Wireless sensor networks, networks of nodes communicating wirelessly with sensing capabilities, are becoming more popular and are utilized by an increasing number of applications. Some wireless sensor networks are implemented because the usual network solutions of an always connected network could not be applied. Specifically this thesis is concerned with the case when the connection between the end-user and the network is not always available, i.e., there is only intermittent connectivity. This masters thesis gives an introduction and provides some background knowledge concerning wireless sensor networks, specifically focusing on disconnected operation. A set of building blocks will be presented to help programmers deal with programming disconnected operations. Examples to demonstrate our solution is implemented as shell commands using the Contiki operating system. Our solution was tested in the field and compared against a common, monolithic, programming approach. This practical example shows the potential significance of this thesis project in real world applications and allowed an evaluation of both the qualitative and quantitative aspects of our solution. The results of our evaluation prove that our solution offers an easier interface for the programmer to work with at the cost of possible less memory space. / Trådlösa sensornätverk, nätverk med noder som kommunicerar trådlöst och har sensorer, blir mer populära och används av i ett ökande antal applikationer. Några trådlösa sensornätverk används för att en vanlig nätverkslösning med ständigt uppkopplade noder inte går att genomföra. Det här examensjobbet är specifikt inriktat på fall när en uppkoppling mellan slutanvändaren och nätverket inte alltid är tillgängligt, t.ex. när det bara är tillfällig uppkoppling. Detta examensarbete ger en introduktion och bakgrund till trådlösa sensornätverk med fokus på programmering av frånkopplade operationer. Ett antal byggstenar har tagits fram för att hjälpa programmerare att programmera frånkopplade operationer. Exempel för att styrka vår lösning i vår rapport kommer att implementeras som shellkommandon i operativsystemet Contiki. Vår lösning kommer att testas i verkligheten och jämföras med ett vanligt, monolitisk, programmeringsangreppssätt. Detta praktiska exempel kommer visa den potentiella nyttan av detta examensarbete i verkliga applikationer och tillåta utvärdering av kvalitativa och kvantitativa aspekter på vår lösning. Resultaten från vår utvärdering bevisar att vår lösning erbjuder ett enkelt gränssnitt för programmeraren att arbeta med till en kostnad av möjligen mindre minnesplats.

[pt] A tecnologia de workflow é bastante utilizada para realização de processos dentro de empresas e instituições. É comum encontrar processos que possuem tarefas que devem ser realizadas em locais de difícil acesso, ou que não tenham disponibilidade de computadores desktop e Internet confiável, dificultando a realização dessas tarefas de forma automatizada. Entretanto, com o avanço das tecnologias móveis, a possibilidade de automatizar a realização de tais tipos de tarefas diretamente em campo tornou-se viável. O objetivo deste trabalho é investigar questões relacionadas a sistemas de gerência de workflows em ambientes com suporte à desconexão utilizando dispositivos móveis. / [en] Workflow technology is heavily used to support many processes within organizations. One frequently finds processes that need to be executed in places that are difficult to access or where desktop computers and reliable Internet are not available, which complicates the automated execution of these activities. However, the advance of mobile technologies made it possible to successfully automate such types of activities directly in the field. The purpose of this work is to investigate questions related to workflow management systems in environments with support for disconnected operation using mobile devices.

There is an increasing awareness that human beings are disconnected from nature. Physical disconnectedness from nature may lead to psychological and spiritual malfunctioning. Those who are aware of this disconnectedness try to compensate by spending leisure time in nature. The urge to go 'back to nature' was the start of ecotourism. The increase in tourist traffic and the concomitant development brings about negative effects, subjecting tourists to disappointment. Development has destroyed the specific experience which the people came for in the first place. Should environmental degradation continue the enriching experiences people have in nature will no longer exist. The preferred outcome for eco tourists is to acquire a sense of spiritual sustenance that could enhance their optimal functioning after experimenting a natural environment. A disregard for sound principles of responsible ecotourism development could result in lost opportunities. The research problem is located in the fact that individuals are seldom aware of their disconnectedness from the natural environment. Secondly, there is a need for more pristine, natural environments where humans can restore their encounters with the nature. Ecotourism development should be sensitive to the tastes of tourists who have as their objectives memorable experiences in natural environments. During this exploratory study, interviews, questionnaires and field observations were used to collect qualitative and limited quantitative data. Findings confirm that human beings are part of nature. Technological progress has led to an indoor lifestyle that causes humans to become disconnected from nature. Disconnectedness also involves a spiritual dimension. To restore a sense of connectedness between human beings and nature, people need to spend time in nature. Ecotourism originated from and exists because of the desire of individuals to reconnect to nature. They fulfil this desire by experiencing unspoilt natural environments, both physically and spiritually. Although a pattern of phases in a nature experience can be distinguished, every individual attaches a personal meaning to the experience. People have satisfying nature experiences in any natural environment. The intensity or fulfilment of such experiences depends on personal perceptions as well as external disturbances, such as litter and inappropriate behaviour. People attach meaning to experiences by structuring them into stories. The more we talk about the nature experience, the more knowledge is added to it. Consequently the experience becomes powerful, adding quality to people's lives and relationships. In this regard, aspects of rituals, metaphors and symbols, as well as spiritual experiences, play a significant role in the meaning people find in natural environments. / Thesis (Ph.D. (History))--North-West University, Vaal Triangle Campus, 2005

There is an increasing awareness that human beings are disconnected from nature. Physical disconnectedness from nature may lead to psychological and spiritual malfunctioning. Those who are aware of this disconnectedness try to compensate by spending leisure time in nature. The urge to go 'back to nature' was the start of ecotourism. The increase in tourist traffic and the concomitant development brings about negative effects, subjecting tourists to disappointment. Development has destroyed the specific experience which the people came for in the first place. Should environmental degradation continue the enriching experiences people have in nature will no longer exist. The preferred outcome for eco tourists is to acquire a sense of spiritual sustenance that could enhance their optimal functioning after experimenting a natural environment. A disregard for sound principles of responsible ecotourism development could result in lost opportunities. The research problem is located in the fact that individuals are seldom aware of their disconnectedness from the natural environment. Secondly, there is a need for more pristine, natural environments where humans can restore their encounters with the nature. Ecotourism development should be sensitive to the tastes of tourists who have as their objectives memorable experiences in natural environments. During this exploratory study, interviews, questionnaires and field observations were used to collect qualitative and limited quantitative data. Findings confirm that human beings are part of nature. Technological progress has led to an indoor lifestyle that causes humans to become disconnected from nature. Disconnectedness also involves a spiritual dimension. To restore a sense of connectedness between human beings and nature, people need to spend time in nature. Ecotourism originated from and exists because of the desire of individuals to reconnect to nature. They fulfil this desire by experiencing unspoilt natural environments, both physically and spiritually. Although a pattern of phases in a nature experience can be distinguished, every individual attaches a personal meaning to the experience. People have satisfying nature experiences in any natural environment. The intensity or fulfilment of such experiences depends on personal perceptions as well as external disturbances, such as litter and inappropriate behaviour. People attach meaning to experiences by structuring them into stories. The more we talk about the nature experience, the more knowledge is added to it. Consequently the experience becomes powerful, adding quality to people's lives and relationships. In this regard, aspects of rituals, metaphors and symbols, as well as spiritual experiences, play a significant role in the meaning people find in natural environments. / Thesis (Ph.D. (History))--North-West University, Vaal Triangle Campus, 2005

No / The FIRE trust and reputation model is a de-centralized trust model that can be applied for trust management in unstructured Peer-to-Peer (P2P) overlays. The FIRE model does not, however, consider malicious activity and possible collusive behavior in nodes of network and it is therefore susceptible to collusion attacks. This investigation reveals that FIRE is vulnerable to lying and cheating attacks and presents a trust management approach to detect collusion in direct and witness interactions among nodes based on colluding node's history of interactions. A witness ratings based graph building approach is utilized to determine possibly collusive behavior among nodes. Furthermore, various interaction policies are defined to detect and prevent collaborative behavior in colluding nodes. Finally a multidimensional trust model FIRE+ is devised for avoiding collusion attacks in direct and witness based interactions. The credibility of the proposed trust management scheme as an enhancement of the FIRE trust model is verified by extensive simulation experiments.

No description available.

A mobile user may voluntarily disconnect itself from the web server to save battery life and also to avoid the high communication price. To allow web pages to be updated while the mobile user is disconnected from the web server, updates can be staged in the mobile unit and propagated back to the web server upon reconnection. In this thesis, we investigate methods for supporting disconnected write operations and develop a performance model which helps identify the optimal length of the disconnection period under which the cost of update propagation is minimized. We validate the analytic model with simulation in the thesis. We also show how the result can be applied to real-time web applications with a deadline requirement to propagate updates of web pages. The analysis result is particularly applicable to web applications which allow wireless mobile users to modify web contents while on the go. The algorithms that we have developed can be generally applied to other data items such as files and databases. / Master of Science

Security is essential to communication between entities in the internet. Delay tolerant and disconnected Mobile Ad Hoc Networks (MANET) are a class of networks characterized by high end-to-end path latency and frequent end-to-end disconnections and are often termed as challenged networks. In these networks nodes are sparsely populated and without the existence of a central server, acquiring global information is difficult and impractical if not impossible and therefore traditional security schemes proposed for MANETs cannot be applied. This thesis reports trust management schemes for peer to peer (P2P) application in delay tolerant disconnected MANETs. Properties of a profile based file sharing application are analyzed and a framework for structured P2P overlay over delay tolerant disconnected MANETs is proposed. The framework is implemented and tested on J2ME based smart phones using Bluetooth communication protocol. A light weight Content Driven Data Propagation Protocol (CDDPP) for content based data delivery in MANETs is presented. The CDDPP implements a user profile based content driven P2P file sharing application in disconnected MANETs. The CDDPP protocol is further enhanced by proposing an adaptive opportunistic multihop content based routing protocol (ORP). ORP protocol considers the store-carry-forward paradigm for multi-hop packet delivery in delay tolerant MANETs and allows multi-casting to selected number of nodes. Performance of ORP is compared with a similar autonomous gossiping (A/G) protocol using simulations. This work also presents a framework for trust management based on dynamicity aware graph re-labelling system (DA-GRS) for trust management in mobile P2P applications. The DA-GRS uses a distributed algorithm to identify trustworthy nodes and generate trustable groups while isolating misleading or untrustworthy nodes. Several simulations in various environment settings show the effectiveness of the proposed framework in creating trust based communities. This work also extends the FIRE distributed trust model for MANET applications by incorporating witness based interactions for acquiring trust ratings. A witness graph building mechanism in FIRE+ is provided with several trust building policies to identify malicious nodes and detect collusive behaviour in nodes. This technique not only allows trust computation based on witness trust ratings but also provides protection against a collusion attack. Finally, M-trust, a light weight trust management scheme based on FIRE+ trust model is presented.

A rating design is a pre-specified plan for collecting ratings. The best design for a rater-mediated assessment both psychometrically and from the perspective of fairness is a fully-crossed design in which all objects are rated by all raters. An incomplete rating design is one in which all objects are not rated by all raters, instead each object is rated by an assigned subset of raters usually to reduce the time and/or cost of the assessment. Human raters have varying propensities to rate severely or leniently. One method of compensating for rater severity is the many-facets Rasch model (MFRM). However, unless the incomplete rating design used to gather the ratings is appropriately linked, the results of the MFRM analysis may not be on the same scale and therefore may not be fairly compared. Given non-trivial numbers of raters and/or objects to rate, there are numerous possible incomplete designs with various levels of linkage. The literature provides little guidance on the extent to which differently linked rating designs might affect the results of a MFRM analysis. Eighty different subsets of data were extracted from a pre-existing fully-crossed rating data set originally gathered from 24 essays rated by eight raters. These subsets represented 20 different incomplete rating designs and four specific assignments of raters to essays. The subsets of rating data were analyzed in Facets software to investigate the effects of incomplete rating designs on the MFRM results. The design attributes related to linkage that were varied in the incomplete designs include (a) rater coverage: the number of raters-per-essay, (b) repetition-size: the number of essays rated in one repetition of the sub-design pattern, (c) design structure: the linking network structure of the incomplete design, and (d) rater order: the specific assignments of raters to essays. A number of plots and graphs were used to visualize the incomplete designs and the rating results. Several measures including the observed and fair averages for raters and essays from the 80 MFRM analyses were compared against the fair averages for the fully-crossed design. Results varied widely depending on different combinations of design attributes and rater orders. Rater coverage had the overall largest effect, with rater order producing larger ranges of values for sparser designs. Many of the observed averages for raters and essays more closely approximated the results from the fully-crossed design than did the adjusted fair-averages, particularly for the more sparsely linked designs. The stability of relative standing measures was unexpectedly low.

Visual analysis of human motion is one of the active research areas in computer vision. The trend shifts from computing motion fields to understanding actions. In this thesis, an action coding scheme based on trajectories of the features calculated with respect to a part based coordinate system is presented. The part based coordinate system is formed using an axis based representation. The features are extracted from images segmented in the form of silhouettes. We present some preliminary experiments that demonstrate the potential of the method in action similarity analysis.