`
`Using the home TV screen, videotex networks can provide easy,
`inexpensive access to vast amounts of information. Here,
`we consider planned and possible network structures.
`
`Videotex Networks
`
`A. J. S. Ball. G. V. Bocltmann. and Jan Geesei
`University of Montreal
`
`1|
`
`l" ll'III|l..l|IIIIII
`
`“Willill IIt
`
`'I' ll
`
`
`
`The service for which the word “videotex” was
`originally coined is essentially a low-cost public data or in-
`formation retrieval service. Since success depended on
`rapid public acceptance and quick market penetration,
`simplicity and economy were the principal design objec-
`tives of the first-generation systems.I Generally.
`they
`were tree-structured. single data base. menu—based sys-
`tems using modified TV sets as terminals. Their basic
`technology. principles. and projections are discussed at
`length in The Wen-data Revolution by Fedida and Malik .3
`Now. foll0wing some operational and field-trial ex-
`perience with England‘s Prestel and other systems.
`second—generation systems are being planned and dis-
`cussed. and viable videotex services are rapidly evolving
`into public information utilities. These utilities will offer
`a variety of information services and transactions. such as
`retrieval from multiple independent data bases. messag-
`ing. electronic mail. conferencing. banking.
`teleshop-
`ping, and interest matching. In second—generation sys-
`tems the emphasis is more on videotex as a communica-
`tion medium rather than asa simpleinforrnation retrieval
`System. Future systems will move toward two-way com-
`munication among users as well as between users and in-
`formation providers.
`The trend toward public information utilities is also ap—
`parent in two parallel developments: the emergence of
`home computer networks3 and proposals for integrated
`broadband distribution systems“5 carrying various infor-
`mation traffic such as digital telephony. video. videotex.
`alarm. and metering services totfrom subscribers.
`in June [930. a workshop held at
`the Dépanement
`d'lnl‘ormatique et de Recherche Operationnelle. Univerv
`site' de Montreal. assessed videotex development in dif-
`ferent countries and explored technological trends. This
`article reflects workshop results in the area of videotex
`
`network structures; other works deal with data base struc-
`tures and information providers.M
`Here, we consider both planned and possible videotex
`net work structures. We use the term "videotex network "
`to stand for the overall system. including not only the
`means of communication but also the user terminals and
`the hardwarcr‘software of the computer systems pro-
`viding the services.
`In the following sections. we in—
`troduce videotex network components and describe ex-
`isting and planned network structures. ranging from sim-
`ple star-like configurations to sophisticated ones involv-
`ing distributed processing. Then. we discuss design issues
`and present a tentative generic structure for future video-
`tex networks.
`To facilitate comparison of some typical network
`models which have been—or soon will be—implernented.
`all diagrams use the set of symbols and acronyms defined
`in Figure l . The sites of some typical network functions
`(such as accounting) are also shown in the network dia-
`grams.
`
`Network components
`
`Before considering particular networks. let's review the
`main functions and physical components found in video-
`tex networks.
`
`User terminals. The user terminal is the equipment at
`the subscriber‘s home or office. A typical videotett UT is
`connected to a communication medium. uses a conven-
`tional TV set for display. and has a keypad for selecting
`the desired information or service. The terminal provides
`a basic character—oriented display mode (alphamosaic
`coding). and in some systems more advanced capabilities
`
`MIMlfltmrlm-IWJS
`
`MUD IEEE
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`COMPUTER
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`Figure 1. Legend o! symbols and tonne.
`
`Network: switched. packet.
`virtual circuit
`
`Htghspsed dedicated llrlfl or circuit
`
`Low-speed dial-up line
`
`Computer: single. multiprocessor.
`front-end procesSor
`
`Mass store:
`Master vldeotex data base
`Replicated videotex data base
`Independent third-party data base
`Local data store tor system
`administrallon
`Partial: subset of master data base
`
`P
`
`Videotex center
`
`Subsystem boundary
`
`Project or system boundary
`
`Accounllng functions
`Control center oomputerlsl
`Database computerlcenter
`Metaservice tunctlons
`
`Information provider
`Information provider terminal
`Information retrieval center
`
`Preprocesslng center
`Relational. records-oriented processor
`Residential unit
`
`We video and data multiplexer
`Statistical processor
`Update cotter tor vtdeotex master data basets]
`User tennlnal
`Vicente: center
`
`RU
`
`5
`UDC
`UT
`VB
`
`such as graphic (alphageometric) and photographic
`modes. A variety of extensions of this basic videotex ter-
`minal can be foreseen, ranging from the replacement of
`the pad by a standard alphanumeric keyboard to the addi~
`tion ofhome computers. hard-copy printers. alarm detec-
`tors, etc.
`
`Services. A subsystem of the videotex network which
`provides a particular service to the user is called a service.
`The main videotex service is information retrieval. but
`others. such as electronic mail and transactions. may also
`be accessible. A service is usually implemented on one or
`several computer systems and/or data bases. which we
`consider to be part of the videotex network. Conversaly. a
`given computer system or data base may be involved in
`the implementation ofseveral services.
`
`Communication media. Components of the videotex
`network are connected by communication media. For
`communication with the User terminal. different media—
`broadcast or cable TV, the telephone system. or integrated
`service networks based on cables or optical fibers—can be
`used. For communication among other network com-
`ponents, general-purpose media are employed—for exam-
`ple, dedicated or switched circuits. satellitelinks. or packet-
`switched data networks.
`
`videotex centers are gaining importance as sites of local
`intelligence where network size and complexity require
`distributed functions. VCs provide the effective interface
`between the network and user terminals. Minimal func-
`tions include line control. terminal handling. echoing; er-
`ror detection; code translation; log-in. user identifica-
`tion; concentration; some of the accounting and stalls-
`tics; and a directory of available services called meroser‘
`ulce'.
`
`Existan and planned videotox networks
`
`Networks with centralized data ballets}. Figure 2 shows
`the simplest possible videotex configuration. consisting
`of a single computer with a centralized data base. All user
`and information provider terminals are connected direct-
`ly to the central computer complex through dedicated or
`dial-up telephone connections. but similar systems could
`be implemented using two-way cable. The obvious dis»
`advantages or this system are the cost of connections over
`longer distances and the performance bottlenecks which
`quickly develop for line handling and data base access.
`Such configurations are typically used in situations where
`
`Information provider terminals. A user terminal is the
`instrument of the consumer; the information provider
`terminal is the equipment used by the information pro-
`vider to prepare and maintain the information available
`in the videotex network. IPTs range from simple charac-
`ter-oriented interactive terminals with editing functions
`provided in the data base computers. through special-
`purpose terminals for picture editing with local storage.
`to general-purpose computer systems.
`
`Videqu centers. Also called concentrators. videotex
`interface machines. videotex switches. or local access.
`
`
`
`Figure 2. Simplest Videolex system.
`
`December 1950
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`the number of active users is not expected to exceed
`several hundred. Examples are the initial'P-restel Interna-
`tional system in England and various. Teli'don' field-trial
`configurations in Canada.
`The network shown in Figure 3. designed to serve
`several
`thousand users,
`is currently used in British
`Telecommunications'Prestel an'd'its'i‘lerivative's.a Theup-
`date center. UDC. maintains a master data'base'and con-
`trols the interaction with information prOViders. A
`number of information retrieval computer-s, 1110:. are
`connected to the UDC throuyt leased synchronous lines;
`all lRCs maintain identical copies of themaster data base
`and provide 200 dial-up ports for user terminals. Limited
`interaction between the information provider and the
`retrieval computer is also possible (for example, collec-
`
`Floure 3. Fractal and derivative cyclonic.
`
`
`
`
`Figure 4. Vidaotait and external data bases.
`
`10
`
`tion cruiser-generated messages and response pages). The
`Prestel network includes a number of other computers
`and terminals for network management. control, and
`billing. Plans call for the inclusion of additional update
`centers; however,
`it is not clear how the problems of
`multiple master data bases and providing local data on
`regional machines will be solved if this expansion techni-
`que is used.
`'
`
`Integration of several data bases and services. As the
`quantity and diversity of information in the system
`grows. holding all information in a single data base
`becomes impractical. The obvious solution is to establish
`several independent data bases, which the user selects
`through a metaserviee direct0ry of services or by gateway
`pages within a given data base. This design approach
`leads to a network of the type shown in Figure 4. An ero-
`tension of Prestel-like systems in two directions. this net-
`work (1) integrates independent third-party data bases
`and (2) includes a peeket-switching network. As the
`number of components in the system grows. packet
`switching may become more cost-effective and efficient
`than dedicated point-to-point links.
`At
`least
`two such systems are currently planned,
`Bildschirrntext" in Germany and a field trial at Velizy,
`France. 1° Both systems. much like Prestel. have several
`videotex retrieval computers with. replicated data bases
`and one update center. (The published material on
`Bildschirtntext. however. is not clear about the existence
`of an update center.)
`Independent third-party data bases and pessiny other
`services may-also be accessed bytheuser. Such services are
`implemented on external computers connected to the
`public data network. An example ofsuch a-service is the
`catalog-lookup and order processing offered by the
`Quelle department store in Germany. Another example is
`a planned link between Germany’s Bildschirmtext and
`PresteI.
`_
`1n the networks discussed above, all network functions
`are performed in a single computer {possibly enhanced
`with front-end computers). Figure-5 shows the structure
`used by: the French Antiope system,I '.-'3 where network
`functions are distributed. Users are connected through
`switched (dial-up) telephone lines to videoten- centers.
`which handle interface functions far the user. The video-
`tex centers. videotex data bases (e.3., Star'systerns”). the
`update computer with the fideotex master data base, and
`independent third-party data bases are all conneCted
`through the Transpac public data network. Another type
`of data base for broadcast videotex (called Didon in the
`French system) is also. connected to and accessible
`through the same network.
`
`Multiservice integrated networks. Although highly
`sophisticated,- the network in Figure 5 isa special-purpose
`structure designed to deliver a relatively narrow class of
`digital information services to business or home users. A
`more metal network architecture. the Omnitel system
`shown in Figure 6 and described by Coyne,‘ will distribute
`a much larger class of information services through a
`singlecommunication medium—hutiallytwo-way cable,
`later Optical fibers. Services will include digital telephony.
`
`COMPUTER
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`digital data transmission. videotex, teletext. cable TV,
`pay TV. switched video. meter readings. alarms. and poll-
`ing. Such integrated broadband systems are especially
`feasible in North America, where CATV cable systems
`have widespread penetration. One. the Granite] system.
`will be used in a field trial in Manitoba. Canada (Project
`Ida).
`Although this type of network is necessarily designed
`with different optimization criteria than a purely digital
`videotex network. it incorporates several features that
`might be applicable in less generalized systems.
`The backbone of the Omnitel system is a two-level
`coaxial cable distribution structure (shown as a switched-
`cable network in Figure 6). The cable’s 300-an band is
`split and dynamically allocated to different users and ser-
`vices. Generally. domtstream transmission is between 50
`and 300 MHz. upstream between 5 and 30 MHz. Most of
`the bandwidth is consumed by the analog video services;
`digital transmission for approximately 300 hom is car-
`ried- on eight 1.5 megabit-per-second channels. Since
`these channels are time»multiplexed among different ser-
`vices to different subscribers. the digital portion of the
`system is in effect a packet switching subnetwork.
`In addition to two levels ofintelligent conth within the
`cable system (not shown in the figure), there is one more
`level of concentration between the cable network and the
`residential units. These concentrators. called remote
`video and data multiplexers or RVDMs, are partly
`analogous to videotex centers and are typically shared by
`12 subscribers. Besides controlling data concentration.
`packet addressing, and similar communication functions.
`RVDMs contain videotex display generators. These are
`
`time-shared by 12 subscribers. which allows for a very low
`cost. "dumb" user terminal: only a TV set and keypad are
`required. A microprocessor-based residential unit inter-
`faces the RVDM to the keypad. sensors. alarms. etc. The
`RU polls all devices for signals and distributes returning
`responses to the appropriate devicds) inside the resi-
`deuce.
`The cable network described above is controlled by a
`
`minicomputer control center and communicates with the
`telephone network, public data networks. videotex. and
`independent data bases as shown in Figures 4 and 5.
`
`Daslgn issues
`
`Data distribution. The merits of the two extreme solu-
`tions—complete duplication of all data in each data base
`vs. partial data bases at different sites—are frequently
`discussed in theliter'atnre. ’3 For videotex applications, we
`can distinguish the three reasons for data bases with par-
`tial information:
`
`x_25
`TRANSPAC
`
`- TELWHONE
`"mom
`
`swrrcHED
`GABLE {cart}
`
`
`
`
`Flgure 5. Distributed Vldaoteit system used In Antlope.
`
`ALA“
`Mgm'l‘da
`SYSTEMS
`_
`_
`
`IPTs
`
`a .
`‘
`VIDEOTEX
`
`(1) Information providers could provide-access to a
`particular kind ofinforntation in-independent third—party
`data bases. In some cases. the data base would exist for
`purposes unrelated to the videotex application.
`(2) Some information providers might prefer to man-
`age their own data base instead of storing information in
`the Communication carrier's main Videmex data 5353- Figure 6. A multlaenlce, distributed processing system such as Om-
`Small IPs could store their information in independent
`nltel.
`
`L.“ m ALAflMS' SENSORS
`
`December 1 980
`
`1 1
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`data bases provided by information brokers in competi»
`tion to the carriers.
`(3}. Data bases are frequently geographically distrib-
`uted in order to reduce communication costs. Therefore.
`it seems natural to keep local information, relevant only
`to acct-Iain geographical area, in the local data base.
`Points (1) and (2) above correct-n the distribution of
`masterdata bases; here we consider the distribution of
`data in replicated data bases, which may contain all or
`part of the master data base. Since one main
`for
`data replication is to reduce the data retrieval bottleneck,
`it is important to replicate the frequently accessed infor-
`mation pages. If the master data base is large, the'second—
`ary data
`may contain only subsets of the master.
`User requests for information not available'iu'tbe second-
`ary data bases must then be automatically forwarded to
`the master data base.
`
`There may be—as in enmputer system memory hierar-
`chy—more than two levels of information storage. The
`most frequently accessed pages may be automatically
`kept in a local store at each videotex center, and with
`sophisticated terminal equipment may keep private
`copies for repeated use—for example, CAI crimes. The
`combination of interactive and broadcast transmission.
`considered in a later section. is also
`on the memory
`hierarchy principle.
`In present videotex networks. both methods—com-
`plete duplication of master data bases and several masrer
`data bases together with-partial (nonLOverlapping) infor-
`mation—are used. In Prestel. for example. all data are
`duplicated in each information retrieval center. This-gives
`a performance advantage (feweraccess bottlenecks) and
`decreases communication costs (no-longdiStanoe calls for
`any pages}. but at the price of additional computer sites
`
`and some difficulties in simultaneous updating. Due to
`update scheduling.
`temporary inconsistencies are a
`potential problem in such applications as stock market
`listings and sports results (betting. eth. Architectures
`like Antiope, on the other hand. permit greater flexibility
`since the contents ofeach constituent data base (Star) can
`be independently defined (i.e.. contain a subset of the
`available services).
`
`Directories and transparency. Partially overlapping
`data bases together with independent third-party data
`bases requiresomekind of metaservice directory' to guide
`the user to the desired service or application. In Antiope,
`directories are implemented in the videotex centers.
`A related issue is whether or not the distribution of in-
`formation into several data bases should be visible to the
`user. Both 'possiblities seem applicable: when logically
`related information is partitioned into several data bases
`with similar retrieval procedures, the user should not be
`aware of transitions between partitionsian example is
`given in Bochmann and Gown"); on the other hand, he
`should be permitted to choose between logically distinct
`applications or different versions of the same service.
`ideally. the user should see the logical but not the physical
`aspects ofdata distribution, provided no user charges are
`associated with the physical distribution.
`
`The two approaches can be combined. For example, in
`Bildschirmtext (Figure 4) the videotex data base contains
`gateway pages which transfer the user into a specific ap-
`plication on another data base. Although transfer is
`automatic in the sense that the user does not log-in to the
`new database, it is not transparent—the user is notified of
`the transfer.
`
`
`
`HIGH-irate
`
`Figure 7. Generic Vldeotoa system.
`
`12
`
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`The role of videotex centers. BasicallyI VCs act as con—
`centrators that save communication costs and provide the
`interface to user terminals. With the growth and decen—
`tralization of videotex systems, their intelligence and im—
`portance will inevitably increase. Additional functions
`naturally fitting into the VC include
`
`user-related accounting, updating CCC files at the end of
`a session. This solution would also help protect the user’s
`privacy since VC records could be erased once the CCC
`was updated with aggregate data.
`Furthermore. transaction-based retrieval would make
`it easier to access data bases with conventional record-
`oriented file structures. it would also simplify adaptation
`of existing data-base systems with different query
`languages. Imagine, for example, a large videotex data
`base with a sophisticated subject index that is actually a
`relational data base running on a separate specialized host
`{see Figure 1’).
`
`Combining transmission channels. Another use of VCs
`would be in a system employing both interactive and
`broadcast transmission of a large page-oriented videotex
`data base. The most frequently requested subset of pages
`would be transmitted in a broadcast cycle (e.g.. on a full
`TV channel. readily available in most CATV systems);
`only those pages not actually in the broadcast cycle would
`be interactively accessed from the data base. This would
`alleviate some serious access bottlenecks. To keep the
`system flexible. the content of the broadcast cycle should
`be allowed to change dynamically in response to user ac-
`cess patterns. A suitably coded index of the cycle’s current
`content would be periodically broadcast and stored in
`each VC. User requests for new pages would be examined
`in the VC and forwarded to the data base for selective
`retrieval only if the page is not found in the index. A
`similar “request intercepting" mechanism could be used
`
`(i) Metaservices. The VC could provide a directory of
`available services and applications. HELP commands,
`user advice. and automatic routing of calls.'2
`(2) Virtual terminal standardization. To simplify the
`interworking of several independent services with dif-
`ferent types of home terminals, the VC might present a
`standard virtual terminal protocol to the different net—
`work services. independent of the particular home ter—
`minal. Functions to be considered include code conver—
`sion, page formatting,
`form display. and data entry
`(especially for transactionoriented applications).
`[3) Access and control. VC functions could include
`log—in, user
`identification. access control accounting
`functions. and possibly encryption.
`(4} Storage management. Down—loading and local
`mass storage of frequently acce5sed data from distant
`data bases are functions that could be activated by the
`user (e.g. , for a CAI course} or by the system management
`(cg, for recent football information).
`(5) Software. As an intermediate form of telesoftware,3
`the VC could execute software supplied by service pro-
`viders.
`(6] Persona! computing. Making the VC a substitute
`for a sophisticated personal computer raises many in-
`teresting possibilities—economic program development.
`personal file keeping. maintenance of user-specific direc-
`tories. labels. and profiles—for satisfying personal data-
`retrieval needs.
`
`PMC Exhibit 219
`
`Technically, the last three features are equally feasible
`in intelligent user
`terminals. However.
`from a cost-
`effectiveness [and thus user-acceptance) point of view.
`sharing such advanced facilities in a common VC might
`be a better solution. An example of this approach is the
`RVDM in Omnitel. where videotcx display generators
`and memories are shared by 12 subscribers. Similar
`assumptions underly an experiment by a Montreal cable
`company ‘5 in which Apple-ll computers at the cable head
`are shared by users playing interactive TV. games.
`
`Transaction-oriented retrieval. In most existing video—
`tex data bases, the system must keep dynamic status infor—
`mation about the progress of a retrieval session. This
`user—context information contains items such as traces of
`previous index choices and billing and statistical in forma~
`tion. Context—keeping becomes a burden when many ac—
`tive users have long sessions. and it can be further com—
`plicated when there are transfers to other services within a
`session.
`A solution to such problems would be to keep all con-
`text pertaining to a user session in the corresponding
`videotex center or a preprocessing center (see Figure 'l);
`interactions between such centers and data-base com-
`puters would be in terms of simple transactions {such as a
`page request). The data—base computers would not need
`to keep traces of such transactions; the VC would handle
`
`December 1980
`
`DIRECTOR OF
`COMPUTER SCIENCES
`
`Honeywell's Corporate Technology Center is selec-
`tively recruiting for a Director of its Corporate
`sciences Center.
`This Center’s current activities focus on
`technological advancements in computer architec-
`ture. software methodology and design automation
`for VISI. The position will be accountable for
`developing research strategies; establishing
`olicies and objectives; monitoring center per—
`ormance; overseeing technology transfers through-
`out the corporation; and selecting and managing a
`proper mix of highl qualified scientific
`reonnel.
`Candidates a cold
`ossesa 8 Ph
`in Com-
`puter Science or related field with progressive expe-
`rience in computer architecture or software meth~
`odology research, and in management. Published
`work in scientific journals desired. Strong com-
`munication abilities necessary.
`This position offers a competitive salary lus
`bonus, a comprehensive benefits package an an
`excellent opportunity for future advancement
`within Honeywell. For immediate consideration,
`submit a resume with salary history in complete
`confidence to: RS. Heinz (CM), Honeywell Ina,
`Honeywell Plaza, MN12-2109, Minneapolis, MN
`
`Hfi‘heywell
`
`An Equal Opportunity Employer MKF.
`
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`

`8. Presrei: The Technology. British Telecommunications.
`London. England. 1979.
`9. Networking in the German Biidscitirmtexr System.
`Deutsche Bundepost. Germany. I979.
`10. D. Le Moign. personal communication.
`II. B. Marti et al.. "The Antiope Videotett System.“ iEE‘E
`Trans. Consumer Electronics, Vol. C525. No. 3. July
`1979. pp. 327-330.
`12. D. Le Moign. Presentation d9 STAR. CCETT. Rennes.
`France. Mar. 1980.
`U. B.H. Liebowitzand J.l-{. Carson. eds.. Tutorial—Distrib-
`tried Processing. IEEE Computer Society. Oct. 1978?
`(3. V. Bochmann and .l. Gecsei. “Towards Videotex Stan-
`dards.“ Proc. Viewdatoa’flCoqf. (Online). London. I980.
`[5. LL. Houle. personal communication.
`
`l4.
`
`'Tht's Iutorial is available from the IEEE Computer Society Publications
`Office. 5855 Naples Plaza. Suite JOI . Long Beach. CA 90803.
`
`Alan Ball retired from academia in l978
`and started his own firm, BCD Library and
`Automation Consultants. Based in
`Regina. Saskatchewan. BCD provides ad-
`vice on library automation to libraries
`across Canada. Now working on library
`applications ofTelidon at the Université de
`Z Montre'al. Ball also serves as acting direc-
`. tor of LABS.
`the Library Automation
`Systems of Sea katchewan. and as chairper-
`son at‘ the UTLAS user's exchange.
`Ball received a BSc in mircrohiology from the University of
`London in 1965. a PhD in molecular biology from McMaster
`University in [969. and an MLS from the University ofWaterloo
`in [977.
`
`-
`
`'
`
`in cases where information is stored locally in the VC. All
`such processing should be hidden from the user. who
`would have the impression of working with a single logical
`data base.
`
`Future network structure
`
`The foregoing discussion leads us to conclude that
`future videotex systems will have distributed architec-
`tures similar to the one shown in Figure 7.
`Information providers. user terminals. and residential
`units will be connected to an integrated local-in formation
`distribution system through videotett centers. This distri-
`bution system will provide access to a variety of services.
`including videotex. via a high-speed'data network.
`Services will be provided by a number of computers
`operating in transaction mode and dedicated to specific
`tasks such as page retrieval. messaging. mail. and finan—
`cial transactions.
`A query from an individual user will be processed by a
`videotex centerts) or larger preprocessing centerts), which
`will transform the query. route it via the high-speed net-
`work to the appropriate service computer. receive the re-
`ply . and return the requested in formation or service to the
`user.
`
`Although considerable development work remains to
`be done. the basic skeleton of such systems is visible in
`both the Antiope and Omnitel implementations. I
`
`Acknowledgment
`
`This work was supported by Strategic Grant No. GO
`363 from the Natural Sciences and Engineering Research
`Council. Canada.
`
`Reteroncoe
`
`i.
`
`“Videotex System
`and AJ-i. Marsh.
`J.M. Costa
`Planning." Proe. Not'i Eieetrom‘er Cord“ Chicago. "1..
`Oct. 1979. pp. 337-342.
`2. S. Fedida and R. Malik. The Viewdota Revolution.
`Halslead Press. Div. of John Wiley 8: Sons. New York.
`1979.
`
`4.
`
`5.
`
`3. A. Kleiner. "A Survey of Computer Networks." Dr.
`Dotti) '5 Journal of Computer Coir'sritenies ti Orthodontic.
`No. 46. .lunea'luly will}. pp. 6-14.
`J .l . Coyne. An integrated Broadband Distribution System
`for the Eighties, Coyne Associates Systems. 87-1313
`Border 51.. Winnipeg. Manitoba. Canada. [980.
`0.1‘. Hopkins. "Multimode Communications on the MI-
`TRENET.“ Proc. Local Area Communication Networks
`Syrup. Boston. Mass.. May 1979. p. I69.
`ti. F.W. Tompa.
`.l. Gecsei. and (1V. Bochmann. "Data
`Structuring Facilities for Interactive Videotex Systems."
`De'parten'tent d‘lnformatique et de Recherche Operation-
`nclle. Universite‘ de Montréal.
`7. D. Leahy and B. Botten. “Videotex and the Information
`Providers." in preparation. For information contact the
`authors at Fintel. London. England.
`
`
`
`Gregor V. Boehmann. an associate pro-
`fessor in the Department d'lnforrnatiquc
`et de Recherche Opérationelle. Université
`de Montreal. has worked in the areas of
`programming languages and compiler
`design. communication protocols. and
`software engineering. His present work is
`aimed at design methods for communica-
`tion protocols and distributed systems. He
`was a visiting professor at the Ecole Poly‘
`technique Féderale de Lausanne. Switzerland {1977-78) and at
`Stanford University. California “979-80).
`Bochmann received the diploma in physics from the Universi-
`ty ofMunich in I968 and the PhD degree from McGill University
`in 1971.
`
`Jen Gemei has been aprofessor ofcomputer
`science at the Universite de Montrdal since
`[975. Before that he was with mm in San
`Jose. California. working mainly on
`memory systems. and with the Research In-
`stitute for Computers in Prague. Czecho-
`sloyrakia. where he worked as a logic de-
`signer.
`Gecsei received the MSEE degree from
`the Czech Technical University in I953 and
`-
`the PhD from the Czechoslovak Academy of Science. Prague. in
`l964.
`
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