Encyclopedia of Database Systems

2018 Edition
| Editors: Ling Liu, M. Tamer Özsu


  • Josep Domingo-FerrerEmail author
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1494


Individual data


A microdata file V with s respondents and t attributes is an s × t matrix where Vij is the value of attribute j for respondent i. Attributes can be numerical (e.g., age, salary) or categorical (e.g., gender, job).

Key Points

The attributes in a microdata set can be classified in four categories which are not necessarily disjoint [ 1, 2]:
  1. 1.

    Identifiers. These are attributes that unambiguously identify the respondent. Examples are the passport number, social security number, name-surname, etc.

  2. 2.

    Quasi-identifiers or key attributes. These are attributes which identify the respondent with some degree of ambiguity. (Nonetheless, a combination of quasi-identifiers may provide unambiguous identification.) Examples are address, gender, age, telephone number, etc.

  3. 3.

    Confidential outcome attributes. These are attributes which contain sensitive information on the respondent. Examples are salary, religion, political affiliation, health condition, etc.

  4. 4.
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Recommended Reading

  1. 1.
    Dalenius T. The invasion of privacy problem and statistics production: an overview. Statistik Tidskrift. 1974;12:213–25.Google Scholar
  2. 2.
    Samarati P. Protecting respondents’; identities in microdata release. IEEE Trans Knowl Data Eng. 2001;13(6):1010–27.CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Universitat Rovira i VirgiliTarragonaSpain

Section editors and affiliations

  • Elena Ferrari
    • 1
  1. 1.DiSTAUniv. of InsubriaVareseItaly