"Unfortunately, just collecting the data in one place and making it easily available isn’t enough. When operational data from transactions is loaded into the data warehouse, it often contains missing or inaccurate data. How good or bad the data is a function of the amount of input checking done in the application that generates the transaction. Unfortunately, many deployed applications are less than stellar when it comes to validating the inputs. To overcome this problem, the operational data must go through a 'cleansing' process, which takes care of missing or out-of-range values. If this cleansing step is not done before the data is loaded into the data warehouse, it will have to be performed repeatedly whenever that data is used in a data mining operation." (Joseph P Bigus,"Data Mining with Neural Networks: Solving business problems from application development to decision support", 1996)
"Processes must be implemented to prevent bad data from entering the system as well as propagating to other systems. That is, dirty data must be intercepted at its source. The operational systems are often the source of informational data; thus dirty data must be fixed at the operational data level. Implementing the right processes to cleanse data is, however, not easy."
"Data archeology (finding bad data), data cleansing (correcting bad data), and data quality enforcement (preventing data defects at the source) should be business objectives. Therefore, data quality initiatives are business initiatives and require the involvement of business people, such as information consumers and data originators." (Sid Adelman et al, "Data Strategy", 2005)
"Data cleansing is dangerous mainly because data quality problems are usually complex and interrelated. Fixing one problem may create many others in the same or other related data elements." (Arkady Maydanchik, "Data Quality Assessment", 2007)
"Data quality program is a collection of initiatives with the common objective of maximizing data quality and minimizing negative impact of the bad data. [...] objective of any data quality program is to ensure that data quality docs not deteriorate during conversion and consolidation projects, Ideally, we would like to do even more and use the opportunity to improve data quality since data cleansing is much easier to perform before conversion than afterwards." (Arkady Maydanchik, "Data Quality Assessment", 2007)
"If you think of a Data Mart as a store of bottled water, cleansed and packaged and structured for easy consumption, the Data Lake is a large body of water in a more natural state. The contents of the Data Lake stream in from a source to fill the lake, and various users of the lake can come to examine, dive in, or take samples." (James Dixon 2010)
"Many organizations need to create data warehouses - massive data stores of timeseries data for decision support. Data are imported from various external and internal resources and are cleansed and organized in a manner consistent with the organization’s needs. After the data are populated in the data warehouse, data marts can be loaded for a specific area or department. Alternatively, data marts can be created first, as needed, and then integrated into an EDW." (Ramesh Sharda et al, "Business Intelligence: A Managerial Perspective on Analytics" 3rd Ed., 2014)
"Data quality in warehousing and BI is typically defined in terms of the 4 C’s - is the data clean, correct, consistent, and complete? When it comes to big data, there are two schools of thought that have different views and expectations of data quality. The first school believes that the gold standard of the 4 C’s must apply to all data (big and little) used for clinical care and performance metrics. The second school believes that in big data environments, a stringent data quality standard is impossible, too costly, or not required. While diametrically opposite opinions may play well in panel discussions, they do little to reconcile the realities of healthcare data quality." (Prashant Natarajan et al, "Demystifying Big Data and Machine Learning for Healthcare", 2017)
"The desire to collect as much data as possible must be balanced with an approximation of which data sources are useful to address a business issue. It is worth mentioning that often the value of internal data is high. Most internal data has been cleansed and transformed to suit the mission. It should not be overlooked simply because of the excitement of so much other available data." (Mike Fleckenstein & Lorraine Fellows, "Modern Data Strategy", 2018)
"Understanding data is really about two types of expertise: data expertise and analytics expertise. Data expertise involves working directly with data - data extraction, cleaning, transformation, and management. Analytics expertise involves data analysis, data visualization, and validation." (Shonna D Watters et al, "The Practical Guide for HR Analytics: Using data to inform, transform, and empower HR decisions", 2019)
"[...] data mesh introduces a fundamental shift that the owners of the data products must communicate and guarantee an acceptable level of quality and trustworthiness - specific to their domain - as an intrinsic characteristic of their data product. This means cleansing and running automated data integrity tests at the point of the creation of a data product." (Zhamak Dehghani, "Data Mesh: Delivering Data-Driven Value at Scale", 2021)
"Data lineage is the path the data took from its source origin, the stops it made along the way, and its destination. This includes information on all the systems it passed through, how it was cleansed, what it was enriched with, and how it was secured. Capturing all that metadata is difficult because many of those systems and applications don’t share information. It’s up to you to assemble the data’s path by pulling metadata from all those systems/applications and assembling them in hopes that you find the path your data took from its current location (destination) to its source system. Lineage is probably the hardest piece of metadata to acquire for either streaming or batching data pipelines." (Hubert Dulay & Stephen Mooney, "Streaming Data Mesh", 2023)
"Data lineage provides the entire history of the data: origin, transformations, enrichments, users who engineered the transformations, etc. Consumers of the data need to trust that the data they will be using is the correct data. Data lineage provides a perspective that creates trust. It does so by mapping out the steps for policies, standards, processes, roles, and responsibilities that were involved with the sourcing, transformation, enrichment, and cleansing of the data." (Hubert Dulay & Stephen Mooney, "Streaming Data Mesh", 2023)
"A data warehouse is a centralized repository of structured, cleaned, and verified data that has been extracted, transformed, and loaded from various sources. These steps are commonly called ETL, which stands for Extract, Transform, Load. This data processing methodology involves extracting data from multiple sources, transforming it to meet business needs, and loading it into a destination for analysis and consultation." (Christopher Maneu et al, "The Definitive Guide to Microsoft Fabric From discovery to building a unified, secure, and scalable data platform", 2025)
"Data transformation sits at the heart of every successful data platform, serving as the critical bridge between data ingestion and data consumption. While basic transformations might involve simple cleaning and formatting, advanced transformation techniques encompass complex operations such as data enrichment, sophisticated deduplication, machine learning-based predictions, and the creation of derived metrics that weren’t present in the original data sources. These processes are essential for organizations looking to extract maximum value from their data investments." (Christopher Maneu et al, "The Definitive Guide to Microsoft Fabric From discovery to building a unified, secure, and scalable data platform", 2025)
"Data may indeed be the new oil. But just like crude oil, data needs refining. It must be transformed into information. This is why we clean, combine, model, and visualize data. The output of all this work - whether you do it on your own, get some help, or use a (semi-)automatic process - includes reports and dashboards that provide insights into various aspects of the organization’s dealings, which decision-makers can then consume to make critical business decisions." (Jeroen ter Heerdt et al, "Microsoft Power BI Visual Calculations: Simplifying DAX", 2026)
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