<?xml version="1.0" encoding="utf-8"?><?xml-stylesheet title="XSL_formatting" type="text/xsl" href="../../style/rss10.xsl"?><rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns="http://purl.org/rss/1.0/" xmlns:dc="http://purl.org/dc/elements/1.1/"><channel rdf:about="http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/index.htm"><title>MIT OpenCourseWare: New Courses in Earth, Atmospheric, and Planetary Sciences</title><description>New courses in Earth, Atmospheric, and Planetary Sciences</description><link>http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/index.htm</link><dc:date>2009-11-19</dc:date><dc:publisher>MIT OpenCourseWare http://ocw.mit.edu</dc:publisher><dc:language>en-US</dc:language><dc:rights>Content within individual OCW courses is (c) by the individual authors unless otherwise noted. MIT OpenCourseWare materials are licensed by the Massachusetts Institute of Technology under a Creative Commons License (Attribution-NonCommercial-ShareAlike). For further information see http://ocw.mit.edu/OcwWeb/web/terms/terms/index.htm</dc:rights><items><rdf:Seq><rdf:li rdf:resource="http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-620JFall-2008/CourseHome/index.htm" /><rdf:li rdf:resource="http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-307Spring-2009/CourseHome/index.htm" /><rdf:li rdf:resource="http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-S56Fall-2008/CourseHome/index.htm" /><rdf:li rdf:resource="http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-003Fall-2008/CourseHome/index.htm" /><rdf:li rdf:resource="http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-842Fall-2008/CourseHome/index.htm" /><rdf:li rdf:resource="12-301Fall2008" /><rdf:li rdf:resource="http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-472Fall-2008/CourseHome/index.htm" /><rdf:li rdf:resource="http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-007Spring-2009/CourseHome/index.htm" /><rdf:li rdf:resource="http://ocw.mit.edu/OcwWeb/web/donate/invest/index.htm?utm_source=RSS" /></rdf:Seq></items></channel><item rdf:about="http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-620JFall-2008/CourseHome/index.htm"><title>12.620J Classical Mechanics: A Computational Approach (MIT)</title><description>Classical mechanics in a computational framework. Lagrangian formulation. Action, variational principles. Hamilton's principle. Conserved quantities. Hamiltonian formulation. Surfaces of section. Chaos. Liouville's theorem and Poincar, integral invariants. Poincar,-Birkhoff and KAM theorems. Invariant curves. Cantori. Nonlinear resonances. Resonance overlap and transition to chaos. Properties of chaotic motion. Transport, diffusion, mixing. Symplectic integration. Adiabatic invariants. Many-dimensional systems, Arnold diffusion. Extensive use of computation to capture methods, for simulation, and for symbolic analysis.</description><link>http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-620JFall-2008/CourseHome/index.htm</link><dc:creator>Wisdom, Jack</dc:creator><dc:creator>Sussman, Gerald</dc:creator><dc:date>2009-09-10T01:47:49-04:00</dc:date><dc:relation>12.620J</dc:relation><dc:relation>8.351J</dc:relation><dc:relation>6.946J</dc:relation><dc:language>en-US</dc:language><dc:subject>Earth, Atmospheric, and Planetary Sciences</dc:subject><dc:subject>Engineering Mechanics</dc:subject><dc:subject>chaos</dc:subject><dc:subject>resonance</dc:subject><dc:subject>invariant curves</dc:subject><dc:subject>kam theorem</dc:subject><dc:subject>birkhoff</dc:subject><dc:subject>Poincare</dc:subject><dc:subject>liouville</dc:subject><dc:subject>canonical transformations</dc:subject><dc:subject>surfaces of section</dc:subject><dc:subject>canonical equations</dc:subject><dc:subject>Hamiltonian</dc:subject><dc:subject>rigid bodies</dc:subject><dc:subject>hamilton principle</dc:subject><dc:subject>equation of motion</dc:subject><dc:subject>variational principles</dc:subject><dc:subject>action</dc:subject><dc:subject>lagrangian</dc:subject><dc:subject>phase space</dc:subject><dc:subject>structure and interpretation of classical mechanics</dc:subject><dc:subject>computational classical mechanics</dc:subject><dc:subject>classical mechanics</dc:subject><dc:subject>Physics</dc:subject><dc:subject>Electrical Engineering and Computer Science</dc:subject><dc:publisher>MIT OpenCourseWare http://ocw.mit.edu</dc:publisher><dc:rights>Content within individual OCW courses is (c) by the individual authors unless otherwise noted. MIT OpenCourseWare materials are licensed by the Massachusetts Institute of Technology under a Creative Commons License (Attribution-NonCommercial-ShareAlike). For further information see http://ocw.mit.edu/OcwWeb/web/terms/terms/index.htm</dc:rights></item><item rdf:about="http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-307Spring-2009/CourseHome/index.htm"><title>12.307 Weather and Climate Laboratory (MIT)</title><description>A laboratory subject intended to illustrate, by means of hands-on projects, the basic dynamical and physical principles which govern the general circulation of the atmosphere and the day-to-day sequence of weather events. Real-time meteorological observations are studied together with laboratory fluid experiments. Projects based on real-time observations stress the analysis and dynamical interpretation of the real phenomena, while complementary rotating tank experiments stress planning and testing of ideas in a more controlled laboratory environment. Written critical summaries of the results of each project and oral presentations are an integral part of the subject.</description><link>http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-307Spring-2009/CourseHome/index.htm</link><dc:creator>Marshall, John</dc:creator><dc:creator>Illari, Lodovica</dc:creator><dc:date>2009-06-30T10:17:57-04:00</dc:date><dc:relation>12.307</dc:relation><dc:language>en-US</dc:language><dc:subject>Earth, Atmospheric, and Planetary Sciences</dc:subject><dc:subject>Atmospheric Sciences and Meteorology, General</dc:subject><dc:subject>Hurricane Gustav</dc:subject><dc:subject>Baroclinic instability</dc:subject><dc:subject>Hydrostatic balance</dc:subject><dc:subject>Mass and Wind</dc:subject><dc:subject>Geostrophic/Ageostrophic Flow</dc:subject><dc:subject>Thermohaline Circulation</dc:subject><dc:subject>Ocean gyres</dc:subject><dc:subject>Stress-driven circulation and Ekman layers</dc:subject><dc:subject>Atmospheric General circulation</dc:subject><dc:subject>Perrot's bathtub experiment</dc:subject><dc:subject>Ekman layers</dc:subject><dc:subject>Slope of a frontal surface</dc:subject><dc:subject>Thermal Wind and Hadley Circulation</dc:subject><dc:subject>Taylor Columns</dc:subject><dc:subject>inertial Circles</dc:subject><dc:subject>Parabolic table</dc:subject><dc:subject>Radial inflow</dc:subject><dc:subject>Convection</dc:subject><dc:subject>Rotation stiffens fluids</dc:subject><dc:publisher>MIT OpenCourseWare http://ocw.mit.edu</dc:publisher><dc:rights>Content within individual OCW courses is (c) by the individual authors unless otherwise noted. MIT OpenCourseWare materials are licensed by the Massachusetts Institute of Technology under a Creative Commons License (Attribution-NonCommercial-ShareAlike). For further information see http://ocw.mit.edu/OcwWeb/web/terms/terms/index.htm</dc:rights></item><item rdf:about="http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-S56Fall-2008/CourseHome/index.htm"><title>12.S56 GPS: Where Are You? (MIT)</title><description>This is a freshman advising seminar. The professor of a FAS is the first year advisor to the (no more than 8) students in the seminar.  The use of Global Positioning System (GPS) in a wide variety of applications has exploded in the last few years. In this seminar we will explore how GPS works, the range of applications, and the conflict between civilian users and military planners. This seminar is followed by a UROP research project in the spring semester where results from precise GPS measurements will be analyzed and displayed on the Web.</description><link>http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-S56Fall-2008/CourseHome/index.htm</link><dc:creator>Herring, Thomas</dc:creator><dc:date>2009-06-30T01:09:51-04:00</dc:date><dc:relation>12.S56</dc:relation><dc:language>en-US</dc:language><dc:subject>Earth, Atmospheric, and Planetary Sciences</dc:subject><dc:subject>Surveying Engineering</dc:subject><dc:subject>military</dc:subject><dc:subject>geophysics</dc:subject><dc:subject>meteorology</dc:subject><dc:subject>navigation</dc:subject><dc:subject>global positioning system</dc:subject><dc:subject>GPS</dc:subject><dc:publisher>MIT OpenCourseWare http://ocw.mit.edu</dc:publisher><dc:rights>Content within individual OCW courses is (c) by the individual authors unless otherwise noted. MIT OpenCourseWare materials are licensed by the Massachusetts Institute of Technology under a Creative Commons License (Attribution-NonCommercial-ShareAlike). For further information see http://ocw.mit.edu/OcwWeb/web/terms/terms/index.htm</dc:rights></item><item rdf:about="http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-003Fall-2008/CourseHome/index.htm"><title>12.003 Atmosphere, Ocean and Climate Dynamics (MIT)</title><description>The laws of classical mechanics and thermodynamics are used to explore how the properties of fluids on a rotating Earth manifest themselves in, and help shape, the global patterns of atmospheric winds, ocean currents, and the climate of the Earth. Theoretical discussion focuses on the physical processes involved. Underlying mechanisms are illustrated through laboratory demonstrations, using a rotating table, and through analysis of atmospheric and oceanic data.</description><link>http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-003Fall-2008/CourseHome/index.htm</link><dc:creator>Ferrari, Raffaele </dc:creator><dc:date>2009-06-17T03:24:35-04:00</dc:date><dc:relation>12.003</dc:relation><dc:language>en-US</dc:language><dc:subject>Earth, Atmospheric, and Planetary Sciences</dc:subject><dc:subject>Atmospheric Physics and Dynamics</dc:subject><dc:subject>thermohaline circulation</dc:subject><dc:subject>Abyssal circulation</dc:subject><dc:subject>inhomogeneity</dc:subject><dc:subject>geostrophic and hydrostatic balance</dc:subject><dc:subject>salinity</dc:subject><dc:subject>seawater</dc:subject><dc:subject>ocean</dc:subject><dc:subject>Hadley circulation</dc:subject><dc:subject>Rossby number</dc:subject><dc:subject>Coriolis force</dc:subject><dc:subject>Ekman layer</dc:subject><dc:subject>Taylor-Proudman Theorem</dc:subject><dc:subject>Geostrophic motion</dc:subject><dc:subject>radial inflow</dc:subject><dc:subject>compressible flow</dc:subject><dc:subject>Incompressible flow</dc:subject><dc:subject>Hydrostatic balance</dc:subject><dc:subject>Fluids in motion</dc:subject><dc:subject>Winds</dc:subject><dc:subject>Pressure and geopotential height</dc:subject><dc:subject>Temperature</dc:subject><dc:subject>Convective clouds</dc:subject><dc:subject>Humidity</dc:subject><dc:subject>adiabatic lapse rate</dc:subject><dc:subject>Convection</dc:subject><dc:subject>pressure and density</dc:subject><dc:subject>Atmospheric layers</dc:subject><dc:subject>greenhouse gases</dc:subject><dc:subject>greenhouse effect</dc:subject><dc:subject>global energy balance</dc:subject><dc:subject>Characteristics of the atmosphere</dc:subject><dc:publisher>MIT OpenCourseWare http://ocw.mit.edu</dc:publisher><dc:rights>Content within individual OCW courses is (c) by the individual authors unless otherwise noted. MIT OpenCourseWare materials are licensed by the Massachusetts Institute of Technology under a Creative Commons License (Attribution-NonCommercial-ShareAlike). For further information see http://ocw.mit.edu/OcwWeb/web/terms/terms/index.htm</dc:rights></item><item rdf:about="http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-842Fall-2008/CourseHome/index.htm"><title>12.842 Past and Present Climate (MIT)</title><description>Meets with graduate subject 12.840, but assignments differ. See description under subject 12.840.  From the course home page:  Course Description  This course introduces students to climate studies, including beginnings of the solar system, time scales, and climate in human history; methods for detecting climate change, including proxies, ice cores, instrumental records, and time series analysis; physical and chemical processes in climate, including primordial atmosphere, ozone chemistry, carbon and oxygen cycles, and heat and water budgets; internal feedback mechanisms, including ice, aerosols, water vapor, clouds, and ocean circulation; climate forcing, including orbital variations, volcanism, plate tectonics, and solar variability; climate models and mechanisms of variability, including energy balance, coupled models, and global ocean and atmosphere models; and outstanding problems.</description><link>http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-842Fall-2008/CourseHome/index.htm</link><dc:creator>Wunsch, Carl</dc:creator><dc:creator>Emanuel, Kerry</dc:creator><dc:creator>Boyle, Edward</dc:creator><dc:date>2009-06-17T03:24:24-04:00</dc:date><dc:relation>12.842</dc:relation><dc:relation>12.301</dc:relation><dc:language>en-US</dc:language><dc:subject>Earth, Atmospheric, and Planetary Sciences</dc:subject><dc:subject>Geophysics and Seismology</dc:subject><dc:subject>Atmospheric Sciences and Meteorology, General</dc:subject><dc:subject>energy balance</dc:subject><dc:subject>climate model</dc:subject><dc:subject>solar variability</dc:subject><dc:subject>solar system</dc:subject><dc:subject>plate tectonics</dc:subject><dc:subject>volcanism</dc:subject><dc:subject>orbital variations</dc:subject><dc:subject>ocean circulation</dc:subject><dc:subject>clouds</dc:subject><dc:subject>water vapor</dc:subject><dc:subject>aerosols</dc:subject><dc:subject>heat and water budgets</dc:subject><dc:subject>carbon and oxygen cycles</dc:subject><dc:subject>ozone chemistry</dc:subject><dc:subject>primordial atmosphere</dc:subject><dc:subject>ice cores</dc:subject><dc:subject>proxies</dc:subject><dc:subject>climate change</dc:subject><dc:subject>climate</dc:subject><dc:publisher>MIT OpenCourseWare http://ocw.mit.edu</dc:publisher><dc:rights>Content within individual OCW courses is (c) by the individual authors unless otherwise noted. MIT OpenCourseWare materials are licensed by the Massachusetts Institute of Technology under a Creative Commons License (Attribution-NonCommercial-ShareAlike). For further information see http://ocw.mit.edu/OcwWeb/web/terms/terms/index.htm</dc:rights></item><item rdf:about="12-301Fall2008"><title>12.301 Past and Present Climate (MIT)</title><description>Meets with graduate subject 12.840, but assignments differ. See description under subject 12.840.  From the course home page:  Course Description  This course introduces students to climate studies, including beginnings of the solar system, time scales, and climate in human history; methods for detecting climate change, including proxies, ice cores, instrumental records, and time series analysis; physical and chemical processes in climate, including primordial atmosphere, ozone chemistry, carbon and oxygen cycles, and heat and water budgets; internal feedback mechanisms, including ice, aerosols, water vapor, clouds, and ocean circulation; climate forcing, including orbital variations, volcanism, plate tectonics, and solar variability; climate models and mechanisms of variability, including energy balance, coupled models, and global ocean and atmosphere models; and outstanding problems.</description><link>http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-842Fall-2008/CourseHome/index.htm</link><dc:creator>Wunsch, Carl</dc:creator><dc:creator>Emanuel, Kerry</dc:creator><dc:creator>Boyle, Edward</dc:creator><dc:date>2009-06-17T03:24:24-04:00</dc:date><dc:relation>12.842</dc:relation><dc:relation>12.301</dc:relation><dc:language>en-US</dc:language><dc:subject>Earth, Atmospheric, and Planetary Sciences</dc:subject><dc:subject>Geophysics and Seismology</dc:subject><dc:subject>Atmospheric Sciences and Meteorology, General</dc:subject><dc:subject>energy balance</dc:subject><dc:subject>climate model</dc:subject><dc:subject>solar variability</dc:subject><dc:subject>solar system</dc:subject><dc:subject>plate tectonics</dc:subject><dc:subject>volcanism</dc:subject><dc:subject>orbital variations</dc:subject><dc:subject>ocean circulation</dc:subject><dc:subject>clouds</dc:subject><dc:subject>water vapor</dc:subject><dc:subject>aerosols</dc:subject><dc:subject>heat and water budgets</dc:subject><dc:subject>carbon and oxygen cycles</dc:subject><dc:subject>ozone chemistry</dc:subject><dc:subject>primordial atmosphere</dc:subject><dc:subject>ice cores</dc:subject><dc:subject>proxies</dc:subject><dc:subject>climate change</dc:subject><dc:subject>climate</dc:subject><dc:publisher>MIT OpenCourseWare http://ocw.mit.edu</dc:publisher><dc:rights>Content within individual OCW courses is (c) by the individual authors unless otherwise noted. MIT OpenCourseWare materials are licensed by the Massachusetts Institute of Technology under a Creative Commons License (Attribution-NonCommercial-ShareAlike). For further information see http://ocw.mit.edu/OcwWeb/web/terms/terms/index.htm</dc:rights></item><item rdf:about="http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-472Fall-2008/CourseHome/index.htm"><title>12.472 Building Earth-like Planets: From Nebular Gas to Ocean Worlds (MIT)</title><description>Examination of the state of knowledge of planetary formation, beginning with planetary nebulas and continuing through accretion (from gas, to dust, to planetesimals, to planetary embryos, to planets). Processes of planetary differentiation, crust formation, atmospheric degassing, and surface water condensation. Integrated discussions of compositional and physical processes, based upon observations from our solar system and from exoplanets. Focus on terrestrial (rocky and metallic) planets, though more volatile-rich bodies are also examined. Includes regular readings from literature, lectures, discussion, and problem solving.</description><link>http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-472Fall-2008/CourseHome/index.htm</link><dc:creator>Elkins-Tanton, Lindy</dc:creator><dc:date>2009-06-01T04:44:30-04:00</dc:date><dc:relation>12.472</dc:relation><dc:language>en-US</dc:language><dc:subject>Earth, Atmospheric, and Planetary Sciences</dc:subject><dc:subject>Planetary Astronomy and Science</dc:subject><dc:subject>biosignatures</dc:subject><dc:subject>habitability</dc:subject><dc:subject>volatiles</dc:subject><dc:subject>magma ocean processes</dc:subject><dc:subject>surface water</dc:subject><dc:subject>atmospheric degassing</dc:subject><dc:subject>dust accretion</dc:subject><dc:subject>embryos</dc:subject><dc:subject>planetesimals</dc:subject><dc:subject>nebulas</dc:subject><dc:subject>planetary formation</dc:subject><dc:subject>planets</dc:subject><dc:publisher>MIT OpenCourseWare http://ocw.mit.edu</dc:publisher><dc:rights>Content within individual OCW courses is (c) by the individual authors unless otherwise noted. MIT OpenCourseWare materials are licensed by the Massachusetts Institute of Technology under a Creative Commons License (Attribution-NonCommercial-ShareAlike). For further information see http://ocw.mit.edu/OcwWeb/web/terms/terms/index.htm</dc:rights></item><item rdf:about="http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-007Spring-2009/CourseHome/index.htm"><title>12.007 Geobiology (MIT)</title><description>The interactive Earth system: biology in geologic, environmental and climate change throughout Earth history. Since life began it has continually shaped and re-shaped the atmosphere, hydrosphere, cryosphere and the solid earth. Subject introduces the concept of "life as a geological agent" and examines the interaction between biology and the earth system during the roughly 4 billion years since life first appeared. Topics include the origin of the solar system and the early Earth atmosphere; the origin and evolution of life and its influence on climate up through and including the modern age and the problem of global warming; the global carbon cycle; and Astrobiology.</description><link>http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-Sciences/12-007Spring-2009/CourseHome/index.htm</link><dc:creator>Bosak, Tanja</dc:creator><dc:creator>Summons, Roger</dc:creator><dc:date>2009-11-18T01:15:33-05:00</dc:date><dc:relation>12.007</dc:relation><dc:language>en-US</dc:language><dc:subject>Earth, Atmospheric, and Planetary Sciences</dc:subject><dc:subject>Atmospheric Sciences and Meteorology, General</dc:subject><dc:subject>phylogenic trees</dc:subject><dc:subject>origin of life</dc:subject><dc:subject>carbon dating</dc:subject><dc:subject>antiquity of life</dc:subject><dc:subject>paleoclimate</dc:subject><dc:subject>mass extinctions</dc:subject><dc:subject>proterozoic</dc:subject><dc:subject>mesozoic</dc:subject><dc:subject>Snowball earth</dc:subject><dc:subject>climate change</dc:subject><dc:subject>climate</dc:subject><dc:subject>geobiochemistry</dc:subject><dc:subject>isotopic analysis</dc:subject><dc:subject>carbon cycle</dc:subject><dc:publisher>MIT OpenCourseWare http://ocw.mit.edu</dc:publisher><dc:rights>Content within individual OCW courses is (c) by the individual authors unless otherwise noted. MIT OpenCourseWare materials are licensed by the Massachusetts Institute of Technology under a Creative Commons License (Attribution-NonCommercial-ShareAlike). For further information see http://ocw.mit.edu/OcwWeb/web/terms/terms/index.htm</dc:rights></item><item rdf:about="http://ocw.mit.edu/OcwWeb/web/donate/invest/index.htm?utm_source=RSS"><title>Power a World of Change.</title><description><![CDATA[<img src="http://ocw.mit.edu/ans7870/banners/rss_track.gif" /><br/>In these times of economic and environmental uncertainty, you may wonder how you can make a difference in the complex issues affecting your world. Knowledge truly is power, and OCW puts MIT’s world-class knowledge in the hands of individuals and organizations around the world seeking solutions to our most difficult challenges.  By supporting OCW, you support a world of change. Please donate today and help keep OCW going and growing.]]></description><link>http://ocw.mit.edu/OcwWeb/web/donate/invest/index.htm?utm_source=RSS</link><dc:creator>MIT OpenCourseWare</dc:creator><dc:date>2009-10-20T11:59:59-04:00</dc:date><dc:relation></dc:relation><dc:language>en-US</dc:language><dc:subject></dc:subject><dc:publisher>MIT OpenCourseWare http://ocw.mit.edu</dc:publisher><dc:rights>Content within individual OCW courses is (c) by the individual authors unless otherwise noted. MIT OpenCourseWare materials are licensed by the Massachusetts Institute of Technology under a Creative Commons License (Attribution-NonCommercial-ShareAlike). For further information see http://ocw.mit.edu/OcwWeb/web/terms/terms/index.htm</dc:rights></item></rdf:RDF>