a distributed service-oriented mediation tool

devices do not use the same data representation and alignment transformations are needed.

mediation: to aggregate disparate information sources in a timely fashion which enables interoperability and integration of services.

mediation also helps with adding new quality of service concerns without modifying the code at the client side.

four categories of mediation

1. control mediation -> routing, filtering, aggregation
   
2. transformation -> matching types
   
3. QoS mediation
4. SLA enforcement -> transcoders

Some open source solutions for ESB providing open solutions based on Java Business Integration (JBI)

1. Apache ServiceMix
2. ObjectWeb Petals
3. Codehaus Mule

The model for mediation can be changed from reactive to proactive. in the current reactive model, there is a mediation service which gets hit by the information that needs to be mediated. This is mainly true in case of transformation mediation, control, and maybe SLA. However, the QoS mediation is still a proactive mediation mechanism as it needs close coupling with the service itself. To bring security, e.g., it is not possible to send data to a third party service in the hope of receiving the encrypted service back.

each mediation application is defined as a set of connected components and each component implements a single mediation operation.

three ways for generating mediators

1. search for pre-existing mediators
2. to use generation code tool that generates the code of a skeleton of mediators with methods to read and write on ports
3. specialized mediators such as the ones for generating Web service clients and service bridges

the nodes for mediation are built over OSGi which provide facilities to load and update Java code dynamically. two modules are required on top of each node

1. the MOM bridge
2. the administration module

administration console manages the relations between administration modules in a centralized mannger. The console take care of monitoring different adminstration modules spanned over several nodes.

a mediator registers a mediator factory taking care of all meatiors installed in the system. also it installs mediators.

MOM in the mediator enables connecting the in ports to the out ports

in -> represents a subscriber to a channel
out -> represents the publisher to a channel.

The publisher to a channel receives messages which then get forwarded to other mediators connected in the other nodes and subscribed to the same channel.

JORAM is a JSM used in the MOM module
a DHT-based algorithm such as Scribe can be a more scalable solution. What is scribe?!

failure detector based on two-ring algorithm which supports new node arrivals and failures in nodes. Does it have anything to do with the mediators on the nodes and detecting whether they stay up or go down?