Conceptual schema

A Semantic Data Model (SDM, English also conceptual schema) is in the context of data modeling an abstract, formal description and representation of a section of in a particular context (eg, a project) ' perceived world '. For the formulation of semantic data models are different modeling languages ​​, of which the Entity- Relationship model is the best known.

Alternative names: For semantic models are, in practice, characterized by different methods approaches or occupational habits, also used other terms, such as: conceptual (data) model, conceptual database schema, logical model, information structure.

Purpose

  • Most commonly it is developed under the design phase of software development projects - ultimately as a basis for the development / commissioning of a database.
  • Division or enterprise data model: For individual operational areas or the entire enterprise models are created to be used in individual projects as design patterns or reference model / can. Be used from this example, the descriptions specified, the textual descriptions or even the names by which the components in user media ( such as screen or list representations ) should be called / can (eg short / long form ... ).
  • Regardless of the objective ' model for databases ' it is appropriate, unambiguous and clearly display any information contexts, such as roles, rights and involved in organization studies, meta-models in methods manuals, etc.

Methodically work has a semantic data model in data-oriented projects the purpose of an early, not to include all aspects of professionally relevant to the topic 'Data' as precisely as possible and completely and uniformly structured IT technically specific project phases and represent. The following applies:

  • There are few means of representation; these are easy to understand and apply.
  • All important technical aspects relating to identified as relevant data are possible precisely defined.
  • IT technical implementation aspects do not play a role.
  • The model is not a ' technical documentation '. Rather know / understand technically oriented project staff ( after a short briefing on the methodology) everything is shown and described therein.

From the point of view of final early Creating semantic models should lead to high data quality, which in turn influenced the quality of the results of a project ( a data management system) and the quality of processes ( efficiency in project work and in the business processes ). Also support data models through their concept and structure-forming effect of corporate communications - in projects and in business operations, business and technical perspective.

Components

What are the components, a semantic model is, depends on the particular modeling language. See also Entity -Relationship Model.

An example of significant work content in the creation of a semantic model:

  • From the determined as context- relevant ' information items ' units ( ' entities ') are identified and - named " ABOUT the " processed information and / or need to be saved - as ' entity '.
  • It involves determining which relations ( also context sensitive) exist between these entities or may exist.
  • The issues identified are described textually and typically represented graphically, eg by an ER diagram.

Form, content and concepts generated data models can be very different and are, for example, upon the following criteria (each with possible examples ):

  • Modeling methodology used: After UML models created look different than created by ERM.
  • Purpose of modeling: Database redesign requires detailed descriptions as if ( for example in a maintenance project ) that already exist data to be processed.
  • Modeling tools used: graphic form of relations (diamond or line ... ), designation of terms (relationship, relation) are specific to the utilities different.
  • Project / company-specific rules: detail of the modeling (eg relationships ); Default " The data model is created only in the design specification "

Modeling languages

The predominant language for the description of semantic data models in 1976, designed by Peter Chen Entity Relationship model (ER model) or one of its many extensions. In practice often simplified models, such as the Martin notation are used. In addition, the Unified Modeling Language ( UML), in particular for object-oriented modeling, used.

Research

Since 1979 takes place ( from 1985 year), the International Conference on Conceptual Modeling ( ER, formerly International Conference on the Entity Relationship Approach) instead.

Metamodeling
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