o Added section on renaming pom.xml in maven-core.jar to pom-4.0.0.xml for future legacy needs

o Added section on minimum required element-set for a unique project pom.xml


git-svn-id: https://svn.apache.org/repos/asf/maven/components/trunk@163085 13f79535-47bb-0310-9956-ffa450edef68

maven-core/src/site/apt/inheritance.apt

@@ -13,6 +13,8 @@ Inheritance in Maven
  * how parent poms are processed
 
  * the order in which elements in the POM are overridden
+ 
+ * minimum element-set for a valid project pom
 
 
 Maven super model
@@ -45,4 +47,37 @@ Maven super model
    <version></version>
  </parent>
 </project>
-+-----+
++-----+
+
+Extending the POM in the future
+
+  In order to anticipate changes in the structure of the POM as new releases of
+  maven occur, the maven inheritance model must be pinned against a particular
+  modelVersion. This is required so that a change from modelVersion 4.0.0 to 
+  4.1.0 doesn't cause compatibility problems with users who have not upgraded 
+  their projects. It also allows for a certain amount of legacy support into the
+  future. Therefore, we should rename this file from pom.xml in the maven-core
+  jarfile to pom-4.0.0.xml (and successive revisions to the base pom made to 
+  accommodate changes in the model will be named accordingly - 4.0.1, 4.0.2, ...).
+  
+Minimum Element-Set for a Project POM
+
+  In order to furnish a basic set of information which we need to distinguish one
+  project from another, maven requires a minimum set of elements to be specified
+  in each project's pom.xml.
+  
+   - [modelVersion] tells maven which version of the object model this project
+       is compliant with (to support future legacy concerns)
+   
+   - [artifactId] tells maven what the artifact name is for this particular
+       project. Each project should have a distinct artifactId.
+       
+   - [version] tells maven what release of this artifact we're trying to produce.
+       The fact that a project has a distinct pom.xml should indicate a separate
+       release cycle that is also distinct to that project, so a concrete version
+       declaration is required.
+       
+   - [name] tells maven what the user-friendly name of this project is. The name 
+       element is similar to artifactId in that it is a unique descriptor for
+       this and only this project, and therefore should be concretely defined.
+