Middleware and CORBA LFTSP 19992000 IS 6'22

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Middleware and CORBALFTSP 1999/2000 IS 6.2(2)

• Major Greg Phillips
• Royal Military College of Canada
• Electrical and Computer Engineering
• greg.phillips_at_rmc.ca
• 01-613-541-6000 ext. 6190

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Middleware

• Middleware is software that allows elements of
  applications to interoperate across network
  links, despite differences in underlying
  communications protocols, system architectures,
  operating systems, databases, and other
  application services.

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Communications Services

• describe interactions between application
  components
• formats and protocols structure of the message,
  including syntax
• protocol services marshalling and unmarshalling
  messages, platform data-format translations,
  message compression, etc
• control services support one or more
  communications models

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• COMMUNICATIONS NETWORK-DEPENDENT
  NETWORK-INDEPENDENT
• MODELS EXAMPLES
  EXAMPLES
• Datagram
• Single outbound Network device
  Paging system
• message status notification
• One-shot
• Single outbound Network-based
  File transfer
• message single calculation server
• response
• Query
• Single outbound LAN-based database
  Web search
• message chained query
• responses
• Asymmetric
• Multiple outbound Customer-service
  Web-based publishing

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Application Models

• Store-and-forward/publish-and-subscribe. Directs
  message to recipient either by pushing data out
  (store-and-forward and publish) or by pulling it
  in (subscribe).
• Work flow. Directs message to recipient according
  to either conditions or policies.
• Distributed transactions. Manages simultaneous
  updates to multiple databases under transaction
  control.
• Remote file access. Redirects file requests
  across a network.
• Remote database access. Transmits SQL requests
  across network to servers.

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Application Models (II)

• Distributed object interaction. Supports
  messaging between objects across a network.
• Access to remote functions. Redirects program
  call to a function across a network.
• Distributed database management. Maintains a
  single local database across multiple physical
  databases.
• Database replication. Synchronises copies of a
  single database.
• Distribution of display. Makes presentation
  functions of an application available to a remote
  client.

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Reference Model Architecture
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Requests
Client
Object Implementation
IDL stub
IDL skeleton
Request
Object Request Broker
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Producing Code
IDL
Language independent
Vendor As IDL Compiler
Language dependent
Object Implementation code
Stub code
Skeleton code
Client code
Programming Language Compiler, Linker
Client
Object Implementation
Machine dependent
IDL stub
IDL skeleton
Vendor As ORB
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ORB Architecture
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CORBAservices

• Event Notification
• Persistence
• Lifecycles
• Naming
• Concurrency Control
• Relationships
• Transactions
• Collections

• Externalization
• Time
• Security
• Query Service
• Licensing
• Trading
• Change Management
• Properties

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Lifecycle Services

• create create a new instance of a given object
  typerequires the existence of a factory object
• delete delete an instance
• move move an instance from one location
  (computer) to another
• copy duplicate an object
• The object programmer is required to correctly
  implement these operations for any object
  connected to an ORB

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Middleware and CORBALFTSP 1990/2000 IS 6.2(2)

• Major Greg Phillips
• Royal Military College of Canada
• Electrical and Computer Engineering
• greg.phillips_at_rmc.ca
• 01-613-541-6000 ext. 6190