Package naming uniqueness for applications?

When creating an android app, we need to supply a package name in the manifest.

<manifest
  xmlns:android="http://schemas.android.com/apk/res/android"
  package="com.me.foo">

I believe this uniquely identifies an application, such that we can't upload an app to marketplace if another app already exists with the same package name.

Is it possible to extend a package name though without collision? For example:

package="com.me.foo"
package="com.me.foo.grok"

Will the second application be accepted by the marketplace, even though it's 开发者_开发百科a substring of the first package name?

Thanks

Yes this works completely fine.

I haven't tested this, but I would expect to be able to do this, otherwise it would be ridiculously easy to block companies, for example by creating com.microsoft, com.google, com, etc.