They are replaced in Maven 4 with Maven 4 API Core's {{{../api/maven-api-core/apidocs/org/apache/maven/api/Type.html}Dependency Types}},
  with default values defined in {{{../maven-resolver-provider/apidocs/org/apache/maven/repository/internal/type/DefaultTypeProvider.html}DefaultTypeProvider}}.

  For compatibility, legacy Maven 3 artifact handlers are still provided:

 their source trees set up in the same way as their colleagues.

 here's what I do currently in the netbeans part of the mavenide project to
 find the relevant subprojects/sibling projects. I check if the user has
 defined the maven.multiproject.includes property in any of his properties
 files for the current project. if yes. then I'm able to find projects that
 can be offered to be opened together with the current project.