In this paper an improved version of a graph matching algorithm is presented, which is able to efficiently solve the graph isomorphism and graph-subgraph isomorphism problems on Attributed Relational Graphs. This version is particularly suited to work with very large graphs, since its memory requirements are quite smaller than those of other algorithms of the same kind. After a detailed description of the algorithm, an experimental comparison is made against both the previous version (developed by the same authors) and the Ullmann’s algorithm. 1.

Despite the significant number of isomorphism algorithms presented in the literature, till now no efforts have been done for characterizing their performance. Consequently, it is not clear how the behavior of those algorithms varies as the type and the size of the graphs to be matched varies in case of real applications. In this paper we present a benchmarking activity for characterizing the performance of a bunch of algorithms for exact graph isomorphism. To this purpose we use a large database containing 10,000 couples of isomorphic graphs with different topologies (regular graphs, randomly connected graphs, bounded valence graph), enriched with suitably modified versions of them for simulating distortions occurring in real cases. The size of the considered graphs ranges from a few nodes to about 1000 nodes. 1.

curvilinear configurations to hand-drawn sketches. It collects observations from our own recent research, which focused initially on the domain of sketched human stick figures in diverse postures, as well as related computer vision literature. Sketch recognition, i.e., labeling strokes in the input with the names of the model parts they depict, would be a key component of higher-level sketch understanding processes that reason about the recognized configurations. A sketch recognition technology must meet three main requirements. It must cope reliably with the pervasive variability of hand sketches, provide interactive performance, and be easily extensible to new configurations. We argue that useful sketch recognition may be within the grasp of current research, if these requirements are addressed systematically and in concert.

Understanding the strategies of attacks is crucial for security applications such as computer and network forensics, intrusion response, and prevention of future attacks. This paper presents techniques to automatically learn attack strategies from intrusion alerts. Central to these techniques is a model that represents an attack strategy as a graph of attacks with constraints on the attack attributes and the temporal order among these attacks. To learn the intrusion strategy is then to extract such a graph from a sequences of intrusion alerts. To further facilitate the analysis of attack strategies, which is essential to many security applications such as computer and network forensics and incident handling, this paper presents techniques to measure the similarity between attack strategies. The basic idea is to reduces the similarity measurement of attack strategies into error-tolerant graph isomorphism problem, and measures the similarity between attack strategies in terms of the cost to transform one strategy into another. Finally, this paper presents some experimental results, which demonstrate the potential of the aforementioned techniques.

Existing approaches to differencing and merging architectural views are based on restrictive assumptions such as requiring view elements to have unique identifiers or exactly matching types.

While the largest common subgraph (LCSG) between a query and a database of models can provide an elegant and intuitive measure of similarity for many applications, it is computationally expensive to compute. Recently developed algorithms for subgraph isomorphism detection take advantage of prior knowledge of a database of models to improve the speed of online matching. This paper presents a new algorithm based on similar principles to solve the largest common subgraph problem. The new algorithm significantly reduces the computational complexity of detection of the LCSG between a know database of models, and a query given online.

Generally, object recognition research falls into three main categories: (a) geometric, symbolic or structure based recognition, which is usually associated with CAD-based vision and 3-D object recognition; (b) property, vector or feature based recognition, involving techniques that vary from specific feature vectors, multiple filtering to global descriptors for shape, texture and colour; and (c) iconic or image based recognition, which either complies with the traditional sensor architecture of an uniform array of sampling units, or uses alternative representations. An example is the log-polar image, which is inspired by the human visual system and besides requiring less pixels, has some useful mathematical properties. The context of this thesis is a combination of the above categories in the sense that it investigates the area of iconic based recognition using image features and geometric relationships. It expands an existing vision system that operates by fixating at interesting regions in a scene, extracting a number of raw primal sketch features from a log-polar image and matching new regions to previously seen ones.

The interpretation of iconic gestures in spatial domains is a promising idea to improve the communicative capabilities of human-computer interfaces. So far, approaches towards gesture recognition focused mainly on deictic and emblematic gestures. Iconics, viewed as iconic signs in the sense of Peirce, are different from deictics and emblems, for their relation to the referent is based on similarity. In the work reported here, the breakdown of the complex notion of similarity provides the key idea towards a computational model of gesture semantics for iconic gestures. Based on an empirical study,we describe first steps towards a recognition model for shape-related iconic gestures and its implementation in a prototype gesture recognition system. Observations are focused on spatial concepts and their relation to features of iconic gestural expressions. The recognition model is based on a graphmatching method which compares the decomposed geometrical structures of gesture and object.

symbols on the documents. We have based our system on a combination of local and global structural approaches. The global approach groups the connected components together according to some closeness and connection constraints. The local approach splits up each connected component into a graph of geometrical objects (vectors, arcs, curves). The extracted graphs are matched thanks to a structural classifier, which permits graph-subgraph and exact-inexact matching. The system adaptability is obtained thanks to the scenarios use. A XML data representation is used, allowing the data manipulations and the graphic representations of results.

Similarity search is a general class of problems in which a given object, called a query object, is compared against a collection of objects in order to retrieve those that most closely resemble the query object. This paper reviews recent work on an instance of this class of problems, where the objects in question are business process models. The goal is to identify process models in a repository that most closely resemble a given process model or a fragment thereof. 1