Introduction

This chapter will describe the essential underlying components in digital library systems. Building upon the previous chapters’ descriptions of the information elements and intellectual foundations, we suggest approaches to the development of interoperability of systems and resources, infrastructures and a model for sustainable design. Digital library development is a complex process, involving many different components, technical, informational and human. We do not propose to examine technical architectures and infrastructures in any depth, although we do discuss some high-level heuristic models of digital library design and implementation for the sake of completeness. We focus this chapter more on the fundamental principles upon which these infrastructures should be built, and offer some pointers to more detailed treatments of these issues elsewhere. In this chapter we will discuss the following issues:

• • digital libraries and communication

• • functionality overlap in digital library environments

• • interoperability

• • crosswalks

• • digital library structures

• • the Open Archival Information System model

• • digital library architectures in overview

• • protocols and standards, including unique information identifiers

• • designing digital library systems for sustainable technical development.

Digital libraries and communication

As described in Chapter 1 ‘Digital futures in current contexts’, once computers were able to exchange information with each other, the idea of the digital library could become a realistic concept. The ability to communicate from computer to computer across networks and from one database table to another, both within a computer system and across systems, allowed for sophisticated integration of functions and sharing of data. It is this sharing and integration that enables the library catalogue and circulation systems to work together to deliver book reservations, overdue notices, quick check-in and check-out of materials, plus further integration with other elements of a library automation system. This sort of integration enables EDI to speed acquisitions and simplify budget control, while detailed management reports can be created to measure and assess the performance of many aspects of the library.