Topic3 Enterprise Application Integration

Enterprise Application Integration Sanjoy Sanyal (Tech for NonGeek)

Application Integration in Perspective Sanjoy Sanyal (Tech for NonGeek) Client Server Systems Separates the presentation layer from the application logic layer Increase of bandwidth and availability of PCs Islands of client server clusters emerged 3 tier architecture and middleware Separates the application logic layer from the resource management layer Allows systems to be built on clusters and integrate different servers This led to proliferation of services in several rounds of abstraction The challenge now is the integration of services EAI is one response to the challenge of bridging 3-tier architectures

The Challenge of Application Integration Sanjoy Sanyal (Tech for NonGeek) Example: Supply Chain Quotation Order Processing Procurement Shipment Management Financials
A single implementation of a company-wide process requires integration between different systems which can:
Run on a different OS
Support different interfaces and functionality
Support different data formats
Support informational formats that cannot be easily cast into parameters of a procedure call
Have different security requirements
Have different communication protocols and infrastructure

EAI Middleware: Message Brokers
Message Brokers create a “hub and spoke” communication infrastructure between applications
Traditional RPC/MOM systems create point-to-point links
Message brokers provide additional functionality to transporting messages:
Provide adapters that makes it possible to access heterogenous systems
Also filters. routes and processes the messages
In other words attaches logic at the middleware layer
Examples:
Tibco ActiveEnterprise, BEA WebLogic Integration, WebMethods Enterprise and WebSphere
Sanjoy Sanyal (Tech for NonGeek)

Advantages of Message Brokers
Message Brokers de-couple receivers and senders:
The message routing logic is specified in the broker unlike in basic MOM where the sender specifies the receiver
Content transformation rules is specified in the broker
Advantages:
Increased flexibility : for e,g. when a new system is neeeded to interact with the supply chain process only the middleware logic needs to change
Integration between heterogeneous data formats/communication protocols

Publish-Subscribe Interaction Model
Applications publish to the middleware system
Applications subscribe to messages specifying:
Type (type.subtype…..)
Parameters (boolean based: type.subtype AND <condition)
Middleware:
receives message
retrieves the list of relevant subscribing applications
delivers a copy to each of them
Widely supported model among message brokers

JMS
JMS tries to stanardize APIs and middleware infrastructure
JMS supports point-to-point middleware
JMS supports publish/subscribe API (based on topic )

Distributed Administration of a Message Broker Sanjoy Sanyal (Tech for NonGeek) Administrative domain A admin Message Broker A client client Administrative domain B admin Message Broker B client client Administrative domain C admin Message Broker C client client The administrator has the authority to define: 1. Type of messages that can be sent and received 2, which users are authorized to send/receive and to customize routing logic Different admin domains can correspond to separate cos/departments Message brokers in different domains can be a client of each other thus allowing clients in one domain to interact with clients in another

Understanding Middleware
Offers programming abstractions that hides the complexities of bridging between heterogeneous platforms
Middleware implements the functionality of the abstraction
Sanjoy Sanyal (Tech for NonGeek) Remote Procedure Call Sockets TCP/UDP IP A simple example Remote Procedure Call: Hides communication details behind a procedure call Sockets: operating system level interface to the underlying communication protocols Underlying communication protocol

EAI with a Message Broker
EAI platforms are based on two components:
Adapters which hide heterogeneity
Message brokers which facilitate communication
Sanjoy Sanyal (Tech for NonGeek) Message broker Integrating application Quotation adapter Database adapter Forecasting adapter Email adapter xyz adapter High Level architecture of a typical EAI system

EAI: Example Sanjoy Sanyal (Tech for NonGeek) RFQ Processing Message Broker Quotation Adapter Forecast Adapter A B C 2 4 1 5 6 7 At system startup A: subscription to message quote B: subscription to message quoterequest C: subscription to message newquote At runtime 1: publication of a quoterequest message 2: delivery of message quoterequest 3: synchronous invocation of getquote function 4: publication of a quote message 5: delivery of message quote 6: publication of a newquote message 7: delivery newquote message 8: invocation of create forecastentry function B 3

EAI: On the Balance
Lower Development and Opportunity Costs
Lower Maintenance Costs
High software License costs

Workflow Management Systems
Origin in office automation
Received interest from business process reengineering
Products:
WebSphere MQ Workflow (IBM)
Vitra Business-Ware
Tibco BPM
BEA WebLogic Integration
Microsoft BizTalk Orchestration

Workflow Definitions
Business Process
E.gs: hiring new employees, process purchase orders
Workflow/Workflow process:
Formal executable description of a business process
Workflow specified by:
Work node: represent work items
Routing node: define order in which work items should be executed
Start and completion nodes: start and end points of workflow

Workflow Execution
Executed by a workflow engine:
Retrieves the workflow definition from a repository
Determines the nodes to be executed
Schedules the work to be done
Assigns it to an appropriate resource (work executor)
Resources:
Retrieve work from a work queue (work can also be pushed)
Executes and returns the work to the engine’s inbound queue
Evaluate the condition and determines which node should be executed next
Resource broker:
Helps in node selection by executing resource selection policy

Workflow Execution Sanjoy Sanyal (Tech for NonGeek) Workflow Engine Resource broker Completed work items Inbound queue resource 1 resource 2 resource n Workflow Definitions Workflow Designer Outbound queues

EAI with WfMS
EAI and WfmS are Complimentary
EAI tackles heterogenity, WfMs tackle workflow
WfMs can sit on top of EAI
Sanjoy Sanyal (Tech for NonGeek) Message broker WfMS adapter Quotation adapter Database adapter Forecasting adapter Email adapter xyz adapter WfMS

WfMS: On the Balance
Generated a lot of interest
But did not live up to its promise:
High software licenses
Difficult to automate real-life processes

Summary
EAI refers specifically to integration of heterogeneous, coarse grained applications
Platforms for choice are message brokers and Workflow Management systems
Message brokers play a much more important role
Message brokers allow an asynchronous communication model and loose coupling
In general, implementations of EAI platforms is still expensive and not seamless
(the material in this topic is based on Web Services: Concepts, Architectures and Applications by Alonso, Casati, Kuno, Machiraju)

Topic3 Enterprise Application Integration

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