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 Which of the following is not a characteristic of a data warehouse? Subject-oriented incorrect Integrated incorrect Time-variant incorrect Volatile correct MC In terms of data manipulation, a data warehouse focusses on... Insert/Update/Delete/Select statements incorrect Insert/Select statements correct Select/Update statements incorrect Delete statements incorrect MC Which statement is CORRECT? A star schema has one large central dimension table which is connected to various smaller fact tables. incorrect The dimension tables of a star schema contain the criteria for aggregating the measurement data and will typically be used as constraints to answer queries. correct To speed up report generation and avoid time consuming joins in a star schema, the dimension tables need to be normalized. incorrect The dimension tables in a star schema are frequently updated. incorrect MC Which statement is NOT CORRECT? A snowflake schema normalizes the fact table of a star schema. correct A fact constellation schema has more than one fact table which can share dimension tables. incorrect Surrogate keys essentially buffer the data warehouse from the operational environment by making it immune to any operational changes. incorrect A factless fact table is a fact table which only contains foreign keys and no measurement data. 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 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 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 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 To decrease the burden on both the operational systems and the data warehouse itself, it is recommended to start the ETL process by dumping the data in a staging area where all the ETL activities can be executed. incorrect During the loading step of ETL, the data warehouse is populated by filling the fact and dimension tables hereby also generating the necessary surrogate keys to link it all up. Fact rows should be inserted/updated before the dimension rows. 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. incorrect MC Which statement is NOT CORRECT? A data mart is a scaled down version of a data warehouse aimed at meeting the information needs of a homogeneous small group of end-users such as a department or business unit (e.g., marketing, finance, logistics, HR, etc.). incorrect Dependent data marts pulls their data from a central data warehouse, whereas independent data marts are standalone systems drawing data directly from the operational systems, external sources or a combination of both. incorrect A virtual data warehouse (sometimes also called a federated database) or virtual data mart contains no physical data but provides a uniform and consolidated single point of access to a set of underlying physical data stores. incorrect A key advantage of virtualization is that it requires no extra processing capacity from the underlying (operational) data stores. correct MC Which statement is CORRECT? A key distinguishing property of a data lake is that it stores raw data in its native format which could be structured, unstructured or semi-structured. correct A data lake is targeted towards decision makers at middle and top management level, whereas a data warehouse requires a data scientist, which is a more specialized profile in terms of data handling and analysis. incorrect In case of a data warehouse, the data schema definitions are only determined when the data is read (schema-on-read) whereas for data lakes it is fixed when the data is loaded (schema-on-write). incorrect A data lake is less agile compared to a data warehouse which has no structure. incorrect MC Which statement is NOT CORRECT? Query and reporting tools are an essential component of a comprehensive business intelligence solution. incorrect A pivot or cross-table is a popular data summarization tool. It essentially cross-tabulates a set of dimensions. incorrect A key disadvantage of OLAP is that it does not allow to interactively analyze your data, summarize it and visualize it in various ways. correct The key fundament of OLAP is a multidimensional data model which can be implemented in various ways. incorrect MC Which statement is NOT 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 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 MC Which statement is CORRECT? Roll-up (or drill-up) refers to aggregating the current set of fact values within or across one or more dimensions. incorrect Roll-down (or drill-down) de-aggregates the data by navigating from a lower level of detail to a higher level of detail. incorrect Slicing represents the operation whereby one of the dimensions is set at a particular value. incorrect Dicing corresponds to a range selection on one or more dimensions. incorrect All statements are correct correct