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Logical data modeling is the exercise to document and define the relationships between data elements. Typically, it involves
# identifying entities (e.g., "customers", "orders") from the business environment # identifying how specific instances of each entity are differentiated from other instances, the logical key (e.g., "customer_id", "order_number")
# grouping together other attributes that describe the entity (e.g., "customer_address", "ship_to_address") AND which can also be uniquely determined based on the entity's key # finally, documenting the business rules (relationships) between the entities (e.g., "a customer may place one or more orders", "each order must be placed by exactly one customer") Note that logical data modeling does not consider any physical representation of how the data will be stored and it doesn't attempt to anticipate or correct any performance issues that may arise during implementation.
Tasks such as these occur during the physical data modeling phase. At this point decisions will have to be made about data storage (Oracle relational DB, VSAM files, JMS message stores, etc.). Considerations for how the data needs to be accessed, combined ("joined") and the performance characteristics of the intended deployment environment will be documented.
Taking the purely logical entities, attributes and relationships, the physical modeler makes (and documents the reasons for!!!) altering the logical model. One-to-many relationships may be "denormalized" into the "one side" of the relationship, forming a repeating group (e.g., collapsing "a customer may have multiple phone numbers" into just a "customer" entity with attributes of "home_phone", "work_phone", "mobile_phone", "fax_phone").
Decisions about where to place the data (same database? different databases on different servers?) as well as partitioning, archival, purging plans have to be done within the constraints of the business requirements.
Oddly enough, logical data modeling is more of a science and physical modeling is more of an art in that two business analysts can discuss the logical model and resolve most differences of opinion logically (so to speak) by providing real-world examples that would negate a particular representation. Physical database design is not so precise, however. The modeler must know (or anticipate) a number of things about future uses of the data and about the characteristics of the particular database management system, programming language(s), communication channels, etc. Many assumptions go into the creation of a physical model. How well that model will eventually perform depends, in large part, in the quality of those assumptions.
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What is a logical database?
A logical database is the structure of data. It is the different pieces of information and the relationships between them.
Explain the Difference between business system option and technical system option?
Business system are the logical system which raise on technical system and these are created in SLD. Technical system are physical system which has system technical information like system server name, host name etc. Business services are used for B2B scenario and these are not created in SLD. These are used when we have not third party system information.
What is organization centered career planning?
Career planning that focuses on jobs and on identifying careers paths that provide for the logical progression of people between jobs in an organization.
What kind of training is required for working in software project management?
There is not any one specific training that is required for working as a software project manager. However in depth knowledge of applications development, logical and physical database design and networking are needed.
List six major steps that you would take in setting up a database for a particular?
1. Requirement Analysis 2. Conceptual Data Base Design 3. Logical Data Base Design 4. Schema Refinement 5. Physical Data Base Design 6. Security Design
Difference between physical and logical DFD?
difference between physical and logical data flow diagrams.
What is difference between physical data flow diagram and logical data flow diagram?
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What are the difference between logical and physical tag?
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.
What is the difference between physical and logical topology?
Physical topology are says how the wire are interconnected, while Logical topology is how the network behaves and interoperates.Sk wasim ul HaqueKharagpur, Madpur
What is the difference between network architecture and network topology?
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.
What is the difference between virtual logical and physical address spaces?
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.
What is the difference between a logical view and a physical view of data?
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.
What is difference between logical file and physical file?
* 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.
What Difference between logical versus physical address storage?
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.
Which type of the data model is being used presently?
There are three levels of data modeling. They are conceptual, logical, and physical."Conceptual" means a definition of the problem, "logical" means a design of a solution to the problem, and "physical" means the solution of the problem.
Differentiate logical and physical database?
After all business requirements have been gathered for a proposed database, they must be modeled. Models are created to visually represent the proposed database so that business requirements can easily be associated with database objects to ensure that all requirements have been completely and accurately gathered. Different types of diagrams are typically produced to illustrate the business processes, rules, entities, and organizational units that have been identified. These diagrams often include entity relationship diagrams, process flow diagrams, and server model diagrams. An entity relationship diagram (ERD) represents the entities, or groups of information, and their relationships maintained for a business. Process flow diagrams represent business processes and the flow of data between different processes and entities that have been defined. Server model diagrams represent a detailed picture of the database as being transformed from the business model into a relational database with tables, columns, and constraints. Basically, data modeling serves as a link between business needs and system requirements. Two types of data modeling are as follows: * Logical modeling * Physical modeling If you are going to be working with databases, then it is important to understand the difference between logical and physical modeling, and how they relate to one another. Logical and physical modeling are described in more detail in the following subsections. Logical modeling deals with gathering business requirements and converting those requirements into a model. The logical model revolves around the needs of the business, not the database, although the needs of the business are used to establish the needs of the database. Logical modeling involves gathering information about business processes, business entities (categories of data), and organizational units. After this information is gathered, diagrams and reports are produced including entity relationship diagrams, business process diagrams, and eventually process flow diagrams. The diagrams produced should show the processes and data that exists, as well as the relationships between business processes and data. Logical modeling should accurately render a visual representation of the activities and data relevant to a particular business. The diagrams and documentation generated during logical modeling is used to determine whether the requirements of the business have been completely gathered. Management, developers, and end users alike review these diagrams and documentation to determine if more work is required before physical modeling commences. Typical deliverables of logical modeling include * Entity relationship diagrams An Entity Relationship Diagram is also referred to as an analysis ERD. The point of the initial ERD is to provide the development team with a picture of the different categories of data for the business, as well as how these categories of data are related to one another. * Business process diagrams The process model illustrates all the parent and child processes that are performed by individuals within a company. The process model gives the development team an idea of how data moves within the organization. Because process models illustrate the activities of individuals in the company, the process model can be used to determine how a database application interface is design. * User feedback documentation Physical modeling involves the actual design of a database according to the requirements that were established during logical modeling. Logical modeling mainly involves gathering the requirements of the business, with the latter part of logical modeling directed toward the goals and requirements of the database. Physical modeling deals with the conversion of the logical, or business model, into a relational database model. When physical modeling occurs, objects are being defined at the schema level. A schema is a group of related objects in a database. A database design effort is normally associated with one schema. During physical modeling, objects such as tables and columns are created based on entities and attributes that were defined during logical modeling. Constraints are also defined, including primary keys, foreign keys, other unique keys, and check constraints. Views can be created from database tables to summarize data or to simply provide the user with another perspective of certain data. Other objects such as indexes and snapshots can also be defined during physical modeling. Physical modeling is when all the pieces come together to complete the process of defining a database for a business. Physical modeling is database software specific, meaning that the objects defined during physical modeling can vary depending on the relational database software being used. For example, most relational database systems have variations with the way data types are represented and the way data is stored, although basic data types are conceptually the same among different implementations. Additionally, some database systems have objects that are not available in other database systems. Typical deliverables of physical modeling include the following: * Server model diagrams The server model diagram shows tables, columns, and relationships within a database. * User feedback documentation Database design documentation Understanding the difference between logical and physical modeling will help you build better organized and more effective database systems.
What is the difference between biological and biopotential amplifiers?
difference is logical and potential
