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Data quality: why provenance and selection matter more than sheer volume

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More training data does not automatically mean better AI. What matters is which content is included, what is missing and how it was selected. Dataset documentation makes these decisions visible. Open corpora such as Dolma enable further investigation, but do not replace checks on suitability, rights, sensitive information and biases in the eventual area of use.

A dataset is already a selection

Training data is not created neutrally through mere collection. The choice of sources, languages and time periods already determines which perspectives occur frequently. Filtering and cleaning then change its composition further. The paper Datasheets for Datasets therefore proposes systematic documentation: the motivation, provenance, composition, collection process and recommended use should be made traceable. The Allen Institute for AI likewise describes the aims, mix of sources and processing of the Dolma corpus. Such information helps researchers investigate the connection between data and model behaviour. However, it does not guarantee that a dataset is suitable for every application. A collection can be useful for general language research while inadequately representing important specialist fields, regional variants or particular groups of people. Without knowledge of this selection, the assessment of a model remains unnecessarily superficial.

Cleaning can solve problems and create new ones

Removing duplicates prevents frequently copied content from being given excessive weight. Filters can reduce obvious spam or certain sensitive data. At the same time, such rules involve value judgements and risks of technical errors. A filter for supposedly low-quality language could disadvantage unusual spellings or certain dialects. Nor does a clear description of sources mean that all questions of rights have been conclusively resolved. Data quality therefore encompasses several dimensions: usefulness of the content, representation, currency, legal usability and protection of the people concerned. These aims can be in tension with one another. Responsible documentation identifies not only successful cleaning steps, but also known gaps and possible side effects. Open datasets in particular benefit when third parties can report problematic content and trace changes, rather than treating a one-off release as a completed quality assessment.

What users should ask before a project

For a specific undertaking, it is worth starting with a list of requirements: which language, text type and specialist knowledge must the model handle? The next step is to check whether the documented data plausibly covers these areas at all. Samples should include not only typical cases, but also rare and difficult ones. For one's own datasets, the documentation should include provenance, consent or other grounds for use, as well as deletion and updating processes. A separate test set that does not inadvertently feed into development is equally important. The purpose of this work is not to claim that the data is perfect. It makes limitations recognisable early on and enables targeted improvements. A smaller, well-documented dataset can be more helpful for a narrowly defined task than a huge collection whose composition no one can adequately explain or control.

Sources & further reading

Written in our own words with AI assistance, based on the sources listed above. The text distinguishes research findings, technical prototypes and established knowledge. This feature is not a breaking-news report.

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