How HATS engine works?

HATS is an IBM Rational tool that transforms IBM 3270, 5350 and VT green screen applications to web applications. To understand better how HATS engine internally works we need to see what “HATS screen recognition criteria” is.

HATS uses screen recognition criteria to match host screens. Host screens can be recognized by HATS engine through any criteria, for example total fields are on the screen, cursor coordinates, and specific text strings on the screen at a defined place or anywhere on the screen. When a host shows a screen, HATS engine picks it and searches to see whether the current screen matches any of the defined screen recognition criteria within the project. If HATS engine catches a match, the programmed actions for the screen customization are executed.

Following diagram illustrates the flow, how HATS engine performs the transformation.


Host shows a screen, HATS performs a comparison among screen recognition criterion defined in the project, this is done in the order defined by project’s event priority.

When a match is found, HATS performs the specified actions for the recognized screen customization, these actions may include,

  • Application of a transformation
  • Execution of business logic
  • Interaction with global variables
  • Forwarding to a URL
  • Playing a specific macro.

If there is no matching screen recognition criteria for the host screen, HATS processes an event designed for unmatched screens. The default action of this unmatched event is to show the host screen by the default transformation and only applying the project’s default template, this creates a webpage on the fly using the text and fields present on host screen.

As the 5250/3270 host displays new screen, HATS initiates with all these steps again and proceeds through these the each step.

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