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3  Phased implementation. Different 

modules of the system are introduced 

sequentially

Good compromise between methods 

1 and 2

Difficult to achieve technically due to 

interdependencies between modules

4  Pilot system. Trial implementation 

occurs before widespread deployment

Essential for multinational or national 

 roll-  outs

Has to be used in combination with 

the other methods

5  ‘Perpetual beta’

Used by on-demand service 

providers such as the search engines 

to introduce new functionality in 

modules

Errors not identified in testing may 

impact large numbers of users, but 

can be updated to users rapidly

Table 12.2

Advantages and disadvantages of the different methods of implementation

Database creation and data migration

A final aspect of changeover that should be mentioned, and is often underestimated, is