Automated deduction procedures for modal logics, and related decidable fragments of first-order logic, are used in many real-world applications. A popular way of obtaining decision procedures for these logics is to base them on semantic tableau calculi. We focus on calculi that use unification, instead of the more widely employed approach of generating ground instantiations over the course of a derivation. The most common type of tableaux with unification are so-called free-variable tableaux, where variables are treated as global to the entire tableau. A long-standing open problem for procedures based on free-variable tableaux is how to ensure fairness, in the sense that "equivalent" applications of the closure rule are prevented from being done over and over again. Some solutions such as using depth-first iterative deepening are known, but those are unnecessary in theory, and not very efficient in practice. This is a main reason why there are hardly any decision procedures for modal logics based on free-variable tableaux. In this thesis, we review existing work on incorporating unification into first-order and modal tableau procedures, show how the closure fairness problem arises, and discuss existing solutions to it. For the first-order case, we outline a calculus which addresses the closure fairness problem. As opposed to free-variable tableaux, closure fairness is much easier to achieve in disconnection tableaux and similar clausal calculi. We therefore focus on using clausal first-order tableau calculi for decidable classes, in particular the two-variable fragment. Using the so-called unrestricted blocking mechanism for enforcing termination, we present the first ground tableau decision procedure for this fragment. Even for such a ground calculus, guaranteeing that depth-first terminations terminate is highly non-trivial. We parametrise our procedure by a so-called lookahead amount, and prove that this parameter is crucial for determining whether depth-first derivations terminate or not. Extending these ideas to tableaux with unification, we specify a preliminary disconnection tableau procedure which uses a non-grounding version of the unrestricted blocking rule.

<p>Three issues will be elaborated and disussed in the proposed thesis. The first is<br />administration and control of data access rights in networks with XML data, with<br />emphasis on data security. The second is the administration and control of<br />access rights to data in computer networks with RDF data, with emphasis on<br />data privacy. The third is prevention of errors and memory leaks, as well as<br />communication errors, generated by programs written in Sing # language in the<br />presence of exceptions. For all three issues, there will be presented formal<br />models with corresponding type systems and showed the absence of undesired<br />behavior i.e. errors in networks or programs.</p> / <p>У тези су разматрана три проблема. Први је администрација и контрола<br />права приступа података у рачунарској мрежи са XML подацима, са<br />нагласком на безбедости посматраних података. Други је администрација и<br />котрола права приступа подацима у рачунарској мрежи са RDF подацима,<br />са нагласком на приватности посматраних података. Трећи је превенција<br />грешака и цурења меморије, као и грешака у комуникацији генерисаним<br />програмима написаних на језику Sing# у којима су присутни изузеци. За сва<br />три проблема биће предложени формални модели и одговарајући типски<br />системи помоћу којих се показује одсуство неповољних понашања тј.<br />грешака у мрежама односно програмима.</p> / <p>U tezi su razmatrana tri problema. Prvi je administracija i kontrola<br />prava pristupa podataka u računarskoj mreži sa XML podacima, sa<br />naglaskom na bezbedosti posmatranih podataka. Drugi je administracija i<br />kotrola prava pristupa podacima u računarskoj mreži sa RDF podacima,<br />sa naglaskom na privatnosti posmatranih podataka. Treći je prevencija<br />grešaka i curenja memorije, kao i grešaka u komunikaciji generisanim<br />programima napisanih na jeziku Sing# u kojima su prisutni izuzeci. Za sva<br />tri problema biće predloženi formalni modeli i odgovarajući tipski<br />sistemi pomoću kojih se pokazuje odsustvo nepovoljnih ponašanja tj.<br />grešaka u mrežama odnosno programima.</p>

Made available in DSpace on 2014-07-29T15:07:47Z (GMT). No. of bitstreams: 1 Dissertacao_Gabriela_Uchoa.pdf: 897498 bytes, checksum: 9761f9b1b5b6c7f028d1d5674bbaa4d8 (MD5) Previous issue date: 2009-02-06 / Urinary disorders are an important discovery in the ileocystoplasties, especially uroliths and bladder crystals, and are partially related to the kind of material used the in suture itself. The purpose of this study is to verify if there are differences regarding the formation of uroliths or bladder crystals after dogs ileocystoplasties practices involving sutures using unabsorbed titanium staples and sutures with polyglatine 910, observing the impact of the procedure in the renal function, modifications in the urinary constituents and differences in the surgery time duration between the groups. For that, two experimental groups of animals, each one with six, have been considered. In one group it has been used a polyglactin 910 suture thread (group A) and in the other, a titanium stapler (group B). In each animal of both groups there was selected a terminal ileac segment with approximately 5 cm for bladder augmentation. In group A, a suture of the detubularized ileum segment in bladder was executed using a polyglactin 910. In group B, the bladder augmentation with the selected ileac segment was done by linear cutter stapler using titanium staples. It was observed the presence of struvite crystals in both groups, in 11 animals of the experiment. In group A the operation duration was longer if compared to group B . It was also observed the formation of urinary mucus in great quantity in all animals in the post-operation first days. It was confirmed the formation of calculi in two animals, one in each experimental group, but in the group A animal the calculi was free from lumen and in the group B animal the stone was adhered to the stapling zone, attached to a staple that got exposed to direct contact with the urine. In the parameters verified in the urinalysis, urea and seric creatinine there was no sign of renal alteration and in the verification of blood count, no alterations were noticed or considered significant. It was possible to conclude that no significant differences were observed between the groups as for the formation of urinary stones and crystals in ileocystoplasties after 100 days. If compared to group B , Group A presented a longer operation and there were not evidences of alteration in the renal function in any phase of the experiment in both groups / Alterações urinárias são um importante achado nas ileocistoplastias, sobretudo os urólitos e a cristalúria, e em parte estão relacionados ao tipo de material de sutura envolvido neste procedimento. O objetivo deste estudo foi verificar se existe diferença na formação de urólitos ou cristalóides urinários após ileocistoplastias em cães, realizadas por meio de sutura com grampos inabsorvíveis de titânio e sutura com poliglactina 910, observando o impacto do procedimento na função renal, alterações nos constituintes urinários e a diferença de tempo cirúrgico entre os grupos. Utilizou-se dois grupos experimentais com seis animais cada, um com fio de poliglactina 910 para a sutura da ileocistoplastia (grupo A), e outro usando grampos de titânio (grupo B). Em cada animal foi selecionado um segmento de aproximadamente 5 cm de íleo terminal para ampliação vesical. No grupo A realizou-se a sutura do segmento ileal detubulizado na bexiga com fio de poliglactina 910. No grupo B foi realizada a ampliação vesical com o segmento ileal selecionado com auxílio de grampeador linear cortante para detubulização e sutura grampos de titânio. Observou-se a presença de cristais de estruvita em 11 animais de ambos os grupos do experimento. No grupo A o tempo operatório foi maior se comparado ao grupo B . Foi possível observar a formação de grande quantidade de muco na urina de todos os animais já nos primeiros dias de pós-operatório. Verificou-se a formação de cálculos em dois animais, um de cada grupo experimental, sendo que no grupo A o cálculo estava livre no lúmen e no grupo B o cálculo estava aderido à zona de grampeamento, ligado a um grampo em contato direto com a urina. Dentro dos parâmetros avaliados na urinálise, uréia e creatina séricas, não houve qualquer sinal de alteração renal e nas avaliações de hemograma não foram percebidas alterações significativas. Foi possível concluir que não houve diferenças significativas entre os grupos quanto à formação de cristais urinários e urólitos após 100 dias das ileocistoplastias, o grupo A apresentou maior tempo cirúrgico se comparado ao grupo B e não houve evidências de alteração na função renal em nenhuma fase do experimento em ambos os grupos.