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Trajectory Discussion Group

Trajectory Discussion Group. Tuesday morning. Natalia's input. Two views of movement (traffic or trajectory oriented) \ classes of tasks (space or entity oriented) – see Gennady's slide #30 Space-centered: study of space use / study of space connectivity, major flows

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Trajectory Discussion Group

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  1. Trajectory Discussion Group Tuesday morning

  2. Natalia's input • Two views of movement (traffic or trajectory oriented) \\ classes of tasks (space or entity oriented) – see Gennady's slide #30 • Space-centered: study of space use / study of space connectivity, major flows • Entity-centered: study of collective movement / comparison of movement behavior •  Language to define patterns: isn't this the DMQL?

  3. Big Communication Problem • DMQL: from the data world to the pattern world •  Discussion on data mining vs db-queries (vs models) • What's the difference between querying and data mining? What data mining does that cannot be done with a combination of SQL queries? • NB: Trajectory mining needs a language with the capability to express spatio-temporal constraints over sequences and sets of objects.

  4. satisfies does not satisfy Querying and Mining • DB query: select the sub-population that satisfies the query predicates (group by?) • Frequent Pattern (?) Data mining : find the predicates that select a significant sub-population • each set of predicates that generates a significant sub-population is candidate to be promoted to the pattern status

  5. Trajectory Discussion Group Wednesday morning "SEMANTIC TRAJECTORIES"

  6. What is a semantic trajectory? • Semantics of movement is anything that goes beyond raw spatio-temporal positioning. movement of a point (x, y, t)

  7. From movement to trajectories • Movement: : time  space • Trajectory:  : [tbegin,tend]  space movement of a point a trajectory another trajectory

  8. From trajectories to semantic trajectories Time end Move Stop begin Space

  9. Another interpretation Time end Move Stop begin Space Lausanne Bern Basel Mainz Turkishmuhle Dagstuhl

  10. Another interpretation Time end Move Stop begin Transport means: foot train train bus foot Space Activity: walk run slow walk rapid walk walk etc

  11. Multiple Semantic Layers • 1) Movement only, no semantics: sequence of ST points • 2) Trajectories as meaningful movement segments(meaningful: from the application viewpoint) • 3) Trajectories as sequences of moves between "places"(geo-places or anything else that changes over time/space) • 4) Trajectories attachedto objects (persons, cars, birds, …)

  12. Trajectory Discussion Group Wednesday afternoon Data Warehousing & aggregation

  13. Work done • Esteban: conceptual (EER) DW model, spatial hierarchies, spatial OLAP, implementation, temporal • Alessandra: dealing with trajectories as sequences of points in cells, not just isolated points • Alejandro • Athens

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