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					       Types of Middleware

• Remote procedure calls
• Message-oriented middleware
• Distributed objects
• Database-oriented middleware
• Transaction-oriented middleware
• Message brokers

 Message Oriented Middleware
• Message-Oriented Middleware (MOM) was
created to address some of the shortcomings of
RPCs (RMI) through the use of messaging.
• Like RPCs, MOM provides a standard API
across hardware, operating system platforms,
and networks.
• MOM is also able to guarantee that messages
will reach their destination, even when the
destination is not available (asynchronous

 Message-Oriented Middleware (2)
• The asynchronous model allows the application
to continue processing after making a
middleware service request. The message is
dispatched to queue manager, which makes
sure that the message is delivered to its final
• This asynchronous paradigm is much more
convenient for developers and users because it
does not block the application form processing
although the model is more complex.

 Message-Oriented Middleware (3)
• There are two models supported by the MOM:
   – point-to-point (both systems must be active)
   – message queuing (MQ, one end has to be active)
• MQ has several performance advantages over
the traditional RPCs
   – each participating program proceeds on its own pace
   without interruption from the middleware layer
   – a program can publish the same the same message to
   many remote programs without waiting the programs to
   be up and running
   – the queue manager can optimize the performance
   through priorization, load balancing, and thread pooling

Message-Oriented Middleware (4)
          Message Brokers
• A message broker is a software system based
on asynchronous, store-and-forward messaging.
• It manages interactions between applications
and other information resources, utilizing
abstraction techniques.
• Simple operation: an application puts (publishes)
a message to the broker, another application
gets (subscribes to) the message. The
applications do not need to be session
        (Message Brokers, MQ)
• MQ is fairly fault tolerant in the cases of
network or system failure.
• Most MQ software lets the message be declared
as persistent or stored to disk during a commit at
certain intervals. This allows for recovery on
such situations.
• Each MQ product implements the notion of
messaging in its own way.
• Widely used commercial examples include IBM’s
MQSeries and Microsoft’s MSMQ.

              Message Brokers
• Any-to-any
The ability to connect diverse applications and other
information resources
– The consistency of the approach
– Common look-and-feel of all connected resources
• Many-to-many
– Once a resource is connected and publishing
information, the information is easily reusable by any
other application that requires it.

   Standard Features of Message
• Message transformation engines
  – Allow the message broker to alter the way
  information is presented for each application.
• Intelligent routing capabilities
  – Ability to identify a message, and an ability to
  route them to appropriate location.
• Rules processing capabilities
– Ability to apply rules to the transformation and
  routing of information.

  Services provided by Message
  Brokers (or Integration servers)
• (A) Message transformation
• (B) Rules processing
• (C) Intelligent routing
• (D) Message warehousing and flow control
• (E) Repository services
• (F) Directory services
• (G) Management
• (H) APIs and adapters
(A) Message Transformation Layer
• The message transformation layer understands
the format of all messages being passed among
the applications and transforms those messages
while they move.
• It provides a common dictionary that contains
information on how each application
communicates outside itself, as well as which
pieces of information have meaning to which

Message Transformation Layer (2)
• Generally contain parsing and pattern-matching
   methods that describe the structure of any
   message format.
• Message formats are then constructed from
   pieces that represent each field encapsulated
   within a message.
• Once the message has been broken down to its
   components parts, the fields may be recombined
   to create a new message.
• Two kinds of transformations: schema
   conversions and data conversions.

Schema and Data Conversions
 •A schema conversion is the process of changing
    the structure of a message, and thus re-mapping
    the schema, so that it is acceptable for the target
 • In other words, general re-mapping of data
 •A data conversion is the process of determining
    the data format of source and target
    applications, assessing the differences between
 • That is, changes within an individual data field.

         (B) Rules Processing
• The rules processing engine provides the ability
   to create rules to control the processing and
   distribution of messages.
• It is an application development environment
   supported by the message broker to address the
   special requirements of integrating applications.
• By using rules engine, it becomes possible to
   implement intelligent message routing and
• The logic for sharing information.

                 The Rules
• Most often, rules engines use traditional Boolean
   logic (IF, ELSE, and OR) with an higher level
   language to associate the rule with appropriate
• Generally relies on scripting languages rather
   than more complex programming languages.
• The implementation of the rules generation
   varies from entering commands to the broker to
   Wizard-assisted management of rules

         (C) Intelligent Routing
• A message broker can identify a message
   coming from the source application and route it
   to the proper target application, transforming it if
• Builds on the capabilities of both the rules layer
   and the message transformation layer.
• This happens virtually instantaneously, with as
   many as a thousand of these operations

   (D) Message Warehousing
• A message warehouse is a database that,
  as an option, is able to store messages
  that flow through the message broker.
• This feature is provided for
  – Message mining
  – Message integrity
  – Message archiving
  Message Mining and Integrity
• Data mining
– Allows extraction of business data to support decision
– For example, the amount and characteristics of new
   customer information processed through the broker
– Rules can be applied to alter the messages prior the
   storing, e.g., for the data to make sense to business
• Message integrity
– A persistent buffer or queue for messages on the event of
   system failures (or for other reasons)
– The messages may be resent or compared with other
   warehouses on the network to insure integrity

Message Archiving and Auditing
• Message archiving
  – Ability to store months (or more) of message
  – For auditing or other purposes
• Auditing
  – Using the warehouse to determine the health
  of the EAI solution
  – One can monitor message traffic loads,
  message content variations, the number of
  messages requiring transformation, etc.
         (E) Repository Services
• A message broker repository is a database of information
  about source and target applications.

• A sophisticated repository is capable of keeping track not
   only rudimentary information (such as directory data),
   but more sophisticated information about the systems:

– Location of system          – Transformation information
– Security parameters         – Design and architecture information
– Rules and logic for message – Object information
– Message schema information
-- Metadata
– Enabling technology

       Value of the Repository
• A common reference point for all connected
   processes and databases.
• Greatly simplifies integrating data and methods: it
   is just about finding their equivalents and joining
   them together.
• Possibility to track all the rules applied within the
   EAI problem domain.
• By containing the schema of both source and
   target system, it also contains information for
   proper transformation of messages flowing from
   source to target.

        (F) Directory Services
• Message brokers deal with distributed systems,
and thus require directory services to
  – locate,
  – identify,
  –use, and
  – authorize network resources for those systems
• Directory services provide a single point of entry
  for applications and middleware – directories
  know where to find resources on behalf of
          Directory Services (2)
• Directory services are nothing more than a way to classify
   resources on the network in a way consistent with any
   other method of classification.
• A multitude of widely available directory services exists:
 – Domain Name System (DNS)
 – Novell’s NetWare Directory System and Directory
 – Netscape Communications’ Directory Server
 – Microsoft’s Active Directory
 – X.500

            (G) Management
• Administration and management of the EAI
   problem domain is primarily the responsibility of
   the management layer of the message broker.
• General purpose management tools, such as
  IBM Tivoli Framework, Microsoft Systems
  Management Server, HP OpenView,
  Novell ZENworks and CA Unicenter, lack
  the ability to monitor message traffic, message
  integrity, and the coordination of the distribution
  of messages among target applications.

         (H) Adapters and APIs
• API is nothing more than the mechanism that allows an
   application to access the services of a message broker.
• Adapters link deeply into an application without having to
   invoke the native interfaces.
   – Layers between the message broker interface and the
   source or target application
   – For example, set of libraries that map the differences
   between two distinct interfaces
   – Adapters for different source and target
   applications(SAP R/3, Baan, Oracle, PeopleSoft,…)
   – Adapters for certain types of databases (Oracle,
   Sybase, DB2,..)
       Enterprise Service Bus
• Enterprise Service Bus
• Found in a category of middleware
  infrastructure products usually based on Web
  services standards, that provides foundational
  services for more complex service-oriented
  architectures via an event-driven and XML-
  based messaging engine (the bus).
• An enterprise service bus generally provides
  an abstraction layer on top of an Enterprise
  Messaging System which allows integration
  architects to exploit the value of messaging
  without writing code.
       ESB common characteristics
1.    it requires the clear separation of message headers and message body
2.    it is usually operating system and language independent; it should work between Java and .Net
      applications, for example
3.    it (often) uses XML and Web services to transport messages
4.    it includes adapter standards (such as J2C) for incorporating existing applications into the bus
5.    it includes support for asynchronous processing
6.    it includes intelligent, content-based routing
7.    it includes a standardized security model to authorize, authenticate, and audit use of the ESB
8.    it includes transformation services (such as XSLT) between the format of the sending application
      and the receiving application, including the transformation of data formats
9.    it includes validation against schemas for sending and receiving messages
10.   it can uniformly apply business rules, enrichment of the message from other sources, splitting and
      combining of multiple messages, and the handling of exceptions
11.   it can conditionally route or transform messages based on a central policy
12.   it is monitored for message latency and other characteristics described in a Service Level
13.   it (often) facilitates "service classes," responding appropriately to higher and lower priority users
14.   it supports queuing, holding messages if applications are temporarily unavailable
15.   it handles a "publish and subscribe" messaging model, including event handling

              ESB / XML
• An alternative view, particularly for high
  performance enterprise service buses, is
  that "standard" message formats should
  flow across the bus, not just XML.
• Generating XML and parsing it can be
  costly in terms of processing and memory,
  and high volume scenarios may not be


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