22 Geographical information systems in networked environments

D J COLEMAN

This chapter examines basic approaches to distributed architectures in GIS, with special emphasis on exploitation of local- and wide-area networks and, more recently, the and wireless communications. The first section reviews the design models inherent in host- based systems, distributed networks, and field-based systems. The second section describes selected applications of these design models, with particular emphasis placed on Internet- based geographical information retrieval and computer-supported cooperative work. The final section deals with system performance considerations in networked environments and describes new developments affecting the performance of future systems.

1 INTRODUCTION associated with Internet-based geographical information retrieval and computer-supported Technical design models supporting mainstream cooperative work. The final section of the chapter GIS technology have evolved from early host-based deals with the issue of system performance in efforts on mainframe and mini-computers, through networked environments under a variety of stand-alone systems operating on personal conditions. After a brief summary of considerations computers and workstations, and on to today’s involved in objectively assessing system performance, environments across local- the author describes new developments affecting the and wide-area networks. Each advance has extended performance of future systems. overall flexibility in terms of the relative location of users, processing capabilities, and data storage units (see also Batty, Chapter 21). Recent advances in broadband and wireless communications 2 HOST-BASED SYSTEMS AND EARLY technologies – as well as the dramatic increase in PERSONAL COMPUTING ENVIRONMENTS Internet usage and extension of Internet browsing technology – promise to extend further the reach 2.1 Host-based systems and range of GIS users working in offices or Early centralised computing environments were laboratories, in the field or at home. characterised by small numbers of large-scale This chapter examines the basic approaches to mini- or mainframe computers, with shared storage distributed architectures in GIS, with special devices attached via hardware input/output channels emphasis on the exploitation of local- and wide-area and multiple users connected via terminals possessing networks and, more recently, the Internet and varying levels of on-board ‘intelligence’ or processing wireless communications. The first section of the power (Katz 1991). Such environments defined the chapter reviews the design models inherent in host- architecture for most major data processing and based systems, distributed networks, and field-based information systems applications until the mid 1980s, systems. The second section describes specific including the GIS installations found in major applications of the latest design models, with forestry organisations, utilities, municipalities, and particular emphasis placed on emerging issues land records management programmes.

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This architecture implied greater control over data ‘Connection-oriented’ service integrity and system security; the was (e.g. via dial up telephone link) managed centrally, with responsibility for system and data administration entrusted to experienced data processing specialists. However, performance of such systems would often degrade in unpredictable ways when growing numbers of users demanded computing resources and database access. Conflicts with system administrators over development and maintenance priorities also often resulted in dissatisfaction among endusers in many large organisations. LAN Mainframe and 2.2 Stand-alone, PC-based systems LAN By 1986, PC-based GIS software packages had ‘Connectionless service’ begun moving geoprocessing out of the hands of Remote (e.g. via Local Area Network) information system managers (Miller 1990). Besides terminals their low cost, these systems offered more predictable response times since the user was the only one on the system. However, the proliferation of stand-alone PC-based systems meant it was much more difficult to share data among several different Fig 1. Examples of alternative wide-area networking services: ‘connection-oriented’ vs ‘connectionless’ models. people in the organisation. Also, the enduser often had to become his or her own system and database administrator. While PC-based systems undoubtedly mail and file transfer, and enabled distributed accounted for the dramatic growth in GIS usage processing. It also allowed users to expand their through the late 1980s, they also put greater onus on facilities with a degree of vendor independence and managers in large organisations to keep effective to incorporate special purpose processors, storage track of the data being collected and processed by units, or input/output devices as required. The term an increasing number of endusers with little distributed computing was coined to describe a experience in routine data management procedures. situation where processing tasks and data are distributed among separate hardware components connected by a network, with all these various 3 COMPUTER NETWORKING AND components capable of being accessed in a relatively DISTRIBUTED SYSTEMS transparent manner (Champine et al 1980). Distributed systems today generally offer a Beginning in the mid 1980s, higher-performance combination of: (1) greater access to GIS data stored workstations connected through local and wide and managed on a central ; (2) faster response area networks (LANs and WANs) became a time due to local computing; (3) tighter system viable alternative to host-based and stand-alone security; (4) less complexity; and (5) in many cases, configurations. Connectionless LAN and lower-cost computing solutions than more ‘LAN-interconnect’ services began displacing earlier traditional mainframe or minicomputer solutions. connection-oriented services which required a At a higher level, the notion of distributed dedicated link between the enduser and the host computing often provides a better fit to the complex computer (Figure 1). structures and often multidisciplinary nature of Based on packet-switching transmission protocols modern organisations and offers greater user which did not require dedicated connections involvement in information management activities. between user and host, networking permitted users Early investigators of formal network-based to share access to scarce equipment resources (e.g. approaches to distributed GIS database printers, plotters, etc.), made possible management systems (DBMS: e.g. Ezigbalike et al inter-site communication applications like electronic 1987; Webster 1988) laid out excellent foundations

318 Geographical information systems in networked environments for future research, but were limited by both the between two communication processes on a network distributed DBMS technology then commercially (Voelcker 1986). Protocols govern data control and available at reasonable cost, and the relatively format across a network, and a variety of protocols limited use of LANs or WANs by the GIS exist to ensure that these communications are community at that time. The subject has been conducted effectively. revisited more recently by Ingoldsby (1991) and Two different stacks or suites of layered Laurini (1994), among others. approaches are in common use today:

● OSI: the seven-layer Open System Interconnect 3.1 The client–server model suite of protocols developed by the International Standards Organisation; Most distributed computing today is based on a ● TCP/IP: the four-layer Transmission Control client–server architecture (Katz 1991). In this model, Protocol/Internet Protocol suite originally a collection of workstations (or clients) relies on one developed for the ARPAnet research network in or more servers residing elsewhere on the network the USA. for access to data files, application software and, in certain cases, more powerful computing resources. Originally developed by computer user groups and Such servers are really high-volume storage devices European telephone companies, the OSI model with processors which have been optimised to helped unify world telephony and provided a clear provide high-speed retrieval of large disk-based data framework and explanation of the functions or database files. In such an environment, the data required for computer communications. However, it retrieval aspects of a database query can be carried was regarded by some as being too cumbersome for out largely independently of the data processing and high-speed networks (Wittie 1991). display tasks. By comparison, the TCP/IP suite of protocols The time required to execute such a data retrieval became a de facto standard by the early 1980s as a operation depends on the individual performance of result of its early use in the implementation of the the storage, processing, and communications US Defense Department-funded Internet. Its longer- components involved in the client–server system. term popularity was secured through subsequent While improvements in all three of these bundling with the 1983 release of the Berkeley technologies have made key contributions, it has UNIX 4.2 operating system. While TCP/IP been the introduction of remote file management protocols do not precisely fit into the more general services which finally provided the transparency OSI model, the functions performed by each OSI required for distributed computing. Remote file layer correspond to the functions of each part of the system implementations like Sun Microsystems’ TCP/IP protocol suite and provide a good Network File System (or NFS) on UNIX framework for visualising the respective workstations, PC-NFS and Novell’s Netware on relationships between the various protocols. PC-compatibles, and Appletalk on Macintoshes are now present in many organisations. 3.3 Local area networks

3.2 Network architecture LANs physically or logically connect together multiple workstations, terminals, and peripheral A computer network architecture can be considered devices via a single cable or shared medium as a set of functions, interfaces, and protocols which (Pretty 1992). Through the 1980s alone, over 100 000 enables devices to communicate with one another LANs were set up in offices and laboratories around on-line. The architecture is composed of a layered the world to link workstations to printers, share files collection of communication, networking, and and send electronic mail (Wittie 1991). LAN usage in application functions implemented such that – while the general computing community grew at a rate of each layer is designed to operate independently – 80 per cent per year between 1985 and 1991 (Pretty higher-level operations are built on functions 1992), with networks extending into schools, provided by the lower layers (Chorafas 1980). libraries, laboratories, and offices around the Network protocols are the formal sets of rules or developed world using telephone lines, optical fibres, specifications for coding messages exchanged and satellite links.

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Several accepted and standardised types of LAN dedicated FDDI networks connect users within technology now share the market, including IEEE limited areas at rates up to 100 Mbit/sec, and higher- 802.3 (CSMA/CD or Ethernet), IEEE 802.4 (Token speed asynchronous transfer mode (ATM) services Bus), IEEE 802.5 (Token Ring), and ANSI FDDI promise to support a wide range of real-time multi- (fibre distributed data interface). To date, the media applications across long distances. Ethernet (Figure 2) and Token Ring technologies Results of the performance testing experiments have dominated the market. described by Coleman (1994) indicated that future users of these broadband services would be able to access remote disks, processors, and output devices 3.4 Metropolitan and wide area networks at near-LAN levels of performance. Today, such Until the early 1990s, most wide-area networking services have already influenced the nature of data and LAN-interconnect services did not deliver the delivery and software support practices to a small performance required either to move large GIS data but growing group of users in the GIS community files quickly or to offer real-time access to remote (e.g. Annitto and Patterson 1995; Streb 1995). users over very long distances (Craig et al 1991). Where data delivery was an issue, magnetic tapes and diskettes were viewed as the media of choice for 3.5 The Internet the distribution or exchange of data among GIS data producers and users (Newton et al 1992). Especially since 1993, it has been the connectionless Modern metropolitan area networks (MANs) and services built atop the Internet which have come to WANs employ different protocols and technology define the current paradigms for mass market in order to offer speeds comparable to LANs network usage. The Internet is a collection of while operating over greater distances. By 1992, interconnected campus, local, provincial, national, fibre-based packet switching services like SMDS in and corporate networks in more than 150 countries. North America and FASTPAC in Australia began Originally designed to connect researchers in providing high-speed (34–45 Mbit/sec) links between university, government, and industrial defence LANs across and between major cities. Today, establishments, the Internet is now estimated to

Terminator

Shared Personal UNIX Minicomputer printer computer workstation (shared data files)

Repeater for Shared extending cable plotter

Personal computer Shared disk Personal storage computer

Terminator

Fig 2. Simplified Ethernet local area network.

320 Geographical information systems in networked environments service more than 20 million users through a loose 4 APPLYING THESE NEW MODELS collection of more than 5000 registered networks (Reinhardt 1994; Thoen 1995). While electronic 4.1 Enterprise computing implementations mail, file transfer, and remote login services Large utilities and municipalities were among the originally accounted for the majority of Internet first to identify the operational requirements to traffic, it has been ease-of-use and the multimedia integrate smaller GIS- and facilities management- capabilities of the World Wide Web (WWW) that related databases on stand-alone systems with larger have attracted most of the mass-market attention corporate databases residing on mainframes and resultant increases in usage. Over 145 000 Web (Popko 1988). As LANs became more widespread, sites have appeared since its introduction in 1993, enterprise computer systems evolved from host- and this number is continuing to rise monthly based (or ‘single-tier’) to two-tier environments with (Webcrawler Survey 1996). networked PCs and workstations in a client-server architecture replacing connected terminals. This modular approach is attractive to many 3.6 Wireless, field-based systems organisations since it allows them to take quicker advantage of price/performance improvements on Recent advances in wireless communications, modular hardware components and the other notebook computing, and the integration of GIS advantages of network computing described earlier and global positioning system (GPS) technology (Mimno 1996). have extended the application of traditional GIS While advantageous in many respects, users have databases into field operations (Lange and Gilbert, found that these two-tier environments may not Chapter 33). Using normal telephone lines and, necessarily retain some of the advantages found in more recently, cellular telephone modems, field users centralised host-based implementations, notably tying into enterprise-wide networks may now access availability, expandability, and reliability of service information resources previously available only from (Strand 1995). As a result, newer three-tier within the branch office or headquarters. New environments have been developed to facilitate the implementations are extending functionality beyond placement of applications and data in locations in traditional records management and modelling roles order to optimise these three factors (see Figure 3). into such areas as property inspection, field Existing mainframes at Tier 3 – possibly updating, facilities maintenance, customer service, connected over long distances via MANs and WANs and emergency response (Elliot 1994). – are used to support legacy applications and At least one industry source predicts the mobile provide access to large databases. To implement a computer/mobile field automation market will grow client/server computing strategy, additional layers of from $30 billion in 1995 to $80 billion by the year hardware and software are added as a front end to 2001 (FieldWorks Inc. 1996). FieldWorks estimates the host computer. These layers consist of shared the 1995 total market for ‘ruggedised’ portable servers at Tier 2 (interconnected by high-speed computers at $500 million with an annual growth LANs), and LAN-based PCs and laptop computers rate of 35 per cent. at Tier 1 (Mimno 1996). GIS and desktop mapping This predicted growth in the ruggedised portable applications are included at this first tier, although market is based on current trends within large the data may reside on either the Tier 2 servers or service firms and government organisations to even the Tier 3 hosts. automate the data collection and communication This enterprise information architecture is highly capabilities of field personnel through greater use of flexible and can be modified easily to accommodate reliable mobile computers. As growth in notebook changes in business requirements. As more large over desktop sales suggests, purchasers want systems customers adopt this approach, commercial GIS which combine the functionality of desktops with software firms and mainstream DBMS vendors alike the ability to fulfil specific applications beyond word are modifying their offerings in response to processing and spreadsheet manipulation. The customer demands. In particular, spatial data integration and use of GIS software and GPS management models and processes are becoming a technology within mobile computers for field data more intrinsic component of an organisation’s larger collection and database updating is one example of information management architecture. ESRI’s such extended functionality. Spatial Database Engine and MapInfo’s 1996

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First Tier Decentralised enduser Workstation PC Workstation PC Workstation PC Workstation

Second Tier LANs Distributed Servers/LAN

WAN Host Third Tier

Fig 3. Three-tier enterprise computing environments. Source: Strand 1995 acquisition of the Spatialware server technology found in GIS packages. Mainstream commercial from Unisys Corporation are two examples of how database vendors are already incorporating some GIS vendors are providing even tighter high- such enhancements into their own RDBMS performance links into mainstream relational offerings, with ORACLE’s SDO and DBMS packages like ORACLE and others, while Informix/Illustra’s Spatial DataBlades offerings being based on de facto industry standards for object two such examples. These developments, combined linking and embedding (OLE), structured query with the recent formal attention being paid to language (SQL), third- and fourth-generation interoperability between software packages languages, and ODBC. Table 1 contains a summary (Sondheim et al, Chapter 24), suggest that future of recent industry offerings in this regard. enterprise implementations may rely less on ‘full- At the same time, the international database solution’ packages maintained by a single vendor or standards community (through ISO/IEC/JTC1/SC21 consortium of vendors. Rather, large institutional – WG3) is extending the proposed SQL MM users may opt for a series of smaller, lower-cost (‘MultiMedia’) to accommodate spatial relationships, software components or applications possessing indexing arrangements, and operators typically limited functionality on their own, but which seamlessly interact with other database, word Table 1 Tighter linkages between GIS and RDBMS: ‘Spatial processing or advanced modelling applications which Middleware’ (from Costello 1996). may be present in those organisations (see Elshaw Thrall and Thrall, Chapter 23). Vendor Client Software Middleware Product To make optimum use of this flexibility, product application developers must have the ability to Vision AutoCAD Vision Server allocate data and processes anywhere in the Intergraph MicroStation Jupiter multi-tier enterprise information architecture – and Corporation also reallocate them as operational requirements ESRI ArcView Spatial Database change. At the time of writing, concerns have been MapObjects Engine (SDE) MapInfo MapInfo SpatialWare expressed that first-generation client/server Corporation application development tools like Visual Basic,

322 Geographical information systems in networked environments

PowerBuilder, and others may not have the datasets stored off-line (e.g. Marmie 1995). In capabilities and performance required to support more sophisticated implementations, the user may more complex, enterprise-wide applications retrieve image, map graphics, or attribute adequately (Mimno 1996). While it is likely that information covering a given area of interest newer versions of these and similar tools will (e.g. Conquest and Speer 1996). address many of these concerns, they must still 2 Custom map creation and display. These sites evolve as the needs and practices of different user represent the results of special-purpose groups in these large organisations change over time. development projects aimed at the composition, display, and downloading of user-defined custom map products. They may or may not involve the 4.2 Data access and delivery use of a GIS package running in the background. Dozens of major land information and resource Currently limited in terms of the extent and inventory programs around the world have variety of data coverage, they nevertheless demonstrated on-line organisation and electronic represent an exciting development in providing distribution of government imagery, mapping, and ‘just-in-time’ mapping to the general public related land information across proprietary networks. (Pleuwe 1997). Early examples included Land Information Alberta 3 GIS/WWW integration. These sites represent the (McKay 1994) and the Manitoba Land Information results of integrating front-end query capabilities Utility (Oswald 1994) projects in Canada, the early (supported through standard Internet and WWW commercial ImageNet service in the United States, interfaces and protocols) with the capabilities of and the Land Ownership and Tenure System (LOTS) commercial DBMS and GIS software packages in South Australia (Sedunary 1988). Numerous other residing in the background. User-defined queries early examples may also be found elsewhere in these are translated into corresponding SQL countries and in Europe. commands and passed to the ‘back-end’ GIS Originally, such projects offered connection- database for handling. The resulting response is oriented access to secure databases utilising either passed back through the gateway to the user and, direct LAN-interconnect services or high-speed in the case of map-based responses, the resulting modems. Especially since late 1993, however, the map is translated into a graphics or bit-map Internet-based WWW has emerged as an alternative format suitable for fast transmission and viewing means of accessing, viewing, and distributing spatial across the Internet. User-developed examples of information. Used in combination with modern Web such GIS/WWW integration are documented by ‘browsing’ software packages like Netscape and Conquest and Speer (1996), Nebert (1996) and Microsoft’s Internet Explorer, the WWW is emerging Liederkerke et al (1995), among others. Software as a mainstream tool for vendors offering WWW interfaces to spatial data servers or map-based spatial data browsers ● the distribution of public-domain spatial information; include Autodesk, ESRI, Genasys, MapInfo, and Universal Systems. ● online ordering of commercial datasets; ● indexing and cataloguing of related spatial The lines distinguishing these categories are fading datasets available off-line (Dawe 1996). quickly. Various electronic telephone and business An analysis of more than 25 home pages classified directories offered in Australia WWW usage in the GIS community into four (http://www.whitepages.com.au), Chile overlapping categories (Coleman and McLaughlin (http://www.chilnet.cl/index.htm), and the USA 1997). Setting aside those sites focusing on product (http://www.bigbook.com) now allow users both to or program advertising, the remaining three obtain contact information and to find the location of categories included: selected individuals or businesses on custom-generated electronic street maps (see Elshaw Thrall and Thrall, 1 Data distribution. At such sites, users may search Chapter 23). Other creative early examples of how for specific spatial information features or these systems may appeal to general users include: datasets based on either keyword searches or Boolean queries of existing database fields 1 The ‘Tripquest’ service (Figure 4) (e.g. Crossley 1994; Nebert 1994; Pleuwe 1994). In (http://www.mapquest.com), which enables users some cases, the user may obtain only pointers to to specify a starting point and destination of a

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Fig 4. ‘Tripquest’ service.

Fig 5. New Brunswick Geographic Information Corporation Property Information Service.

324 Geographical information systems in networked environments

road trip, then receive detailed driving vendors and standards organisations (e.g. the Open instructions based on a road network database GIS Consortium) now including it as an important contained at the server site. component of an overall network-based GIS 2 The LandData BC site (http://www.landdata. architecture, Java-based technology may eventually gov.bc.ca), which offers on-line access to a wide be one of the keys to developing more open systems variety of mapping and land information of distributed processing of geographical data. products from different provincial government At the time of writing, more extensive and well- departments in British Columbia, Canada. maintained lists of WWW sites falling into all these 3 The New Brunswick Geographic Information categories may be found at the ‘ and Corporation Property Information Server WWW Mapping’ home page maintained by Katz (Figure 5), which allows NBGIC subscribers to (http://www.blm.gov/gis/nsdi.html) and the access and download property ownership, ‘GeoWeb’ site (http://wings.buffalo.edu/geoweb) registration, assessment, and parcel-centred maintained by Pleuwe. mapping information covering any property in New Brunswick, Canada via keyword search, database query or map-based index (Arseneau et al 1996). 4.3 Collaborative production and group decision-making The advent of Java – a portable, object-oriented Internet language developed by Sun Microsystems Hardware, software, and procedures to support Inc. – promises to remove many of the constraints computer-supported cooperative work (CSCW) have inherent in early WWW protocols and further been discussed and compared for more than 30 years extend the capabilities of Web-based data browsing (Englebart 1963). In the corporate world, shared systems (Strand 1995). By moving much of the access to corporate resources and innovative new requisite display, processing, and analysis approaches to collaborative production using functionality to the client end of the Internet groupware tools like Lotus Notes (Coleman 1995) connection, performance delays due to server load and, more recently, the WWW (Pilon et al 1996) are and Internet bandwidth limitations may be greatly now being investigated. reduced (Figures 6 and 7). When considered in combination with emerging Early examples of Java-based applications in GIS groupware products, the developments in GIS and have tended to focus on limited tasks, including broadband communications mentioned earlier may improved client-based spatial data browsing also offer a new approach to both collaborative group (Mapguide 1996) and network analysis engines decision-making and digital map production – (Fetterer et al 1996). More recent research efforts enabling some processes to be conducted concurrently (Choo 1996) are aimed at using Java to provide an rather than sequentially (for examples see Churcher even wider suite of GIS display and modelling and Churcher 1996; Coleman and Brooks 1995; capabilities across the Internet. With a number of Faber et al 1995; Karacapilidis et al 1995).

WWW client WWW server WWW client WWW server

Query Response Query Response

• Query handling and database inquiry • Downloading of selected datasets • Interactive point selection • Interactive point selection • Zooming/panning across graphics dataset • Zooming and panning Java moves • Selection/clipping of graphics data of interest • Selected analytical functions processing load off • Raster-to-GIF conversion server and increases functionality of client

Fig 6. Internet spatial data request handling using HTTP. Fig 7. Internet spatial data request handling using Java language.

325 D J Coleman

Network-based collaborative applications depend own groupware applications using modular toolkits on more than just electronic mail. Specifically, they rather than expecting any single shrink-wrapped are predicated on the presence of a shared ‘database’ package or technology to serve their needs or collection of files, and rules which permit the adequately (Schrage 1995). definition of group members’ roles, task status reporting and tracking, and gateways to electronic mail and other sources of data. Such systems should 5 SYSTEM PERFORMANCE IN permit the organisation of correspondence, NETWORKED ENVIRONMENTS comments, reports etc. associated with a project or product and should support the management of Forthcoming generations of system architecture and multiple versions of objects (e.g. images, vector- broadband telecommunication technology promise based charts, video, and sound). Finally, a limited to change fundamentally the way many number of applications may require two or more organisations manage, transfer, and utilise their remote users to be able to view the same file spatial data. However, before adopting such simultaneously, modify or add comments to specific technology, both suppliers and potential customers entities in the same file where necessary, and require a clear understanding of potential network communicate via voice, video, or e-mail while usage and the performance, capacity, and cost trade- making these changes. offs involved in existing and emerging applications. A number of organisations are already A study carried out for the Government of Canada prototyping the WWW as the medium for (IDON 1990) suggested that designing and building collaborative decision-making (Gordon et al 1996), cost-effective GIS networks within and between enhanced design, and concurrent engineering federal government organisations would require applications. Moreover, recent extensions to WWW defensible answers to six important groups of viewers like Netscape are now introducing much of questions. These questions concerned the kind of information to be moved, the data volumes involved, the communication and threaded-discussion, file response-time requirements of the users, the distance transfer, data management and simultaneous data the data were being transferred, the frequency or viewing functionality required in these applications regularity of data transmissions and, perhaps most (Forrester Research Inc. 1996; Ziegler 1995). important, the available funds which could be However, while some major corporations have devoted to such operations. made significant productivity gains through Given the ability of today’s WWW servers to track adoption of early groupware packages. The costs the volume and nature of user transactions at and and cultural changes involved in such adoptions are between given sites, it is now easier to address such likely to blunt the near-term impact of CSCW in the questions than it was seven years ago. Further, given marketplace. Technically, vigorous adoption of the ubiquity of the Internet today, the justification of collaborative technology will depend on: such a network may appear a moot exercise. However, ● acceptance of the Internet or corporate intranets the continuing requirement for ‘hard numbers’ as the preferred medium for communications and reinforces the need to determine defensibly the information delivery; performance of a particular application or group of ● acceptance of common standards for threaded applications across a network under known discussions and calendar management; conditions, in order to predict the performance of the ● subsequent development of a wider variety of same application(s) under other conditions. inexpensive and compatible components or ‘plug- Numerous authors have suggested the fundamental in’ tools capable of operating atop the standards importance of performance determination within the extended from or similar to Netscape’s ONE and overall framework of the system life cycle and Microsoft’s COM (Forrester Research Inc. 1996). structured system and database design processes (e.g. Ferrari et al 1983; Jain 1991). However, while Culturally, successful groupware implementations performance analysis has formed an important are likely to be shaped more by prevailing component of many GIS selection processes since the organisational cultures and constraints than by the early 1980s, test procedures and results have largely technology itself. Since organisations work in remained unavailable because of the constraints of different ways, it is best to let them customise their commercial confidentiality and competitive pressures.

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Researchers have been developing more ● the accelerating introduction of special plug-ins, systematic and rigorous approaches to the Java ‘applets’ and other modular software determination of GIS performance on stand-alone components which balance client and server configurations since the mid 1980s (e.g. Goodchild processor loads and further optimise data traffic and Rizzo 1986; Hawke 1991; Marble and Sen 1986; between workstations on a network; Wagner 1991). Investigations at the University of ● (perhaps most importantly) improvements in the Edinburgh (Gittings et al 1993) and the University collections of underlying algorithms and of Tasmania (Coleman 1994) have extended these procedures defining the application software studies into client/server environments across LANs packages themselves, removing many existing and WANs. The latter two references in particular bottlenecks and optimising older code to run on provide extensive reviews of the literature related to newer systems. GIS performance testing. A key limitation of GIS performance testing research to date has been its lack of extendibility. References Absolute performance figures are tied closely to the Annitto R, Patterson B 1994 A new paradigm for GIS data hardware configurations employed. Further, even communications. Journal of the Urban and Regional under controlled network conditions, it is extremely Information Systems Association 7: 64–7 problematic to model end-to-end GIS performance Arseneau B, Kearney A, Quek S, Coleman D 1997 Internet and to predict how response times will be affected by access to real property information. Proceedings GIS 97 changes in server load and network data traffic. Conference, Vancouver. GIS World Inc. As an increasing number of applications take Champine G A, Coop R D, Heinselman R C 1980 Distributed advantage of the Internet – which, in itself, can send computer systems. Amsterdam, Elsevier Science data packets across randomly changing Choo Y K 1996 ‘Interactive distributed geographical combinations of high- and low-speed network information systems (IDGIS)’. Unpublished Master’s connections with ever growing traffic loads – it will Research Project, Department of Rangeland Ecology be increasingly difficult to make any claims (apart and Management, Texas A&M University. from criticisms) concerning application performance http://starr-www.tamu.edu/choo/idgis/intro.html in a given setting. Further, if events over the past 15 Chorafas D 1980 Computer networks for distributed years are any indication, the storage, memory, and information systems. New York, Petrocelli Books processing requirements of application software and Churcher M, Churcher C 1996 GROUPARC: a collaborative operating systems have a tendency to expand to approach to GIS. In Pascoe R T (ed.) Proceedings, Eighth surpass eventually the capabilities of a given Annual Colloquium of the Spatial Information Research generation of computers and networks alike. Centre. Dunedin, University of Otago: 156–63 That being said, the following advances in Coleman D J 1994 ‘Geographic information systems technology and services will – along with many performance in a broadband communications environment’. others – help improve GIS application performance Unpublished PhD dissertation, Department of Surveying over the next five years: and Spatial Information Science, University of Tasmania Coleman D J 1995 An overview of groupware. In Coleman D ● the increasing optimisation of high-performance J, Khanna R (eds) Groupware technology and applications. disk arrays and parallel processors for use in Englewood Cliffs, Prentice-Hall networked GIS environments (Sloan 1996); Coleman D J, Brooks R 1995 Applying collaborative ● the proliferation of fibre-based broadband production approaches to GIS data collection and electronic communication services in both the workplace chart production. Santa Barbara, NCGIA and see and the home; http://www.ncgia.ucsb. edu/research/i17/i17papers.html ● the introduction of higher-speed satellite and Coleman D J, McLaughlin J D 1997a Information access and cellular data communication links into areas not usage in a spatial information marketplace. Journal of Urban served by normal services; and Regional Information Systems 9(1) ● the introduction of higher-speed Internet services Conquest J, Speer E 1996 Disseminating ARC/INFO dataset (e.g. the proposed ‘Internet II’) and value-added documentation in a distributed computing environment. service offerings which improve performance by Proceedings 1996 ESRI User Conference. Redlands, ESRI. ‘detouring’ subscriber traffic around high-volume http://www.esri.com/resources/userconf/proc96/TO200/PAP16 links and nodes; 5/P165.HTM

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Costello B 1996 Trends in client-server architecture in GIS Hawke D 1991 Characterising the performance of geographic environments. Slide from invited presentation at 1996 information systems. Proceedings of Third Annual Geomatics Atlantic Conference, Fredericton, New Colloquium of the Spatial Information Research Centre, Brunswick, Canada Dunedin. University of Otago Craig W J, Tessar P, Ali Khan N 1991 Sharing graphic data IDON Corporation 1990 Final report: a federal geographic files in an open system environment. Journal of the Urban information systems (GIS) network requirements study. and Regional Information Systems Association 3: 20–32 Contract report prepared for the Data Communications and Networking Subcommittee, Interagency Committee on Crossley D 1994 WAIS through the Web: discovering Geomatics, Government of Canada environmental information. 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