The Exploratorium, an interactive hand-on science museum, is developing an online collection of science learning and teaching resources to better serve educators’ needs for pedagogically-rich instructional resources via the Web. Several challenges arise when designing a digital library for formal K12 education audiences using the Learning Object Metadata standard. These problems are multiplied when attempting to catalog the wide variety of informal learning digital resources from the Exploratorium’s ever growing website and exhibit-based resource collections. This paper shares key challenges and early solutions for the creation of an educational metadata scheme, new vocabularies, and strategies for retrofitting existing informal learning science resources into learning objects. Categories and Subject Descriptors H.3.7 [Information Storage and Retrieval]: Digital Libraries-Collection, Dissemination, Standards Systems General Terms Design, Experimentation, Standardization Keywords S...