Referencing a WorkManager (ExecutorService) in a Web module or EJB module or at App level

at WAR level you can have a work-manager clause:
https://docs.oracle.com/cd/E24329_01/web.1211/e21049/weblogic_xml.htm#WBAPP627
but it's available also at EAR level:
https://docs.oracle.com/cd/E24329_01/web.1211/e24368/app_xml.htm#WLPRG487
http://xmlns.oracle.com/weblogic/weblogic-application/1.4/weblogic-application.xsd
and also at EJB level: https://docs.oracle.com/cd/E12840_01/wls/docs103/ejb/DDreference-ejb-jar.html

Useful links:
https://developer.ibm.com/answers/questions/168264/how-to-use-resources-defined-in-applicationxml-des.html
http://stackoverflow.com/questions/2887967/what-is-resource-ref-in-web-xml-used-for