What are the open source tools and techniques to build a complete data warehouse platform? [closed]

Answer 1

Expanding on what Pascal wrote:

OLAP server: Mondrian

AJAX pivot tables: Saiku

OLAP schema designer: Pentaho Schema Workbench

OLAP aggregate designer: Pentaho Aggregation Designer

ETL: Pentaho Kettle

Report designer: Pentaho Report Designer

Data Quality: DataCleaner

Columnar Data Warehouse: MonetDB

Data Mining: RapidMiner