## 1 Introduction  
Participatory GeoInformation technologies have evolved exponentially and profoundly in the past decade. In the wake of Geoweb 2.0, Volunteered Geographic Information (VGI) (e.g., OpenStreetMap and WikiMapia) and crowdsourced geodata are increasingly being produced by the public, while attracting more and more professionals. Some VGI tools and systems like GeoDeliberator or ArgooMap target professional purposes where a multidisciplinary team (professionals from different domains) must work collaboratively. This is particularly the case of Geodesign, a very dynamic emerging field [1]. Since its emergence in 2008, and in GeoDesign summits that have taken place in Redlands every year, many definitions have been given to this new term by a group of thought leaders from academia and a variety of professions. However, to date, no consensus has been reached. We can simply state that GeoDesign describes the integration of GIS and spatial design [1]. In this study, we define GeoDesign as \"art by the creativity of design, and science by the rationale of GIS to improve multidisciplinary group analysis, solution building and decision making with controlled public participation\".  
Essentially, technological innovations such as CommunityViz [2] and CityEngine [3] have been designed primarily to support GeoDesign practices and, in particular, to allow groups of people from different professions, places and time frames to work together on the same project and produce plans and designs. However, these technologies are expensive and require expertise to work with. For this reason, we propose the concept of WikiGIS as an alternative and complementary solution to support the collaborative, iterative and creative dimensions of GeoDesign [4,5]. The main strength of WikiGIS is its ability to dynamically manage the traceability of contributions so users can navigate the history.  
In fact, WikiGIS is a geocomlaborative platform based on Web 2.0 technologies and principles [4]. The conceptual framework of WikiGIS combines the strengths of wiki to ensure the tracking editing process, the power of GIS to provide users with basic geoprocessing capabilities, and the main drawing tools for sketch-mapping. WikiGIS provides a collaborative environment where participants can exchange opinions, and discuss and collaborate through a dynamic user interface where all contributions are displayed to everyone. WikiGIS ensures the traceability of changes to spatial-temporal geographic components (geometric location and shape, graphics: iconography and descriptive), while providing dynamic access to the previous versions of geographic objects, as well as documentation on data quality [5].  
This paper is a follow-up to the paper published in 2012 [5]. More precisely, it aims at formalizing the innovative WikiGIS concept from the analysis and testing of the first draft-prototype developed in 2012 [5]. In the next section, we describe the main features of WikiGIS. The third section is dedicated to the temporal dimension, since time is a crucial component of WikiGIS. In the fourth section, traceability issues and the conceptual solution adopted are presented. Section 5 deals with data quality issues and, more specifically, the validation and communication of contributions (likelihood level of a contribution). In Section 6, we propose the \"deltification\" function as a new means for WikiGIS to allow comparisons between two scenarios. Section 7 is dedicated to the formalization of the WikiGIS concept using UML diagrams. Before concluding and discussing new perspectives, we propose a brief overview of the cartographic interface to demonstrate how the WikiGIS proposal works.