"I can go with the "title" field and have that include the synonyms in
analysis. Only problem is that the number of fields and number of synonyms
files are quite a lot (~ 8 synonyms files) due to different weightage and
type of expansion (exact vs partial) based on these. Hence going with this
approach would mean creating more fields for all these synonyms
(synonyms.txt)

So, I am looking to build a custom parser for which I could supply the file
and the field and that would expand the synonyms and return a score. "

Having a binary or scalar feature is completely up to you and the way you
configure the Solr feature.
If you have 8 (copy?)fields with same content but different expansion, that
is still ok.
You can have 8 features, one per type of expansion.
LTR will take care of the weight to be assigned to those features.

"So, I am looking to build a custom parser for which I could supply the file
and the field and that would expand the synonyms and return a score. ""
I don't get this , can you elaborate ?

Regards

-----
---------------
Alessandro Benedetti
Search Consultant, R&D Software Engineer, Director
Sease Ltd. - www.sease.io
--
Sent from: http://lucene.472066.n3.nabble.com/Solr-User-f472068.html
NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB