Carapace Videotex Server

The Carapace Videotex Server provides multiple simultaneous Viewdata sessions onto a back-end engine which itself has no Viewdata capabilities. For example, the engine could be an XML server offering availability and booking information, or it could be a relational database system such as Oracle etc.

The Carapace Videotex Server runs on Microsoft's NT/Win2000 and receives Viewdata sessions across TCP/IP. The powerful data mapping capability within Carapace mean the data received from the Viewdata user can be put into the correct form required by the back-end engine. Similarly, the communications components within Carapace mean a wide variety of back-end engines can be accommodated. For example, the engine might be a COM object which accepts XML data across its interface. Alternatively, the engine might be accessible across an internal TCP/IP connection with XML or another protocol transferred across the connection.

The Carapace Videotex Server is driven from a set of page specifications which define:

  1. page name -- this must be unique amongst all defined pages for the service
  2. input fields -- those areas on the screen where the user-entered data is displayed. Each field is given a name, location on screen, expression to generate the initial value, text for the screen prompt etc.
  3. output data -- this generates the data to be sent down the line to the user for display on their Videotex emulator
  4. validation -- to be performed on the data received from the user
  5. post-processor -- a function which takes the field name/field values holding the data entered by the user, does whatever is necessary with it (e.g. store it, send it to the underlying service etc.) and returns the name of the next page to present

The Server then repeatedly cycles through the following sequence:

  1. generate the Videotex page data from the current page definition -- i.e. generate the block graphics to send, move the cursor around the screen with the relevant cursor control characters, display fixed or generated text etc.
  2. receive input from the user -- this might be data entered into the input fields or field-movement commands such as ** for moving back a field
  3. process the received data and determine the next Videotex page to present

Contents Current topic: videotex Related topics: Carapace Hub