An outer <dependencies> tag, apply <dependencyManagement>,
dependencyManagement element in Maven provides a way to manage dependencies version number.
In a statement dependencyManagement elements dependent jar package information such as version number, then you do not need all subprojects reintroduces explicit version number listed when this dependency jar package.
Maven will find elements of the project have dependencyManagement up the parent-child hierarchy, then it specifies a version number