|
Enhanced Entity–relationship Model
The enhanced entity–relationship (EER) model (or extended entity–relationship model) in computer science is a high-level or conceptual data model incorporating extensions to the original entity–relationship (ER) model, used in the design of databases. It was developed to reflect more precisely the properties and constraints that are found in more complex databases, such as in engineering design and manufacturing ( CAD/CAM), telecommunications, complex software systems and geographic information systems (GIS). Mechanics The EER model includes all of the concepts introduced by the ER model. Additionally it includes the concepts of a subclass and superclass (Is-a), along with the concepts of specialization and generalization. Furthermore, it introduces the concept of a union type or category, which is used to represent a collection of objects that is the union of objects of different entity types. EER model also includes EER diagrams that are conceptual models that accurat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conceptual Schema
A conceptual schema is a high-level description of informational needs underlying the design of a database. It typically includes only the main concepts and the main relationships among them. Typically this is a first-cut model, with insufficient detail to build an actual database. This level describes the structure of the whole database for a group of users. The conceptual model is also known as the data model that can be used to describe the conceptual schema when a database system is implemented. It hides the internal details of physical storage and targets on describing entities, datatypes, relationships and constraints. Overview A conceptual schema or conceptual data model is a map of concepts and their relationships used for databases. This describes the semantics of an organization and represents a series of assertions about its nature. Specifically, it describes the things of significance to an organization (''entity classes''), about which it is inclined to collect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Union (computer Science)
In computer science, a union is a value that may have any of several representations or formats within the same position in memory; that consists of a variable that may hold such a data structure. Some programming languages support special data types, called union types, to describe such values and variables. In other words, a union type definition will specify which of a number of permitted primitive types may be stored in its instances, e.g., "float or long integer". In contrast with a record (or structure), which could be defined to contain both a float ''and'' an integer; in a union, there is only one value at any given time. A union can be pictured as a chunk of memory that is used to store variables of different data types. Once a new value is assigned to a field, the existing data is overwritten with the new data. The memory area storing the value has no intrinsic type (other than just bytes or words of memory), but the value can be treated as one of several abstract dat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Structured Type
The SQL:1999 standard introduced a number of object–relational database features into SQL, chiefly among them structured user-defined types, usually called just structured types. These can be defined either in plain SQL with CREATE TYPE but also in Java via SQL/JRT. SQL structured types allow single inheritance. Structured types are supported to varying degrees in Oracle Database, IBM Db2, PostgreSQL and Microsoft SQL Server, although the latter only allows structured types defined in CLR. SQL examples Object structured type In order to define a custom structure type using Oracle Database one could use statements such as these: CREATE TYPE Person_Type AS OBJECT ( person_title VARCHAR2(10), person_first_name VARCHAR2(20), person_last_name VARCHAR2(20), ) NOT FINAL; Such structure type can be then used to create a table that would also hold all columns defined in ''Person_Type'': CREATE TABLE Person_Table OF Person_Type; Custom structure types support inher ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Slowly Changing Dimension
A slowly changing dimension (SCD) in data management and data warehousing is a dimension which contains relatively static data which can change slowly but unpredictably, rather than according to a regular schedule. Some examples of typical slowly changing dimensions are entities as names of geographical locations, customers, or products. Some scenarios can cause referential integrity problems. For example, a database may contain a fact table that stores sales records. This fact table would be linked to dimensions by means of foreign keys. One of these dimensions may contain data about the company's salespeople: e.g., the regional offices in which they work. However, the salespeople are sometimes transferred from one regional office to another. For historical sales reporting purposes it may be necessary to keep a record of the fact that a particular sales person had been assigned to a particular regional office at an earlier date, whereas that sales person is now assigned to a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Object–relational Database
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. In addition, just as with pure relational systems, it supports extension of the data model with custom data types and methods. An object–relational database can be said to provide a middle ground between relational databases and object-oriented databases. In object–relational databases, the approach is essentially that of relational databases: the data resides in the database and is manipulated collectively with queries in a query language; at the other extreme are OODBMSes in which the database is essentially a persistent object store for software written in an object-oriented programming language, with a programming API for storing and retrieving objects, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PowerDesigner
SAP PowerDesigner (or PowerDesigner) is a collaborative enterprise modelling tool produced by Sybase, currently owned by SAP. It can run either under Microsoft Windows as a native application or in an Eclipse environment through a plugin. It supports model-driven architecture software design, and stores models using a variety of file extensions, such as .bpm, .cdm and .pdm. The internal file structure can be either XML or a compressed binary file format. It can also store models in a database repository. The PowerDesigner data modeling tool's market share in 2002 was 39%. It's priced from $3,000 to $7,500 USD per developer seat. Features PowerDesigner includes support for: *Business Process Modeling (''ProcessAnalyst'') supporting BPMN * Code generation (Java, C#, VB .NET, Hibernate, EJB3, NHibernate, JSF, WinForm (.NET and .NET CF), PowerBuilder, ...) *Data modeling (works with most major RDBMS systems) *Data Warehouse Modeling (''WarehouseArchitect'') *Eclipse plugin * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Skipper (computer Software)
Skipper is a visualization tool and code/schema generator for PHP ORM frameworks like Doctrine2, Doctrine, Propel, and CakePHP, which are used to create database abstraction layer. Skipper is developed by Czech company Inventic, s.r.o. based in Brno, and was known as ORM Designer prior to rebranding in 2014. Overview * Generates visual model from the schema definition files * Repetitive import/export of schema definitions in supported formats (XML, YML, PHP annotations) * Schema definition files are automatically generated from the visual model * Visual representation uses ER diagram extended by concepts of inheritance and many-to-many * Supports customization using .xml configuration files and JavaScript * Does not support direct connections to the database * Crude and simplistic visual representation and menus Architecture Skipper was built on the Qt framework. Import/export of the schema definitions uses XSL transformations powered by LibXslt library. Imported source f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MySQL Workbench
MySQL Workbench is a visual database design tool that integrates SQL development, administration, database design, creation and maintenance into a single integrated development environment for the MySQL database system. It is the successor to DBDesigner 4 from fabFORCE.net, and replaces the previous package of software, MySQL GUI Tools Bundle. History fabFORCE.net DBDesigner4 DBDesigner4 is an open source visual database design and querying tool for the MySQL database released under the GPL. It was written in 2002/2003 by the Austrian programmer Michael G. Zinner for his fabFORCE.net platform using Delphi 7 / Kylix 3. While being a physical-modeling only tool DBDesigner4 offers a comprehensive feature set including reverse engineering of MySQL databases, model-to-database synchronization, model poster printing, basic version control of schema models and a SQL query builder. It is available for MS Windows, Mac OS X and Linux. In late 2003, Zinner was approached by represe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Entity–relationship Model
An entity–relationship model (or ER model) describes interrelated things of interest in a specific domain of knowledge. A basic ER model is composed of entity types (which classify the things of interest) and specifies relationships that can exist between entities (instances of those entity types). In software engineering, an ER model is commonly formed to represent things a business needs to remember in order to perform business processes. Consequently, the ER model becomes an abstract data model, that defines a data or information structure which can be implemented in a database, typically a relational database. Entity–relationship modeling was developed for database and design by Peter Chen and published in a 1976 paper, with variants of the idea existing previously, but today it is commonly used for teaching students the basics of data base structure. Some ER models show super and subtype entities connected by generalization-specialization relationships, and an ER mode ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Attribute (computing)
In computing, an attribute is a specification that defines a property of an object, element, or file. It may also refer to or set the specific value for a given instance of such. For clarity, attributes should more correctly be considered metadata. An attribute is frequently and generally a property of a property. However, in actual usage, the term attribute can and is often treated as equivalent to a property depending on the technology being discussed. An attribute of an object usually consists of a name and a value; of an element, a type or class name; of a file, a name and extension. * Each named attribute has an associated set of rules called operations: one doesn't sum characters or manipulate and process an integer array as an image object—one doesn't process text as type floating point (decimal numbers). * It follows that an object definition can be extended by imposing data typing: a representation format, a default value, and legal operations (rules) and rest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Entity
An entity is something that exists as itself, as a subject or as an object, actually or potentially, concretely or abstractly, physically or not. It need not be of material existence. In particular, abstractions and legal fictions are usually regarded as entities. In general, there is also no presumption that an entity is animate, or present. The term is broad in scope and may refer to animals; natural features such as mountains; inanimate objects such as tables; numbers or sets as symbols written on a paper; human contrivances such as laws, corporations and academic disciplines; or supernatural beings such as gods and spirits. The adjectival form is ''entitative''. Etymology The word ''entity'' is derived from the Latin ''entitas'', which in turn derives from the Latin ''ens'' meaning "being" or "existing" (compare English ''essence''). ''Entity'' may hence literally be taken to mean "thing which exists". In philosophy Ontology is the study of concepts of existence, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Generalization
A generalization is a form of abstraction whereby common properties of specific instances are formulated as general concepts or claims. Generalizations posit the existence of a domain or set of elements, as well as one or more common characteristics shared by those elements (thus creating a conceptual model). As such, they are the essential basis of all valid deductive inferences (particularly in logic, mathematics and science), where the process of verification is necessary to determine whether a generalization holds true for any given situation. Generalization can also be used to refer to the process of identifying the parts of a whole, as belonging to the whole. The parts, which might be unrelated when left on their own, may be brought together as a group, hence belonging to the whole by establishing a common relation between them. However, the parts cannot be generalized into a whole—until a common relation is established among ''all'' parts. This does not mean that th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
