* 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 790 results

query3: return 9492 results

query4: return 111962 results

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