A transitive dependency is an indirect dependency relationship between software components. This kind of dependency is held by virtue of a transitive relation from a component that the software depends on directly.
A transitive dependency is an indirect dependency relationship between software components. This kind of dependency is held by virtue of a transitive relation from a component that the software depends on directly.
In a computer program a direct dependency is functionality from a library, or API, or any software component that is referenced directly by the program itself. A transitive dependency is any dependency induced by a different component, that in turn is directly or indirectly referenced by the program. E.g. a call to a log() function may induce a transitive dependency to a library that manages the I/O of writing a message to a log file.
Dependencies and transitive dependencies can be resolved at different times, depending on how the computer program is assembled and/or executed: e.g. a compiler can have a link phase where the dependencies are resolved. Sometimes the build system even allows management of the transitive dependencies.[ citation needed ]
Similarly, when a computer uses services, a computer program can depend on a service that should be started before to execute the program. A transitive dependency in such case is any other service that the service we depend directly on depends on, e.g. a web browser depends on a Domain Name Resolution service to convert a web URL in an IP address; the DNS will depend on a networking service to access a remote name server. The Linux boot system systemd is based on a set of configurations that declare the dependencies of the modules to be started: at boot time systemd analyzes all the transitive dependencies to decide the execution order of each module to start.
Suppose entities A, B, and C exist such that the following statements hold:
Then the functional dependency A → C is a transitive dependency (which follows the axiom of transitivity).
In database normalization, one of the important features of third normal form is that it excludes certain types of transitive dependencies. E.F. Codd, the inventor of the relational model, introduced the concepts of transitive dependence and third normal form in 1971. [1]
A transitive dependency occurs in the following relation:
| Book | Genre | Author | Author nationality |
|---|---|---|---|
| Twenty Thousand Leagues Under the Seas | Science fiction | Jules Verne | French |
| Journey to the Center of the Earth | Science fiction | Jules Verne | French |
| Leaves of Grass | Poetry | Walt Whitman | American |
| Anna Karenina | Literary fiction | Leo Tolstoy | Russian |
| A Confession | Autobiographical story | Leo Tolstoy | Russian |
The functional dependency {Book} → {Author nationality} emerges; that is, if we know the book, we can know the author's nationality. Furthermore:
Therefore {Book} → {Author nationality} is a transitive dependency.
In computing, a database is an organized collection of data or a type of data store based on the use of a database management system (DBMS), the software that interacts with end users, applications, and the database itself to capture and analyze the data. The DBMS additionally encompasses the core facilities provided to administer the database. The sum total of the database, the DBMS and the associated applications can be referred to as a database system. Often the term "database" is also used loosely to refer to any of the DBMS, the database system or an application associated with the database.
Database normalization is the process of structuring a relational database accordance with a series of so-called normal forms in order to reduce data redundancy and improve data integrity. It was first proposed by British computer scientist Edgar F. Codd as part of his relational model.
In engineering, functional decomposition is the process of resolving a functional relationship into its constituent parts in such a way that the original function can be reconstructed from those parts.
A relational database (RDB) is a database based on the relational model of data, as proposed by E. F. Codd in 1970. A database management system used to maintain relational databases is a relational database management system (RDBMS). Many relational database systems are equipped with the option of using SQL for querying and updating the database.
The relational model (RM) is an approach to managing data using a structure and language consistent with first-order predicate logic, first described in 1969 by English computer scientist Edgar F. Codd, where all data is represented in terms of tuples, grouped into relations. A database organized in terms of the relational model is a relational database.
In database theory, relational algebra is a theory that uses algebraic structures for modeling data and defining queries on it with well founded semantics. The theory was introduced by Edgar F. Codd.
First normal form (1NF) is a property of a relation in a relational database. A relation is in first normal form if and only if no attribute domain has relations as elements. Or more informally, that no table column can have tables as values. Database normalization is the process of representing a database in terms of relations in standard normal forms, where first normal is a minimal requirement. SQL-92 does not support creating or using table-valued columns, which means that using only the "traditional relational database features" most relational databases will be in first normal form by necessity. Database systems which do not require first normal form are often called NoSQL systems. Newer SQL standards like SQL:1999 have started to allow so called non-atomic types, which include composite types. Even newer versions like SQL:2016 allow JSON.
Second normal form (2NF), in database normalization, is a normal form. A relation is in the second normal form if it fulfills the following two requirements:
Third normal form (3NF) is a database schema design approach for relational databases which uses normalizing principles to reduce the duplication of data, avoid data anomalies, ensure referential integrity, and simplify data management. It was defined in 1971 by Edgar F. Codd, an English computer scientist who invented the relational model for database management.
In relational database theory, a functional dependency is the following constraint between two attribute sets in a relation: Given a relation R and attribute sets , X is said to functionally determineY if each X value is associated with precisely one Y value. R is then said to satisfy the functional dependency X → Y. Equivalently, the projection is a function, that is, Y is a function of X. In simple words, if the values for the X attributes are known, then the values for the Y attributes corresponding to x can be determined by looking them up in any tuple of R containing x. Customarily X is called the determinant set and Y the dependent set. A functional dependency FD: X → Y is called trivial if Y is a subset of X.
Database design is the organization of data according to a database model. The designer determines what data must be stored and how the data elements interrelate. With this information, they can begin to fit the data to the database model. A database management system manages the data accordingly.
In software development, code reuse, also called software reuse, is the use of existing software, or software knowledge, to build new software, following the reusability principles.
Dependency, dependence, dependent or depend may refer to:
In object-oriented design, the dependency inversion principle is a specific methodology for loosely coupled software modules. When following this principle, the conventional dependency relationships established from high-level, policy-setting modules to low-level, dependency modules are reversed, thus rendering high-level modules independent of the low-level module implementation details. The principle states:
Boyce–Codd normal form is a normal form used in database normalization. It is a slightly stricter version of the third normal form (3NF). By using BCNF, a database will remove all redundancies based on functional dependencies.
Sixth normal form (6NF) is a normal form used in relational database normalization which extends the relational algebra and generalizes relational operators to support interval data, which can be useful in temporal databases.
Raymond Francis Boyce (1946–1974) was an American computer scientist known for his research in relational databases. He is best known for his work co-developing the SQL database language and the Boyce-Codd normal form.
A database model is a type of data model that determines the logical structure of a database. It fundamentally determines in which manner data can be stored, organized and manipulated. The most popular example of a database model is the relational model, which uses a table-based format.
Incremental computing, also known as incremental computation, is a software feature which, whenever a piece of data changes, attempts to save time by only recomputing those outputs which depend on the changed data. When incremental computing is successful, it can be significantly faster than computing new outputs naively. For example, a spreadsheet software package might use incremental computation in its recalculation features, to update only those cells containing formulas which depend on the changed cells.
The following is provided as an overview of and topical guide to databases: