Ruby is an open-source and fully object-oriented programming language, which combines syntax inspired by Perl with Smalltalk-like features. Ruby was created in the mid-1990s by Yukihiro Matsumoto, also known as "Matz," in Japan. The Ruby standard library is generally quite extensive and offers a wide range of functionality. Data sets are collections of data that can be used for testing purposes or for training machine learning models. Dataset is a Ruby library for accessing datasets stored in relational databases. It provides a common API for working with different database backends such as Postgres, MySQL and SQLite. Ruby Dataset is a simple and fast library for data processing and analysis. Popular Ruby Dataset open source libraries include: ISO-3166-Countries-with-Regional-Codes - ISO 31661 country lists merged; devise-pwned_password - Devise extension that checks user passwords; mlcomp - Website for standardized execution and evaluation of algorithms on datasets.