assembly descriptor id should be mandatory

I can create assembly using descriptor like this:

<assembly>
  <id></id>
  <formats>
    <format>zip</format>
  </formats>
  <fileSets>
    <fileSet>
      <directory>src/main/java</directory>
    </fileSet>
  </fileSets>
</assembly>

the file created does not have a classifier, and it's not the main artifact either, so it's impossible to locate it using maven coordinates.
the id should be mandatory so there will always a classifier.