Sisteme de regasire a informatieiBaza de date ARXIV

O baz de date este o colecie de date centralizate, creata i meninut computerizat, n scopul prelucrrii datelor n contextul unui set de aplicaii. Prelucrarea datelor se refer la operaiile de introducere, tergere, actualizare i interogare a datelor. Colectiile de fise sau fisierele care contin date,dar nu permit operatii de interogare,nu sunt considerate baze de date.Spre exemplu fisierele memorate aplicatii de calcul ca Microsoft Excel,sau aplicatii de texte ca Microsoft Word,nu sunt luate in considerare ca baze de date.

Proprietatile bazelor de date:

Baza de date este o colecie logic coerent de date ce are cel puin un neles Baza de date este destinat, construit i populat de date despre un domeniu bine precizat. Ea are un grup de utilizatori i se adreseaz unui anumit grup de aplicaii O baz de date reprezint cteva aspecte ale lumii reale crend orizontul propriu. Schimbrile orizontului sunt reflectate n baza de date. Spre deosebire de metodele mai vechi de inregistrare a datelor(documente scrise),sistemele de baze de date sunt mult mai avantajoase.Printre avantajele oferite se Numara: Controlul centralizat al datelor, putnd fi desemnat o persoan ca responsabil cu administrarea bazei de date Vitez mare de regsire i actualizare a informaiilor Sunt compacte: volumul ocupat de sistemele de baze de date este mult mai redus dect documetele scrise

Flexibilitatea ce const n posibilitatea modificrii structurii bazei de date fr a fi necesar modificarea programelor de aplicaie

Redundan sczut a datelor memorate, care se obine prin partajarea datelor ntre mai muli utilizatori i aplicaii. n sistemele de baze de date, mai multe aplicaii pot folosidate comune, memorate o singur dat. De exemplu, o aplicaie pentru gestionarea personalului dintr-o universitate i o aplicaie pentru gestionarea rezultatelor la examene din aceeai universitate care folosete o singur baz de date, pot folosi aceleai informaii referitoare la structurarea facultilor.

Posibilitatea introducerii standardelor privind modul de stocare a datelor, ceea ce permite interschimbarea datelor ntre organizaii

Meninerea integritii datelor prin politica de securitate (drepturi de acces difereniate n funcie de rolul utilizatorilor), prin gestionarea tranzaciilor i prin refacerea datelor n caz de funcionare defectuoas a diferitelor componente hardware sau software. Independena datelor fa de suportul hardware utilizat.Sistemul de gestiunea a bazelor de date ofer o vizualizare a datelor, care nu se modific atunci cnd se schimb suportul de memorare fizic, ceea ce asigur imunitatea structurii bazei de date i a aplicaiilor la modificri ale sistemului hardware utilizat.Baza de date despre care am ales sa vorbesc se numeste ARXIV.( lanl.arXiv.org).Este o baza de date de preprinturi(lucrari prepublicate).A fost conceputa de Paul Ginsparg in 1991.Subiectele lucrarilor sunt din mai multe domenii.

Spre exemplu:Physics

Astrophysics :Astrophysics of Galaxies; Cosmology and Nongalactic Astrophysics; Earth and Planetary Astrophysics; High Energy Astrophysical Phenomena; Instrumentation and Methods for Astrophysics; Solar and Stellar AstrophysicsCondensed Matterincludes: Disordered Systems and Neural Networks; Materials Science; Mesoscale and Nanoscale Physics; Other Condensed Matter; Quantum Gases; Soft Condensed Matter; Statistical Mechanics; Strongly Correlated Electrons; SuperconductivityGeneral Relativity and Quantum CosmologyHigh Energy Physics - ExperimentHigh Energy Physics - LatticeHigh Energy Physics - PhenomenologyHigh Energy Physics - TheoryMathematical PhysicsNonlinear SciencesAdaptation and Self-Organizing Systems; Cellular Automata and Lattice Gases; Chaotic Dynamics; Exactly Solvable and Integrable Systems; Pattern Formation and SolitonsNuclear ExperimentNuclear TheoryPhysicsincludes: Accelerator Physics; Atmospheric and Oceanic Physics; Atomic Physics; Atomic and Molecular Clusters; Biological Physics; Chemical Physics; Classical Physics; Computational Physics; Data Analysis, Statistics and Probability; Fluid Dynamics; General Physics; Geophysics; History and Philosophy of Physics; Instrumentation and Detectors; Medical Physics; Optics; Physics Education; Physics and Society; Plasma Physics; Popular Physics; Space PhysicsQuantum PhysicsMathematics

MathematicsAlgebraic Geometry; Algebraic Topology; Analysis of PDEs; Category Theory; Classical Analysis and ODEs; Combinatorics; Commutative Algebra; Complex Variables; Differential Geometry; Dynamical Systems; Functional Analysis; General Mathematics; General Topology; Geometric Topology; Group Theory; History and Overview; Information Theory; K-Theory and Homology; Logic; Mathematical Physics; Metric Geometry; Number Theory; Numerical Analysis; Operator Algebras; Optimization and Control; Probability; Quantum Algebra; Representation Theory; Rings and Algebras; Spectral Theory; Statistics Theory; Symplectic GeometryComputer Science

Computing Research RepositoryArtificial Intelligence; Computation and Language; Computational Complexity; Computational Engineering, Finance, and Science; Computational Geometry; Computer Science and Game Theory; Computer Vision and Pattern Recognition; Computers and Society; Cryptography and Security; Data Structures and Algorithms; Databases; Digital Libraries; Discrete Mathematics; Distributed, Parallel, and Cluster Computing; Emerging Technologies; Formal Languages and Automata Theory; General Literature; Graphics; Hardware Architecture; Human-Computer Interaction; Information Retrieval; Information Theory; Learning; Logic in Computer Science; Mathematical Software; Multiagent Systems; Multimedia; Networking and Internet Architecture; Neural and Evolutionary Computing; Numerical Analysis; Operating Systems; Other Computer Science; Performance; Programming Languages; Robotics; Social and Information Networks; Software Engineering; Sound; Symbolic Computation; Systems and ControlQuantitative Biology

Quantitative BiologyBiomolecules; Cell Behavior; Genomics; Molecular Networks; Neurons and Cognition; Other Quantitative Biology; Populations and Evolution; Quantitative Methods; Subcellular Processes; Tissues and OrgansQuantitative Finance

Quantitative FinanceComputational Finance; Economics; General Finance; Mathematical Finance; Portfolio Management; Pricing of Securities; Risk Management; Statistical Finance; Trading and Market MicrostructureStatistics

Statistics :Applications; Computation; Machine Learning; Methodology; Other Statistics; Statistics TheoryArxiv este detinuta si gestionata de Universitatea Cornell.Baza de date are o pagina principala pe care se gasesc toate domeniile din care se pot gasi lucrari.Se poate face cautare pe baza domeniului sau titlului sau a unui cuvant.Se pot cauta toate lucrarile,pe baza titlului,autorului,etc.Se poate face un cont dar se poate cauta si fara.Documentele rezultate pentru a fi vazute in intregime,pot fi downloadate in mai multe formate:PDF,POSTSCRIPT,sau pot fi alese alte formate.Arxiv contine 936,435 de lucrari,dupa cum suntem informati pe pagina principala.A fost creata pentru aproximativ 100 de upload-uri pe an,ajungand in jumatate de an la 400 de upload-uri.In 2011,primea aproximativ 75.000 de upload-uri pe an,din informatiile pe care le primim dintr-un eseu al autorului,scris pentru a comemora 20 de ani de la crearea Arxiv.Articolele pot fi editate sau inlocuite de catre cei care le- au postat(autorii).

Bibliografie: Crstoiu, Dorin, Baze de date relaionale, Editura Printech,1999 Rdulescu, Florin, Baze de date n Internet, EdituraPrintech, 2000 Ionescu, Felicia, Baze de date relaionale i aplicaii,Editura Tehnic, 2004 Baltac, Vasile, ECDL-Excel, Access, PowerPoint n 20 leciii 75 de simulri, Editura Andreco, 2003 Browne, Allen, Balter Alison, Bazele Access 95, EdituraTeora, 1999 Pribeanu, Costin, Baze de date i aplicaii, EdituraMatrixRom, 2000 Pascu, C., Pascu A., Totul despre SQL, Editura Tehnic,1994-www.cs.ubbcluj.ro