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"An ER model is an abstract way of describing a database. In the case of a relational database, which stores data in tables, some of the data in these tables point to data in other tables - for instance, your entry in the database could point to several entries for each of the phone numbers that are yours. The ER model would say that you are an entity, and each phone number is an entity, and the relationship between you and the phone numbers is 'has a phone number'. Diagrams created to design these entities and relationships are called entity–relationship diagrams or ER diagrams.
Using the three schema approach to software engineering, there are three levels of ER models that may be developed. ...
Conceptual data model ... is the highest level ER model in that it contains the least granular detail but establishes the overall scope of what is to be included within the model set.
Logical ER model ... contains more detail than the conceptual ER model. In addition to master data entities, operational and transactional data entities are now defined.
The physical ER model is normally developed to be instantiated as a database. Therefore, each physical ER model must contain enough detail to produce a database and each physical ER model is technology dependent since each database management system is somewhat different.
Physical model ... is normally forward engineered to instantiate the structural metadata into a database management system as relational database objects such as database tables, database indexes such as unique key indexes, and database constraints such as a foreign key constraint or a commonality constraint." [Entity–relationship model. Wikipedia]
This crow's foot entity-relationship diagram (ERD) example "Educational data base" was created using the ConceptDraw PRO diagramming and vector drawing software extended with the Entity-Relationship Diagram (ERD) solution from the Software Development area of ConceptDraw Solution Park.
ERD
ERD, entity,
Used Solutions

entity-relationship diagram, ER-diagram, database ERD Entity-Relationship Diagram (ERD)

entity-relationship diagram, ER-diagram, database ERD
Entity-Relationship Diagram (ERD) solution extends ConceptDraw DIAGRAM software with templates, samples and libraries of vector stencils from drawing the ER-diagrams by Chen's and crow’s foot notations.

entity-relationship diagram, ER-diagram, database ERD Entity-Relationship Diagram (ERD)

entity-relationship diagram, ER-diagram, database ERD
An Entity-Relationship Diagram (ERD) is a visual presentation of entities and relationships. That type of diagrams is often used in the semi-structured or unstructured data in databases and information systems. At first glance ERD is similar to a flowch

ConceptDraw Solution Park ConceptDraw Solution Park

ConceptDraw Solution Park
ConceptDraw Solution Park collects graphic extensions, examples and learning materials

interactive voice response system, IVR Interactive Voice Response Diagrams

interactive voice response system, IVR
Interactive Voice Response Diagrams solution extends ConceptDraw DIAGRAM software with samples, templates and libraries of ready-to-use vector stencils that help create Interactive Voice Response (IVR) diagrams illustrating in details a work of interactive voice response system, the IVR system’s logical and physical structure, Voice-over-Internet Protocol (VoIP) diagrams, and Action VoIP diagrams with representing voice actions on them, to visualize how the computers interact with callers through voice recognition and dual-tone multi-frequency signaling (DTMF) keypad inputs.

ERD, entity-relationship diagram, ER-diagram, Chen Notation Chen Notation

ERD, entity-relationship diagram, ER-diagram, Chen Notation
The Chen Notation solution extends ConceptDraw DIAGRAM software with rich collection of ERD samples and selection of special Chen's notation icons for effective database design, data modeling, and visual representation of relationships between the entities on the ER diagrams designed with Chen notation.

ConceptDraw DIAGRAM Compatibility with MS Visio

The powerful diagramming and business graphics tools are now not exception, but the norm for today’s business, which develop in incredibly quick temp. But with the abundance of powerful business diagramming applications it is important to provide their compatibility for effective exchange the information between the colleagues and other people who maybe use different software in their work. During many years Microsoft Visio™ was standard file format for the business and now many people need the visual communication software tools that can read the Visio format files and also export to Visio format. The powerful diagramming and vector drawing software ConceptDraw DIAGRAM is ideal from the point of view of compatibility with MS Visio. Any ConceptDraw DIAGRAM user who have the colleagues that use MS Visio or any who migrates from Visio to ConceptDraw DIAGRAM , will not have any problems. The VSDX (Visio′s open XML file format) and VDX formatted files can be easily imported and exported by ConceptDraw DIAGRAM , you can see video about this possibility.