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Monet And Its Geographic Extensions: A Novel Approach to High Performance GIS Processing
Overview: |
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< | Monet is an extensible (relational) database system. The authors implemented a set of GIS extension modules (Point, Box and Polygon) to demonstrate their approach and its applicability to GIS databases. |
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> | Monet is an extensible (type- and algebra-extensible) main memory database management system. A set of GIS extension modules (Point, Box and Polygon) are described to demonstrate their approach and its applicability to GIS databases. |
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< | Features:
- Decomposed Storage Model (DSM)
- Involves the decomposition of all relations into binary (association) tables, one for each attribute in the original relation
- Main memory dbs
- Algebra-extensible
- Shared-memory parallelism
- All processes share the same memory (or address) space
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> | Background:
It is important to note that Monet is part of a bigger project, the MAGNUM project, whose goal is to build a "high performance parallel GIS database system with ODMG compliant O-O technology, employing a spatial reasoning system for query optimization."
Focus:
- Ability to deal with large data volumes typical of GIS databases
- Monet's design focuses on memory management
- All operations done in main memory
- Large tables are mapped into virtual memory (which allows the system to access it as if it were in main memory) circumventing the need to provide additional code to handle memory/buffer management
- It incorporates shared memory parallelism
- Units for parallel execution = algebraic operators (not tuple- or segment-pipelining)
- Implication: results completely materialized at each phase in the query plan
- Extensibility to spatial data types
- Monet employs an extensible tool-kit approach (resembling Gral) in which an extension is encapsulated in a module (defined by an ADT interface)
- Monet provides support for user-defined data types, search accelerators and primitives
- GIS data types implemented:
- Vector data model - only point and polygon datatypes implemented (what about lines?)
- Raster data model - implemented as 'unary tables' and not as distinct data types (how are pixel sizes recorded in this format?)
- Note: spatial query optimization not a main concern
Evaluation:
- It is evaluated against the Sequoia Benchmark (i.e., the Sequoia 2000 storage benchmark for GIS)
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Concerns:
- Main memory:
- Can even large raster databases fit into main memory as required by Monet?
- For example, the authors state that they "did not have sufficient disk space to generate all 130 rasters for the National benchmark" (Section 5)
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- What about raster data? Are there any modules for it?
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- What's a database hot-set?
- What are typical sizes for GIS dbs? Raster files? Vector files?
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- What's a 'Box' wrt GIS data?
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Reference:
Peter A. Boncz, Wilko Quak, Martin L. Kersten: Monet And Its Geographic |
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