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Spatial Database Systems

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Spatial Database Applications GIS applications (maps): Urban planning, route optimization, fire or pollution monitoring, utility networks, etc Other applications: VLSI design, CAD/CAM, model of human brain, etc Traditional applications: Multidimensional records

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What is a Spatial Database? A SDBMS is a DBMS It offers spatial data types/data models/ query language Support spatial properties/operations It supports spatial data types in its implementation Support spatial indexing, algorithms for spatial selection and join

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Spatial Representation Raster model: Vector model:

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Spatial data types Point : 2 real numbers Line : sequence of points Region : area included inside n-points point line region

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Spatial Relationships Topological relationships: adjacent, inside, disjoint, etc Direction relationships: Above, below, north_of, etc Metric relationships: “distance < 100” And operations to express the relationships

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Models, Algebras, Languages Extent relational model, or use Object- relational model: define new ADTs Spatial algebra: ex. ROSE algebra Query languages: Extend SQL : GEOQL, PSQL New graphical languages: GEO-SAL

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Examples A database : Relation states(sname: string, area: region, spop: int) Relation cities(cname: string, center: point; ext: region) Relation rivers(rname: string, route:line) SELECT * FROM rivers WHERE route intersects R SELECT cname, sname FROM cities, states WHERE center inside area SELECT rname, length(intersection(route, California)) FROM rivers WHERE route intersects California

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Spatial Queries Selection queries: “Find all objects inside query q”, inside-> intersects, north Nearest Neighbor-queries: “Find the closets object to a query point q”, k- closest objects Spatial join queries: Two spatial relations S1 and S2, find all pairs: {x in S1, y in S2, and x rel y= true}, rel= intersect, inside, etc

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Access Methods Point Access Methods (PAMs): Index methods for 2 or 3-dimensional points (k-d trees, Z-ordering, grid-file) Spatial Access Methods (SAMs): Index methods for 2 or 3-dimensional regions and points (R-trees)

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Indexing using SAMs Approximate each region with a simple shape: usually Minimum Bounding Rectangle (MBR) = [(x1, x2), (y1, y2)] x1 x2 y1 y2

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Indexing using SAMs (cont.) Two steps: Filtering step: Find all the MBRs (using the SAM) that satisfy the query Refinement step:For each qualified MBR, check the original object against the query

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Indexing using PAMs Map the MBR in 2-d into a point in 4-d: [(x1, x2), (y1, y2)] (x1, x2, y1, y2) Transform the query into the new space Use a 4-d PAM to answer queries. ab Q Q a b

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Suggested Projects Density and Event Queries in Moving Object Database Trajectory similarity models Spatio-temporal Aware R-tree Spatio-temporal Join Algorithms Main-memory Structure for Indexing Moving Objects

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Suggested Projects 1. Indexing Video for similarity retrieval 2. Indexing Audio for similarity retrieval 3. Indexing for medical databases: feature selection and high dimensional indexing 4. Buffer management using Hidden Markov Models 5. Text Mining 6. Non-linear dimensionality reduction

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Suggested Projects 1. Analysis of network graphs in space and time 2. HMMs for Time Series and Trajectories 3. Summarize Streams for analysis of network data 4. Cycle and periodicity detection in multidimensional time series data 5. Indexing multidimensional data with mixed attributes (numerical and categorical attributes)

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Maps as Numbers GIS requires that both data and maps be represented as numbers. The GIS places data into the computer’s memory in a physical data structure.

Maps as Numbers GIS requires that both data and maps be represented as numbers. The GIS places data into the computer’s memory in a physical data structure.

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