* Description

• Use no prior knowledge such as predicates and statistics information of the source endpoints -- up-to-date information of each source

• Contact each source with "ask" query in real time to determine the target source -- no predicates bound limitation

• Save the predicate information in cache for future use

• Join order: a heuristics-based cost estimation(based on a variation of the variable counting technique)

• Use exclusive group and bound join technology to minimize the number of requests sent to federation members

* source code:

FedX3.1

 http://www.fluidops.com/en/company/training/open_source

* execute:

example:

[fsearch@cl38 FedX]$ java -jar FedX3.1.jar -d bio2RDF.ttl -f STDOUT -q  "select
 ?s1 ?o1 ?o2 where{ ?s1 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http
://bio2rdf.org/omim_vocabulary:Gene>.?s1   <http://bio2rdf.org/omim_vocabulary:
refers-to> ?o1. ?o1   <http://bio2rdf.org/omim_vocabulary:x-snomed> ?o2.<http:/
/bio2rdf.org/pharmgkb:PA446359> <http://bio2rdf.org/pharmgkb_vocabulary:x-snome
dct> ?o2.}"

Result:

query1: return 5 results query2: return 40 results

query3: return 790 results

query4: return 9492 results

query5: return 111962 results

Query\time(ms)	time 1	time 2	time 3	time 4	time 5
case1	11624	9469	10377	8978	9355
case2	|47152	43902	43569	42418	43393
case3	113629	108622	109989	109297	109796
case4	106218	108579	109989	107731	106713
case5	792628	794677	806516	819745	812255