Just found this interesting presentation,
Map-Reduce-Merge: Simpli?ed Relational Data Processing on Large Clusters
by Hung-chih Yang, Ali Dasdan Ruey-Lung Hsiao, D. Stott Parker; as presented by Nate Rober (PDF)
1. Change to reduce phase
2. Merge phase
3. Additional user-de?nable operations
a. partition selector
d. con?gurable iterators
Implementing Relational Algebra Operations
4. Set Operations: Union, Intersection, Difference
5. Cartesian Product
[for more detail see full slides]
MapReduce & GFS represent a paradigm shift in data processing: use a simpli?ed interface instead of overly general DBMS.
Map-Reduce-Merge adds the ability to execute arbitrary relational algebra queries.
Next steps: develop SQL-like interface and a query optimizer.
Nearby: LargeTripleStores in ESW wiki
Not entirely unrelated: Google Social Graph API (which parsers FOAF/RDF from ‘The Web’ but discards all but the social graph parts currently)