I guess I am not sure I understand the question. So if this does not answer it, let us know.
The "${..}" syntax is used to access the value of a property within the build. Consider this property setting:
The property 'basedir' is a built-in property whose value is the directory containing the build.xml file. For example, its value might be "/home/peter/myproject". Ant set the property 'src.dir' to the value "/home/peter/myproject/src".
Put it another way, the above property statement is similar to the following statement in a scripting language, or even in
Java (if such languages allowed dots in their variable names):