In this paper we describe the e-LD approach for the design and repurposing of Units of Learning (UoLs). This approach is centered in domain-specific Educational Modeling Languages (EMLs) built with the close collaboration between instructors and developers. The products of this collaboration are: (i) the definition of a suitable authoring EML, and (ii) the construction of software tools to allow the importation and authoring of UoLs. The domain-specific authoring EMLs and tools simplify the production and repurposing of UoLs.