The document discusses the development of digital libraries from experimental stages to mature and sustainable interoperable systems. It describes three stages: 1) Experimental stage in the 1990s focusing on collections of digital materials, 2) Developing stage in the late 1990s considering custodianship and sustainability, and 3) Potential future mature stage with real interoperable digital libraries supported through normal funding channels. The goal is moving from isolated digital collections to interconnected digital libraries.