In order to build/install/deploy an artifact, you must choose a group id.
If the artifact comes from a public repository, the choice is easy-- use the existing group id.
But if it is a jar from a commercial product or something you are building internally, you'll have to make a decision.
Search repo1.maven.org/maven2 or mvnrepository for the artifact. If you find an exact match, use that.
Look at the package structure within the jar. The groupId does not have to exactly match the package. Define logical groups of artifacts-- com.ibm.websphere is fine, you don't need com.ibm.websphere.util.proxy and com.ibm.websphere.request (those are invented...)
For internal artifacts, again groupIds should be logical groups, not necessarily an exact match for the package structure.