Category Archives: Data Warehouse

Data Unification at scale

This term Data Unification is new in the Big Data lexicon, pushed by varieties of companies such as Talend, 1010Data, and TamR. Data unification deals with the domain known as ETL (Extraction, Transformation, Loading), initiated during the 1990s when Data Warehousing was gaining relevance. ETL refers to the process of extracting data from inside or outside sources (multiple applications typically developed and supported by different vendors or hosted on separate hardware), transform it to fit operational needs (based on business rules), and load it into end target databases, more specifically, an operational data store, data mart, or a data warehouse. These are read-only databases for analytics. Initially the analytics was mostly retroactive (e.g. how many shoppers between age 25-35 bought this item between May and July?). This was like driving a car looking at the rear-view mirror. Then forward-looking analysis (called data mining) started to appear. Now business also demands “predictive analytics” and “streaming analytics”.

During my IBM and Oracle days, the ETL in the first phase was left for outside companies to address. This was unglamorous work and key vendors were not that interested to solve this. This gave rise to many new players such as Informatica, Datastage, Talend and it became quite a thriving business. We also see many open-source ETL companies.

The ETL methodology consisted of: constructing a global schema in advance, for each local data source write a program to understand the source and map to the global schema, then write a script to transform, clean (homonym and synonym issues) and dedup (get rid of duplicates) it. Programs were set up to build the ETL pipeline. This process has matured over 20 years and is used today for data unification problems. The term MDM (Master Data Management) points to a master representation of all enterprise objects, to which everybody agrees to confirm.

In the world of Big Data, this approach is very inadequate. Why?

  • data unification at scale is a very big deal. The schema-first approach works fine with retail data (sales transactions, not many data sources,..), but gets extremely hard with sources that can be hundreds or even thousands. This gets worse when you want to unify public data from the web with enterprise data.
  • human labor to map each source to a master schema gets to be costly and excessive. Here machine learning is required and domain experts should be asked to augment where needed.
  • real-time data unification of streaming data and analysis can not be handled by these solutions.

Another solution called “data lake” where you store disparate data in their native format, seems to address the “ingest” problem only. It tries to change the order of ETL to ELT (first load then transform). However it does not address the scale issues. The new world needs bottoms-up data unification (schema-last) in real-time or near real-time.

The typical data unification cycle can go like this – start with a few sources, try enriching the data with say X, see if it works, if you fail then loop back and try again. Use enrichment to improve and do everything automatically using machine learning and statistics. But iterate furiously. Ask for help when needed from domain experts. Otherwise the current approach of ETL or ELT can get very expensive.