query-federation/Query_Federation at master · noorbakerally/query-federation · GitHub

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DARQ
====

A query is processed in 4 stages:
1. Parsing: conversion of query string into an abstract syntax tree
2. Query Planning:
	- engine decompose query
	- builds multiple sub-queries according to information in service descriptions
3. Optimization:
	- build optimized query execution plan

Federation System
------------------
- Source description
	- RDF Indexes
	- Statistical information
- Query planning
	- Source Selection
	- Build Sub-Queries
		- Query Rewriting
- Query Optimization
	- Logical Optimization
	- Physical Optimization
- Query Costing
	- Cost Model
		- Cardinality
		- Selectivity
- Query Execution
	- Adaptive Query Engine (ANAPSID)
	- Result Merging


Source Description
------------------


Query Optimization
------------------

Cost Model
----------