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You can pull data from an Oracle Calendar Server via web services. There is at least one project that interfaces with Oracle Calendar using a PHP client. Also, Oracle themselves provide a couple of tools (both include Java APIs).
- The web services toolkit for Oracle Calendar
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- uses Apache SOAP (not Apache Axis) and returns data in xCal format.
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- See e.g.:
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- A Calendar SDK which returns calendar data in iCalendar format (non-XML) and contacts data in vCard format (non-XML). See e.g.:
So in theory it should be possible to interface an uPortal channel with Oracle Calendar, although you would also have to deal with Oracle's Single Sign On mechanism somehow.
There is also a command line utility called UNIICAL which can be used to import iCAL iCal objects into the calendar server (found inside Oracle Calendar Reference Manual).