schema or reference for maven-metadata.xml in maven 3 (specifically for <latest/>, <release/>)?

Question

I see Nexus OSS repo manager (re)generating the following maven-metadata.xml and cannot find any info on what do the following properties mean (or where can i find reference to maven-metata.xml - similar to pom.xml )

• latest - not latest by version or lastUpdated timestamp in our case. Nexus FAQ says this only applies to plugin artifacts. Is that really so? Is it benign or harmful when present in for non-plugin artifacts?
• release - what is the significance of this property? When used for SNAPSHOT artifacts?

Artifact's maven-metadata.xml - as re-generated by Nexus:

<metadata>
  <groupId>com.castanealabs</groupId>
  <artifactId>castanealabs-config</artifactId>
  <versioning>
    <latest>10-SNAPSHOT</latest>
    <release></release>
    <versions>
      <version>1.0-SNAPSHOT</version>
      <version>7-SNAPSHOT</version>
      <version>8-SNAPSHOT</version>
      <version>10-SNAPSHOT</version>
      <version>11-SNAPSHOT</version>
    </versions>
    <lastUpdated>20120321194127</lastUpdated>
  </versioning>
</metadata>

Answer 1

Here are some references about the maven-metadata.xml file. In that case simple Google would have helped.

1. http://maven.apache.org/guides/getting-started/index.html
2. http://maven.apache.org/ref/3.3.9/maven-repository-metadata/index.html
3. https://issues.apache.org/jira/browse/MNG-3125