Research On Service Encapsulation Method Of Geographical Model

Over half a century’s rapid development, Geographical Information System (GIS) has already evolved into a comprehensive system including GIS Technologies, Geographical Information Science and Geographical Information Services. Meanwhile, with the expansion of its application in various areas, GIS is facing serious challenges in spatio-temporal analysis, simulation, forcast, prediction and decision support, etc. Strengthening the ability of geographical analysis by integrating and sharing geographical models (geo-models) will bring new vitality and benefits into GIS.Domestic and foreign geographers have already created mass geo-models in terms of various research purposes. However, the differences of model’s design and implementation create much difficulty in model sharing and reuse, and further lead to "Solitary Island of Geographical Model" obviously. Many problems (e.g., problems of model utilization and protection) exist in the traditional model sharing approaches which directly distribute geo-model’s programs or integrate geo-models into other systems, thus models could not be effectively shared on the web and cause serious waste. With advances of geographic data sharing methods, technologies and standards, GIS has strengthened its focus and trend on the sharing of geo-models. The concentration of GIS service is transforming from data service to function service, and will further promote the research on geographical model service. It is an important and urgent task to develop geographical model service and explore service encapsulation method of geographical models for the sharing and integration of geo-models as well as for the development of GIS.Aiming to the sharing and reuse of geo-models, this dissertation analyzes the essential characteristics of the data, functions and operations of geo-models. Learning from the existing standards, implementation methods and technologies of Web Service and GIS Service, we change the traditional concept of geo-model encapsulation that converting the data format, and presentes a set of new concepts and methods of model encapsulation and model service. It breaks through the core and key problems of service encapsulation of geo-models, and provides well-designed methods and technologies to solve these problems and realize the service encapsulation of geo-models. The main research achievements of this dissertation are as follows:(1) Characteristic analysis and classification of computer implementation of geographical model. The dissertation analyzes the characteristics of geo-models in terms of three components, i.e. data, program and document. Accordingly, the methods of model classification are designed.(2) Description of geographical model service. The dissertation presents a data format markup model which centers on "location" and with a core of data type and delimiter, and designs Data Format Markup Language (DFML). DFML realizes the unique description of data format. Based on DFML, the description method of geographical model service is put forward with the focus of model’s function, input and output. A description language of geographical model service called Geographical Model Service Description Language (GMSDL) is designed, and finally the unique description of geographical model service is realized.(3) The generation of the description document of geographical model service. According to the characteristics of different components of geo-models, three categories, seven types generation methods of the description document are designed. They are data paring method, source code reversing method, head file paring method, intermediate code reversing method, static analyzing method, dynamic debugging method and user-aided describing method. The concepts, principles, realization, applicability and selection of each method are illustrated in detail. The methodology of generating description documents of geographical model service is preliminarily formed.(4) Service encapsulation of geographical model interactive operation. The dissertation analyzes the operating steps of using geo-models, and points out the key problems of service encapsulation of geo-model’s operation. It presents three-step encapsulation method:data operating encapsulation, function calling encapsulation and converting operation to service. Three methods for the service encapsulation of geo-model’s data operation are designed, i.e. input/output redirection method, OS file operation intercept method and GUI automated testing method. File-based and command-based encapsulation method of geo-model’s function calling is designed, and thus the basic approach of geographical model service is achieved.Through the implementation of service encapsulation tools of geo-models, service system and case studies, the well-designed concept of service encapsulation of geographical model is verified to be viable and effective. A series of methods proposed by the dissertation can effectively solve the main problems of service encapsulation of geographical model. It realizes the geographical model service with the characteristic of state and strong interaction. The dissertation provides feasible ways to share and reuse geo-models, and to eliminate the "Solitary Island of Geographical Model". It is expected to promote the sharing and integration of geographical model, enrich the research of geography with new methods, and further enhance the analyzing ability of GIS and expand GIS service.