An alternative interpretation of queries involves splitting a query into parts that cover different but connected aspects of the information needed.
In this paper we show the impact of Design Patterns in the generation of the software architecture underlying a GIS application. We first discuss the problem of adding spatial features to Iegacy object oriented applications, then we present three Design Patterns specific to this domain: Reference System, Roles and Appearances to illustrate our claims.We introduce Design Patterns as a conceptual tool both, to record design experience and to support evolvable design micro-architectures, and describe the previously mentioned patterns, exemplifying their use within the design of GIS applications. Finally, we discuss some further issues in our research. l-IntroductionThe complexity of the underlying domains of GIS applications, the variety of data types including spatial data and sophisticated relationships and the strong need of performance and accuracy in the final product, usually lead the GIS design task as a process closer to the implementation than to a software engineering process.However, expert GIS designers do not solve every problem from scratch. Most of the time they reuse previous solutions to solve similar problems. But this reuse of experiences is difficult to transmit to non-expert designers and therefore, lacking an adequate procedure to record experience, the sharing of knowledge is not effective in helping the designer to reason in term of GIS structures; critical design decisions, such as relationships between spatial features and conceptual ones remain hidden in the code or are poorly documented. Many other decisions cannot be even deduced from either code or documentation. These strategies of reuse are caged in the designer's mind.The problem of reusing design in GIS applications has become also a need because in the last times, more and more users are building GIS applications based on open systems instead of using a particular GIS product (like ARCInfo, GENAMAP, etc). The rapid growing of the WWW as a host for different kind of applications and the emergence of Java as an object-oriented programming language well suited for developing efficient, distributed applications, also shows us the need to find a systematic approach for reusing design experience in the context of GIS applications. This is particularly true when a designer must face hybrid applications dealing with conventional transactionbased systems and must be upgraded to incIude spatial features that are not built in the underlying software.Permission to mnke digital/hard copies ol'all or p:u~ ofthis material for personnl or clnssroom use is grmkd without fee provided that the copies are 1101 made or distributed liar prolit or comlcrcinl ndvantny. lhr copyright notice. the title ofthe publication and its date nppenr, and tloticu is given lhnt copyrighl is by pcnnissio~l ofthe ACM. Inc. To copy olhenvise, to republish. IO posl 011 swvcm or IO rcdislrihrlc to IisLx rcquiresspccific pernlissio~~ sndlor Ite. GlS 97 Lmvegl7s iveI'c7dr7 11,Y.l Copyright 1997 ACM I-5X113-017-l/97/1 l.XI.50Examples of solutions extending traditional applicat...
One of the most elusive targets in hypermedia research has been to provide effective support for user navigation [6]. The popularity of the World Wide Web and its inherent vastness has only made things worse: many of the tools that were proposed to alleviate this problem in closed systems do not scale well when applied to WWW. We designed a tool, that we call The Aleph, that addresses the support of user navigation with two views, known as the Travel Map and the Content View. The Travel Map assists the user at the stage of traveling trough the docuverse, and the Content View helps him at the moment of recalling and organizing the known space. We developed a novel approach based on document collections, that takes advantage of 3D space, to give much more information than is usually available in 2D representations, and to simplify the map layouts. The maps provide a framework that relates document and terms with specific positions in space. The structure of the paper is as follows: Section 1 positions The Aleph in the context of a large-scale hypertext system as WWW. Section 2 shows the structure of The Aleph, the two views it provides, explains why to use different views, how they are related, and how they work. Finally Section 3 relates The Aleph to other tools that address similar user needs and design objectives.
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