Annals of Library Science and Documentation 1988, 35(3), 105·110

OPTICAL STORAGE DEVICES AND THEIRIMPACT ON LIBRARIES AND INFORMATIONRETRIEVAL SYSTEMS

INTRODUCTION

Optical storage devices represent some of themost viable innovations for the improvement ofthe cost-performance relationships in computerand information management fields. About tenyears ago it was becoming evident that opticalstorage of information would have revolutionaryimpact on the office automation as well as thepublishing industry. Commercial exploitation ofoptical storage has come more slowly than ex-pected in the industry. But everything is now setfor rapid growth in at least some segments ofthis new technology. Just ten years ago it wasnot possible to even dream that the most pro-mising element of the optical storage technologywould be based on a new form of consumer pho-nograph. One -of the most important optical sto-rage technologies viz., CD-ROM ( CompactDisk- Read Only Memory) - is based on this newform of consumer phonograph and it offerstremendous application potential specially in thefield of information storage and retrieval sys-tems involving large bibliographic databases.

One of the main reasons for this rapid grow-th is the continuing demand placed by databaseusers for cheaper, more reliable and high densi-ty data storage devices to keep up with the ca-pacities of their mainframe systems l3]. As thevolume of data that a machine is capable ofprocessing becomes greater, the capacity of theaccompanying storage devices must also increaseto handle this large volume. For the last 35years, the density of magnetic recording mediahas doubled every two years. Increase in record-ing density in rigid devices has reduced theread/write head to medium spacing from 25 mi-crons to 0.3 micron during the period. Thoughcurrent laboratory experiments are investigatinga spacing of just 0.1 micron, it is thought thatfor many purposes, magnetic media have rea-ched their optimum. Though removable winchester disks of 300 MB capacity are expectedin the near future, many are look ing to optical

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erasable disks with a capacity measured in giga-bytes as the future solution to their storageproblems.

BILLION DOLLARS INDUSTRY

Already up to 11,000 CD ROM players have beensold and the majority of them have gone to sys-tem integrators. By 1990 the optical storage de-vices are expected to outperform the magneticstorage devices such as floppy disks in terms ofsales. Though estimates vary, Mr. William Gates,Chairman, Microsoft, however expects only 10%penetration of office desktop systems.

Whatever may be the exact rate of growth,the market is expected to be measured in hund-reds of millions of dollars. The San Jose marketresearch firm "Dataguest", gives a conservativeestimate that sales will have reached a value of$ 700 million by 1990. Ed Rothchild, consulta-nt and publisher of "Optical Memory News"goes further to predict a market of $ 13 billionby the same date. Wherever the truth may lie,optical disks seem to stay, displacing magneticdisks from their more than 3 decades of utilities[3] .

ORIGIN OF THE TECHNOLOGY

Progress achieved in home audio entertainment,consumer electronics or high fidelity (Hi-H) sys-tems is remarkable. With the entry into the ageof computerised electronics, a revolution is be-ing. witnessed in the machines for playbackmusic. The digital audio disk (DAD) has becnlaunched carrying the commercial name of C0111-

pact disk (CD) and is most likely to supplementif not completely replace the audio disk or LP.

DAD OR CD AUDIO TECHNOLOGY

Now a new type of 'record' and 'record player'are in the western market. The CD is only 120

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mm (about 5")in diameter, yet it has a playingtime of 60 minutes with the sound informationon one side.

The CD rotates like a record, it is not touch-ed by a stylus but scanned by a small low pow-ered laser built into the CD player. The disk pro-vides information about the sound in the formof binary pulses or Os and Is , in digital terms.The rate at which the bit stream is obtained bydetecting microscopic pits 011 the disk js cons-tant and is equivalent to 4 million bites per se-cond. the Disk rotates at 500 rpm when the la-ser starts at the center and slows down to 200rpm as it follows the spiral of pits to the out-side.

Having been detected by the laser and con-verted to electrical pulses by a photo-diode, thedigital codes are seperated into two channels forstereophonic reproduction, and eventually con-verted to analogue sound using digital to analo-gue converters (DACs).

In practice, a CD player is an extremelycomplex piece of equipment. Being compatiblewith most existing systems, conventional diskscan still be used alongside the CD player with-out abandoning the treasured collection ofLPs[21

WHAT IS CD-ROM

CD-ROM player and disk technology is an exten-sion of CD-audio technology using exactly thesame recording and reading techniques as themost successful DAD players. Thus optical disksare going to be practically of very low cost. Gigadisks, as they are called sometimes, are expectedto cost between $10 and $20 per gigabyte in thenext few years. In addition they provide massstorage (currently between 500 MB and 4 GB)enabling a lot of data to be stored on very littlephysical space. Being small and light weight,optical disks are transportable and thereforeoffer an alternative means of database distribu-tion to on-line services. Already it is possible tobuilt up a complete database system includingall the hardware for just $ 30,000 to $ 40,000.Optical disk drives now cost $ 1000 to $ 1500with a disk capacity equivalent to 10,000 pagesof typed script. Within few years this capacity isexpected to increase to over 250,000 pages forthe same price. Linked via a suitable interface

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to a personal computer (PC) a CD-ROM playerand disk allow an end user access to databasewithout the cost constraint of variable charges(such as telecommunication tariffs and host'stime related access prices).

With these cost, storage and distributioncharacteristics CD-ROM is widely considered tohave important application potentials, notablyin publishing, library, documentation, archivaland information retrieval systems[ 1].

Presently there are three main types of opti-cal storage devices viz.:

(i) the read only optical disk (CD-ROM)

(ii) the write once read many (WORM) opti-cal disk and

(iii) the erasable/rerecordable optical disk.

There are also other kinds of compact diskcalled Compact Disk- Interactive (CD-I), Com-pact Disc Video (CD-V), Compact Disc- Inter-active Video (CD-IV), Laser Vision-Read OnlyMemory (LV-ROM) etc. whose description isbeyond the scope of this article.

Currently only the CD-ROM and WORMdisks are in manufacture. In the future writeonce optical disks are expected to dominate themarket. Erasable disks are also in the horizon.Already at the prototype stage, they may beseen in use very shortly [3] .

STRUCTURE OF CD ROM

The basis of the composition of CD ROMsis a plastic substrate. Usually the substrate isa polycarbonate, but there are experiments us-ing polymethyl metacrylate (PMMA) instead.The plastic substrate supports a reflective allu-minium layer just 5000 A thick. Over this thereis another very thin protective layer of plastic.The interface between the layers has a series ofmore or less equally spaced pits or bumps. Suchpits would be about 0.6 mm across and 1.6 mmapart on a typical disk. The pits follow a longcircular pattern- usually a spiral as on an LP re-cording.

The information embossed on the disk atmanufacture in this way is read by a 780 nano-

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meter laser beam focussed on the aluminium la-yer. The laser beam passes through the thin plas-tic coating without difficulty, and also throughsmall amounts of debris and dust on the disk.11hedisks are recorded in a constant-linear-velo-city mode. This gives the disks a capacity of atleast 540 MB; a figure which is rapidly increas-ing. The storage face is divided into blocks of2048 bytes with a typical field of 270,000 blockson one disk. The linear density of optical disksis about 35,000 bits per inch. With a track spac-ing of 1.6 microns, an optical disk can store atleast 20 times the capacity of a magnetic disk-some 560 million bits per square inch of surface.

STRucrURE OF CD PLAYER

A series of prisms, beam splitters, mirror lenses,wavelength filters and polarising filters directsthe laser beam and detects the patterns of sca-ttered light from the disk. The major compo-nents are mounted at the side of the drive whileothers are transported on a moving carriagewhich carries the optical-head reader across thedisk surface. It is this moving carriage whichgives the optical disks their high random accesscapability ..

Apart from the tracking mechanism, thereare two types of movement in aiming the laserbeam at the disk. The first of these is a fine ad-justment galvo-mirror which deflects the laserbeam to modify its angle of incidence in relationto the CD ROM. This gives the tracking head thefine degree of accuracy that is necessary. The se-cond is the in and out movement of lens mount-ed voice-coil type actuator, which maintains thefocus of the aluminium surface in relation to thetracking head.

Many optical disk systems contain embossedtracking grooves that absorb or scatter light. Thetracking photodetector regulates the running ofthe drive according to the intensity of light fall-ing on the walls of the tracking grooves and onthe bottom of them. The variation in intensityof light is picked up by the photodetector whichadjusts the lead orientation angle accordingly [3}.

ADVANTAGES

The main attractive feature of optical disk stor-age is the flexibility of the media. The opticaldisk can store data in four forms viz.:

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(i) audio

(ii) compressed audio

(iii) video and

(iv) compressed video

It can also store in usual data formats. With theintroduction of optical disk technology, thecomplex formatting procedures used by compu-ters for storage of data generated from varied in-puts such as sound and video are simplified.

In future, optical disks are expected to haveextremely high access speeds reaching upto 150K bytes/ sec. For small systems their speed willshow a great advantage over the on-line baud(bits/see) rates of 1200 bits/sec.

The compact nature of optical disk systemsgives them a great advantage where space is li-mited. Disk densities are 40 times more thanthose of magnetic disks. Storage modules of theorder of tens of gigabytes in a few cubic feet canbe built up in a single system.

There are two main reasons which hold backoptical disk storage at the moment. The first isthe fact that few write-once disks and no eres-able disks are currently available in the market.Until these are available, optical disks are onlyuseful for databases which seldom need updat-ing. A good example of such databases is thebibliographic databases of the secondary or theabstracting periodicals. As soon as erasable disksare available, the situation will change dramati-cally [3] .

Another attractive feature of CD-ROM isthat it uses the same technology as CD audio.Hence manufacturers' investment in productionfacilities are minimised. Given the capital costsinvolved, this is an important economic advanta-ge.

LIBRARY AND INFORMATION SCIENCEAPPLICATIONS

Hutnik [3] opines that library applications fea-ture high on the list of products available onoptical disk. Groiler Electronic Publishing haveproduced an optical disk version of the "Ameri-can Academic Encyclopaedia" for :5 199. A

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library of public-domain-PC-software (:ioftwareavailable freely for copying and use as popularlyknown gin USA) is offered by Library Corp. Afirm by name Reference Technology has pro-duced a CD ROM disk which offers over 9000different software packages. Most of these pro-ducts are also sold along with complete systemhardware because of the low cost of optical diskreaders.

In general it is library applications which willfirst see the influence of CD ROMs. Libraries,archives, hospitals and insurance records are allideal sites for optical disk storage technology.With this in mind Oxford University Press is put-ting the Oxford English Dictionary on opticaldisk. The product should be available by 1990.

SOME OF THE DATABASES AVAILABLE ONCD ROM

Chemical Abstracts (Health and Safety in Che-mistry)

A portion. of Chemical Abstracts service is beingmade available on CD ROM. Some 50,000 abs-tracts in the area of environmental chemistryand toxicity are readable on compact opticaldisks as "Chemical Abstracts:Health and Safetyin Chemistry". The disks use search and retrie-val software for use with Digital's Micro VAX Iand II and VAX station II computers and theIBM PC XT. The CD ROM file is offered on anannual subscription basis with quarterly diskupdates for $ 1195.

UKMARC file, the Whitaker file and the Con-ference Proceedings Index

The British Library demonstrated the advantagesof using the compact disk for storage at theLondon Online Meeting and earlier at the Octo-ber 85 Frankfurt Book Fair. The demonstrationdisk which has the potential for accommodating150,000 pages, contained samples of three ofthe library's Blaise online bibliographic files, i.e.the UKMARC, the Whitaker file and the Confe-rence Proceedings Index [6] .

CAB Abstracts

The compact disk version of CommonwealthAgricultural Bureax is now being tested in Mexi-

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co, Italy and Malawi. The CD ROM which repre-sents an alternative form for the online version,contains nearly a quarter of a million abstractsrecord for 1984 and part of 1985, a 40,000word thesaurus, and the Micro Basis retrievalsoftware in two versions for IBM PC and MicroVAX 1/11.

The disks will eventually be tested in 30countries many of them in the Third World.The CAB system group are presently assessingthe viability of CD ROM application for fur-ther distrib ution of CAB abstracts database,expert systems, books and unique databasesformed from subsets of various source data-bases[ 4].

H. W. Wilson Company Database

H.W. Wilson Company is bringing out 12 sepe-rate CD ROM databases such as Applied ScienceTechnology Index, Art Index, Biography Index,Social Science Index etc., with four differentaccess modes.

Educational Resources Information Centre(ERIC) databases

OCLC has become the third organisation afterDialog and Silver platter to market ERIC data-bases on CD-ROM.

Library and Information Science Abstracts(LISA)

Silver platter has released the Library and Infor-mation Science Abstracts on CD-ROM. The discincludes the database from 1969 to 1986 andthe database and the software would be updatedannually. This is even operational for retrievalwith Informatics India - a Bangalore based pri-vate firm.

OTHER DATABASES

Some of the other databases available on CD-ROM are:

1. Dissertation Abstracts

2. Aquatic Science and Fisheries

3. MEDLINE CD

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4. Poisindcx: A toxicology database

5. Dialog on disc

6. Books-in-print and Ulrich plus

7. INVESTEXT

8. DISCLOSURE II

9. PROMT

10. ABI/INFORM

11. Media general's Market File

12. Marquis' who's who in Finance andIndustry

13. Academic American Enclopaedia(Electronic Encyclopaedia etc. [7].

ACTIVITIES CONCERNING CD ROM

The world's first international conference on CDROM technology was held in March 86 andbrought together over 900 software developersand database publishers. Organised by Microsoft,the conference was an official recognition of theincreasing importance of optical storage devicesto the computer industry.

Another body, the Optical Disk Forum, metunder the auspices of the European Commission(DG XIII) in Luxembourg on 22nd January1986, to discuss the early implementation ofstandards for data retrieval from optical disks.Standards already exist at the level of hardwarefor CD ROM, and agreements on standards forthe rapidly evolving database market are urgent-ly needed to maximise the potential of the newtechnology.

The Optical Disk Forum assembled informa-tion providers, CD ROM manufacturers and ven-dors with the aim of achieving a joint workingstandard for both Europe and US. It was pro-posed to set up a technical committee to analysethe emerging American recommendations, toreact to them, and propose modifications wher-ever necessary to suit European requirements.

A conference to discuss the European re-quirements was held on 16th May 1986 in Lux-embourg[ 6 J.Vol 35 No 3 September 1988

Harwel, the producer of STATUS software,made an announcement to hear from publi-shers who wish to exploit CD ROM technologyso that a CD ROM club could be formed. About50 enquiries were received by July 86 regardingthe proposed CD ROM club. The club wouldenable the new technology to be aimed at spe-cialised professional groups.

CD ROM clubs could offer new cross roadsfor information providers to exploit the full po-tential of the European market [5) .

CONCLUSIONS

CD-ROM technology works and is most likelyto penetrate the conventional storage techno-logy and stay long. However, if optical disks areto succeed, some kind of standard must be ag-reed upon on both hardware and software.Efforts are also on in this direction among theEuropean countries and the US. Since CD ROMsare interchangeable and retrieval is intrinsic,they bring in considerable amount of flexibilityin their use. Closer assessment of the impact ofCD-ROM on library and information sciencewould indicate that it might act as an initialsubstitute for host on-line services such asDIALOG, ORBIT, ESA-IRS etc. The futuretendency might be to use host on-line servicesfor current search and also for general subjectsnot falling directly in line with the specialsubject fields of interest. For retrospectivesearch for 5 yearly periods, CD-ROMs arelikely to be used. Ultimately the end userswill be the professionals from institutions andoccasionally individuals for whom on-linesearches would become an independent day-to-day routine.

Optical disks wil be a boon for India pro-viding a cheap and satisfactory solution to da-tabase problems. The working conditions hereare radically different when compared with theWest. Telecommunication networks are oftenunreliable, and so in-house CD-ROM based sys-tems may become more prominent. Moreover,high humidity during monsoon, and the summerdust will not affect these new storage deviceswhich are made of very stable material (poly-carbonate covered with thin aluminium la-yer followed by another very thin protectivelayer of plastic) and are not easily damaged.They can even be read through a layer of dustsince laser beam is used for reading.

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Large databanks can be stored securely onCD-ROMs. Handbooks, encyclopaedias andother reference materials, besides bibliographicdatabases in the fields of agriculture, medicine,engineering etc., will be available on CD-ROMsfor the first time at the touch of a key on thekey board of PCs. Thus, information transfer -which is as important as technology transfer inmodern times- will be enormously speeded upand India's access to technical information anddata will be 'at par with the West.

REFERENCES

1. The challenges of CD ROM. Information Market1985/86,42,4.

llO

2. Keely Christ: Compact disc· the technology. Prac-tical Eleetronics 1984,30.3.

3. Hutnik Ivan: Optical storage CD·ROM: bigger me-mory. Computers Today 1986,2(14),21-7.

4. Compact CAB. Information Market 1986, 44, 7

5. CD ROM brings European publishers together. In·formation Market 1986,44,7.

6. European CD ROMsters call for standards. Infor-mation Market 1986, 43, 6.

7. Devaciason, F J: Microcomputers, databases andCD ROM. (paper presented at the MicrographicCongress of India Convention and Exposition MCI·88, New Delhi, 20·22 Jan. 1988).

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