Managing Location Information for Billions of Gizmos on the Move – What’s in it for the Database Folks Ralf Hartmut Güting Fernuniversität Hagen, Germany

ICDE 2001Page 2 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 2001Page 3 1. Describing Moving Objects Static spatial object: position:point Moving object: position:f: time  point distance(mo, obj) f: time  real inside(mo, obj) f: time  bool Continuous functions must be handled in DBMS models and languages. x y t

ICDE 2001Page 4 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 2001Page 5 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 2001Page 6 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.