## 1 Towards Semantic GIS  
A geographic information system (GIS) is a functional and data infrastructure designed to perform complex tasks involving geographical data, e.g., to capture, store, manipulate, analyze, manage, and represent geographically-based data.  
When applied to geographically-oriented computer technology and integrated systems, GIS have been generating massive interest worldwide in the context of different domains and applications [1]. Their intrinsic flexibility and diversity, their multi-disciplinary features combined with their commercial focus, have not assisted in producing a clear and unambiguous definition of GIS [1]. A satisfactory and generic set of domain or application-independent fundamental principles, as well as an exhaustive description and evolution of applications, are hard to convey [1].  
Today GIS appears as a core concept in a wide domain of applications involving any kind of classic geographic data (e.g., sensors [2]), rich contents (e.g., multimedia-contents [3]) as well as complex dynamics (e.g., social content [4, 5]). Expectations around GIS's capabilities and performance are quickly growing. Consequently, GIS technology is constantly evolving and is evidencing a progressive and unrelenting convergence with web technologies (_Web GIS_[6]).  
Such convergence is much more than a simple technological trend: the current generation of GIS is intrinsically designed and developed to work at a global level on the web using web-scale data resources (_Big Data_[7]).  
The scale and the complexity of the information on the internet have led researchers to design the next version of the internet (known as _Web 3.0_ or the _Semantic Web_[8]): the model assumes that published data will be integrated with its \"meaning\" (_i.e._, semantic description) through a machine-processable specification. Such integration would potentially allow for the processing of contextual information by machines in a context of interoperability and with a lack of ambiguity. Semantic processes on the internet are not limited to data, but can also involve web services. Indeed, _Semantic Web Services_[9] extend the common web service concept by using semantic descriptors (e.g., those regarding modeling, service behavior, and capacity) to perform dynamic tasks. These involve the discovery, matchmaking, and execution of services that are supplied by different providers scattered throughout the global network.  
The next generation GIS is expected to address an extended set of issues that reflect a new understanding of requirements in terms of scale, interoperability [10] and complexity. Those requirements could propose further relevant tradeoffs and challenges if GISs are understood as integrated systems in the context of upper frameworks (e.g., _Spatial Data Infrastructure_ (SDI) [11]).  
More than one technologic aspect is evidently involved in the GIS evolution but, in practice, if the current development of GIS are naturally suited to the consolidated technological and conceptual environment of the second version of the web (_Social Web_[12]), then the next generation GIS should be reasonably designed according to the semantic web model (_Semantic GIS_ ([13, 14]). Here is the core of the problem: regardless of the current availability of _semantic technologies_[15], semantics is a debatable open research issue, and the understanding of the third generation web is a continuously evolving concept [16]. Therefore, semantic GIS has to be designed and developed in the context of a not-yet-mature and consolidated technological framework.  
The next subsections deal with the possible impact of semantics on GIS and the main challenges of next generation GIS. Anticipated improvements will also be defined for the most important features of next generation applications and services of GIS.