Transcript Kein Folientitel
CoopIS, Trento, Italy, 05/09/2001
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Schema design and query processing in a federated multimedia database system
Henrike Berthold & Klaus Meyer-Wegener Dresden University of Technology, Germany Problem A Federated Multimedia Database System Global schema construction Query processing Summary DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
Problem
Application 1
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Application n SDBS 1 SDBS k MRS 1 MRS m MSS 1 MSS n • SDBS: Database system with a schema, a query language, ...
• MRS: Media retrieval system • MSS: Media storage system DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
Media retrieval systems
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• Perform content-based search based on automatically extracted features (perception + semantical primitives) • work for a set of media objects of a certain media type such as image, text, video, audio or a subset with a certain semantics such as passport photos • Retrieval functions –
single
: search argument (example, feature, weighting), media object -> similarity value –
coll
: search argument -> list if tuples (similarity value, MID) – result restrictions of coll: lower bound for similarity values, subset of media objects, top n • Example systems: QBIC (IBM), Excalibur Image Datablade, Melodiscov (LIP6) • Problem: only interactive interface and no programming one DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
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Media storage systems
• Store and manage media objects like images, videos • provide operations for those • support especially timed playout of continuous media objects • all systems provide media description data such as size, format • some systems support transactional concepts like durability, atomicity • Example systems: Tiger Shark (IBM), Symphony (Uni Texas), Fellini (Bell Labs), Kangaroo/Memo.REAL (Dresden University of Technology) DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
A Federated Multimedia Database System
Application 1
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Application n
-
Database schema and query processing
-
Operations on media objects
-
Transactions
FMDBMS
SDBS 1 SDBS k MRS 1 MRS m MSS 1 MSS n
FMDBS
DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
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Global schema construction
based on two intermediate schemas: • Structured-data schema (SDS) = global schema of all SDBS-Schemas • Media schema (MS) = global schema of all MSS schemas Structured-data Schema (SDS) integrates SDBS1-Schema SDBSk-Schema Media Schema (MS) MSS1-Schema MSSn-Schema DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
Example media schema
Common data model: ODMG, CROQUE • Types and subtype-relation • Classes and subclass-relation :TSingleMedia
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:TObject ContMedia:TContMedia Video:TVideo Audio:TAudio Image:TImage Text:TText PassportPhoto:TImage City:TImageWithPart 1 * CityPart:TImagePart DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
Step 1: Base integration
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Schema architecture: Global Schema Structured-data Schema (SDS) integrates SDBS1-Schema SDBSk-Schema Media Schema (MS) MSS1-Schema MSSn-Schema DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
Step 2: Integration of media retrieval functions
• •
single
: objekt method +
coll
: class method -, function -
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•
allows combination of boolean queries with media retrieval queries
DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
Step 2: Example
t2 t5 (=t1‘) t6 (=t3‘) t7 (=t4‘) DRESDEN UNIVERSITY OF TECHNOLOGY
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c2:t1 c3:t2 c7:t3 Henrike Berthold
Step 3: Extension
• Simple extension: relationships • complex extension: new objects + relationships
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TLecture 1 1..* TSlide TVisualElement Time interval Region y TVideoElement TTextElement Region for video Region for text Region for image Video Image1 Text1 Image2 Text2 x DRESDEN UNIVERSITY OF TECHNOLOGY 2 TImageElement 8 TVideo TSingleMedia TText TImage t in min Henrike Berthold
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Schema architecture
Global Schema Structured-data Schema integrates SDBS1-Schema SDBSk-Schema Media Schema MRS1-Function MRSm-Function Internal Schema MSS1-Schema MSSn-Schema DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
Construction data
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DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
Query processing
Global OQL Query DATABASES
Global query computation Modification Decomposition and global optimization Local optimization and execution Type checking and mapping to intermediate representation Construction data Replacing global specifiers by local ones Decomposition and optimization by the global query processor Optimization by the local query processors and local execution Global execution Combining local results globally
Result
DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
FMDBS-specific problems
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• Modification – Vertical fragmentation GT1 GT2 GT3 GT4 complete replacement of a global object is not possible – Replacement of search methods DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
Comprehension syntax
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DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
Monads and algebras
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DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
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Advantages
• uniform representation of collections (set, bag, list) and aggregations • readability • there are equivalences defined – easy manipulation • there is a mapping to an algebraic expression – embedding in traditional query processing is possible • thus: better suited for manipulations than an object algebra DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
Modification
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DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
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Improvements
• Paths that belong to one source are replaced completely; so far: replacement of each single function • A generator which binds a global object is replaced by a sequence of qualifiers which produce all local objects that are used in the query; so far: production of local objects there, where they are used • exploit function
coll
and its result restrictions DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
Replacement of function
single
by
coll
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DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
Identification of a lower bound
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DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
Identification of a subcollection restriction
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DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
Prototype
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DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
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Summary
• An FMDBS manages structured data and media data. It takes the integration efforts from the applications.
• Development of a procedure to construct the global schema – data (relationships, new types and classes) and media retrieval functions can be added • Development of a procedure to modify queries – can handle the vertical fragmentation – choses efficiently executable media search functions • Applications have a powerful mean to find suitable data DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold
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Outlook
• Problem: Chose a result restriction if some are applicable • Need of a general cost model of media search systems • Construction of a complete FMDBS • Need of tools which support the construction and the administration DRESDEN UNIVERSITY OF TECHNOLOGY Henrike Berthold