Improving the Quality of Web-GIS Modularity Using Aspects

Spatial concerns of Web Geographical Information Systems (Web-GIS) are inherently crosscutting and volatile: crosscutting because they affect multiple functionalities of Web-GIS systems, such as visualization of a route in a map, volatile because their status may change often (e.g., in a map, a route can be obstructed temporarily due to a car accident or festivity, so alternative routes should be provided dynamically). The quality of Web-GIS services, in particular the efficiency required for their adaptation and evolution, can be compromised if volatility and the crosscutting nature of spatial concerns are not taken into consideration during modularization. This paper presents an aspect-oriented approach for Web-GIS applications. This approach models crosscutting spatial concerns and handles the volatile nature of some spatial concerns as if these were crosscutting. Thus, both types of concerns, crosscutting and volatile, are modeled as candidate aspects. By modularizing volatile concerns as aspects, it is simple to add and remove them at runtime from an application by using dynamic weaving. The approach starts with the identification and specification of crosscutting concerns and follows by composing them using MATA, an aspect-oriented modeling technique. GIS crosscutting concerns are stored and documented in a concern catalogue for promoting their reuse. Conflicts regarding the ordering of composition are also taken into account.