Most of the Web is published in languages that are not accessible to many potential users who are only able to read and understand their local languages. Many of these local languages are Resources Scarce Languages (RSLs) and lack the necessary resources, such as machine translation tools, to make available content more accessible. State of the art preprocessing tools and retrieval methods are tailored for Web dominant languages and, accordingly, documents written in RSLs are lowly ranked and difficult to access in search results, resulting in a struggling and frustrating search experience for speakers of RSLs. In this thesis, we propose the use of language similarities to match, re-rank and return search results written in closely related languages to improve the quality of search results and user experience. We also explore the use of shared morphological features to build multilingual stemming tools. Focusing on six Bantu languages spoken in Southeastern Africa, we first explore how users would interact with search results written in related languages. We conduct a user study, examining the usefulness and user preferences for ranking search results with different levels of intelligibility, and the types of emotions users experience when interacting with such results. Our results show that users can complete tasks using related language search results but, as intelligibility decreases, more users struggle to complete search tasks and, consequently, experience negative emotions. Concerning ranking, we find that users prefer that relevant documents be ranked higher, and that intelligibility be used as a secondary criterion. Additionally, we use a User-Centered Design (UCD) approach to investigate enhanced interface features that could assist users to effectively interact with such search results. Usability evaluation of our designed interface scored 86% using the System Usability Scale (SUS). We then investigate whether ranking models that integrate relevance and intelligibility features would improve retrieval effectiveness. We develop these features by drawing from traditional Information Retrieval (IR) models and linguistics studies, and employ Learning To Rank (LTR) and unsupervised methods. Our evaluation shows that models that use both relevance and intelligibility feature(s) have better performance when compared to models that use relevance features only. Finally, we propose and evaluate morphological processing approaches that include multilingual stemming, using rules derived from common morphological features across Bantu family of languages. Our evaluation of the proposed stemming approach shows that its performance is competitive on queries that use general terms. Overall, the thesis provides evidence that considering and matching search results written in closely related languages, as well as ranking and presenting them appropriately, improves the quality of retrieval and user experience for speakers of RSLs.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In southern Africa, the ticks Amblyomma hebraeum and Hyalomma rufipes are the main vectors of animal Heartwater and human Crimean Congo Haemorragic Fever, respectively. In order to investigate the phylogeographic structure of these ectoparasites, population genetic studies were conducted throughout southern and partly eastern Africa. Knowing the levels of genetic diversities and population connectivities throughout the species’ native ranges, may be useful for implementing control measures (cross country borders for example), evaluate the potential for drug resistance in introduced locations as well as for elucidating its vectorial capacities in the region. Mitochondrial cytochrome oxidase I (COI) and the internal transcriber spacer 2 (ITS-2) sequences were obtained from eleven sampled localities. In general, haplotype networks and molecular diversity values showed significant genetic structure between most of the sampled populations. Fu’s Fs and mismatch distributions suggested recent population expansions following a bottleneck. A Mantel regression analysis also revealed a significant isolation by distance for H. rufipes. Comparing the two species, H. rufipes showed much stronger signals of geographic genetic population structure in relation to A. hebraeum. A single taxonomic unit is suggested for A. hebraeum while H. rufipes is characterized by the existence of at least three distinct genetic assemblages that may point to incipient speciation. The difference between the two species may be explained by gene flow restriction within the region, by the number of hosts required to complete the life cycle (2 and 3 hosts, respectively), type of host species (domestic and wild animals; small and big mammals, birds) and its availability, and host species overlap. Also, a geographic break between possible host species during the Pleistocene, domestication of animals and climatic conditions in the region played a role on the genetic structure of H. rufipes. / AFRIKAANSE OPSOMMING: Die suider Afrikaanse bosluise, Amblyomma hebraeum en Hyalomma rufipes is die hoof vektore van Hartwater in diere en Crimean Kongo Haemorargiese koors in mense. Om die filogeografiese struktuur van hierdie ektoparasiete te ondersoek, is bevolking-genetiese studies uitgevoer in suidelike Afrika asook gedeeltelik in oos Afrika. Deur die vlakke van genetiese diversiteit en bevolkingsverbindings regdeur die spesies se natuurlike verspreiding te weet, sal dit dalk moontlik wees om: beheermaatreëls (byvoorbeeld oorgrens) in te stel, die waarskynlikheid van weerstandbiedendheid in nuut losgelate gebiede te verstaan, en meer insigte in die vektoriale kapasiteit te verkry. Mitochondriale sitochroom oksidae (COI) en die interne transkriberende spasieerder 2 (ITS- 2) basisnukleotiedopeenvolgings van elf bevolkings is versamel. Haplotiepe netwerke en molekulêre diversiteitwaardes het in die algemeen, betekenisvolle genetiese verkille tussen meeste van die versamelde bevolkings aangetoon. Fu’s Fs en gemiste-paringverspreidings het voorgestel dat die bevolkings onlangs uitgebrei het nadat hulle 'n bottelnek ondergaan het. 'n Mantel regressie analise het ook betekenisvolle isolasie met afstand aangetoon vir H. rufipes. As die twee spesies vergelyk word het H. rufipes baie sterker seine van genetiese geografiese bevolkingstruktuur gewys as A. hebraeum. 'n Enkele taksonomiese eenheid word voorgestel vir A. hebraeum terwyl H. rufipes gekarakteriseer word deur ten minste drie taksonomiese eenhede. Die verskil tussen die twee spesies kan moontlik verklaar word deur geen-vloeibeperkings in die gebied, die aantal gasheer spesies wat benodig word om die lewenssiklus te voltooi (2 of 3 gashere onderskeidelik), tipe gasheer (domestikeerd- of wildlewend; klein of groot soogdiere, voëls) en hulle beskikbaarheid, en die gasheerspesies se oorvleueling. Dit is ook moontlik dat 'n geografiese breek tussen moontlike gasheerspesies gedurende die Pleistoseen, domestikering van diere en klimaatstoestande in die streek 'n rol kon speel by die genetiese struktuur van H. rufipes. / The NRF and the University of Stellenbosch for funding and bursary