Generating the architecture of GIS applications with design patterns

Abstract

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...

Specifying analysis patterns for geographic databases on the basis of a conceptual framework

“…Another problem that can be observed is that when the data either do not exist, or are not appropriate for reusing, the respective existent geographic database design is in most cases also not reused, and new databases are developed from scratch [11]. For example, an information system for urban territorial tax collection, developed for a certain municipal district, could serve several other municipal districts (perhaps with minor adaptations), even though its related data can by no means be reused.…”

Designing adaptable geographic objects for mobile applications

“…However, and even taken into account that the root of LBS is GIS software (and that from the functionality point of view, a GIS module is necessary to build a LBS), the evolution patterns of LBS are clearly different from those of GIS software, and accordingly the software design requirements change dramatically as discussed in [3]. Different architectures and design solutions have been presented in [12] and [13] to deal with the mobility issue; nevertheless, the subject of integrating GIS software with ubiquitous computing from the object oriented point of view has been recently introduced and studied in [3], [8] and [10]. In this paper we address a more complex problem when dealing with GIS software in the context of mobility: how to adapt the structure, representation, topology and behavior of geographic objects when the user moves.…”

“…This framework is fully described in [8], [9], [10], and [18]. Geo-Framework provides a set of basic classes and abstract behaviors that can be either extended or customized for specific applications (and domains).…”