Architecture of a multimedia communication system for technical documentation in a modern factory

Ž .Computers in Industry 36 1998 83–93

Architecture of a multimedia communication system for technicaldocumentation in a modern factory

Constantine A. Papandreou a,), Dionisis X. Adamopoulos b,1

a ( )Training and Research Centre, Hellenic Telecommunications Organisation OTE , 17 Kalliga Street, GR-114 73 Athens, Greeceb Centre for Satellite Engineering Research, Department of Electronic and Electrical Engineering, UniÕersity of Surrey, Surrey, UK

Abstract

This paper examines the influence of multimedia communication services and electronic document systems in themanagement of technical documentation within a modern factory. After a brief introduction in Computer-Integrated

Ž .Manufacturing CIM and multimedia communication systems, the role of technical documentation in a CIM environment isŽ .examined, and the architecture of a Distributed Multimedia Electronic Document System DMEDS is proposed. The basic

featuresroperations and the constituent parts of the proposed DMEDS are then analysed. Two of them, the networkinfrastructure and the necessary software structure, are examined in considerable detail. Finally, a number of importantdesign issues are addressed, and some conclusions are drawn. q 1998 Elsevier Science B.V. All rights reserved.

Keywords: Multimedia communications; CIM; Electronic document systems; Technical documentation

1. Introduction

Manufacturing organisations are under intensecompetitive pressures as they experience majorchanges with respect to resources, markets, manufac-

w xturing processes, and product strategies 1 . As aresult of international competition, only the mostproductive and cost-effective industries will survive.

Manufacturing industries are thus faced with theneed to optimise the way in which they function inorder to achieve the best possible performance within

) ŽCorresponding author. Tel.: q30-1- 6440924, 6854899,. Ž .6114041 ; fax: q 30-1- 6830699, 6842671 ; e-mail:

[email protected] Address: 88 Digeni Akrita Street, GR-122 43 Athens, Greece.

Tel.: q 30-1-5981496; fax: q 30-1-5986754; e-mail:[email protected]; [email protected]

necessary constraints. This is a difficult task, both interms of understanding the nature of the problem andthe most effective solution strategies, and in formingand implementing plans that develop from this un-derstanding.

Many of the efforts in this direction are focusingŽ .in Computer-Integrated Manufacturing CIM . CIM,

combined with new technologies, such as multime-dia, can provide the appropriate conceptual frame-work that will enable manufacturing organisations torespond effectively to situations associated with thedifficult environment in which they operate. Onesuch situation of significant importance appears inthe management of technical documentation in amodern factory and is examined in this paper byproposing an architecture for a Distributed Multime-

Ž .dia Electronic Document System DMEDS for thispurpose.

0166-3615r98r$19.00 q 1998 Elsevier Science B.V. All rights reserved.Ž .PII S0166-3615 97 00101-2

( )C.A. Papandreou, D.X. AdamopoulosrComputers in Industry 36 1998 83–9384

2. Multimedia and CIM

CIM is a management philosophy which involvesthe design or redesign of an entire manufacturingenterprise so that all aspects of the system worktogether effectively. In the context of CIM, the func-tions of design and manufacturing are rationalisedand coordinated using computer, communication, and

w xinformation technologies 2 . Thus, the entire manu-facturing system, from product definition and rawmaterial acquisition to the disposition of the finalproduct, is carefully analysed such that every opera-tion and element can be designed to contribute in themost efficient and effective way to the achievement

w xof clearly enunciated goals of the enterprise 3 .It should be noted that CIM is not a specific

technology that can be purchased. Rather, CIM is astrategic goal that a factory strives to achieve over

w xtime 4,2,5 . The term ‘integrated’ should possiblybe changed to ‘integrative’, because in a CIM envi-ronment, all processes are involved in a continuallyevolving integrative process. Nevertheless, CIM is,because of its potential benefits, a very important

w xphilosophy for every modern factory 2 .In the framework of CIM, many new technologies

can be utilised. One of these technologies is multi-media technology.

Multimedia is a term with many different defini-w xtions 6 . One of them that is widely accepted defines

multimedia as the computer controlled integration ofdifferent basic information types where the informa-tion can be transmitted, processed, and represented

w xdigitally 7 . This definition refers to some basicinformation types, which include data, text, vector

Žgraphics, pixel-oriented images, video signals mov-. Ž .ing pictures , and audio signals voice and sound . It

also encompasses the three key elements in realisingmultimedia solutions: communications networksŽ .transmission, switching , computing end stationsŽ . Žprocessing , and applications software representa-

.tion . From the definition of multimedia, it is quiteevident that multimedia is not a pure and self-con-tained technology or a toolrapplication in it’s ownright. Multimedia is rather a set of enabling tech-

w xnologies 8 .A multimedia system or a multimedia information

system is a system which enables the user to create,edit, transmit, receive, store, retrieve, compute, and

delete multiple types of information in an integratedw xmanner 9 . It must be noted that multimedia systems

require synchronisation of some of the informationtypes in communication, processing and presenta-tion, and in the longer term, will be characterised bythe completely digital integration of all informationtypes. Multimedia systems can be categorised mainlyto standalone multimedia systems and to multimedia

Žcommunication systems or distributed multimedia. w xsystems 10,9 .

In standalone multimedia systems, which are incommon use today, multimedia information is stored

Žfor playback in suitable storage media most com-.monly CD-ROMs . Characteristic example of such

systems are the multimedia kiosks, used as Point OfŽ . Ž .Sale POS or Point Of Information POI systems. It

must be noted that the fact that these systems arestandalone does not limit their interactivity with the

Žuser especially if a suitable Personal Computer is.used as the main hardware platform .

Several standalone multimedia systems connectedtogether via telecommunication networks form thebasis of multimedia communication systems. Thesesystems usually incorporate a central database, andtheir operation is based on the use of multimedia

w xcommunication services 8 . In this way, informationcan be updated quickly, and the system can evolve tocover the needs of its users in the best possible way,because it can collect information about how it isbeing used. Thus, multimedia communication sys-

Žtems can realise the true benefit of multimedia in-creased productivity, improved efficiency and effec-

.tiveness , and for this reason one application of themin the CIM environment will be examined in thispaper.

3. Multimedia technical documentation in a CIMenvironment

The activities which are performed in a modernfactory can be hierarchically grouped according tocertain features they have in common. A hierarchicaldifferentiation implies a layer-type representation inwhich the activities are carried out in the form ofservices required by a higher layer in the hierarchyfrom the next layer down. The most common hierar-chical structure of the various layers of management

( )C.A. Papandreou, D.X. AdamopoulosrComputers in Industry 36 1998 83–93 85

and control information in a modern factory can beseen in the model of Fig. 1.

A typical grouping of the activities from whichthe model of Fig. 1 is comprised leads to 12 mainactivities: plant management, financial management,sales and marketing, research and development,product planning and production engineering, pro-duction management, supply, delivery, treatment ofwaste materials, resource management, maintenance,

w xand shop floor production 11 . The first 11 activitiesform the context of the shop floor production activityand are located in the Enterprise and the

Ž .FacilityrPlant layers Fig. 1 .Information flow in the model of Fig. 1 occurs,

either between adjacent layers, in the form of servicerequests and reports on the execution of these re-quests or within a single layer, in the form ofcommunication between separate activities belonging

Žto the same layer. The flow of information i.e.,.communication is both vertical and horizontal. Ver-

tical flow is either downwards, in which case itcorresponds to the request made by a hierarchicallyhigher layer for a service to be provided by a lowerlayer, or upwards, in which case it is a report oncurrent status sent by a lower layer to its immediatesuperior. On the other hand, horizontal flow corre-sponds to communications within a single layer be-tween peer activities.

The information transmitted inside the model ofŽ .Fig. 1 in one layer or among several layers is

considered to be mostly technical documentation,Ž .which can take the form among others of Com-

Ž .puter-Aided Design CAD drawings, photographs,product and customer specifications, operations andmaintenance manuals, competition data, funds mar-ket data, parts lists, schematics, computer listings,rework instructions, video scenes of shop floor oper-ations, blueprints, and vendor manuals.

The effective and efficient management of techni-cal documentation is very important in a modernfactory, as studies have shown that as much as 90%

w xof part costs are related to documentation 2 , andbecause it is a prerequisite for the successful applica-tion of configuration management in a CIM environ-ment.

Configuration management is the definition andcommunication of the form and function of a com-pleted entity and the control and incorporation of

w xchanges to that entity throughout its life cycle 12 .An entity can be an engineering design, a softwareprogram, a strategy, or a product. The objective ofconfiguration management is first to describe clearlywhat end result is desired and then control changesthat are made in the means to obtain this end result.Thus, configuration management is an extremelyimportant function within a manufacturing company.

The four main functions of configuration manage-ment are definition, communication, control of

w xchanges, and incorporation of changes 2,12 . Therole of technical documentation management in thelast three of these functions is vital. Effective com-munication requires a mechanism that ensures theintegrity of technical documentation. Furthermore,change control and incorporation demands that tech-

Fig. 1. Layered model of a modern factory and the typical grouping of manufacturing activities.


nical documents changes must be synchronised. Asproduct traceability requirements increase, the asso-ciated demands for technical documentation manage-ment increase significantly.

4. Proposed architecture for a DMEDS

From the previous section, it is evident that thetechnical documentation utilised in a modern factoryhas a multimedia nature, in the sense that it encom-passes documents containing data, text, graphics,video, voice, sound, or a combination of these infor-mation types. It is also evident that it has to be usedin a distributed manner as it ‘covers’ the completehierarchical structure of the factory.

For this reason, for the effective and efficientmanagement of technical documentation in a modern

Ž .factory or even a number of cooperating factories ,a multimedia communication system in the form of aDMEDS is proposed. This system will ensure thattechnical documentation is produced and updatedreliably, and delivered to the right place, to the rightperson, at the right time, and in the right format.

The basic featuresroperations of the proposedDMEDS, which can be seen in the layered model ofFig. 2, are discussed below.

Ž .1 Image capturing. It encompasses the digitalencoding of the various types of technical documen-tation. The result is a digital replica of the document,which can be displayed on a computer screen. Inputdevices for image capture include scanners, digitalcameras, and video recorders. Scanners and digitalcameras input images directly into an application.

Fig. 2. Layered model of the basic featuresroperations of theproposed DMEDS.

Input from video recorders must be passed throughspecial video boards known as frame grabbers. It

Ž .must be noted that editing software tools allow thescanned items to be appropriately sized and cropped.

Ž .2 Indexing. Scanned documents can be indexedŽ .by key word s , to facilitate retrieval from the image-

base. A number of indexing systems can be devised,according to the needs of the specific company. Theindex can include key words found in the documentitself, after it has been scanned with Optical Charac-

Ž .ter Recognition OCR software. Entire documentscan also be indexed by product, part number, topic,department or division. In addition to indexing, doc-uments can be customised with notes. Each user whoaccesses the document can append comments, ques-tions, and instructions to the file, so that furtheraction can be taken in processing the transaction.Other documents can also be appended, building acase file.

Documents do not have to be indexed individuallyor on a discretionary basis. A number of documentscan be indexed together in a process called batchindexing. With batch indexing, a number of docu-ments are collected in an electronic version of anin-basket for processing according to predefined in-dexing rules. This speeds up the indexing processand eliminates the confusion that can result fromindividual indexing preferences. Once a document isproperly indexed, individuals are allowed to cus-tomise it with preferred key words that will aid

w xsearch and retrieval and to append notes 13 .Ž .3 Compression. Because multimedia technical

documents are much larger than ordinary text orbinary files, the proposed DMEDS has to supportone or more compression schemes. These schemes

Žare based on compression algorithms implemented.either in software or in hardware , which allow

image files to be ‘shrunk’ by a ratio of at least 2:1and as high as 100:1 without any loss of image

Ž .quality lossless compression . Further compressionŽ .ratios up to 250:1 result in a slight loss of imageŽ .quality lossy compression . The most important

Žcompression standards are JPEG Joint Photographic. ŽExperts Group with compression ratio 15:1 full

. Žcolour still-frame applications , H.261 px64 videocoderrdecoder for audio–visual services at px64

.Kbps with compression ratio 100:1 to 2000:1Ž .video-based telecommunications , and MPEG


Ž .Moving Pictures Experts Group with compressionŽ . w xratio 200:1 motion-intensive applications 14,10 .

Compression algorithms work by removing extra-neous or repetitive data from a document. This per-mits more efficient storage, as well as faster trans-mission over a network. When the document isretrieved from storage, it is decompressed so it canbe viewed on a computer screen.

Ž .4 Storage and retrieval. Technical documenta-tion can be stored on a variety of high-capacitystorage mediums, such as CD-ROMs, WORM opti-cal disks, magneto-optical disks, CD-Recordables,and optical tapes. Several of these high-capacitystorage mediums can be combined and used togetherin multifunction optical drives, Redundant Arrays of

Ž .Inexpensive Disks RAIDs , and optical jukeboxesw x13 .

Retrieval is a basic function of the DMEDS deter-mined by the required speed of document retrieval,and by the amount of flexibility afforded to the user.Several document retrieval approaches are available,including index and full text. With text-based re-trieval, the user can access documents using anyword appearing inside them, rather than having tochoose from a limited selection of key words in anindex. With the index approach, the user enters a keyword and is presented with a list of documentsassociated with the word. The user may have to callup several documents before finding the item ofinterest. The main benefit of the full-text approach isthat users can locate documents based on their pre-cise informational needs and inquiry preferences. Asthe retrieval needs of the users in a modern factory

vary considerably, the proposed DMEDS is sug-gested to support both document retrieval methodsand allow a fair degree of user customisation.

Ž .5 Workflow automation. Workflow software au-tomates the flow of documents from one processingstep to another, eliminating many intervening pro-cessing stages and streamlining others. Workflowprocessing actively routes documents through theDMEDS using rules that reflect the decision criteriathat are used to process the documents. Instead of‘dumping’ all information into an ‘in-basket’, logicalqueues of documents are established that enableusers to obtain the next available document for pro-cessing. This results in streamlined processing ofdocuments, speedier distribution that requires fewerpeople, and more productivity from the people whomust process the information.

Ž .6 Transmission. Multimedia technical documen-tation is transmitted via a network, which enables theend-user to communicate. This network can be eithera LAN, a MAN, a WAN, or the Internet, which isconsidered to be a globally expanded WAN based on

Ž .the use of special protocols TCPrIP . It must benoted that the DMEDS should be compatible with

Ž .the Manufacturing Automation Protocol MAP ,which is a broadband, token–bus network protocol

Ž .based on the Open Systems Interconnection OSIreference model, as MAP is used in a broad range of

w xmanufacturing environments 15 .Ž .7 Information management. Information man-

agement focuses mainly on the way that informationis used inside the whole DMEDS. Thus, it refers tothe characteristics and the structure of the software

Fig. 3. Constituent parts of the architecture of the proposed DMEDS.


that is used, and in the way that information ispresented to the end-user. It also aims to support thecooperation between the users of the DMEDS.

As can be seen in Fig. 2, the featuresroperationsof the management layer are information manage-ment and workflow automation and the featuresrop-erations of the documentation production layer areimage capturing, indexing, compression, and storageand retrieval. The flowchart indicates the order inwhich the operations of the documentation produc-tion layer can take place. Technical documentation is

Ž .the intermediate and final outcome of this flowchart.Finally, the transmission of technical documentationtakes place in both layers.

The constituent parts of the architecture of theproposed DMEDS, which can be seen in Fig. 3, are:communication networks; software designed to man-age document retrieval and workflow automation,perform communication functions, facilitate coopera-tion between the users, and present information;workstations with high-resolution displays; docu-ment image servers; scanners and OCR software, fordigitising hard-copy information; output devices,such as printers and plotters; and storage mediaŽ .most commonly optical disks .

From these constituent parts, the most importantin a CIM environment are the network infrastructureand the necessary software, which are examined inconsiderable detail in the following paragraphs.

4.1. Network infrastructure of the DMEDS

The network infrastructure of the DMEDS has tobe incorporated into the wider communication archi-tecture of the factory, which can be seen in Fig. 4,

w xfollowing the layered paradigm of Fig. 1 16,11 .From Fig. 4, it is evident that the proposed DMEDSŽ . Ž . Ž .Fig. 3 affects: 1 the Wide Area Network WANat the Enterprise Layer which connects more than

Ž .one plantsrfactories together; 2 the plant LocalŽ . ŽArea Network LAN which can considered to be a.LAN backbone at the FacilityrPlant Layer. It also

affects the communication architecture of each de-partment of the factory, which usually consists of aŽ . Ž . Ž .number of interconnected LAN s ; and 3 the con-trol LAN at the Shop Floor Layer. This happens onlyif the factory has a shop floor information systemwith an information terminal at every work centreŽ . w xmachine 17,18 .

Fig. 4. Communication architecture of a modern factory.

For the delivery of multimedia technical docu-mentation, a broadband network infrastructure is aprerequisite as bandwidth limitations cannot be ig-nored, taking into account their constraining effectson video quality and the rapid transmission of large

w xquantities of data 14 . As far as reliability is con-cerned, it must be noted that most multimedia appli-cations can tolerate errors in transmission due tocorruption or packet loss without retransmission orcorrection. In some cases, to meet real-time deliveryrequirements or to achieve synchronisation, somepackets are even discarded. Additionally, multimedianetworks must provide the low latency required forinteractive operation, and must be able to supportmultipoint communication, as opposed to traditional

w xpoint-to-point communication 19 . The table of Fig.5 contrasts traditional data transfer and multimediatransfer.

New techniques like SDH and ATM allow voice,data, and video traffic to be transported easily over

Fig. 5. Traditional communications vs. multimedia communica-tions.


the same network at a variety of speeds. Morespecific, in ATM, units of information called cellscorrespond to packets in the packet transmissionmode. These cells are of a fixed length. The ATMtransmission protocol is simpler than for the packettransmission mode, and, as a result, can be imple-mented in hardware, improving speed and enablinggreater bandwidth. While retaining the advantages ofthe packet transmission mode, ATM’s high-speedprocessing enables it to accommodate a heteroge-neous mix of data, and offers the flexibility to re-spond to diverse and uncertain demands.

An FDDI network is also sufficient for a DMEDSin a modern factory as it provides a bandwidth of100 Mbps, a low access latency, and guarantees abounded access delay and a predictable averagebandwidth for synchronous traffic. However, due tohigh cost, FDDI networks are used primarily forbackbone networks, rather than networks of worksta-tions. Less expensive alternatives include enhancedtraditional networks, such as Fast Ethernet, whichprovides up to 100 Mbps bandwidth, and prioritytoken ring.

Present optical network technology can supportthe B-ISDN standard, which is expected to becomethe key network at the Enterprise and the

w xFacilityrPlant Layers of a modern factory 10 . Thechannel rates envisaged for B-ISDN are:Ø H21: 32.768 Mbps.Ø H22: an integer multiple of 64 Kbps in the range

5–43 Mbps.Ø H4: an integer multiple of 64 Kbps in the range

8–132 Mbps.Proposed B-ISDN networks are in either Syn-

Ž .chronous Transfer Mode STM , or AsynchronousŽ .Transfer Mode ATM , to handle both constant and

variable bit-rate traffic applications.For this reason, in the LAN field of the DMEDS

for technical documentation in a modern factory theuse of technologies, such as Fast Ethernet, prioritytoken ring, FDDI, and ATM is suggested. For in-creased flexibility the use of intelligent hubs androuters is proposed. In the WAN field, the requiredproperties can be realised with the use of technolo-gies, such as ATMrSDH, FDDI, SMDS, and B-ISDN.

To build this infrastructure, optical fibres are pre-ferred as an enabler, in combination with the use of

the SONET standard, because in industrial environ-ments there is a greater need for resistance to me-chanical and electric stress. Optical fibres minimise

Ž .the effect of Electro-Magnetic Interference EMI .In order to provide flexibility, the network which

will be the basis of the proposed DMEDS must beself-healing, integrated, intelligent, and customercontrolled. In addition, a flexible network and ser-vice management must support the dynamic opera-tion and utilisation of the overall system, and, indoing so, also guaranteeing consistency, privacy,

Žsecurity, and economy advanced intelligent net-.work . This will ensure that the DMEDS will be able

to work in the hostile or dangerous environmentfound in many industrial plants, providing a highlyreliable service.

4.2. Software structure of the DMEDS

The software part of the proposed DMEDS aimsto ensure the effective use of the network infrastruc-ture, to facilitate the cooperation between the users,to support workflow automation, to efficiently man-age document retrieval, and to provide the user asuitable interface.

Thus, the software structure of the DMEDS isproposed to follow the layered model of Fig. 6.

The main element of the distributed processinglayer is the operating system. In order to satisfy therequirements posed by the DMEDS, the operatingsystem must be able to offer the following additional

w xservices 20–22 :Ø Unified media input and output controlØ Compression and decompression functionalities

for video

Fig. 6. Layered model for the software structure of the DMEDS.


Ø Support for new data typesŽ .Ø Priority control pre-emptive scheduling

Ø Fast interrupt processingØ Inter-media synchronisation

Ž .Ø Graphical User Interface GUI with voice andvideo

Ž .Ø Application Programming Interface API whichkeeps physical input and output transparent

Ø Standard multimedia format and protocolØ High-speed communication control

ŽØ Distributed file system, e.g., NFS Network File.System

Ø Distributed object managementØ Remote database accessØ Distributed transaction processing for database

applicationsŽ .Ø Global directory nameraddress management for

assuring wide area distribution transparencyTo provide these services, a multitaskingrmulti-

threading operating system based on the principles ofobject oriented design and clientrserver architectureis proposed. Object orientation can be applied tosuch an operating system, in the sense of transport-

Žing, whenever necessary, objects groups of data and.functions modifying or accessing the data rather

than just the data contained in the objects. On theother hand, the clientrserver architecture encouragesgenerally distributed computing, while de facto in-dustry standards, such as the Distributed Computing

Ž .Environment DCE proposed by the Open SoftwareŽ .Foundation OSF , allow data to be transferred be-

tween clientrserver applications.The term groupware has the meaning of inten-

tional group processes and procedures aim to achievespecific purposes, together with software tools de-signed to support and facilitate the work of a groupw x19,23 . Computer Supported Co-operative WorkŽ .CSCW shares a concept similar to groupware, andmeans support for group collaborative work in ageographically distributed environment using com-puter and communication integrated networksw x21,24 .

For this reason, the groupware layer includessoftware tools that facilitate workflow automationinside the factory and the cooperation of users as faras technical documentation is concerned. These soft-ware tools, in order to be part of the proposedDMEDS, must be characterised by the following

Ž .CSCW principles: a Changes in content and ap-Ž .pearance of information technical documentation

must be consistent and immediately recognisable byall the group members concerned, using the WYSI-

Ž .WIS What You See Is What I See principle amongŽ .others; b For the utilisation of data bases, a quick

Ž .response to queries is indispensable; c The distribu-tion of information, such as high-resolution pictures

Ž .or video scenes, must be sufficiently fast; and dŽThe time delay of actions and events e.g., cursor.movement or field and object markings , as well as

Žthe authorisation administration who has access to.what information must be negligible.

Beside the above mentioned software tools, thegroupware layer is proposed to include also hyper-

Ž .media software tools for the organisation of theway that information is presented and interrelated,and an appropriate Data Base Management SystemŽ .DBMS .

More specific, hypermedia, as an extension ofhypertext incorporating information types other thantext, denotes an organisational concept of nonlinearnetwork-like structuring of multimedia documentsw x14 . It provides computer-supported nonsequentialauthoring and reading, i.e., interactive branching anddynamic display using information objects and mul-tichoice links in between. Hypermedia documentsenable the ‘reader’ to navigate along defined multi-ple paths through related information material, anno-tations, figures, film scenes, bibliographical data,etc., within an information network of links andnodes. This requires some support for user-friendlybrowsing and navigating through hypermedia infor-mation.

A DBMS suitable for the DMEDS under exami-w xnation must have the following features 2 : data

integration across heterogeneous computer systems,transaction processing, real-time interactions, multi-ple views of data, levels of security, data integrity,geometry management, versioning, backup and re-covery, knowledge-base support, materials manage-ment integration, quality assurance integration, andconfiguration management.

Because the proposed DMEDS spans the com-plete factory, the DBMS has to support the dis-tributed processing of technical documentation. Thus,it is necessary to have the following characteristicsw x Ž .25 : a Location transparency: A user can submit a


query that accesses distributed document objectsŽ .without having to know where the objects are; b

Performance transparency: A query can be submittedfrom any node, and it will run with comparable

Ž .performance; c Copy transparency: The DBMSsupports the optional existence of multiple copies of

Ž .document objects; d Transaction transparency: Auser can run an arbitrary transaction that updates

Ž .documents at a number of sites; e Fragment trans-parency: The DBMS allows a user to segment arelation into multiple pieces and place them at multi-

Ž .ple sites according to certain distributed criteria; fScheme change transparency: Users who add ordelete a document need to make the change only

Ž .once to the DBMS dictionary; and g Local database management transparency: The DBMS must beable to provide its services without regard for thelocal data base systems that are actually managinglocal data.

ŽFinally, the application layer includes the soft-.ware application which interacts with the user. This

application, in the framework of the DMEDS, isŽ .proposed to: a Provide a friendly and consistent

user interface designed according to strict ergonomiccriteria. Such a user interface is necessary to presentthe information in convenient and comprehensibleformats, by the use of fixed or moving images,combined with text and voice, providing also theuser with aids for navigation and selection of multi-media content. Caution is needed to avoid creating

w x Ž .information overload to the user 9 . b Provideintelligent support to users with the use of suitablesystem error and information messages, and help

Žservices tutorial, hierarchical, context-sensitive, and. Ž .real-time help . c Allow the users great flexibility

in finding their way through the technical documen-Ž .tation, which is made available to them. d Take

into account possible hardware limitations of theuser.

For this reason, the DMEDS application must bemodular, with a manageable number of distinct parts,predictable in its behaviour, easily comprehensible,integrated and coherent in the ways in which itsdifferent parts relate, helpful, with quick and effi-cient access to relevant information, tolerant of er-rors and supportive in enabling the effects of errorsto be easily undone, extensible, adaptable, and self

w xdocumenting 26,13 .

5. Planning issues

The implementation of the proposed DMEDS in amodern factory requires proper and careful planningto ensure that the expected benefits from the systemwill be realised.

For this reason, a number of important planningconsiderations is necessary to be taken into accountw x4,27,2,1 . These are discussed in the following para-graphs.

Ž .1 Interfacing of the DMEDS with the otherinformation systems of the factory. The planningprocess should include all affected parties. Thus, itshould be participative and should start with anarticulation of the factory’s goals and anticipatedbenefits that the DMEDS is intended to achieve. Thiswill assist the participants that represent the otherinformation systems of the factory understand itsrole, and make proposals for the best possible com-munication with it.

Ž .2 Indexing and workflow requirements. In in-dexing, the application supports the storage and re-trieval of large quantities of technical documentation.Indexing requires strong data management capabili-ties, but is usually fairly straightforward to imple-ment. On the other hand, workflow applications aremuch more difficult to implement than indexingapplications, and require a detailed analysis of workprocesses inside the factory.

Fig. 7. Anticipated benefits of the proposed DMEDS.


Ž .3 Understanding processing requirements. Thesuccess of the DMEDS often hinges on the extent towhich factory processes and workflows can be un-derstood. For this reason, an evaluation of documentprocessing needs must be performed prior to theimplementation of the DMEDS. Any proceduralproblems discovered, such as processes that result induplication of effort, employees working at cross-purposes, and situations that produce unnecessarypaperwork and filing requirements, must be encoun-tered as soon as possible.

Ž .4 Identifying the appropriate levels of imple-mentation. One of the major decisions that has to beaddressed early is whether the DMEDS will span theentire factory, or will be limited at the EnterpriseLayer, the FacilityrPlant Layer, or the Shop FloorLayer.

Ž .5 Ensuring system reliability. For many facto-ries, the technical documentation managed by theDMEDS is critical for their operation. These facto-ries should try to keep the DMEDS reliable andstable. This can be done with the use of Uninterrupt-

Ž .ible Power Supplies UPSs , redundant componentsand subsystems, alternate routes between corporatelocations on the WAN and bypass circuitry betweenLAN hubs and major subsystems, local service andsupport from vendors to minimise system downtime,etc.

6. Conclusions

The main benefits that the proposed DMEDS isexpected to deliver can be seen in the table of Fig. 7w x28 .

Because of the multitude of benefits that theDMEDS can deliver, and because the evolutionarytrend is towards the highest possible integration be-tween industrial automation systems in the frame-

w xwork of CIM 11 , the use of DMEDS in modernfactories is expected to mature quickly and providenew opportunities for the effective and efficientmanagement of technical documentation.

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Dr. C. Papandreou is the director ofthe Training and Research Centre of theHellenic Telecommunications Organisa-

Ž .tion OTE . He holds Master degrees inEngineering and Business Administra-tion from the Technical University ofMunich and a doctorate in Telematicsfrom the University of Munich. For sev-eral years, he has been teaching infor-mation technology at the Athens Univer-sity of Economics and Business, theUniversity of Piraeus, and the Higher

School of Telecommunications of OTE. He is a consultant ininformation technology and Telematics and he participates as anexpert in the field in various national and European Union bodies.His research interests include telematic services, Computer-In-

Ž .tegrated Manufacturing CIM , telecommunications management,and information systems development.

Mr. D. Adamopoulos holds a degree inComputer Science from the Athens Uni-versity of Economics and Business, anda Master degree with distinction inTelematics from the department of Elec-tronic and Electrical Engineering of theUniversity of Surrey. He is currentlyregistered for a PhD Degree in the Cen-tre for Satellite Engineering ResearchŽ .CSER of the department of Electronicand Electrical Engineering of the Uni-versity of Surrey. His research interests

include telematic services management and modelling, multimediacommunication systems, groupware, and Computer-Integrated

Ž .Manufacturing CIM .