Logical and Physical Network Design

Logical Design and Physical Network Design Logical Design logical design is a conceptual, abstract design. At this stage, the system analysts do not deal with the physical implementation details; they are only concerned with defining the types of information that the organization needs to access through the networks (Hoffer, George, and Valacich, 2002). The process of logical design involves arranging data into a series of logical relationships, which are referred as entities and attributes. An entity represents information about a place, object, events, and concepts.

In relational databases, an entity often maps to a table. An attribute is a component of an entity and helps define the uniqueness of the entity. In relational databases, an attribute maps to a column. One output of the logical design is a set of entities and attributes corresponding to fact tables and dimension tables. Another output of mapping is operational data from the source into subject-oriented information in a target data warehouse schema.

In this approach, the system analysts identify business subjects or fields of data, define relationships between business subjects, and name the attributes for each subject. In other words, a logical design can be considered as a high level map of information systems on which an information system builder maps the physical design of the system. The logical models show what a system is or what a system can do. However, logical design does not specify how the system will be implemented (Whitten and Bentley, 2001).

To a large extent, the logical models provide the conceptual understanding of the information systems. Example An example of logical design for networks will be the map of a network schema that identifies all the computing labs, computers, and network specification that will allow different business offices to access important information. This will also map the geographical distance between different business centers and look for how they could be connected.

Physical Design In a physical design process, the system builders convert the data gathered during the logical design phase into a description of the physical schema, including tables and constraints. Physical design decisions, such as the type of index or partitioning have a large impact on query performance (Sigal, 1998). During the physical design, the system builder translates the expected schemas into actual physical structures.

For example, in a database, the builder maps entities to Tables; relationships to Foreign Keys; attributes to columns; primary unique identifiers to the primary key; and unique identifiers to unique keys. At this point, the system builder also decides whether to use a one-to-one mapping or alter the mapping for optimization of the queries (Manino, 2001). In other words, a physical design shows not only what a system does, but also it shows how the system will physically be implemented.

So physical design is implementation dependent because it reflects the choice of.