When should AJAX be used?
- Form driven interaction
Use it when there is need to edit the field and submit action.
- Deep hierarchical tree navigation
Multiple levels of hierarchy by navigation.
- Rapid user-user communication
Can be used in message posting application, that creates immediate discussions between people. For example, gmail inbox
- Voting, Yes/No boxes, Ratings submissions.
In places where people can vote/rate an article.
- Filtering and involved data manipulation.
Sorting the fields by date and name, applying a filter.
- Commonly entered text hints / autocompletion.
When entering the same text phrases or predictable text phrases. For example, in gmail for adding the email addresses. Can be used to suggest the text phrases while entering the text in a text box. For example, google autosuggest search.