Content-aware compression for big textual data analysis

A substantial amount of information on the Internet is present in the form of text. The value of this semi-structured and unstructured data has been widely acknowledged, with consequent scientific and commercial exploitation. The ever-increasing data production, however, pushes data analytic platforms to their limit. This thesis proposes techniques for more efficient textual big data analysis suitable for the Hadoop analytic platform. This research explores the direct processing of compressed textual data. The focus is on developing novel compression methods with a number of desirable properties to support text-based big data analysis in distributed environments. The novel contributions of this work include the following. Firstly, a Content-aware Partial Compression (CaPC) scheme is developed. CaPC makes a distinction between informational and functional content in which only the informational content is compressed. Thus, the compressed data is made transparent to existing software libraries which often rely on functional content to work. Secondly, a context-free bit-oriented compression scheme (Approximated Huffman Compression) based on the Huffman algorithm is developed. This uses a hybrid data structure that allows pattern searching in compressed data in linear time. Thirdly, several modern compression schemes have been extended so that the compressed data can be safely split with respect to logical data records in distributed file systems. Furthermore, an innovative two layer compression architecture is used, in which each compression layer is appropriate for the corresponding stage of data processing. Peripheral libraries are developed that seamlessly link the proposed compression schemes to existing analytic platforms and computational frameworks, and also make the use of the compressed data transparent to developers. The compression schemes have been evaluated for a number of standard MapReduce analysis tasks using a collection of real-world datasets. In comparison with existing solutions, they have shown substantial improvement in performance and significant reduction in system resource requirements.

Ó Sheán Clárach Mac Domhnaill go dtí Nioclás Tóibín: traidisiún na hamhránaíochta ins na Déise

Féachann an tráchtas seo le solas a chaitheamh ar an amhránaíocht mar a chleachtaítí agus mar a chleactaítear fós i gcontae Phort Láirge í. Ardaítear ann ceisteanna a bhaineann le seachadadh agus le sealbhú na n-amhrán I measc an phobail i gceantar na nDéise sa tréimhse c.1750-1960, ó aimsir Sheáin Chláraigh go dtí an ré sin ina raibh Nioclás Tóibín, ‘rí-amhránaí Éireann’, ar bhuaic a réime. Cuirtear spéis anseo i bhfás agus i dteacht chun cinn an Rómánsachais agus (a leathchúpla) an náisiúnachais ar Mhór-roinn na hEorpa in earr an 18ú haois agus amach san 19ú haois; ar thionchar na ngluaiseachtaí sin i bhfad ó bhaile ar Éirinn i gcoitinne san aimsir úd; orthu sin a raibh díolamaí amhrán á gcur in eagar acu in Éirinn san 19ú agus amach san 20ú haois; agus, ar deireadh, ar an stór amhrán mar atá le clos inniu I measc na ndaoine i nGaeltacht na Déise.