Setter and Getter to make a virtual field which stores the actual value in a user's cookie.
Also it can be used to store a default value for the next time a user creates on node of this type:
<field name="from">
<gui>
<guiname xml:lang="nl">Uw naam</guiname>
<guiname xml:lang="en">From</guiname>
</gui>
<datatype base="eline" xmlns="http://www.mmbase.org/xmlns/datatypes">
<required value="true" />
<minLength value="3" />
<maxLength value="32" />
<defaultprocessor>
<class name="org.mmbase.datatypes.processors.Cookies$Getter">
<param name="cookie">eo.miniforum.name</param>
</class>
</defaultprocessor>
<setprocessor>
<class name="org.mmbase.datatypes.processors.Cookies$Setter">
<param name="cookie">eo.miniforum.name</param>
</class>
</setprocessor>
</datatype>
</field>