The POM may have certain prerequisites in order to execute correctly. For example, perhaps there was a fix in Maven 2.0.3 that you need in order to deploy using sftp.
In Maven 3, use Maven Enforcer Plugin's requireMavenVersion rule, or other rules to check other aspects.
In Maven 2, here is where you give the prerequisites to building: if these are not met, Maven will fail the build before even starting. The only element that exists as a prerequisite in POM 4.0 is the maven element, which takes a minimum version number. It is checked with Maven 2, it is not any more in Maven 3.
The
<prerequisites>
element is deprecated and isn't checked in Maven 3 so we add the Maven Enforcer plugin as well. (See http://maven.apache.org/pom.html#Prerequisites)