Recording media

Since records may have to be kept for very long periods, the media used for storage are of crucial importance. On the basis of past experience with record keeping, a few basic requirements on the media and technology for recording can be formulated. These requirements include that records ideally should:

— Be readable without the aid of proprietary technology;

— Be capable of duplication and transfer to new media without loss of infor-mation;

— Preserve the context surrounding the information contained and its use.

The advantages and disadvantages of different recording media are summarized in Table 6. However, as has been discussed above, not all records may need to be stored for a very long time. Therefore, the choice of recording medium can be made appropriate to the length of the required retention time.

Records of only short term relevance may be stored on ordinary office paper or proprietary magnetic media, whilst those records that need to be preserved for a very long time would need to be made on special papers or even on such exotic materials as silicon carbide.

In addition to concerns over the long term stability of the base medium, the stability of the actual inscription and possible detrimental interaction of the chosen materials with the base medium need to be assessed. It is known, for instance, that certain inks will fade or that they will destroy the paper due to chemical reactions. The preservation of written records on organic fibres such as papyrus leaves, or prepared animal hides (vellum), for several thousand years indicates their long term stability. Inks that form a stable inorganic compound (e.g. iron gallate or soot) after the medium has evaporated are preferable to those that rely on organic polymers. A concern is the cheap

modern papers and computer inks that seem to be in general use currently to produce hard copy records. These papers may not be acid-free, and the inks or dyes are usually based on organic polymers or use binders such as those employed in laser printing technology.

TABLE 6. TYPES OF MEDIA AND THEIR RESPECTIVE ADVANTAGES AND DISADVANTAGES

Medium Advantages Disadvantages

Paper Easily readable (by the current generation) Relatively robust

Degrades slowly

Relatively easy to duplicate

Relatively inexpensive, so inexpensive to store duplicates in several places

Occupies significant space

Inks and paper degrade in the long term

Negatives require smaller storage space than paper

Media degrade Easily destroyed by fire and water

Microfiche Storage space significantly smaller than that for many other media

Can be read using relatively simple technology (magnifying glasses)

Degrades in the long term (though some fiche media have been developed that potentially last longer than paper)

Requires a tool to be read Digital records Can be retrieved relatively easily, rapidly and

from a number of areas

Storage space (disks, servers, etc.) very small, and one source that is networked can be read by a number of readers

Easy to attach metadata

Easy to arrange contextually or by multiple contextual relationships

Very durable in the long term Corrosion resistant

Wear and abrasion resistant

Do not require sophisticated environmental controls to ensure no degradation

9.10.2. Digital records

Over the past two or three decades, digital data processing, and hence storage of digital records, has become ubiquitous and it is now more prevalent than other forms of data storage. The main incentives have been the high data density that can be achieved, with the associated savings in storage space, the versatility of the digital format, which allows use of the stored information for a variety of purposes, and the ease of data retrieval for further use.

Given the rapid changes in information management technologies, preserving data is a major issue for a programme that must extend into the indefinite future. Many systems that were once considered high technology simply no longer exist. For instance, data stored on 5.25 in. floppy disks are now virtually useless, as very few users have been able to retain the necessary hardware (disk drives) and associated software. A similar future awaits the 3.5 in. floppy disk and other magnetic media (e.g. tape streamers) in the light of rewritable CDs and DVDs becoming common. Optical disk (CD and DVD) technology is also being challenged by issues such as media durability (disk delamination) and the changing wavelength of the light source used to read or write disks. The problem of rapid technological change and the associated technical obsolescence has been widely recognized and extensively discussed for many years, but without any agreement on how this can be resolved [106].

A recent report on spatial data preservation and archiving [107] reviewed the issues relevant to data preservation. Most newer digital media are much less robust than printed books or other paper documents because:

(a) They are less chemically stable than even poor quality paper.

(b) They deteriorate more rapidly even when stored unused in good environ-ments.

(c) Digital data are machine dependent, i.e. they must move within machines to provide their information. Simply reading the data incurs wear on the media.

(d) They are totally system dependent for retrieval of their information.

When the system (hardware, software or both) is no longer sustained, the information will be lost unless it is migrated to a newer system.

(e) Digital information technologies rely on ever greater data packing densities, making the information ever more vulnerable to large losses from small incidents.

(f) Failure of many newer digital media is often unpredictable and sudden, and may result in total loss of the information recorded.

(g) There is little experience with the maintenance and preservation of many newer types of media.

Technological obsolescence is a major concern, particularly since technical developments are not driven by, and do not take into consideration, long term information preservation needs [108]:

(a) Accessibility of digital information depends entirely on intricate edifices of hardware, operating systems, applications software and storage media.

(b) Most systems are heavily proprietary, which leaves those concerned with long term preservation dependent on the marketplace.

(c) Changes in technology are almost wholly driven by business and market forces; libraries, archives and other government institutions have virtually no influence on these developments.

(d) Although there are many crucial standards, both formal and de facto, in the digital domain, developments in technology often outpace the standards setting process.

A data mining procedure, i.e. transformation of existing records into current and long term formats might be needed to preserve records. In other words, digital media typically have very high maintenance requirements compared with those of other media, for instance paper. When deciding on the medium, these disadvantages may need to be balanced against the advantages of ease of data retrieval. In general, it appears that digital media are of more value for data preservation on the ten year time span than for the long term.