Doubles-jeux de Sophie Calle : le livre comme espace ludique

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Reliability analysis of transform-based stereo matching techniques, and a new matching constraint

Stereo vision is a method of depth perception, in which depth information is inferred from two (or more) images of a scene, taken from different perspectives. Practical applications for stereo vision include aerial photogrammetry, autonomous vehicle guidance, robotics and industrial automation. The initial motivation behind this work was to produce a stereo vision sensor for mining automation applications. For such applications, the input stereo images would consist of close range scenes of rocks. A fundamental problem faced by matching algorithms is the matching or correspondence problem. This problem involves locating corresponding points or features in two images. For this application, speed, reliability, and the ability to produce a dense depth map are of foremost importance. This work implemented a number of areabased matching algorithms to assess their suitability for this application. Area-based techniques were investigated because of their potential to yield dense depth maps, their amenability to fast hardware implementation, and their suitability to textured scenes such as rocks. In addition, two non-parametric transforms, the rank and census, were also compared. Both the rank and the census transforms were found to result in improved reliability of matching in the presence of radiometric distortion - significant since radiometric distortion is a problem which commonly arises in practice. In addition, they have low computational complexity, making them amenable to fast hardware implementation. Therefore, it was decided that matching algorithms using these transforms would be the subject of the remainder of the thesis. An analytic expression for the process of matching using the rank transform was derived from first principles. This work resulted in a number of important contributions. Firstly, the derivation process resulted in one constraint which must be satisfied for a correct match. This was termed the rank constraint. The theoretical derivation of this constraint is in contrast to the existing matching constraints which have little theoretical basis. Experimental work with actual and contrived stereo pairs has shown that the new constraint is capable of resolving ambiguous matches, thereby improving match reliability. Secondly, a novel matching algorithm incorporating the rank constraint has been proposed. This algorithm was tested using a number of stereo pairs. In all cases, the modified algorithm consistently resulted in an increased proportion of correct matches. Finally, the rank constraint was used to devise a new method for identifying regions of an image where the rank transform, and hence matching, are more susceptible to noise. The rank constraint was also incorporated into a new hybrid matching algorithm, where it was combined a number of other ideas. These included the use of an image pyramid for match prediction, and a method of edge localisation to improve match accuracy in the vicinity of edges. Experimental results obtained from the new algorithm showed that the algorithm is able to remove a large proportion of invalid matches, and improve match accuracy.

A prioritised fuzzy constraint satisfaction approach to model agent negotiation for railway scheduling

With the recent regulatory reforms in a number of countries, railways resources are no longer managed by a single party but are distributed among different stakeholders. To facilitate the operation of train services, a train service provider (SP) has to negotiate with the infrastructure provider (IP) for a train schedule and the associated track access charge. This paper models the SP and IP as software agents and the negotiation as a prioritized fuzzy constraint satisfaction (PFCS) problem. Computer simulations have been conducted to demonstrate the effects on the train schedule when the SP has different optimization criteria. The results show that by assigning different priorities on the fuzzy constraints, agents can represent SPs with different operational objectives.

Delegation constraint management

The paper addresses the issue of providing access control via delegation and constraint management across multiple security domains. Specifically, this paper proposes a novel Delegation Constraint Management model to manage and enforce delegation constraints across security domains. An algorithm to trace the authority of delegation constraints is introduced as well as an algorithm to form a delegation constraint set and detect/prevent potential conflicts. The algorithms and the management model are built upon a set of formal definitions of delegation constraints. In addition, a constraint profile based on XACML is proposed as a means to express the delegation constraint. The paper also includes a protocol to exchange delegation constraints (in the form of user commitments) between the involved entities in the delegation process.

A model for constraint and delegation management

This paper introduces a model to facilitate delegation, including ad-hoc delegation, in cross security domain activities. Specifically, this paper proposes a novel delegation constraint management model to manage and track delegation constraints across security domains. An algorithm to trace the authority of delegation constraints is introduced as well as an algorithm to form a delegation constraint set and detect/prevent potential conflicts. The algorithms and the management model are built upon a set of formal definitions of delegation constraints.

Seeking a life in the literary position : the writing of Charmian Clift

An examination of the published and unpublished writing of Charmian Clift.

Ontology-based specific and exhaustive user profiles for constraint information fusion for multi-agents

Intelligent agents are an advanced technology utilized in Web Intelligence. When searching information from a distributed Web environment, information is retrieved by multi-agents on the client site and fused on the broker site. The current information fusion techniques rely on cooperation of agents to provide statistics. Such techniques are computationally expensive and unrealistic in the real world. In this paper, we introduce a model that uses a world ontology constructed from the Dewey Decimal Classification to acquire user profiles. By search using specific and exhaustive user profiles, information fusion techniques no longer rely on the statistics provided by agents. The model has been successfully evaluated using the large INEX data set simulating the distributed Web environment.

Re-Presenting/Representing Melbourne: A literary and cultural analysis of Melbourne’s inner city and outer suburbs in contemporary fiction

This article provides an overview of a research project investigating contemporary literary representations of Melbourne’s inner and outer suburban spaces. It will argue that the city represented by local writers is an often more complex way of envisioning the city than the one presented in public policy and cultural discourses. In this view, the writer’s vision of a city does not necessarily override or provide a “truer’ account but it is in the fictional city where the complexity of the everyday life of a city is most accurately portrayed. The article will also provide an overview of the theoretical framework for reading the fictional texts in this way, examining how Soja’s concept of Thirdspace (2006) provides a place to engage “critically with theoretical issues, while simultaneously being that space where the debate occurs” (Mole 2008: 3).

Beyond MOF constraints : multiple constraint set metamodelling for lifecycle management

The management of models over time in many domains requires different constraints to apply to some parts of the model as it evolves. Using EMF and its meta-language Ecore, the development of model management code and tools usually relies on the meta- model having some constraints, such as attribute and reference cardinalities and changeability, set in the least constrained way that any model user will require. Stronger versions of these constraints can then be enforced in code, or by attaching additional constraint expressions, and their evaluations engines, to the generated model code. We propose a mechanism that allows for variations to the constraining meta-attributes of metamodels, to allow enforcement of different constraints at different lifecycle stages of a model. We then discuss the implementation choices within EMF to support the validation of a state-specific metamodel on model graphs when changing states, as well as the enforcement of state-specific constraints when executing model change operations.