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Topic: Relational model

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In the News (Wed 24 Apr 19)

  Emu and the Relational Model   (Site not responding. Last check: 2007-10-09)
Importantly, the relational model has well understood mathematical properties, if Emu annotation structures are readily mapped onto relational tables, then the formal results of relational database theory might also be applied to reasoning about Emu databases and the implementation of database search tools.
Relational database systems have been used to store speech database annotations [3] but the structures used are generally specific to one project or method of annotation.
Since an Emu annotation is a set of segments and optional relations between these segments, it is possible to recast an Emu database as a set of tables in the relational model.
emu.sourceforge.net /eurospeech99.shtml   (2543 words)

 Relational model Information - converting spreadsheets to a relational database model
The relational model was invented by Dr. Ted Codd as a general model of data, and subsequently maintained and developed by Chris Date and Hugh Darwen among others.
Usually in the relational model a database schema is said to consist of a set of relation names, the headers that are associated with these names and the constraints that should hold for every instance of the database schema.
A relation schema (H, C) consists of a header H and a predicate C(R) that is defined for all relations R with header H.
www.inanot.com /Ina-Electronics_Topics_Rc_-_Rz-/Relational_model.html   (1872 words)

 Relational Model
Besides the structure of data, the relational model also defines the means for data manipulation (relational algebra and relational calculus) and the means for specifying and enforcing data integrity (integrity constraints).
It is not the case; relation is a well-established mathematical concept and the relational model builds upon mathematical properties of relations.
Relational operators are deterministic and functional, in that the same inputs always result in the same outputs, and they don't change what they operate on.
c2.com /cgi/wiki?RelationalModel   (1750 words)

 A UML Profile for Data Modeling
Similarly, on a physical data model for a relational database it is assumed that any class box without a stereotype is a table.
Data attributes on conceptual and logical data models, as well as columns on physical data models, are modeled using the standard attribute notation.
It is optional to model the type of an attribute on a conceptual or logical data model although in practice this is often done.
www.agiledata.org /essays/umlDataModelingProfile.html   (3718 words)

 Relational model - Wikipedia, the free encyclopedia
The relational model was invented by E.F. (Ted) Codd as a general model of data, and subsequently maintained and developed by Chris Date and Hugh Darwen among others.
The relational model depends on the law of excluded middle under which anything that is not true is false and anything that is not false is true; it also requires every tuple in a relation body to have a value for every attribute of that relation.
Such a relation closely corresponds to what is usually called the extension of a predicate in first-order logic except that here we identify the places in the predicate with attribute names.
en.wikipedia.org /wiki/Relational_model   (3496 words)

 Wellesley Relational Model Instrument Development   (Site not responding. Last check: 2007-10-09)
In 1991, the Relational Model was first proposed by feminist scholars at Wellesley College's Stone Center as an innovative theoretical paradigm for the assessment of women's psychological development and well-being.
Since its introduction, the Relational Model has inspired a critical discourse on the model's relevance to women's developmental needs and adjustment, as well as the cross-cultural and cross-gender generalizability of the model.
The project is strategically based at the Stone Center to accommodate collaboration between researchers and Relational Model theorists associated with the Jean Baker Miller Training Institute.
www.wcwonline.org /relationalmodel/index.html   (244 words)

 The Relational Data Model   (Site not responding. Last check: 2007-10-09)
In the relational model, data is represented as a two-dimensional table called a relation.
The contents of a relation are rarely static thus the addition or deletion of a row must be efficient.
A relational database is a finite set of relation schemas (called a database schema) and a corresponding set of relation instances (called a database instance).
cs.wwc.edu /~aabyan/415/RelationalModel.html   (454 words)

 Data Modeling: Overview of the Relational Model
That is, the form in which a relational database presents data to the user and the programmer.
A basic understanding of the relational model is necessary to effectively use relational database software such as Oracle, Microsoft SQL Server, or even personal database systems such as Access or Fox, which are based on the relational model.
This section discusses the basic concepts—data structures, relationships, and data integrity—that are the basis of the relational model.
www.utexas.edu /its/windows/database/datamodeling/rm/overview.html   (259 words)

 Amazon.ca: Temporal Data & the Relational Model: Books: C.J. Date,Hugh Darwen,Nikos Lorentzos   (Site not responding. Last check: 2007-10-09)
The relational model once again provides a foundation which leads to confidence even though the full temporal datbase picture is not yet in sight.
The overall approach is to develop a model of data which is highly related to an audit trail, which should be viewed distinctly from the concept of a database transaction log.
Unfortunately, in order to implement the model, an interval timestamp is required for every attribute, and historical data must be presented in the Sixth Normal Form, which they introduce as a decomposition of each historical record into a relation for each data attribute, with its associated timestamp.
www.amazon.ca /Temporal-Relational-Model-C-J-Date/dp/1558608559   (1353 words)

 Relational Model: Normalization   (Site not responding. Last check: 2007-10-09)
A relational table is said to be a particular normal form if it satisfied a certain set of constraints.
A column, Y, of the relational table R is said to be functionally dependent upon column X of R if and only if each value of X in R is associated with precisely one value of Y at any given time.
Simply stated, normalization is the process of removing redundant data from relational tables by decomposing (splitting) a relational table into smaller tables by projection.
www.utexas.edu /its/windows/database/datamodeling/rm/rm7.html   (1390 words)

 eXtropia | Tutorials | Introduction to Databases for the Web | Relational Databases
Because he was a mathematician, he naturally built the model on mathematical concepts which he expounded in the famous work called "A Relational Model of Data for Large Shared Databanks".
At the core of the relational model is the concept of a table (also called a relation) in which all data is stored.
This is quite a bit different from the hierarchical and network models in which the user had to have an understanding of how the data were structured within the database in order to retrieve, insert, update, or delete records from the database.
www.extropia.com /tutorials/sql/relational_databases.html   (611 words)

 Youth EE - Relational Model of EE
Relational evangelism emphasizes that the incarnation is the ultimate example of God initiating personal, intimate contact with mankind in the context of a relationship.
The major problem with relational evangelism often lies in the lack of ability of the witness to discern when the relationship has been sufficiently developed to effectively share the Gospel.
Hence, we hear the criticism: “relational evangelism is 90% relational and 10% evangelism”.
www.youthee.org /articles/relmodelee.htm   (1290 words)

 DBAzine.com: A Review of Relational Concepts
A relation of degree one is said to be unary, a relation of degree two binary, a relation of degree three ternary, …, and a relation of degree n n-ary.
The predicate corresponding to relation r is the relation predicate for that relation.
Note that this example involves a relational comparison; to be specific, it requires that the body of the relation that is the projection of SP on {S#} be a subset of the body of the relation that is the projection of S on {S#}.
www.dbazine.com /ofinterest/oi-articles/date1   (10994 words)

 [No title]   (Site not responding. Last check: 2007-10-09)
The relational view (or model) of data described in Section 1 appears to be superior in several respects to the graph or network model [3, 4] presently in vogue for non-inferential systems.
The network model, on the other hand, has spawned a number of confusions, not the least of which is mistaking the derivation of connections for the derivation of relations (see remarks in Section 2 on the "connection trap").
Finally, the relational view permits a clearer evaluation of the scope and logical limitations of present formatted data systems, and also the relative merits (from a logical standpoint) of competing representations of data within a single system.
www.acm.org /classics/nov95/s1p1.html   (347 words)

 PostgreSQL: Documentation: Manuals: PostgreSQL 7.1: Operations in the Relational Data Model
Relational Algebra which is an algebraic notation, where queries are expressed by applying specialized operators to the relations.
Relational Calculus which is a logical notation, where queries are expressed by formulating some logical restrictions that the tuples in the answer must satisfy.
It is sometimes said that languages based on the relational calculus are "higher level" or "more declarative" than languages based on relational algebra because the algebra (partially) specifies the order of operations while the calculus leaves it to a compiler or interpreter to determine the most efficient order of evaluation.
www.postgresql.org /docs/7.1/static/relmodel-oper.html   (742 words)

 ON THE RELATIONAL MODEL AND PHYSICAL IMPLEMENTATIONS   (Site not responding. Last check: 2007-10-09)
“A common criticism of the relational model is that it is not practical because it “does not address” physical implementation, while in reality this is a huge practical advantage.
The relational model is nothing but logic applied to databases, and logic has nothing to say about physical implementation.
Moreover, as I explained in my article, this is a major relational advantage, because it leaves implementers free to do whatever they darn please at the physical level to maximize performance, as long as they do not expose it to users in applications.
www.dbdebunk.com /page/page/622171.htm   (288 words)

 Objects integrated into the Relational Model
For this to fit with the relational model we will enhance Domains to be able to take their "values" from a pool of existing objects or to be able to create a new object when asked.
Because the relational model has a complete approach for changing the state of the database we should not add a second one.
Attributes are read from relational expressions and state modifying behavior must alter the state of relation variables in the database.
www.chimu.com /publications/objectRelational/part0005.html   (1188 words)

 3. The Relational Model.
A useful aspect of the relational model is that the data definition may itself is represented in tabular form; data descriptions may be created and examined using extensions to the relational query language.
Given this simple and restricted data structure, it is possible to define some very powerful relational operators which, from the users' point of view, act and#144;in parallel' on all entries in a table simultaneously, although their implementation may require conventional processing.
Takes two relations, one binary and one unary, and builds a relation consisting of all values of one column of the binary relation that match, in the other column, all values in the unary relation.
www.soi.city.ac.uk /~tony/dbms/relational_dm.html   (2149 words)

 Database Models: Hierarcical, Network, Relational, Object-Oriented, Semistructured, Associative and Context.
These record types are the equivalent of tables in the relational model, and with the individual records being the equivalent of rows.
In contrast to a relational DBMS where a complex data structure must be flattened out to fit into tables or joined together from those tables to form the in-memory structure, object DBMSs have no performance overhead to store or retrieve a web or hierarchy of interrelated objects.
Such databases subsume the modelling power of recent extensions of flat relational databases, to nested databases which allow the nesting (or encapsulation) of entities, and to object databases which, in addition, allow cyclic references between objects.
unixspace.com /context/databases.html   (2376 words)

 Course Technology--InfoWeb: Relational Databases
In "Overview of the Relational Model" at www.utexas.edu/cc/dbms/utinfo/relmod/index.html from the University of Texas at Austin's Database Management Services, you can find a simple explanation of the relational model and reasons why you might need to understand it.
The Web-based document discusses the relational data structure, including notation, properties of relational tables, relational keys, and data integrity; manipulation of relational data; and normalization.
The first article in the series is "The Birth of the Relational Model - Thirty Years of Relational." You can find all of the articles in the series listed in the sidebar at the right side of the page.
www.cciw.com /content/relationaldb.html   (442 words)

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