Relational Database Theory

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Abstractions about structuring and querying relational data — schema and normalization concepts (database schema, third normal form, entity cardinality), transactional guarantees (database transaction, bitemporal modeling), and query or identifier mechanisms such as query rewriting, the Hi/Lo algorithm and Codd's theorem.

13 abstractions in this family — domain-specific abstractions that sit near one another in structural-signature space (k-means over structural-signature embeddings). Each is shown with its short description.

• Bitemporal modeling — Record each fact along both valid time—when it holds in the modeled world—and transaction or system time—when the database records it—so corrections preserve what was believed earlier while enabling as-of knowledge and as-of reality queries.
• Codd's theorem — The database-theory result that relational algebra and domain-independent relational calculus have exactly the same expressive power.
• Data retrieval — The execution of a structured request against a managed data store to locate, select, and return records or values satisfying declared identifiers, predicates, relations, and access rules.
• Database schema — Specify a database’s permitted structures, relations, constraints, and object organization in the formal language of its data model or management system.
• Database transaction — A bounded database unit of work whose reads and writes commit together or abort together under declared atomicity, consistency, isolation, and durability guarantees.
• Hi/Lo algorithm — A distributed identifier-allocation strategy that reserves a high-value block centrally and generates low values locally within that block.
• Object–relational model — An object–relational database (ORD), or object–relational database management system (ORDBMS), is a database management system (DBMS) similar to a relational database, but with an object-oriented database model: objects, classes and inheritance are directly supported in database schemas and in the query language.
• One-to-many (data model) — A relationship cardinality in which one parent entity may relate to multiple child entities while each child participates with at most one parent in that relationship, commonly enforced by a child-side foreign key.
• Query rewriting — Transformation of a database query into a semantically equivalent form intended to improve execution or use available views.
• Relational database — A database that represents data as relations of tuples and attributes governed by keys, constraints, and relational operations.
• Relational transducer — A state-machine model whose input, output, memory and transition state are finite relational database instances transformed by declarative queries.
• Structured entity relationship model — An entity–relationship extension that organizes large data schemas through existence dependencies and structured entity types.
• Third normal form — A relational-database normal form in which every nontrivial functional dependency has a superkey determinant or a prime dependent attribute, eliminating problematic transitive non-key dependencies.