ONLINE MAPS IN GEOMED Internet Mapping, online GIS and their application in Collaborative Spatial Decision-Making Claus RINNER

This paper gives an overview of Internet Mapping and discusses its use for Geographical Mediation. Internet Mapping summarizes a variety of tools, ranging from geodata and map servers up to online Geographic Information Systems (GIS). First, a classification is proposed, according to the services offered and to the techniques used. Then, the requirements of Collaborative Spatial Decision-Making (CSDM) for online maps are discussed in more detail with reference to the European Union research project "Geographical Mediation System" (GeoMed).

KEYWORDS:

Internet Mapping, Internet Map Server, WebGIS, Online GIS, Geographical Mediation, CSDM.

1. INTRODUCTION

Geographic Information Systems (GIS) are tools to analyse geographic situations through their computer representation, geo-referenced data. While stand-alone GIS have become specialized and highly complex software packages, Internet Mapping summarizes a variety of relatively small pieces of software, which perform particular GIS operations, especially cartographic visualization. We use the terms WebGIS as a complement to Internet Mapping, where we mean not only simple mapping applications but GIS-like analysis tools. Plenty of mapping applications that came up in the Internet during the last two or three years make it desirable to find some criteria for classification. We think that these tools can be distinguished from each other by the services they offer for a client’s workflow, and/or by the techniques used for their implementation. Section 2 proposes a classification of Internet Mapping services into the following categories: Geodata Server, Map Server, Online Retrieval System, Online GIS, and GIS Function Server. Section 3 describes three general technical approaches to Internet Mapping. Geographical Mediation means moderated discussion in spatial planning procedures. In this sense, mediation is becoming an important part of Collaborative Spatial Decision-Making (CSDM) processes, especially in spatial planning. The specific requirements for the use of online maps in CSDM is outlined in section 4. Section 5 presents a model solution, elaborated within the European Union project GeoMed , and based on Zeno, GMD’s platform for computer-mediated group decision-making.

2. CATEGORIES OF INTERNET MAPPING APPLICATIONS

In this section, we attempt to adapt and refine a classification of Internet Mapping applications (mostly prototypes), proposed in a former publication, Fitzke et al. (1997). We focus on services provided by specific applications, rather than on the potential of generic software tools, and refer to the next section for a statement on so-called "Internet map server" (IMS) software like ESRI’s ArcView IMS or MapObjects IMS, Autodesk’s MapGuide, or Intergraph’s GeoMedia WebMap. The Internet is based on a client/server philosophy, where client computers request data from remote server stations. In the following, the term "server" (e.g. map server) stands for a complete solution, including the client side.

Data Management

Visualization

Retrieval

GIS Analysis

Geodata Server

X

Map Server

X

X

Online Retrieval System

X

X

X

Online GIS

X

X

X

X

X

X

X

GIS Function Server

Table 1: Categories of Internet Mapping applications and their functionality (modified from Fitzke et al. (1997)) In Fitzke et al. (1997), we proposed five categories for Internet Mapping applications, which differ from each other in the GIS operations they provide for a client’s workflow. Four functional groups of GIS operations are considered, namely data management , visualization , retrieval , and analysis . This schema results from a modification of the well-known IMAP concept: Data Input and Management are put together, while the Analysis group is split into simpler retrieval functions and complex analysis. Retrieval means getting existing data from a database using a standard query language, GIS analysis signifies deriving new information using spatial operators. The Presentation class of IMAP is labeled "visualization". The resulting Internet Mapping categories are shown in table 1, and explained below. A Geodata Server provides its clients with functions for searching for geo-referenced data files, to be downloaded for further local processing (offline or online) with the client’s GIS software. Therefore, geodata servers can substitute client’s data input and management operations, e.g. digitizing or file catalogue handling. Map Servers provide online visualization of geodata, including map handling functions like "zoom" and "pan". This means the selection among prepared sets of - typically raster - maps (static map server), or the choice of some visualization parameters (layers, symbols, colors), server-side processing and client-side display of raster or vector maps (interactive map server). An Online Retrieval System adds thematic and simple spatial retrieval functions to a map server, while Online GIS offer access to analysis functions and data of a remote GIS via the Internet. Finally, a GIS Function Server allows clients to use remote GIS functions on their uploaded data ( GIS Compute Server ) or to download GIS functions for local processing (GIS Function Library). Table 1 gives the overall impression of four homogeneous, increasingly powerful WebGIS categories, and a fifth class, in a sense apart from the others. Geodata Servers replace (or extend) local data handling, Map Servers provide data handling and map presentation, Retrieval Systems add thematic and spatial query functionality to the latter, and, finally, Online GISs include spatial analysis capacity. GIS Function Servers can provide their clients with any GIS operation, like Online GISs, ranging from visualization over query up to analysis. This also includes data handling functions like projections or format conversion. The cross for data management in table 1 is missing, because clients work on their own data. spatial data Geodata Server

graphics

report data

X

Map Server

X

Online Retrieval System

X

X

X

X

X

(X)

(X)

(X)

Online GIS GIS Function Server

functions

X

Table 2: Types of result of a client’s request (modified from Fitzke et al. (1997)) This observation leads to a second criterion to differentiate between Internet Mapping applications, besides groups of GIS operations: the type of the result of a client’s request (see table 2). All categories, but the last, deliver data, partly in explicit form (Geodata Servers: GIS files), partly implicitly through (carto)graphics (Map Server, Online Retrieval System, Online GIS: maps). With report data, Online Retrieval Systems and Online GIS may produce an additional data type. GIS Function Servers may supply functions (GIS Function Library: software components, algorithms) but also data, when remotely processing clients’ data sets and returning the results of a remote session as a file or as an online

map (GIS Compute Server). Compared to Fitzke et al. (1997), we here split the "data" column into two, "spatial data" (raster or vector format) and "report data". Report data are textual or tabular data possibly resulting from queries in Online Retrieval Systems. The modification was motivated by Plewe’s (1997) description of possible forms of distribution of Geographic Information, where he distinguishes our first four WebGIS categories based on the question "What would we share?". It is obvious that the installation of GIS on the Internet moves the focus away from complex GI systems to modular GI services (cf. Günther, 1997). This recent development finds its complement in the technical development of the OpenGIS specifications, which is further looked at in the following section. Geodata Server "Raw Data Download" "Metadata Search" "Net-savvy GIS Software" Map Server - static - interactive

"Static Map Display" "Dynamic Map Browser"

Online Retrieval System

"Web-based GIS Query and Analysis"

Online GIS

"Web-based GIS Query and Analysis"

GIS Function Server - compute server - function library

"Data Preprocessor" -

Table 3: Correspondence between WebGIS categories and Plewe’s (1997) types of DGI applications Plewe (1997) describes eight types of Distributed Geographic Information (DGI) applications, which correspond very well to our findings. Table 3 shows the respective terminology for comparison. The three classes "Raw Data Download", "Metadata Search", and "Net-savvy GIS Software" are not distinguished in our approach, because they all provide clients with GIS data for further local processing. To offer a differentiation beyond services, we have to consider WebGIS techniques.

3. WEBGIS TECHNIQUES

In Fitzke et al. (1997), we distinguished three general technical approaches to WebGIS, guided by the following question: "Did the development start with connectivity functions or with computing, or do they follow a third way, programming components?" The connectivity-first approach takes netware, especially WWW browsers, and adds geo-processing functionality to those (browser-based GIS). Computing-first augments stand-alone GISs with netware features (Internet-enabled GIS). Components-first denotes an approach, where both, geo-processing and net-awareness, are implemented from scratch. GIS in the Internet is independent of the World-Wide Web, because also traditional protocols for Internet connectivity, like FTP (File Transfer Protocol) and TELNET, allow clients to transfer data files and to login to remote server workstations, thus enabling simple geodata servers and advanced online GISs as defined in the previous section. But with respect to the user-friendliness through the graphic capabilities and the quantity of potentially interested world-wide users, only the WWW raised today’s interest in Internet Mapping. Within a WWW browser, a GIS user interface can be emulated with HTML (Hypertext Markup Language) and JavaScript. Commands generated by the client can be sent to a server and processed through CGI (Common Gateway Interface) scripts. The result of an eventual, automated GIS session is sent back to the client browser in a standard graphic format (see Plewe (1997) for a detailed description). This is how several browser-based GIS applications add GIS features to clients’ connectivity tools. The advantage of using the above mentioned techniques is the platform-independence of the resulting tools. Some of the commercially available, generic Internet Map Servers, though, use a platform-dependent plugin concept to add functionality to Web browsers. For example, Autodesk’s MapGuide uses a plugin, restricted to Netscape Navigator and Microsoft Internet Explorer on Windows platforms, to view their proprietary vector format MWF, map window file.

The fact that with connectivity-first solutions clients’ Web browser are often coupled with a remote GIS leads us to computing -first, a second technical approach to Internet Mapping. These applications add, in contrast, Internet connectivity to a full-featured GIS. In its purest form, this is a virtual category, because up to now, no implementation is known to the author. But Internet-enabled GIS seem to be a desirable solution, where complex GIS software and workflows exist, and simple net-based services, e.g. access to distributed data sources, are required. Finally, more and more interactive map servers and online geo-retrieval systems are written as Java applets, which re-implement GIS functions. Java allows GIS function libraries to be realized using an object-oriented programming approach. This means that Java is not only used to provide an advanced client interface to some conventional server GIS (as done with several commercial Internet Map Servers), but "true" GIS modules can be transferred to the client side. A related recent trend is the OpenGIS concept of encapsulating geographic data together with the methods to process them. In the object-oriented view, GIS modules (data and functions) soon will be shipped via the Internet and clients have to get (and pay for) only those components that they really need. Will Geographic Information (GI) soon be replaced by Geographic Objects (GO)? Indeed, it should be mentioned that OpenGIS uses component technology independently of distributed computing platforms. Distributed components, which belong to the subject matter of this paper, build the synthesis of these two separate OpenGIS features. Data Management

UI & Visualization

Retrieval & Analysis

Browser-based GIS (connectivity-first)

S

C

S

Internet-enabled GIS (computing-first)

S

C

C

Component GIS

S

C

C+S

Table 4: Distribution of tasks between client (C) and server (S) What is the distribution of load between client and server? Table 4 attempts to give general indications for the three technical WebGIS approaches. It is clear that the user interface (UI), which is needed to activate any functionality, must be placed on the client. The UI is coupled most often with the map visualization at the client. The data management is equally insufficient for a distinction between WebGIS techniques, as it generally takes place on the server-side. The difference can be found in the retrieval and analysis functions: With browser-based GIS, in principal, geo-processing takes place on the server. Using techniques like Javascript and plugins for vector maps, advanced user interface and simple mapping functions can be shifted from the server to the client. This is an elegant way of taking advantage of powerful client PCs and reducing the load on popular servers. Internet-enabled GIS with distributed data access feature client -side computing load. The components approach with downloadable GIS modules also means client-side processing, but with Servlets, Java components could also be used to extend Web server capabilities with server-side geo-processing.

4. INTERNET MAPPING IN CSDM

Collaborative Spatial Decision-Making (CSDM) as discussed in NCGIA (1995), is a research domain at the intersection of Geographic Information Science and Computer-Supported Cooperative Work (CSCW), and is closely related to negotiation in spatial planning. Jankowski (1998) cites three phases of a public participation process: exploration of data to clarify issues, establishing a set of decision objectives, evaluation of feasible options. The role of Geographic Information in a CSDM workflow is reflected in Carver et al. (1998): Participants of a decision problem are enabled to ... explore a spatial decision problem, experiment with choice alternatives, and

formulate alternatives. All these tasks have to do with inspecting existing information and providing new information. Thus, we can identify two very general actions of users, to inform oneself, and to communicate with others. This is what CSDM inherits from GI Science and CSCW, namely spatial information processing and communication / cooperation facilities. Table 5 shall also indicate that groupware tools can connect together isolated Spatial Decision-Support Systems (SDSS) for CSDM procedures. Maps are used as documents in shared workspaces. A specific groupware type are Issue-Based Information Systems (IBIS, cf. Kunz and Rittel, 1970), which have been used to enrich online discussion forums. The atoms of a geo-referenced discussion are arguments (contained in messages) and geographical objects (e.g. houses, parcels, roads).

central task principal tool typical document basic entity

GI Science

CSCW

geographic information

communication, cooperation

SDSS

Groupware, IBIS

map

shared workspace, discussion forum

geo-object

message, argument

Table 5: What CSDM inherits from GIS and CSCW The visualization and query of the relations between geo-objects and arguments can be used for an additional feature (cf. Rinner and Schmidt, 1998): exploration of the state of a planning discussion. Looking at the technical categories of Internet Mapping in section 3, connectivity-first and computing-first, we see a parallel to the two concepts communication and information in CSDM. Connectivity tools like Web browsers and email clients are the base for communication between planning parties over the Internet. Computing systems like GIS are used to generate, manipulate, and manage information about a planning project. A map is a hybrid document, because it comprises information and communication aspects. Therefore, maps may well be used to integrate connectivity and computing software under the auspices of CSDM. Online maps as provided by Map Servers and Online Retrieval Systems for use in CSDM could be defined as follows. Later categories offer additional features to preceeding ones, for example more interactivity or increased information density. (This is an analytical classification without empirical background.) Descriptive Maps Static raster images, used to visualize a geographic situation. Intelligent Maps Maps, whose cartographic design is adapted to the information requirements of the task at hand and to users’ abilities. The visualization algorithms may be an outcome of a knowledge-based system. Interactive Maps Here, the user can influence the graphical and thematic appearance of the map, within the limits of the underlying geodata (colors, shading; layers). Retrieval Maps Thematic data, underlying the mapped geo-objects, can be retrieved in textual or tabular form by querying map features. Navigation Maps Maps (of any previous type) that offer access to other maps and multimedia documents through mouse clicking

(also known as "hypermaps" or maps with "hot spots"). The previous types of online maps are independent from any specific application domain and are centered on providing information. A recent workshop on "Groupware for Urban Planning", held in Lyon, France, in February 1998, dealt with visualizing planning alternatives (e.g. Sarjakowski, 1998) and recording argumentation (Tweed, 1998), among other aspects of computer-aided planning. Communication in spatial decision-making includes the exchange of positions and arguments for or against some proposed solutions. This cooperative aspect is more specific to map use in CSDM. The following online map categories are specific to spatial planning and emphasize discussion and cooperation features: Argumentation Maps Maps that concurrently visualize the topography of a planning problem and the contributions to a discussion, which turns around the represented area. Topographic and discussion "space" shall both be navigable. Annotation Maps Users may add graphical or textual comments to a draft map. Alternative Maps Skilled users can manipulate the contents of a map by modifying geographic features, to visualize their favorite planning solution. As far as public participation in a different place/different time scenario (like in German planning procedures) is concerned, the World-Wide Web can be considered as an appropriate medium for collaboration among planning parties. Then, plan visualization requires Internet Mapping, while recording argumentation needs online discussion forums like GMD’s Zeno system (Gordon, 1995). For this purpose, the GeoMed platform (Gordon et al., 1997), described in the following section, aims at integrating map visualization with argumentation elements.

5. THE GEOMED EXAMPLE

Mediation means arbitration in group decision-making through a neutral third party, the mediator, who controls the discussion process, but also conciliates actively when conflicts occur. Geographical Mediation is mediation applied to spatial planning. GeoMediation, therefore, can be part of broader CSDM processes and may pose specific requirements on the use of online maps. We will shortly review two implementations which are related to our CSDM and GeoMediation activities and describe the way in which they combine the map categories of the previous section. The Descartes system (formerly "IRIS") produces intelligent, interactive retrieval maps for visual exploration of statistical data (Andrienko and Andrienko, 1997, 1998). Descartes’ maps are intelligent in the sense that the system uses a knowledge-base which implements rules for cartographic design, according to the characteristics of the thematic data at hand. As a client/server system for the Internet (or Intranet), Descartes shall be usable by a large number of clients, possibly non-experts in mapping. Through this automation, visualization is adapted to the addressee - a criterion for intelligent maps as defined above. Descartes’ maps are interactive, because the user can change the visualization proposed by the system. For example, it is possible to change the default classification and to have the display adapted instantly, or the user can select an entity, whose data value is taken as reference for visual comparison. At any time it is feasible to retrieve the thematic data behind the map objects. According to the classification of section 2, applications developed with Descartes can reach the category of Online Retrieval Systems including an advanced interactive Map Server. Spatial retrieval functions (as opposed to thematic ones), indeed need to be implemented in the near future. Another plan is the integration of Descartes with the Web-based CSDM platform Zeno. Descartes seems to be very well suited for providing access to statistical "background" data, before and during the discussion of a spatial planning project. Thereby it could be useful for professionals, e.g. planners, before the elaboration of a draft map, or for citizens to understand more about the properties of a planned area and its neighbourhood.

The Zeno system was designed and implemented since 1995 as an Internet-based mediation system. The computer (network) is used not only as a medium for group discussions, but moreover for assisting a mediator in controversial decision problems. When a software tool like Zeno supports a human mediator, we speak of a computer-mediated discussion. The theoretical background for Zeno was established by Gordon (1994) with Computational Dialectics, the study of computational models of norms of rational discourse. The Zeno argumentation framework is a variant of an Issue-Based Information System, which defines a set of argumentation elements, and the relations between them. This concept allows the implementation of groupware tools, comparable to newsgroups but with a much richer argumentation logic. Within the scope of the GeoMed project (EU DG XIII, IE 2037), Zeno’s discussion forum is applied to urban and regional planning and has been extended with shared workspaces and user management features, which make it a Web-based platform for CSDM. Unique resource locators (URL) are used to request any document available on the GeoMed server. This includes maps as one type of document resources. Within GeoMed, a map viewer is provided, which is started when a user loads a map URL. This module, called Ptolemeus, is developed by our project partners from the Netherlands Organization for Applied Scientific Research (TNO). The user interface of Ptolemeus is a Java applet, which appears in the client’s Web browser. Client requests are handled through JDBC (Java Database Connectivity) on a direct socket connection (in contrast to a state-less HTTP connection). The server part uses an object-relational geographical database. Ptolemeus provides map visualization, mapping functions, map manipulation including layer management, and queries in the server database, and therefore can be classified as an Online Retrieval System. According to the map use categories in section 4, Ptolemeus not only provides interactive retrieval maps, but also annotation map functionality. This is achieved through a feature which allows the user to create a new (annotation) layer and draw graphical or textual remarks on a planning map. Technically, Ptolemeus is a browser-based GIS with a thin client, because the processing of most mapping and query functions takes place on the server. The first reason for this load distribution is that on the server a spatial database extension is installed which performs complex spatial queries. This reduces the size of the Java applet and the download time. As a side effect the data volume also is diminished, since the results of mapping and query requests (e.g. a zoom-in) are, in any case, generated on demand on the server. Another issue in multi-user environments is the synchronization of user interactions, which hinders taking advantage of an improved load distribution between client and server.

6. CONCLUSION

For scientists and technicians, it is important to find a common language for Internet Mapping concepts. This paper proposed several approaches to classifying WebGIS applications, according to the services they provide and the techniques used. We hope that one or the other will be the base for the further analysis of Internet Mapping. What are the implications of recent trends on a classification of Internet Mapping applications? As a consequence of object-oriented programming, we may observe in the future that Geodata Servers and GIS Function Servers will be merged to provide Geographical Objects (GO) together with adequate processing methods. If interfaces between GOs become standardized (e.g. through the OpenGIS specifications), we will not be able to distinguish between more or less powerful WebGIS applications any more, because an Internet client software can access any spatial query and analysis function that the user seeks for. Instead, it could be sensible to compare those GIS modules that provide services for the same or closely related application domains. This approach corresponds to the "information communities", defined by the OpenGIS Consortium. Two-dimensional maps (paper as well as digital ones) can be associated with traditional planning procedures. Some authors claim the substitution of maps by realistic 3D representations of planning projects, which could allow lay persons to better understand a planning situation. We do not expect that formal planning procedures will soon be changed to take advantage of new technological possibilities like Virtual Reality (VR). But we see a large potential of augmenting traditional planning workflows by the development and use of online maps of the categories described in section 4. Furthermore, we anticipate that more or less traditional maps will not only be used for topographic and thematic mapping, but rather will serve as a base for: Cartographic User Interfaces for distributed Web servers, realistic, immersive VR representations, and Collaborative Virtual Environments.

When speculating about future development of social activities (like planning) on the Internet, of course, we have to keep in mind that the accessibility to the Internet still needs much improvement. Another important issue that could not be addressed in this paper is the need for empirical research on the use of computer planning systems (see for example Nyerges and Jankowski, 1998).

ACKNOWLEDGEMENTS

Parts of the ideas presented in section 4 (Internet Mapping in CSDM) emerged from discussions with Dirk Schmidt, Oliver Märker, and Dietmar Fleischhauer. The author also expresses his thanks to Hans Voß, Thomas Gordon, and Dirk Schmidt for helpful comments on this paper. The information about the GeoMed project was partially taken from the "GeoMed Services Functional Specification - Full Version" dated 10/30/97.

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Claus RINNER [email protected] Claus Rinner is a PhD student in the CSDM group of GMD, the German National Research Center for Information Technology. He is working on the argumentative relations between geographical objects in hypermedia planning information systems. His thesis is supervised by Prof. Klaus Greve, chair for Geographic Information Systems at the University of Bonn. Among his interests are geodata modeling, cartographic design for the Internet, 3D-GIS and VRML. Claus graduated in applied systems sciences at the University of Osnabrück, Germany, where he studied environmental modeling and GIS. GMD - German National Research Center for Information Technology System Design Technology Institute (SET.KI) Schloß Birlinghoven 53754 Sankt Augustin Germany Tel: +49-2241-14-2401 Fax: +49-2241-14-2072 URL: http://www-fit-ki.gmd.de/persons/claus.rinner/