Creating Globally Unique Identifiers (GUIDs)
When storing data, either in a database or other storage medium, it is usual to assign an identifying value or key against each item held. There are many ways in which to generate such a key. In an accounting system, the ID for each customer may be entered by the user or generated from other data using a standard that is easy to remember. In this case, the software will perform a validation check to ensure no duplication. In other systems a sequential series of numbers may be used to ensure that the keys remain unique.
These methods, and many others, are useful when all users have access to the data at all times. However, many applications are now becoming disconnected with mobile users taking copies of the data on their notebooks or PDAs. When these users add new information to their local copy of the data they have no database connectivity and therefore no way of knowing which IDs have already been allocated.