Siempre ten presente que la piel se arruga, el pelo se vuelve blanco, los días se convierten en años..... Pero lo importante no cambia, tu fuerza y tu convicción no tienen edad. Tu espíritu es el plumero de cualquier telaraña.Detrás de cada día de llegada, hay una partida. Detrás de cada logro, hay otro desafío. Mientras estés vivo, siéntete vivo.Si extrañas lo que hacías, vuelve hacerlo. No vivas de fotos amarillas. Sigue aunque todos esperen que abandones. No dejes que se oxide el hierro que hay en tí. Haz que en vez de lástima, te tengan respeto.Cuando por los años no puedas correr, trota. Cuando no puedas trotar, camina. Cuando no puedas caminar, usa el bastón. Pero nunca te detengas.
Madre Teresa de CalcutaAlways keep in mind that your skin will wrinkle and that your hair will go white and that your days will become years... But the most important thing never changes, your strength of will and your convictions don't have an age limit.Your spirit is like a feather duster to wipe away the cobwebs.After every arrival there is a leaving. After every accomplishment there is another challenge.While you are alive, feel and know that you are alive.When you are feeling sorry for yourself about what you used to be able to do, do something new. Don't live surrounded by the yellowed photos of yesterday. Continue forward, even though you feel abandoned by others. Don't let rust take away the steel that is in you. Behave in a way that others respect you, not pity you.When, due to your years, you cannot run, trot.When you can no longer trot, walk. When you can no longer walk, grab a cane and keep on going.Never stop yourself. However, the people with whom I have worked on this thesis deserve a dedication, because I am sure that without their help, patience, corrections, emails, long hours, etc..., this work could not have been completed. This thesis produced more friends than papers!!! I do not believe that it is possible to reach an agreement about this and be fair to everyone.The truth is that the process of creating this thesis is like a long road which began in Rio Cuarto as an abstract idea between two friends, and then took shape to reach the corridors of the DSIC. This pilgrimage was made with old and new friends, each of whom contributed a little of their time towards organizing all my time. They do not need to see their names written here. They know that are part of the road I followed, and how much I owe to them. If you have read this far, then you are sure to be one of them. If you stopped in the middle, it is because our paths did not cross, but no matter, you never know.
Daniel Valencia, July 2011
AbstractThe increasing complexity of Web system has led to the development of sophisticated formal methodologies for verifying and correcting Web data and Web programs. In general, establishing whether a Web system behaves correctly with respect to the original intention of the programmer or checking its internal consistency are non-trivial tasks as witnessed by many studies in the literature.In this dissertation, w...