Reuven Feuerstein y el Aprendizaje Mediado 50 

many libraries lack digital preservation policy, and many librarians do not have training on digital resource preservation. They further stated that, the low awareness was caused by preservation challenges which include lack of management support, standard and policy, as well as poor funding and low capacity building for libraries and librarians.

On the issue of funding, Oluwaniyi (2015) opined that finance is an essential ingredient for the preservation of information materials in libraries. After acquiring information resources in the library, the next thing step of thought should be on how these information resources would be preserved for the needed users. Finance is very important for the provision of digital materials in the library and likewise, the preservation of the digital materials is very imperative.

Adequate funding on the aspect of preservation of digital materials is very

imperative so that all the equipment and materials required for sustainable

preservation programme like fumigators, fire extinguishers, adequate shelves and

racks, air conditioners, internet subscriptions, purchase of antiviruses, computers,

refreshing machines, personnel trainings etc can be actualized.

the materials. The UNESCO (2003) guidelines on digital heritage preservation have this to say concerning factors that can inhibit the utilization of digital resources in the library: the world‟s digital heritage is at risk of being lost to posterity. Contributing factors include the rapid obsolescence of the hardware and software which brings it to life, uncertainties about resources, responsibility and methods for maintenance and preservation, and the lack of supportive legislation.

Igboejesi (2003) noted that lack of interest and commitment to library development on the part of the school administrators E.g Vice Chancellors, Rectors and Provosts can inhibit the utilization of digital library resources.

Rosenthal (2005) in firm support to the UNESCO (2003) statement concerning the threat of loss said that there are interrelated factors that cause digital library materials to deteriorate. They are threats and are seen as enemies of library collection. They are capable of leading to loss of vital digital documents. Many of these threats are not unique to digital preservation system, but their specific mission and very long time horizons incline such systems to view the threats differently from more conventional systems. These threats include:

- Media failure – All storage media must be expected to degrade with time,

causing irrecoverable bit errors, and to be subject to sudden catastrophic

irrecoverable loss of bulk data such as disk crashes or loss of off-line media

- Hardware failure – All hardware components must be expected to suffer transient recoverable failures, such as power loss, and catastrophic irrecoverable failures, such as burnt – out power supplies

- Software failure – All software components must be expected to suffer from bugs that pose a risk to the store data

- Communication errors – Systems cannot assume that the network transfers they use to ingest or disseminate content will either succeed or fail within a specific time period, or will actually deliver the content unaltered

- Failure of network services – Systems must anticipate that the external network services they use, including resolvers such as those for domain names and persistent Universal Resource Locators (URLs), will suffer both transient and irrecoverable failures both of the network services and of individual entries in them. As example, domain names will vanish or be re-assigned if the registrant fails to pay the registrar, and a persistent URL will fail to resolve if the resolver service fails to preserve its data with as much care as the digital preservation service

- Media and hardware obsolescence – All media and hardware components

will eventually fail. Before that, they may become obsolete in the sense of

no longer being capable of communicating with other system components

or being replaced when they do fail. This problem is particularly acute for removable media, which have a long history of remaining theoretically readable if only a suitable reader could be found

- Software obsolescence – Similarly, software components will become obsolete. This will often be manifested as format obsolescence when, although the bits in which some data was encoded remain accessible, the information can no longer be decoded from the storage format into a legible form

- Operator error – Operator actions must be expected to include both recoverable and irrecoverable errors. This applies not merely to the digital preservation application itself, but also to the operating system on which it is running, the other application sharing the same environment, the hardware underlying them, and the network through which they communicate

- Natural disaster – Natural disasters such as flood, fire and earthquake must be anticipated. Other types of threats, such as media, hardware and infrastructure failures, will typically manifest them

- External attack – Paper libraries and archives are subject to malicious attack; there is no reason to expect their digital equivalents to be exempt.

Worse still, all systems connected to public networks are vulnerable to

viruses and worms. Digital preservation systems must either defend against the inevitable attacks, or be completely isolated from external networks - Internal attack – Much abuse of computer systems involves insiders, those

who have or used to have authorized access to the system. Even if a digital preservation system is completely isolated from external networks, it must anticipate inside abuse

- Economic failure – Information in digital form is much more vulnerable to interruptions in the money supply than information on paper. There are ongoing costs for power, cooling, bandwidth, system administration, domain registration, and so on. Budgets for digital preservation must be expected to vary up and down, possibly even to zero, over time.

- Organizational failure – The system view of digital preservation must

include not merely the technology but the organization in which it is

embedded. These organizations may die out, perhaps through bankruptcy,

or their missions may change. This may deprive the digital preservation

technology of the support it needs to survive. System planning must

envisage the possibility of the asset represented by the preserved content

being transferred to a successor organization, or otherwise being properly

disposed of.

Rosenthal (2005) therefore advises that for each of these types of failure, it is necessary to trade off the cost of defense against the level of system degradation under the threat that is regarded as acceptable for that cost.

Meanwhile, for convenience sake, these failures can be grouped into three factors thus:

- Technological factor – under this factor, all the media and technological issues that contribute as threats to the life and existence of digital resources are grouped together. They include media failure, hardware failure, software failure, communication errors, failure of network services, media and hardware obsolescence, software obsolescence, operator error, external attack etc.

- Natural disasters – include flood, fire, earthquake etc and,

- Man – made disasters – include internal attacks, wars, felony, arson, economic failures, management/organizational failures etc. They are contributory factors to the destruction of digital resources in the library.

In supporting this fact, Nwanguma (2006) stated that a great deal of damage and

deterioration is caused by unnecessary use and over use of materials. The actual

break, tear, or smudge does not occur until the material is handled. Nwanguma

(2006) pointed out vandalism and theft as human factors of determination and

guidelines to curb them.

However, National institute of standards and technology as cited by Fynnette Eaton in his paper presentation (CF- www.cci-icc.gc.ca/PID/faq-e.pdf), stated that, one of the most important factors in the preservation of digital resources is the ENVIRONMENT. Electronic records, like other audio-visual records require temperatures between 62-68 degrees Fahrenheit, with an optimum of 65degrees, which is probably within the range required for textual records. The humidity requirements, however, are different for magnetic tape than for paper. Lower humidity between 35 and 45%, with an optimum of 40% is the recommended level. But this is less than the 50% recommended for paper records. George Cunha as cited by Eaton, noted that the commonly accepted view currently held is if audiovisual materials (including magnetic tape) cannot be isolated in a mini-environment, then the overall humidity in the building should be kept between 40% and 50%.

Greater care however should be taken to make sure that stable environment is attained. Studies indicate that one of the major contributions reducing the life expectancy of electronic media is fluctuating temperature and humidity. Stability rather than occasional optimum conditions should be strived.

The hardware should also be properly taken care of, the rooms where they are

kept should be properly fumigated as to avoid rodents and harmful insects from

destroying the wires of such gadgets. Similarly, UNESCO (2003) stated

appropriate storage and handling conditions for carriers: digital data carriers

(storage media) must be stored in conditions that do not accelerate their rate of deterioration. The main risks for data carriers are excessive temperature and humidity which endanger the carrier; dust or other particulates which may obscure access to the data; and in the case of optically encoded material, light, which may damage the optically inscribed data. Modern data tapes are of such a high coercivity, that accidental erasure by a magnetic field does not constitute a major risk. Magnetic data tapes may be integrated into a digital storage system.

Typically this would be housed in a clean computer room with controlled temperature and relatively humidity set at 18°C, and 40% RH, a continuous influx of clean, dust-free air, with daily cleaning to prevent contamination. The conditions would fluctuate not more than 2°C and 10% RH in any given 24 hour period. Magnetic data tapes stored for optimum carrier life (away from the computer room environment) should be stored under more stringent conditions, at a temperature between 18°C and 10°C, with a daily tolerance of no more than 1°C, and between 30 and 40% RH with a tolerance of no more than 3%RH.

Optical carriers, such as CD-Recordable, should be stored under similar

conditions, in a darkened environment due to their sensitivity to light. There are

suggestions that very low temperatures (approaching or lower than 0°C), may be

detrimental to the life expectancy of certain carriers, however, this has not been

proven”.