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Managing Location Information for Billions of Gizmos on the Move – What’s in it for the Database Folks Ralf Hartmut Güting Fernuniversität Hagen, Germany Panel: Managing Location Information ... My background: – spatial database systems – some work on models and query languages for moving objects DBMS technology should be extended as follows: 1. Describing moving objects (gizmos) – Extending data models so that moving objects can be described (new data types, in my view). – Extending query languages so that all (well, many) kinds of questions about moving objects and their relationships to static spatial objects can be formulated. ICDE 2001 Page 2 1. Describing Moving Objects Static spatial object: position: point Moving object: position: f: time point distance(mo, obj) inside(mo, obj) t f: time real f: time bool y Continuous functions must be handled in DBMS models and languages. ICDE 2001 x Page 3 1. Describing Moving Objects Specific challenges: – Integrate proposals dealing with moving objects in the past with those describing them at present/future. – Integrate modeling and querying of networks with modeling of movement (objects move in networks in many cases). – Model aggregation of moving objects. Given observations of (lots of) cars on highways, compute traffic jams. – Integrate position uncertainty into modeling and querying. May come from observations or from descriptions. “On monday morning, I arrived in Heidelberg. I took a walk downtown. From about 11am to 2pm I visited the castle. I then took a train to Munich ...” ICDE 2001 Page 4 2. Location Dependent Queries A person or device on the move issues a query, e.g. “Finde the five Italian restaurants closest from here.” In principle a normal spatial query (substitute current position for here), but ... – Indexing might continuously adapt to current position. For example, restaurants always ordered by distance. – For a PDA with limited memory, a cache might be continuously updated to contain the current environment information. Query depending on moving location: “Notify me as soon as we get within 5 kms of a gas station.” Can also be viewed as a continuous query: “Find gas stations within 5 kms from now on” – stop query n Result can also be dynamic due to movement of queried objects: “How many police cars are in the city center?” from now on. “Notify me whenever their number changes by more than 3.” ICDE 2001 Page 5 3. More ... Implementation issues: – Indexing of current / past movement – Algorithms for operations on spatio-temporal (= moving object) data types – Mapping of abstract, continuous models into finitely representable, discrete models Problems of scale: – Handle position updates for two million cars moving around in Germany, reporting their position every ten seconds. Distributed, localized management of information – Allow uniform, integrated access to local, space-related information residing on many heterogeneous servers. ICDE 2001 Page 6