Image database design based on 9D-SPA representation for spatial relations

Spatial relationships between objects are important features for designing a content-based image retrieval system. We propose a new scheme, called 9D-SPA representation, for encoding the spatial relations in an image. With this representation, important functions of intelligent image database systems such as visualization, browsing, spatial reasoning, iconic indexing, and similarity retrieval can be easily achieved. The capability of discriminating images based on 9D-SPA representation is much more powerful than any spatial representation method based on minimum bounding rectangles or centroids of objects. The similarity measures using 9D-SPA representation provide a wide range of fuzzy matching capability in similarity retrieval to meet different user's requirements. Experimental results showed that our system is very effective in terms of recall and precision. In addition, the 9D-SPA representation can be incorporated into a two-level index structure to help reduce the search space of each query processing. The experimental results also demonstrated that, on average, only 0.1254 percent /spl sim/ 1.6829 percent of symbolic pictures (depending on various degrees of similarity) were accessed per query in an image database containing 50,000 symbolic pictures.     

空间方向关系形式化描述研究进展

空间方向关系的表示与建模作为空间方向关系领域的一个基础性问题,近年来逐渐成为地理信息系统、空间数据库和人工智能等领域研究的热点和难点并取得了一系列研究成果。从二维空间精确对象方向关系模型、三维空间对象方向关系模型、模糊空间方向关系模型等几个方面全面地综述了空间方向关系形式化描述的研究进展, 并对各种模型进行了对比与分析,指出了它们的优势与不足。最后明确指出三维空间方向关系和模糊空间方向关系建模是未来工作的重点,特别是三维模糊对象方向关系的研究是未来空间方向关系研究的重中之重,并指出进一步研究中几个迫切需要解决的关键问题。     

基于空间球理论的定性空间表示

主要研究了三维空间中空间对象的关系表示,介绍了利用部分学理论和形态学理论定义空间球的方法.根据Bran-don Bennettd的RBG理论,定义了空间球的形态关系及判断方法,提出了空间球全等的公理系统,给出了利用空间球模型定性表示方向关系和距离关系的方法.智能体对空间关系的确定是通过空间球实现的,该模型为智能体在约束空间环境中的行动推理提供了一个新的表示方法.     

Content-based Access in Image Database by Quantitative Relationships

In this paper, we describe a novel technique to perform content-based access in image databases using quantitative spatial relationships. Usually, spatial relation-based indexing methods fail if the metric spatial information contained in the images must be preserved. In order to provide a more robust approach to directional relations indexing with respect to metric differences in images, this paper introduces an improvement of the virtual image index, namely quantitative virtual image, using a quantitative methodology. A scalar quantitative measure is associated with each spatial relation, in order to discriminate among images of the image database having the same objects and spatial relationships, but different degree of similarity if we also consider distance relationships. The measure we introduce does not correspond to any significant increase of complexity with respect to the standard virtual image providing a more precise answer set.     

知识表示学习方法研究综述

近年来,知识表示学习已经成为知识图谱领域研究的热点。为了及时掌握当前知识表示学习方法的研究现状,通过归纳与整理,将具有代表性的知识表示方法进行了介绍和归类,主要分为传统的知识表示模型、改进的知识表示模型、其他的知识表示模型。对每一种方法解决的问题、算法思想、应用场景、评价指标、优缺点进行了详细归纳与分析。通过研究发现,当前知识表示学习主要面临关系路径建模、准确率、复杂关系处理的挑战。针对这些挑战,展望了采用关系的语义组成来表示路径、采用实体对齐评测指标、在实体空间和关系空间建模,以及利用文本上下文信息以扩展KG的语义结构的解决方案。     

空间数据的表示方法研究

为了提高空间数据的表示和处理能力，对空间对象进行准确的描述是非常必要的。根据空间对象的四类内在属性，设计出了能够准确表达空间对象的空间语义规则。通过用空间本体表示空间数据和用空间分类法对空间数据进行分类，将以往的空间数据处理提升为知识发现，从而提高了空间信息查询的查准率。     

Symbolic picture retrieval by relative–metric spatial relations

Symbolic pictures can be used for iconic indexing, spatial reasoning, and similarity retrieval in the design of intelligent image database systems. [S. K. Chang, C. W. Yan, Donald C. Dimitroff, and Timothy Arndt, IEEE Trans. Software Engineering 1988, 14, 681–688; S.‐K. Chang, Principles of Pictorial Information Systems Design, Prentice‐Hall, New York, 1989.] However, previous approaches to designing such systems usually ignore relative‐metric information on symbolic pictures and cause several deficiencies in indexing, spatial reasoning, and retrieval. In our approach, we extract relative‐metric information from symbolic pictures and use such information to help establish indexes based on an improvement from a minimal perfect hashing scheme. As a result, more accurate picture retrieval can be achieved through our indexing mechanism. Capabilities in spatial reasoning and query representation/processing are also improved. By utilizing relative‐metric spatial relations, an image database system becomes more flexible and intelligent. ©2000 John Wiley & Sons, Inc.     

时空相点移动对象数据索引PM-Tree

随着移动定位技术和无线通讯技术发展,移动对象的应用领域越来越广阔.位置随时间而变化的移动对象产生的时空数据具有规模大、多维性、结构复杂和关系复杂等特点.由于移动对象的运动轨迹大多被限定在特定的交通网络中,因此基于路网的移动对象索引成为时空数据索引研究的一个重要应用分支.目前,针对移动对象历史数据的区域查询优化的研究重点是如何提高窗口查询的效率.这类索引通常以同一线路为单位来组织轨迹数据的存储.索引通常采用两层的R-tree索引结构,上层的2D R-tree用于索引在某个区域内的线路,下层的2D R-tree用于索引某个时间段内在这些区域的移动对象.这类索引在处理轨迹信息的时间维度的时候,仅仅是把时间维度等同于空间的维度来进行R树维度的扩展.由于R树算法不能有效地降低最小限定矩形的空间堆叠问题,尤其是在数据量较大、数据维数增加时表现得更为明显.所以,为了提高路网中移动对象时空信息的存储以及查询的效率,本文则将轨迹信息中的时间数据和空间数据整合起来,提出了一种移动对象数据索引PM-tree(Phase-point Moving Object Tree).首先运用映射函数把路网中移动对象运动轨迹的二维时空矩形投影成带参数的一维"时空相点",并讨论了时空相点之间的偏序关系,建立了基于相点偏序划分的相点序分枝结构,为索引的建立提供了理论支撑.接着论文以MON-tree索引为基础,以相点序分枝结构来改进其下层索引结构,提出了时空相点移动对象数据索引,该索引能完成运动轨迹时空的一体化查询,能避免类R-tree索引中最小限定矩形堆叠导致的效率低下的问题,有效地缩小搜索空间.最后论文实现了索引的增量式动态更新管理.通过实验的对比分析,表明PM-tree索引不但能有效提高储存空间的利用率,"一次一集合"的查询模式还提高了查询性能.     

Directional relative position between objects in image processing: a comparison between fuzzy approaches

The importance of describing relationships between objects has been highlighted in works in very different areas, including image understanding. Among these relationships, directional relative position relations are important since they provide an important information about the spatial arrangement of objects in the scene. Such concepts are rather ambiguous, they defy precise definitions, but human beings have a rather intuitive and common way of understanding and interpreting them. Therefore in this context, fuzzy methods are appropriate to provide consistent definitions that integrate both quantitative and qualitative knowledge, thus providing a computational representation and interpretation of imprecise spatial relations, expressed in a linguistic way, and including quantitative knowledge. Several fuzzy approaches have been developed in the literature, and the aim of this paper is to review and compare them according to their properties and according to the types of questions they seek to answer.     

A formal framework to represent spatial knowledge

Visual representations are an essential element in human–computer interaction and can be conceived as a collection of graphical objects arranged in a two-dimensional space. It is quite natural to model visual representations through the qualitative relationships holding between their objects, and therefore, qualitative spatial relations are a fundamental way of representing spatial knowledge. To this aim, in this paper we present a framework of qualitative spatial relations providing a general, domain-independent approach to specify visual representations.     

Modeling the Shape of the Scene: A Holistic Representation of the Spatial Envelope

In this paper, we propose a computational model of the recognition of real world scenes that bypasses the segmentation and the processing of individual objects or regions. The procedure is based on a very low dimensional representation of the scene, that we term the Spatial Envelope. We propose a set of perceptual dimensions (naturalness, openness, roughness, expansion, ruggedness) that represent the dominant spatial structure of a scene. Then, we show that these dimensions may be reliably estimated using spectral and coarsely localized information. The model generates a multidimensional space in which scenes sharing membership in semantic categories (e.g., streets, highways, coasts) are projected closed together. The performance of the spatial envelope model shows that specific information about object shape or identity is not a requirement for scene categorization and that modeling a holistic representation of the scene informs about its probable semantic category.     

Qualitative reasoning with directional relations

Qualitative spatial reasoning (QSR) pursues a symbolic approach to reasoning about a spatial domain. Qualitative calculi are defined to capture domain properties in relation operations, granting a relation algebraic approach to reasoning. QSR has two primary goals: providing a symbolic model for human common-sense level of reasoning and providing efficient means for reasoning. In this paper, we dismantle the hope for efficient reasoning about directional information in infinite spatial domains by showing that it is inherently hard to decide consistency of a set of constraints that represents positions in the plane by specifying directions from reference objects. We assume that these reference objects are not fixed but only constrained through directional relations themselves. Known QSR reasoning methods fail to handle this information.     

基于R树的方向关系查询处理

方向关系描述了对象间的空间顺序关系.近年来,方向关系查询处理逐渐受到空间数据挖掘和地理信息系统等空间数据库应用领域研究者的关注.方向关系查询处理需要执行方向连接操作,目前有关空间连接的研究主要集中在拓扑关系和距离关系方面,而较少考虑方向关系.研究了基于R树的方向关系查询处理方法,定义了四元组模型表示对象MBR间的方向关系,提出了基于R树的处理方向关系查询过滤(filter)步骤的方法,并将提炼(refinement)步骤细化为3种不同的操作.所提出的方法能够高效处理任意对象间的方向关系查询.考虑到空间数据挖掘中方向关系查询通常是在满足一定距离约束条件的对象之间进行,还提出了一种同时利用方向和距离约束限制R树搜索空间的查询处理算法.实验证明,与不利用R树的方向关系查询处理方法相比,所提出的方法在I/O开销和CPU开销两方面都具有很高的性能.     

优势-等价关系下序贯三支决策的属性约简

序贯三支决策方法是一种能够表示问题中的多重层次粒度,并将多粒度结合起来解决不确定决策问题的有效途径。优势-等价关系粗糙集则是针对条件属性具有偏好关系的分类问题,提取有序信息,对目标概念进行近似,从而形成决策知识。利用传统的优势关系粗糙集方法进行知识约简和提取的效率低下,而目前大部分序贯三支决策方法则局限在符号值属性的信息系统中,对连续值和有序值不能进行有效处理,造成一定程度的信息丢失。因此,将序贯三支决策的思想应用于优势关系粗糙集模型中,定义了一种新的基于序贯三支决策的属性约简及相应的属性重要度,对具有偏好值属性的信息系统进行更加高效的处理,通过多粒度的表示和关系的研究,加速了知识约简过程。选取了多组UCI数据进行实验,结果表明所提出的基于优势关系的序贯三支决策方法能够在保证约简质量的基础上明显降低时间耗费。     

Topological Spatio–Temporal Reasoning and Representation

We present here a theory of motion from a topological point of view, in a symbolic perspective. Taking space–time histories of objects as primitive entities, we introduce temporal and topological relations on the thus defined space–time to characterize classes of spatial changes. The theory thus accounts for qualitative spatial information, dealing with underspecified, symbolic information when accurate data are not available or unnecessary. We show that these structures give a basis for commonsense spatio–temporal reasoning by presenting a number of significant deductions in the theory. This can serve as a formal basis for languages describing motion events in a qualitative way.     

2D Z-string: A new spatial knowledge representation for image databases

The knowledge structure called the 2D C⁺-string, proposed by Huang et al., to represent symbolic pictures allows a natural way to construct iconic indexes for images. According to the cutting mechanism of the 2D C⁺-string, an object may be partitioned into several subparts. The number of partitioned subparts is bounded to O(n²), where n is the number of objects in the image. Hence, the string length is also bounded to O(n²). In this paper, we propose a new spatial knowledge representation called the 2D Z-string. Since there are no cuttings between objects in the 2D Z-string, the integrity of objects is preserved and the string length is bounded to O(n). Finally, some experiments are conducted to compare the performance of both approaches.     

Composing Cardinal Direction Relations Based on Interval Algebra

Direction relations between extended spatial objects are important commonsense knowledge. Skiadopoulos proposed a formal model for representing direction relations between compound regions (the finite union of simple regions), known as SK-model. It perhaps is currently one of most cognitive plausible models for qualitative direction information, and has attracted interests from artificial intelligence and geographic information system. Originating from Allen first using composition table to process time interval constraints; composing has become the key technique in qualitative spatial reasoning to check the consistency. Due to the massive number of basic directions in SK-model, its composition becomes extraordinary complex. This paper proposed a novel algorithm for the composition. Basing the concepts of smallest rectangular directions and its original directions, it transforms the composition of basic cardinal direction relations into the composition of interval relations corresponding to Allen''s interval algebra. Comparing with existing methods, this algorithm has quite good dimensional extendibility, that is, it can be easily transferred to the tridimensional space with a few modifications.     

Vagueness and Rough Location

This paper deals with the representation and the processing of information about spatial objects with indeterminate location like valleys or dunes (objects subject to vagueness). The indeterminacy of the location of spatial objects is caused by the vagueness of the unity condition provided by the underlying human concepts valley and dune. We propose the notion of rough, i.e., approximate, location for representing and processing information about indeterminate location of objects subject to vagueness. We provide an analysis of the relationships between vagueness of concepts, indeterminacy of location of objects, and rough approximations using methods of formal ontology. In the second part of the paper we propose an algebraic formalization of rough location, and hence, a formal method for the representation of objects subject to vagueness on a computer. We further define operations on those representations, which can be interpreted as union and intersection operations between those objects. The discussion of vagueness of concepts, indeterminacy of location, rough location and the relationships between these notions contributes to the theory about the ontology of geographic space. The formalization presented can provide the foundation for the implementation of vague objects and their location indeterminacy in GIS.     

GIS空间目标间距离表达方法及分析

空间目标间的距离是约束和表达空间目标分布关系的一个重要度量指标。如何表达和计算空间目标间的距离将直接影响空间查询、推理和空间分析结果的有效性。经典的欧氏距离只适合于点目标,而简单扩展的最近、最远和质心距离未顾及空间目标的整体形状、位置分布等特征。针对这些传统距离的局限性,学者们基于实际应用问题分别发展了一些较有代表性的距离表达方法,如Hausdorff距离、Hausdorff边界距离、对偶Hausdorff距离、广义Hausdorff距离、Fréchet距离、旋转函数距离以及对称差的面积度量。着重阐述这些距离的表达方法以及适用性,以便于发展更稳健的距离度量方法,更好地解决地理信息科学领域中的实际问题。