MC	Which of the following is not a characteristic of a data warehouse?	Subject-oriented	incorrect	Volatile	correct	Integrated	incorrect	Time-variant	incorrect	
MC	Which statement is CORRECT?	The extraction strategy of ETL can be either full or incremental.  In the latter case, only the changes since the previous extraction are considered.	correct	A factless fact table contains no measurement data and is therefore useless.	incorrect	A charecteristic of data warehouses is that they are volatile.	incorrect	Slowly changing dimensions in a data warehouse environment can be tackled by duplicating records and adding Start_Date, End_Date and Current_Flag attribute types.  This approach only allows to retain partial historical information.	incorrect	
MC	Which statement is NOT CORRECT?	MOLAP scales better to more dimensions than ROLAP.  The query performance may however be inferior to ROLAP unless some of the queries are materialized or high-performance indexes are defined.	correct	Multidimensional OLAP (MOLAP) stores the multidimensional data using a Multidimensional DBMS (MDBMS) whereby the data is stored in a multi-dimensional array-based data structure optimized for efficient storage and quick access.	incorrect	Relational OLAP (ROLAP) stores the data in a relational data warehouse, which can be implemented using a star, snowflake or fact constellation schema.	incorrect	Hybrid OLAP (HOLAP) tries to combine the best of both MOLAP and ROLAP.  An RDBMS can then be used to store the detailed data in a relational data warehouse whereas the pre-computed aggregated data can be kept as a multidimensional array managed by a MDBMS.	incorrect	
MC	Which statement is CORRECT?	A star schema has one large central dimension table which is connected to various smaller fact tables.	incorrect	OLAP allows you to interactively analyze the data, summarize it, and visualize it in various ways	correct	Star schemas have a more efficient use of storage.	incorrect	A virtual data warehouse or virtual data mart can be used to relieve underlying (operational) data sources from intensive processing.	incorrect	
MC	Which statement is NOT CORRECT?	At the operational level, day to day business decisions are made, typically in real-time or with a short time frame.	incorrect	At the tactical level, decisions are made by middle management with a medium-term (e.g. a month, a quarter, a year) focus.	incorrect	At the strategic level, decisions are made by senior management with long term implications (e.g., 1, 2, 5 years or more)	incorrect	A data warehouse provides a centralized, consolidated data platform by integrating data from different sources and in different formats.  As such, it provides a separate and dedicated environment for operational decision making.	correct	
MC	In terms of data manipulation, a data warehouse focusses on...	Insert/Update/Delete/Select statements	incorrect	Select/Update statements	incorrect	Delete statements	incorrect	Insert/Select statements	correct	
MC	Which statement is NOT CORRECT?	Some estimates state that the ETL step can consume up to 80% of all efforts needed to set up a data warehouse.	incorrect	In a data warehouse context, the definition of junk dimensions greatly contributes to the maintainability and query performance.	incorrect	The key difference between the CUBE and ROLLUP OLAP operators is that the former generates a result set showing the aggregates for a hierarchy of values of the speci?ed attribute types, whereas the latter generates a result set showing the aggregates for all combinations of values of the selected attribute types.	correct	A data warehouse subject-oriented, integrated, time-variant and non-volatile.	incorrect	
MC	Which statement is NOT CORRECT?	Junk dimensions can be defined to efficiently accommodate low cardinality attribute types such as flags or indicators.	incorrect	For slowly changing dimensions, surrogate keys can be handy to store the historical information by duplicating a record and adding, e.g., Start_Date, End_Date and Current_Flag attribute types.	incorrect	One way to deal with rapidly changing dimensions is by splitting the information into stable and rapidly changing information.  The latter can then be put into a separate mini-dimension table with a new surrogate key.  The connection can then be made by using the fact table or by introducing a new table connecting both.	incorrect	An outrigger table can be defined to store a set of attribute types of a dimension table which are uncorrelated, high in cardinality and updated simultaneously.	correct	
MC	Which statement is NOT CORRECT?	At the strategic level, decisions are made by senior management with long term implications (e.g., 1, 2, 5 years or more)	incorrect	At the operational level, day to day business decisions are made, typically in real-time or with a short time frame.	incorrect	A data warehouse provides a centralized, consolidated data platform by integrating data from different sources and in different formats.  As such, it provides a separate and dedicated environment for operational decision making.	correct	At the tactical level, decisions are made by middle management with a medium-term (e.g. a month, a quarter, a year) focus.	incorrect	
MC	Which of the following is not a characteristic of a data warehouse?	Integrated	incorrect	Subject-oriented	incorrect	Volatile	correct	Time-variant	incorrect