3. ESB:Why do we need them?
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Information Systems Context:
•IS (Information Systems) are heterogeneous from a technological point of view.
•Each domain builds it’s own IS .
Need for Integration:
•How to trigger a process within a system from another system?
•How to insure the consistency and the propagation of data between many sub-
systems?
Two types of solutions:
•Extract-Transform-LoadTools
•Middleware solutions
4. 3
ETL Tools: Extract-Transform-Load
ETL comes from Data Warehousing and stands for
Extract-Transform-Load. ETL covers a process of how
the data are loaded from the source system to the data
warehouse, source system and destination system are
generally heterogeneous.
ETL Performs:
◦ Data extraction: extracts data from homogeneous or
heterogeneous data sources
◦ Data transformation: transforms the data for storing it
in the proper format or structure for the purposes of
querying and analysis
◦ Data loading: loads it into the final target (database,
more specifically, operational data store, data mart, or
data warehouse)
Disadvantages:
◦ Data centric approach.
◦ Cannot garantee the processes integration
5. 4
Network-Centric Middlewares (1/2)
MOM: Message Oriented Middleware:
◦ System Store and Forward
◦ Asynchroneous : The client builds a message and
sends it to the middleware, who routes it to the
destination.
◦ There is no technical coupling between different
third-parts.
◦ All third-parts must know the interfacing mode of
the middleware.
◦ Limited routing capacity, necessity of explicitly
configuring the routes.
Disadvantages :
◦ Require an extra component in the architecture, the
message transfer agent (message broker).
◦ Adding another component can lead to reductions
in performance and reliability, and can also make
6. 5
Network-Centric Middlewares (2/2)
ORB: Object Request Broker: is a
middleware which allows program calls to
be made from one computer to another via
a computer network. It takes care of all of
the details involved in routing a request
from client to object, and routing the
response to its destination.
Disadvantages :
◦ Deployment is very complex.
◦ Development and interoperability issues.
◦ A solution that needs important technical
skills.
7. EAI: EnterpriseApplication Integration
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◦ Object-oriented programming.
◦ Distributed, cross-platform program communication using message
brokers with Common Object Request Broker Architecture and COM+.
◦ Modification of enterprise resource planning (ERP) to fit new objectives.
◦ Enterprise-wide content and data distribution using common databases
and data standards implemented with the Extensible Markup Language
(XML).
◦ Middleware, message queueing, and other approaches.
Disadvantages:
◦ High startup and initial development costs.
◦ Requires smart business design, which may not be able to be envisioned
with the help of a consulting firm.
◦ Need special development for connectors.
◦ SPOF (Single Point of Failure).
◦ Does not separate roles of mediation and orchestration.
8. 7
ESB: Entreprise Service Bus
EAI were transformed to two types of products:
◦ ESB to accompish the interconnections and mediation.
◦ BPM (Business Process Management) for orchestration
Data are not processed/treated on the on the ESB itself, they are sent to
the applications to through connectors.
ESB are designed basing on SOA principals: they are loosely coupled
and can be deployed seperatly.
ESB are designed basing on standards.
9. 8
ESB: Definition
ESB stands for Enterprise Service Bus and it’s fundamentally an architecture.
It is a set of rules and principles for integrating numerous applications together over a
bus-like infrastructure.
The "bus" concept decouples applications from each other.
The data that travels on the bus is a canonical format and is almost always XML.
There is an "adapter" between the application and the bus that marshals data
between the two parties.
The adapter is responsible for talking to the backend application and transforming
data from the application format to the bus format.The adapter can also perform a
host of other activities such as message routing transaction management, security,
monitoring, error handling, etc.
ESBs are generally stateless; the state is embedded in the messages passing through
the bus.
