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  2. RDFLib - Wikipedia

    en.wikipedia.org/wiki/RDFLib

    RDFLib is a Python library for working with RDF, [2] a simple yet powerful language for representing information. This library contains parsers/serializers for almost all of the known RDF serializations, such as RDF/XML, Turtle, N-Triples, & JSON-LD, many of which are now supported in their updated form (e.g. Turtle 1.1).

  3. Relation (database) - Wikipedia

    en.wikipedia.org/wiki/Relation_(database)

    Relation, tuple, and attribute represented as table, row, and column respectively In database theory, a relation , as originally defined by E. F. Codd , [ 1 ] is a set of tuples (d 1 ,d 2 ,...,d n ), where each element d j is a member of D j , a data domain .

  4. Database normalization - Wikipedia

    en.wikipedia.org/wiki/Database_normalization

    Recall that the Book table below has a composite key of {Title, Format}, which will not satisfy 2NF if some subset of that key is a determinant. At this point in our design the key is not finalized as the primary key , so it is called a candidate key .

  5. Relational model - Wikipedia

    en.wikipedia.org/wiki/Relational_model

    The body is a set of tuples. A tuple is a collection of n values, where n is the relation's degree, and each value in the tuple corresponds to a unique attribute. [6] The number of tuples in this set is the relation's cardinality. [7]: 17–22 Relations are represented by relational variables or relvars, which can be reassigned.

  6. Tuple relational calculus - Wikipedia

    en.wikipedia.org/wiki/Tuple_relational_calculus

    where v is a tuple variable, H a header and f(v) a formula in F[S,type] where type = { (v, H) } and with v as its only free variable. The result of such a query for a given database db over S is the set of all tuples t over D with dom(t) = H such that f is true for db and val = { (v, t) }. Examples of query expressions are:

  7. Row (database) - Wikipedia

    en.wikipedia.org/wiki/Row_(database)

    In a relational database, a row or "record" or "tuple", represents a single, implicitly structured data item in a table. A database table can be thought of as consisting of rows and columns. [1] Each row in a table represents a set of related data, and every row in the table has the same structure.

  8. Database model - Wikipedia

    en.wikipedia.org/wiki/Database_model

    The basic data structure of the relational model is the table, where information about a particular entity (say, an employee) is represented in rows (also called tuples) and columns. Thus, the "relation" in "relational database" refers to the various tables in the database; a relation is a set of tuples. The columns enumerate the various ...

  9. Tuple-generating dependency - Wikipedia

    en.wikipedia.org/wiki/Tuple-generating_dependency

    In relational database theory, a tuple-generating dependency (TGD) is a certain kind of constraint on a relational database. It is a subclass of the class of embedded dependencies (EDs). An algorithm known as the chase takes as input an instance that may or may not satisfy a set of TGDs (or more generally EDs) and, if it terminates (which is a ...