Remarks on the Algebra of Non First Normal Form Relations. Jaeschke, G. & Schek, H.̈ In pages 124-138.
doi  abstract   bibtex   
Usually, the first normal form condition of the relational model of data is imposed. Presently, a broader class of data base applications like office information systems is considered where this restriction is not convenient. Therefore, an extension of the relational model is proposed consisting of Non First Normal Form (NF$^2$) relations. The relational algebra is enriched mainly by so called nest and unnest operations which transform between NF$^2$ relations and the usual ones. We state some properties of these operations and some rules which occur in combination with the operations of the usual relational algebra. Since we propose to use the NF$^2$ model also for the internal data model these rules are important not only for theoretical reasons but also for a practical implementation.
@inproceedings{ jae82,
  crossref = {pods82},
  author = {Gerhard Jaeschke and Hans-J̈org Schek},
  title = {Remarks on the Algebra of Non First Normal Form Relations},
  pages = {124-138},
  index = {1nf[0.8] nfnf[1]},
  uri = {http://www.informatik.uni-trier.de/~ley/db/conf/pods/JaeschkeS82.html},
  doi = {10.1145/588111.588133},
  abstract = {Usually, the first normal form condition of the relational model of data is imposed. Presently, a broader class of data base applications like office information systems is considered where this restriction is not convenient. Therefore, an extension of the relational model is proposed consisting of Non First Normal Form (NF$^2$) relations. The relational algebra is enriched mainly by so called nest and unnest operations which transform between NF$^2$ relations and the usual ones. We state some properties of these operations and some rules which occur in combination with the operations of the usual relational algebra. Since we propose to use the NF$^2$ model also for the internal data model these rules are important not only for theoretical reasons but also for a practical implementation.}
}
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