Enterprise System Architecture

This is a motivation why workflow management systems are needed

Evolution of Integration

No Integration

esa-no-integration.png

There are 3 systems:

  • HR: human resources
  • POM: purchase order management
  • WM: warehouse management

No integration:

  • a change in one DB is not propagated to others (automatically)
  • this has to be maintained
  • suppose an address changes in HR, but the rest don't know about it
  • $\Rightarrow$ inconsistency


Central ERP System

This is also called 2-tier client-server architecture

esa-central-erp.png

  • there's a central ERP system that explicitly integrates all the data into one source
  • but there are performance issues
  • and what if the ERP server goes down?


Application Integration

There are several ways to integrate different application

Point-To-Point

esa-central-p2p.png

  • every system communicated with all other systems
  • $N^2$ connections for $N$ systems - a lot!


Message-Oriented Middleware

esa-mom.png

  • each client connects to the Integration Application
  • IA dispatches the messages to the receivers
  • this approach takes away the burden of implementing all the connectors
  • but it's still point-to-point: all must know about others
  • $\cfrac{N \cdot (N - 1)}{2}$ connections in this scheme


Application Integration

esa-central-hub.png

  • now there's a hub: a centralized integration middleware: it orchestrates the flow
  • the hub acts as a message broker: it defines the rules for communication and transformation
  • system no longer need to know about each other
  • it's similar to emailing: no need to know about the received: where is he, whether he can read now or not, etc

The differences between it and central ERP:

  • in the central ERP there's one single DB
  • here each application has it's own database


Workflow Management Systems

There are three kind of workflow management systems:

  • hard-coded workflows (process and organization specific)
  • custom-made (with some generic wokrkflow but still organization specific)
  • generic software with embedded workflow functionality
    • workflow components of one particular type of systems, say ERP
  • generic software focused on workflow
    • how we can connect different components from different manufactures
    • allows great flexibility


Sources

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