation
• Air Conditioning
• Lighting
• Fire Safety

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Web Services Example

• Requirement
• Make the system easy for the customer to extent.
• Provide an easy interface for outside Vendor
  Integration.
• Improve User Interface

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Web Services Example

• Decision Use Web Services Interface.
• Result
• Standardized interface through HTTP, XML, and
  SOAP
• Remote Web Interfaces
• Easy Debugging though Visual Studio
• 18 Month Rollout

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Comparison
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Conclusion

• CORBA Object Oriented framework that provided
  complex Services.
• Trade-Off Interoperability, Openness, Firewall
  Traversal.
• Web Services XML Message Passing System based
  on proven Internet Standards.
• Trade-Off No Service Support, Immature
  Standards, Performance.

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Conclusion
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Web Services Demo

• Local Adding/Dividing Service (Consumer and
  Service)
• Amazon.com Web Service Client (Consumer)

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Questions?