Integrating GIS Web services based on mediating architecture

The geographic information service is enabled by the advancements in general Web service technology and the focused efforts of the OGC in defining XML based Web GIS service. Based on these models, this paper addresses the issue of services chaining, the process of combining or pipelining results from several interoperable GIS Web Services to create a customized solution. This paper presents a mediated chaining architecture in which a specific service takes responsibility for performing the process that describes a service chain. We designed the Spatial Information Process Language (SIPL) for dynamic modeling and describing the service chain, also a prototype of the Spatial Information Process Execution Engine (SIPEE) is implemented for executing processes written in SIPL. Discussion of measures to improve the functionality and performance of such system will be included.

An index method for continuous moving objects

There are current, historical and future information about continuously moving spatio temporal objects. And there are correspondingly spatio temporal indexes for current, past and future querying. Among the various types of spatio temporal access methods, no one can support historical and future information querying. The Time Parameterized R tree(TPR tree) employs the idea of parametric bounding rectangles in the R tree. It can effectively support predictive querying to continuously moving objects. Unfortunately, TPR tree can not used to historical querying. This paper presents a partial persistence method in order to extend TPR tree for querying past information of moving objects. In this method, several TPR trees will be created for more effectively predictive querying, because TPR tree has a time horizon limit for predictive querying. Further more, a B tree will be used to index time dimension. Since the partial persistence method brings about huge storage space using, this paper also discusses some methods on how to reduce storage space. Finally, this paper presents an extensive experimental study for the proposed method and gives some interesting directions for future work.

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations: retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R tree. The difference between the generalization and the R tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value, too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub blocks, and vertexes are total ordered by their importance value. With the help of the generalized R tree, one can easily retrieve data at different detail levels. Some experiments are performed on real life data to evaluate the performance of solutions that separately use normal spatial index and multi scale spatial index. The results show that the solution using multi scale index in SISP is satisfying.

A solution of spatial query processing and query optimization for spatial databases

Recently, attention has been focused on spatial query language which is used to query spatial databases. A design of spatial query language has been presented in this paper by extending the standard relational database query language SQL. It recognizes the significantly different requirements of spatial data handling and overcomes the inherent problems of the application of conventional database query languages. This design is based on an extended spatial data model, including the spatial data types and the spatial operators on them. The processing and optimization of spatial queries have also been discussed in this design. In the end, an implementation of this design is given in a spatial query subsystem.

A solution for digital image management in spatial databases

Digital Orthographic Map (DOM) can be used in various applications because it contains both image features and terrain information. Spatial database management systems aim at the effective and efficient management of data related to a space, engineering design and so on. Thereby spatial database provides an efficient solution for managing DOM. According to large amounts of the DOM data in storage, a data compression based on wavelet is introduced into the storage. Another strategy to solve this problem is to decompose the raw image into tiles and store the tiles individually as separate tuples. The metadata of DOM can be used to organize and manage spatial information, especially for spatial data sharing and fast locating. A tool for browsing, zooming and querying the DOM data is also designed. We implemented these ideas in SISP(Spatial Information Sharing System) and applied the subsystem into the DOM management of Beijing City, which is an component of the Beijing Spatial Information Infrastructure.

A solution for concurrency control and long transaction management in SDBMS

The problem of long transactions is a significant problem in spatial database. The checkout mechanism and multi version mechanism are two kind methods of solving the problem of long transactions. In this paper, we present a Shallow Version Management mechanism to realize multi version mechanism in spatial database. And we introduced a increment storage and dynamic version views building method to improve efficiency of storing and consulting. We also illuminate how to resolve the problem of long transaction concurrency control in spatial database by using multi version mechanism. At the end of this paper, we introduce some required means to version management in spatial database, like converge, compress and delete.

A prototype for spatial information services based on J2EE

J2EE(Java 2 Platform ,Enterprise Edition) is a kind of architecture that simplifies the development ,design and management of multilevel enterprise solution. The spatial middlewares based on J2EE can easily resolve the problems which the traditional Geographic Information Systems(GIS) now have to face with, such as transplantability, stability, easy maintainability and many more. This paper first introduces some conceptions and principles about J2EE, spatial middleware. then proposes a concrete J2EE based solution of spatial middleware, namely SISP AS, which develops on JBoss(an open sources application server of J2EE) and uses the SISP spatial database. SISP AS follows Open GIS specifications, and implements a subset of OGC services. it improves interoperability and commonality by using XML/GML for communication and data transmission, resolves the transmission efficiency problem of large spatial data by using raster pyramid and vector pyramid. Finally, the related work will be presented. Notably, the experiments on this prototype system can proves that it is available to manage, distribute and share large scale spatial data by using SISP AS.