When vipers fail to resolve when rendering pages in a channel, you end up showing SXML markup to the end user. Although this is a rare situation, you don't want this to happen in production environments. On development machines however, you might want to trace these faulty vipers quickly to be able to get everything right for production.

The unresolvedviperhandling attribute of the publication tag can be used to specify the Render Engine behavior on a given channel:

The possible settings are:

• Ignore,
• Remove
• ThrowException

By default, nothing is done, and unresolved vipers are kept in the output. On production servers however you might want to use the remove setting, whereas on test servers and development machines, you could use throwexception in order to quickly identify problems with a site.

When the remove setting is chosen, a Trace log entry will be written whenever an unresolved viper is removed.