Tuesday, April 29, 2008
Between the 1950s and the 1980s, the Bering Land Bridge theory came to be viewed as proven beyond any doubt. Most archaeologists came to believe that the native cultures of the Americas had been isolated from the Old World after the closing of the Bering land route, when they were still in the hunter-gatherer stage and developed without any outside influences for the next 9,000 years until the time of Columbus. It was also believed at the time that trans-oceanic travel only became possible in the 15th century, after key advances in Old World shipbuilding and navigation. This belief is supported by the lack of substantial evidence of Old World influences on American civilizations.
Tuesday, April 22, 2008
Transport engineering (alternatively transportation engineering) is the science of safe and efficient movement of people and goods (transport). It is a sub-discipline of civil engineering.
The planning aspects of transportation engineering relate to urban planning, and involve technical forecasting decisions and political factors. Technical forecasting of passenger travel usually involves an urban transportation planning model, requiring the estimation of trip generation (how many trips for what purpose), trip distribution (destination choice, where is the traveler going), mode choice (what mode is being taken), and route assignment (which streets or routes are being used). More sophisticated forecasting can include other aspects of traveler decisions, including auto ownership, trip chaining (the decision to link individual trips together in a tour) and the choice of residential or business location (known as land use forecasting).
Tuesday, April 15, 2008
Navigational databases are characterized by the fact that objects in the database are found primarily by following references from other objects. Traditionally navigational interfaces are procedural, though one could characterize some modern systems like XPath as being simultaneously navigational and declarative.
Navigational access is traditionally associated with the network model and hierarchical model of database interfaces and have evolved into Set-oriented systems . Navigational techniques use "pointers" and "paths" to navigate among data records (also known as "nodes"). This is in contrast to the relational model (implemented in relational databases), which strives to use "declarative" or logic programming techniques in which you ask the system for what you want instead of how to navigate to it.
Tuesday, April 08, 2008
A prototype typically implements only a small subset of the features of the eventual program, and the implementation may be completely different from that of the eventual product.
The purpose of a prototype is to allow users of the software to evaluate proposals for the design of the eventual product by actually trying them out, rather than having to interpret and evaluate the design based on descriptions.
Friday, April 04, 2008
Traditionally databases have been protected from external connections by firewalls or routers on the network perimeter with the database environment existing on the internal network opposed to being located within a demilitarized zone. Additional network security devices that detect and alert on malicious database protocol traffic include network intrusion detection systems along with host-based intrusion detection systems.