DORoTy is a DLMS whose novelty is to provide Digital Library Systems designers and developers with tools inspired by the traditional typed approach of Database Management Systems. Using DORoTy, DLS developers first declare the types of the objects to be manipulated and than realize applications counting on type-checking and optimized storage and access methodologies. DORoTy's data model offers a wide range of abstractions common to Digital Library objects modeling. Examples are object collections, named relationships, object versioning, metadata descriptions, and others, as well as operations to manipulate them. Beyond recovering type correctness and data integrity properties, the adoption of types in DLMS foundations allows for the design of an efficient and optimized DLMS store, capable of exploiting type information to achieve best performances in object persistence and access. As such DORoTy can ease the design and implementation of Digital Library Systems, such as multimedia archives and institutional repositories. The DLMS is currently used as back-end for the repository technologies developed in the DRIVER-II project (Enhanced Publication Service), the EFG project (European Film Information Space Service) and R2D2.