Past research on multi-agent simulation with cooperative reinforcement learning (RL) for homogeneous agents focuses on developing sharing strategies that are adopted and used by all agents in the environment. These sharing strategies are considered to be reciprocating because all participating agents have a predefined agreement regarding what type of information is shared, when it is shared, and how the participating agent's policies are subsequently updated. The sharing strategies are specifically designed around manipulating this shared information to improve learning performance. This thesis targets situations where the assumption of a single sharing strategy that is employed by all agents is not valid. This work seeks to address how agents with no predetermined sharing partners can exploit groups of cooperatively learning agents to improve learning performance when compared to Independent learning. Specifically, several intra-agent methods are proposed that do not assume a reciprocating sharing relationship and leverage the pre-existing agent interface associated with Q-Learning to expedite learning. The other agents' functions and their sharing strategies are unknown and inaccessible from the point of view of the agent(s) using the proposed methods. The proposed methods are evaluated on physically embodied agents in the multi-agent cooperative robotics field learning a navigation task via simulation. The experiments conducted focus on the effects of the following factors on the performance of the proposed non-reciprocating methods: scaling the number of agents in the environment, limiting the communication range of the agents, and scaling the size of the environment. / Master of Science

This thesis reports on aspects of information exchange in an online network whose members share an interest in travel. The Thorn Tree resembles a real thorn tree on which travellers hang messages. Using social network analysis, the network resulting from members participating in online discussions considers the importance of structure and position in an exchange network to travel information exchanges on the Africa category. Different ways and frequency of participation result in communication patterns giving structure to an exchange network in which participation in a thread determines the presence of a tie between actors. Actors are placed in various relations to others; network analysis makes measurements such as levels of reciprocity, density and centrality possible. At the heart of this study lies an inquiry into the Internet’s impact on society, more so, human interaction in cyberspace where spaces, places and even communities are qualified as being “virtual”. Scholars have different views in this regard. Some commentators claim that the Internet has spawned unique forms of community. The term “virtual communities” suggests new kinds of social interaction, with revolutionary consequences for local and global communication. Online communication could be a substitute for the loss of “traditional” physical communities, or even the cause of their demise. Others, however, praise the Internet for spawning communities even in the physical world. More complex theoretical perspectives are indicative of a need to interrogate the very notions of community and contemporary social networks resultant from the many-to-many communication capabilities of computer-mediated communication (CMC). Apart from community formation on the Internet, the concept community has not been tested among travellers yet. Networks, the ties people form and the exchanges that take place as a result of such ties relate to social capital. The notion of social capital in a computer-mediated environment needs more intense academic scrutiny. Nevertheless, for travellers and destination areas alike, information exchanges can be beneficial. However, not all information exchanges on the Thorn Tree or on the Internet per se are necessarily beneficial since verification is not always possible in a cyber environment. Nevertheless, for travellers with a need for travel information in a sparse network characterised by weak ties, content analysis linked to a network analysis proves that weak ties are beneficial for spreading useful information. On the Africa category discussions are short while threads have very limited life spans. Of the total number of actors in this dataset (1 282), it was found that a few are particularly active, while many contribute a few messages to a limited number of threads and clearly do not interact regularly on the Thorn Tree. / Thesis (DPhil (Information Science))--University of Pretoria, 2007. / Information Science / unrestricted

Introduction – The building industry is evolving, this urges for innovative methodologies to facilitate the construction processes including the information exchanges between these to accomplish a sustainable future. In addition, new requirements are being set by the Swedish government and other national authorities with the objective of reducing the climate impact caused by the construction industry, which is responsible for a large amount of carbon dioxide emissions. A helpful tool to estimate the total carbon dioxide emission value is the Life Cycle Analysis (LCA) which depends on the Information Exchanges (IE) and the Level of Development (LOD) in BIM (Building Information Modelling) based projects to achieve a reliable result. Therefore, this research aims to find a better understanding of the relation between LOD, IE and LCA in BIM-based projects. Method – This research is based on an authentic ongoing construction project (casestudy), an assembled theoretical framework based on knowledge of the different subjects: LOD, BIM, LCA and IEs. And how previous researchers have faced similar issues. Also, on various thorough document analysis (BIM model and EIs) obtained from the case study. The mentioned above forms a support basis for this paper. Results – Two different BIM models were used to perform two LCA-simulations. One formed with LOD 200 provided a generic presentation of the studied element, which in this case was the model’s exterior walls. While the other model with LOD 300 generated a complex presentation of the model’s exterior walls. The simulation generated a comparative data showing that the Low LOD model had a climate impact value of 248 000 kg CO2. On the other hand, the High LOD model generated a climate impact value of 137 850 kg CO2, resulting in a 45% difference. The results presents that a lower carbon dioxide emission was caused when utilizing a higher LOD which contains more complex and specific information. The results argue for that a BIM model with the adequate amount of LOD is crucial for obtaining more reliable results when performing an LCA. Analysis – The results obtained from the LCA-simulations enhance the theories about the importance of LOD when performing an LCA. Higher LOD in a model generates more reliable results. Moreover, using a BIM software and an LCA plugin as tools facilitate the various IEs in a project. Discussion – The approach was limited to explore the environmental impact of one construction element, exterior walls, and its different LOD. Also, only the stage A1-A3 was analysed. However, trustworthy results were obtained due to the use of reliable data and research methods.