The Logical Data Model (LDM) is derived from the Conceptual Data Model (CDM).
The CDM consists of the major entity sets and the relationship sets, and does not state anything about the attributes of the entity sets.
The LDM consists of the Entity Sets, their attributes, the Relationship sets, the cardinality, type of replationship, etc.
The Physical Data Model (PDM) consists of the Entity Sets (Tables), their attributes (columns of tables), the Relationship sets (whose attributes are also mapped to columns of tables), along with the Datatype of the columns, the various integrity constraints, etc.
Erwin calls the conversion / transformation of LDM => PDM as Forward Engineering which further leads to the actual code generation and the conversion of Code => PDM => LDM as Reverse Engineering!
Though the question says specifically about Erwin, the above explanation is independent of the datamodeling tool used for the purpose.
The difference between architecture and topology is logical vs physical. Architecture is about the logical design of something. Topology is about the physical elements required to enable the architectural design. The difference between architecture and topology is logical vs physical. Architecture is about the logical design of something. Topology is about the physical elements required to enable the architectural design. The difference between architecture and topology is logical vs physical. Architecture is about the logical design of something. Topology is about the physical elements required to enable the architectural design.
The logical data independence is the ability to modify a logical schema without making external view or application program change. The physical data independence is the ability to modify a physical schema without making external view or application prrogram change.
- Physical - Logical - View
logical data independence is harder to achieve bcoz all the manipulation is belonging in logical data independence but physical data independence only show the physical view...
A schema separates the physical aspect of data storagefrom the logical aspects of data representation.
difference between physical and logical data flow diagrams.
The difference between architecture and topology is logical vs physical. Architecture is about the logical design of something. Topology is about the physical elements required to enable the architectural design. The difference between architecture and topology is logical vs physical. Architecture is about the logical design of something. Topology is about the physical elements required to enable the architectural design. The difference between architecture and topology is logical vs physical. Architecture is about the logical design of something. Topology is about the physical elements required to enable the architectural design.
While physical tags are also referred to as presentational mark-up, logical tags are useless for appearances. Physical tags are newer versions while logical tags are old and concentrate on content.
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The logical database is how the data is percieved in the tables, the way the data is actually stored on the storage medium is the physical view of the database.
well of course one is logical and the other is physical. but one involves the brain while the other has to do with your body or movement
Physical topology are says how the wire are interconnected, while Logical topology is how the network behaves and interoperates.Sk wasim ul HaqueKharagpur, Madpur
The concept of a logical address space is simply involved the process of mapping the Logical addresses to their Physical Addresses . Logical addresses are generated by the CPU; also referred to as virtual addresses.while Physical Address is the actual address of the data stored on the physical device and mapped by MMU.
A physical network is different from a logical network. Logical networks are defined at the Network layer by the arrangement of the hierarchical addressing scheme. Physical networks represent the interconnection of devices on a common media. Sometimes, a physical network is also referred to as a network segment
The logical view presents data as they would be perceived by end users or business specialists, whereas the physical view shows how data are actually organized and structured on physical storage media.
* Physical file (PF) contains the data and have only one record format. Logical file (LF) is a view of the physical file which does not contain any data may be based on one physical file or more then one physical file. Logical file can have more then one record format. Logical can be non join or join logical file. Performance becomes better if you use the logical file in the program.
A physical address is concrete and never changes. It is set in memory. A logical address is made up of a base pointer and an offset.It keeps programs running parallel and not intertwining.