The digital computer technology revolution continues to open up concepts, many of which are only just beginning to be understood or accepted. These concepts are critically important to librarianship in general and preservation in particular. In a world historically dominated by paper, the same medium is used for document capture (creation, recording), storage, access, distribution and use, and there has been no compelling need to consider these as separate entities. There has also been no compelling need to distinguish between the format of a document and the medium in which it is embodied, since there is only one dominant choice of medium. Indeed, the terms have traditionally been used somewhat interchangeably and indiscriminately. The introduction of non-paper forms such as phonograph recordings and films has modified this straightforward view somewhat, but traditional cataloging makes every effort to foster the constraint that there is a one-to-one correspondence between the format and the medium, with the objective of identifying the combined format-medium with some physical shelf location.
Further efforts to foster this constraint increasingly break down when digital technologies enter the picture. Digital technologies open a world that paradoxically is simultaneously more complex and, in some ways, simpler. It is more complex because now the same document or document format may intrinsically be represented in different media for different purposes, forcefully motivating the need to distinguish carefully between the format and the medium. Furthermore, different media may be used interchangeably for different stages of document handling, that is, for capture, storage, access, distribution, and use. To complicate the situation even more, the documents may be encoded in a myriad of ways at each of these stages.
And yet, separation of the format and the medium--and treating each stage of document handling separately--may open up a more logical structure free from traditional constraints. In this sense, digital technologies may simplify certain aspects of librarianship.
Digital technologies present many new challenges, however, that must be considered. For example, although these varying formats may be decoded and translated back and forth among each other, many fear that the means of decoding may become lost as a result of technological obsolescence, conceivably making digitally stored documents inaccessible. There are also many who question the longevity of the physical media used in digital technologies. Others suggest that the appropriate way to address both of these problems--as well as to take advantage of the declining costs of computer storage and of increasing storage densities--may well be to copy stored documents periodically onto new media.
Indeed the main advantage of the world of digital technologies, namely that they represent a kind of "esperanto" of mutually comprehensible and interchangeable formats, may, if not properly managed, also represent their biggest weakness, because of the rapidity of change and obsolescence, and because of the wide range of choices available at any given time. Their very attractiveness could lure the unwary or the uninformed into dangerous territory.
Periodic recopying onto new media represents a whole new approach for libraries to the operation and financing of "inventory management" (although though such practices are quite common in data centers). The implications could be quite extensive. Librarians tend to think in terms of periods of centuries rather than having (or wanting) to recopy every few years. Such considerations may either hinder the adoption of digital technologies for preservation or other purposes or eventually cause some rethinking of the underlying economics of librarianship.
The incentive for such potential reevaluation, however, is not limited to the preservation of older materials, nor is the influence of technology the only driving factor. The underlying stimulus is a gradual transition over the centuries--perhaps spurred by the exponential growth of recorded knowledge and information--from documents with associated physical or conceptually useful lifetimes, times between new editions, or, more generically, times between "instances", that can be measured in decades or centuries; to documents with associated times between instances measured in much shorter units of time--even, in the case of "active documents" (see below), measured in minutes or seconds.
In essence, this represents a transition from "batch processing" to "continuous processing."  The financial and other implications of this could undoubtedly be far-reaching for libraries (a full discussion is beyond the scope of this Glossary), introducing into the library milieu unfamiliar (or, at least, largely unused) concepts associated with continuous processes or processes with relatively short lifetimes, such as "depreciation" and "lifecycle costing." These are concepts that are familiar to the world of digital electronic processing and quite normal outside of universities, but that have been avoided in worlds--such as research libraries--that depend to a greater or lesser extent upon irregular gifts or grants of varying or unpredictable size, donations directed to the purchase and immediate storage of documents, but not to their maintenance. Indeed, one of the most serious questions facing librarians in the future may be how to effect a match between the changing economic demands of "continuous processes" and the traditional nature of many funding sources. Will donors, for example, be as willing to support the continuous demands of technological processing as they have historically and generously supported the periodic construction of library buildings? What implications does the financing of continuous processes have for the "free" and openly accessible library? 
Yet the potential of digital technologies and of the flexibility they offer is boundless. Over the coming decades, these technologies may open up vistas of ever-increasing storage densities to where entire libraries can be electronically stored in the space of a single room; of blinding access and distribution speeds allowing whole documents to be moved almost instantly across the nation's (and indeed the world's) data networks, leading to the concept of the "distributed library;" of ease of replication at very modest cost (another cause for alarm, particularly to those concerned with protection of intellectual property); of "print-on-demand" where paper copies of documents are only printed "just in time" and not inventoried in advance of need; of accessibility at a distance away from where the "digital document" or preservation copy was created or is stored; and of intelligent automated document analysis. Indeed, the means of creation and production of documents have already been revolutionized by these technologies.
These technologies also open up horizons for totally new document formats, such as active documents whose contents may combine different media such as text, sound, video or voice; or whose contents may change dynamically with time, what Harvey Wheeler called "the fungible book."  The preservation of these new "active" formats is not of direct interest to the subject of preservation of more traditional formats (and therefore beyond the scope of this Glossary), but is of indirect interest because digitally preserved traditional documents can be incorporated into such active documents. Furthermore, contemporary active documents will become a subject of future preservation interest.
Some view the introduction of digital technologies into the world of libraries as likely to cause a revolution as far-reaching as that caused by the printing-press: a massive paradigm shift. Others view the introduction with concern (one cannot help but recall that the monks at first also viewed the introduction of the printing press with equal concern), an intimidating perturbation that disturbs an equilibrium and modalities of scholarship that have served well for many decades or even for centuries.
Either way, digital technologies cannot be ignored. They are already with us. The question is not whether they will have a presence, but the pace and degree to which that presence will grow and influence. The next twenty years are likely to be times of extraordinary change. Our libraries--indeed our universities, colleges, and our scholarly communities--may well be remade by the consequences of this technological revolution.
And yet--in spite of technology's impact and of the revolutionary consequences of that impact--it must be recognized that technology itself is not the ultimate driving force. It is the inexorable pressure caused by the exponential growth of recorded knowledge, and the ever-increasing complexity, costs, and other problems associated with the storage and distribution of, and access to, such information. Technology can provide some solutions: it is not an end in itself.
Furthermore--for many reasons too numerous to detail here--the "digital library" is not about to replace the "paper library." Both will need to coexist in a shifting environment, at least for the foreseeable future. This in itself will present librarians with many economic, organizational, social, technical, and other challenges.
Between the eager apostles of technology and those who approach change with extreme caution lies the mass of professionals who are trying to understand and grapple with the potential of this shifting environment, many of them implementing prototype activities designed to elucidate greater insight,  many working to close the gap between promise and reality.
It is to these professionals--from all fields--that this Glossary is dedicated, to provide a common language for dialogue and mutual understanding, particularly as is required to address the problems of preservation, and the potential application of digital technologies to those problems. The Glossary is not intended to be so comprehensive as to satisfy the technologist only concerned with technologies, or the librarian exclusively concerned with librarianship and preservation. It is intended to satisfy the intersection of their concerns. On the other hand, issues of preservation and access raise concepts that have implications for librarianship as a whole, so that, in that sense, this Glossary has consequences that are not limited to the preservation arena alone.
Timestamp: Sunday, 23-Nov-2008 15:20:17 PST
Retrieved: Friday, 23-Feb-2018 12:31:17 GMT