What Is Data Scheme?
A schema or data schema (in the plural “schemata” or “schema”) is in computer science a formal description of the structure of data. Special schemes have meanings associated with databases. Here is a scheme of a linguistically articulated, universal aspect of an object (file / program) which transmits information.
Typically, the schema itself is defined in a formal language, so that data can be automatically checked to see whether they conform to the schema. A well known example of such a description language is XML Schema for XML.
Aspects of data scheme
Schemes may in complexity from simple lists to complex attribute ontologies rich. In principle, regimens contain definitions of relations as a tuple of attributes, which can be assigned in many cases such as data types. Depending on the nature of the scheme of relations and also relations between different conditions and additional rules are possible.
Data types (such as number, string, date formats, etc.) as part of a schema are themselves described by rules which are assumed, however, usually given. In the context of object-oriented modeling of complex data types are composed of simple data types, where one speaks instead of data types and objects.
Schemata in database systems
Schemes play an important role in connection with databases. This is called often by the database schema. The schema defines the process which data can be stored in a database in any form and there are the relationships between the data. Especially with relational databases, sets the pattern down the tables and their attributes and to ensure the consistency of integrity constraints.
These include in particular the definition of value ranges of individual attributes and foreign key relationships and existence and uniqueness conditions. Database systems store the patterns of managing databases in a particular area, from the Data Dictionary.
The ANSI-SPARC architecture, including three-tier architecture, describes the basic structure of a relational database system, with three schemes are used:
- 1st – The external schemas, which describe formally how the database the user (group represents s) and applications (application-customized view).
- 2nd – The conceptual or conceptual scheme, in which it is based semantic data model of the factual logic described formally (technical term).
- 3rd – The internal schema, which is formal, decides how and where the data is stored in the database.
Design of schemas
The design of schemas (data modeling) depends strongly on the approach. In principle, it can be distinguished among other things, the entity-relationship model and object-oriented modeling.
To data, which are based on different schemes to convert or merge, is also a transformation and integration of their schedules necessary. This is necessary in practice, especially during the data migration and information integration.
The heterogeneity, both the structure and the semantics of concern, can overcome the structural differences more easily. The transition from structural to semantic difference is not always clear.
Typical structural differences relate to the order of attributes, name conflicts, which are different names for the same attributes (synonyms) or the same names for different attributes (homonyms), flat structures (SQL) as opposed to hierarchical structures (XML), the degree of normalization and different data formats with the same expression.
Semantic heterogeneity exists when the individual concepts do not correspond to the different regimens. Instead, the subject of a inclusion or overlap, up to a certain extent, must be tolerated.
A chessboard between structural and schematic heterogeneity are the details differing data types (units, accuracy, etc.). A schema is a formal variant of a concept system, which is usually a part of reality (or an idea of it) is to be modeled.
Study: From Wikipedia, the free encyclopedia. The text is available under the Creative Commons.
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