SPARQL 1.1 computational complexity and/or optimisation

Dear list,

Apologies if this has come up before (my searches so far have drawn a 
blank), but I'm wondering if anyone can point me to any research papers 
which attempt to determine the computational complexity of SPARQL 1.1 or 
which suggest methods for optimising SPARQL 1.1 queries.

I'm specifically looking for 1.1 related material - I can find plenty of 
papers for the original SPARQL, e.g.

Jorge Pérez, Marcelo Arenas, and Claudio Gutierrez. 2009. Semantics and 
complexity of SPARQL. /ACM Trans. Database Syst./ 34, 3, Article 16 
(September 2009), 45 pages. DOI=10.1145/1567274.1567278 
http://doi.acm.org/10.1145/1567274.1567278

Michael Schmidt, Michael Meier, and Georg Lausen. 2010. Foundations of 
SPARQL query optimization. In /Proceedings of the 13th International 
Conference on Database Theory/ (ICDT '10), Luc Segoufin (Ed.). ACM, New 
York, NY, USA, 4-33. DOI=10.1145/1804669.1804675 
http://doi.acm.org/10.1145/1804669.1804675

but I'm particularly interested in 1.1-specific features such as 
subqueries and aggregate functions.


Best regards,

Steve Hargreaves


Centre for Digital Music
Electronic Engineering
Queen Mary University of London
Mile End Road
London E1 4NS
UK