The information era has brought with it the wellknown problem of 'Information Explosion'. There are many and varied search engines on the Internet but it is still hard to locate and concentrate only on materials relevant to a specific task. Digital libraries, on the other hand, provide better services for focused discovery of relevant Web resources. However, digital libraries have been much less researched and implemented than search engines. The 'Katsir/Harvest' project laid the ground for our understanding that a new paradigm should to be developed - the Harvested Digital Library (HDL). The contribution of this article is in presenting a new framework and harvesting model for constructing HDLs. The open harvesting architecture proposed here uses advanced information retrieval tools and provides a set of integrated DL services to its users. This model and architecture are discussed throughout the article, including description of the implemented Katsir system and discussion of future research directions. The future DLs will be knowledge rich in the sense that each DL contains relevant meta-information on its domain and employs advanced knowledge management techniques.