--- title: "Data warehouse architecture and components" subject: "Data Mining" chapter: 1 key: "semester_7/data_mining:dw-architecture-components" source: https://www.bctengineer.com/q/semester_7/data_mining/dw-architecture-components site: BCT Engineering --- # Data warehouse architecture and components Data Mining · Chapter 1: Introduction - Asked in: 2065 Baisakh; year not given, 8 marks - Video: [#3 Data Warehouse Components |DWDM|](https://www.youtube.com/watch?v=P-WWMgRnOYs) — Trouble- Free - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/data_mining/dw-architecture-components - Whole chapter: https://www.bctengineer.com/md/semester_7/data_mining/chapter-1 ## Question Describe the architecture of a data warehouse along with the different components of it. ## Short answer A data warehouse uses a three-tier architecture: sources feed ETL, which loads the warehouse server, which is accessed through an OLAP server by front-end tools. Components include data sources, ETL tools, the warehouse database, metadata repository, data marts, OLAP server, front-end tools, and management/administration. ## Answer A data warehouse architecture shows how data moves from the sources into the warehouse and then to users. The common three-tier architecture is: ```text Operational DBs External Flat files \ | / v v v [ Extract - Clean - Transform - Load ] | v +----------------------------------------+ | DATA WAREHOUSE SERVER | | Detailed data | Summary data | Metadata| | Data marts (dependent) | +----------------------------------------+ | [ OLAP Server ] | Query/report | OLAP/analysis | Data mining tools ``` #### Components 1. **Data sources**: operational databases (ERP, CRM, billing), flat files and external data. They are heterogeneous. 2. **ETL / back-end tools**: extract data from the sources, clean it (remove errors, fill missing values), transform it (format, aggregate, derive) and load it into the warehouse. Periodic refresh keeps it up to date. 3. **Warehouse database (bottom tier)**: usually a relational DBMS storing detailed data and lightly and highly summarised data. 4. **Metadata repository**: data about data: source definitions, schema, transformation rules, data lineage, load history and business definitions. 5. **Data marts**: department-specific subsets of the warehouse, dependent or independent. 6. **OLAP server (middle tier)**: ROLAP, MOLAP or HOLAP engine that gives the multidimensional view and performs roll-up, drill-down, slice and dice. 7. **Front-end tools (top tier)**: query and report tools, OLAP/analysis tools and data mining tools used by managers and analysts. 8. **Management and administration**: security, backup and recovery, monitoring and scheduling. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What does the ETL/back-end tool layer do? A. Extracts, cleans, transforms and loads source data into the warehouse B. Only stores backups C. Draws charts for managers D. Answers end-user queries Answer: A. ETL moves data from heterogeneous sources into the warehouse after cleaning and transforming it. (Key point: ETL role) 2. What does the metadata repository hold? A. Data about data: schema, transformation rules, lineage and load history B. Only the detailed sales rows C. User passwords only D. Raw copies of source files Answer: A. Metadata describes sources, schema, rules, lineage and load history. (Key point: Metadata repository) 3. What is the OLAP server (middle tier) responsible for? A. Giving a multidimensional view with roll-up, drill-down, slice and dice B. Loading flat files C. Backup scheduling D. Removing duplicates Answer: A. The OLAP server (ROLAP, MOLAP or HOLAP) provides the multidimensional view and operations. (Key point: OLAP server) 4. In the three-tier architecture, which is the top tier? A. Warehouse database B. ETL tools C. OLAP server D. Front-end query, analysis and data mining tools Answer: D. Bottom tier is the warehouse DB, middle is the OLAP server, top is the front-end tools. 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