About Feed and Design Triggers

A Feed Trigger is an entry point to alter the behavior of a Feed.

It is called by the Mashup API before and after the feed execution, allowing for query manipulation, context modification and results manipulation.

Therefore, Feed Triggers can do the following:

• Decide to override the query to be issued to the actual ‘execute’ method based on query expansion (beforeQuery method)

• Decide to replay the feed execution because the result obtained is not satisfying, for example, if there are no results (afterQuery method that returns Result.EVAL_AGAIN)

Example:

You can use a Feed Trigger on any Feed in your configuration to customize query processing or feeds behavior for different purposes such as:

• Query rewriting

• Query computing from previously retrieved results

• Enabling / Disabling feeds

Design triggers are called by the Mashup Builder

They include:

• Pre-request triggers which can be used to decide whether the user should be redirected to another page or not. The back end is not yet called, so no special load is triggered on the system. For example, redirect the user to the page called /imagesearch if the query starts with ‘image(s)’.

• Page and widget triggers which have the possibility to alter the behavior of the display by making decisions to draw things or even change the configuration (each user request gets a fresh copy of the original configuration, so any changes at query time are safe). For example: decide whether a widget should be displayed or not.

• Application triggers which are executed on all application pages.

The Mashup trigger sequence is as follows: