Ideas for building a system that parses medical research publications/articles

Hello

I am imagining a system that can parse papers from various sources 
(web/files/etc) and in various formats (text, pdf, etc) and can store 
metadata for this paper ,some kind of global ID if applicable, authors, 
areas of research, whether the paper is "new", "highlighted", 
"historical", type (e.g. Case reports, Clinical trials), symptoms (e.g. 
tics, GI pain, psychological changes, anxiety, ), and other key 
attributes (I guess dynamic), it must be full text searchable, etc.

I am at the very beginning in this and it is done on a fully volunteer 
basis.

Lots of questions : is there any scientific/scholar analysis software 
already available? If yes and is really good and open source , then this 
will influence the rest of decisions. Otherwise , I'll have to form a 
team that can write one, in this case I'll have to decide DB, language, 
etc. I work 20 years with pgsql so it is the natural choice for any kind 
of data, I just ask this for the sake of completeness.

All ideas welcome.