<span>A wiki is this type of site. The users can, anonymously or with a profile, add to or delete content already posted. This gives the community the ability to add to the overall knowledge base on a specific subject. The site tracks changes through IP addresses to make sure that changes are not done maliciously.</span>
The union of two tables is basically the total of the two tables, so "or" questions would be my guess.
<span>Before GUIs became popular, the command line interface (CLI) was the most commonly used.
</span>GUI stands for Graphical User Interface . Like its name says it is a graphical interface <span>that allows interaction with users through graphical icons and visual indicators , rather than through text-based interface.</span><span>
Command line interace (CLI) is text-based interface in which </span>the user <span>issues commands to the program in the form of successive lines of text.</span>
Th e most important external issue when using social media in emergency management is the disaster response. Disseminating information through social media is very effective especially when there are calamities and a disaster respond from both private and public sector is very urgent.
