Chapter 8. JBoss Portal Explicit Coordination

8.1. Explicit vs implicit coordination

Portlet 2.0 coordination features are mediated by the portal between several portlet windows, therefore the portal at runtime needs to be able to define relationships between windows. Relationship can be established from an implicit model (i.e a set of predicates applied on some state that will answer TRUE/FALSE to the question are the portlet windows foo and bar in a relationship) or from an explicit model (that states that foo and bar have a relationship). The implicit model is very good for defining default configuration as it does not require much configuration but is not able to cover the exceptional case, that's why we need to combine it with an explicit model that will take precedence over the implicit model, it is the well known principle of convention over configuration.
Similar to implicit Coordination, currently all explicit coordination happens only in the scope of the same page.