Extending your own mxml components

Came across this problem in flex :
Error: Multiple sets of visual children have been specified for this component (base component definition and derived component definition).

Googled and found that almost everyone has this problem

Hope to have it resolved.

In increasing order of protection

1. READ UNCOMMITTED :
- "dirty read"
- shows "phantom rows", i.e. rows from even the uncommitted transactions are returned.
- if someone tries to modify a phantom row, he will be locked till that row is committed.

2. READ COMMITTED :
- "phantom rows are not shown"

3. REPEATABLE READ :
- All SELECT statements within a transaction see consistent results.
- even if someone else updates/inserts a row in between.
- "consistent read"
- default isolation level for InnoDB

4. SERIALIZABLE :
- blocks other threads from even modifying the information that has merely been viewed
with a SELECT statement.

Good UI Design

From the same source :

1. Reduce short term memory load for the user

2. If you have to show an error message, save user's face,
not computer's.

So, avoid error messages like :
"Illegal operation"

"Fatal error"

Shneiderman’s 8 Golden Rules of UI design

Well, I am not writing about all of them, just one :-)

Source

Dialog Closure

Action sequences should be designed with a beginning, a middle,
and an end. For example, think about drag and drop:

At the beginning, you press the mouse button and see the object picked up with your cursor.
In the middle, you move the object across the screen towards your target, getting feedback that it’s coming along.

At the end, you release the mouse button, and see the effects of the drop.
The key feature of closure is the feedback you get at the end of the operation.

This assurance that the operation completed provides the user with a sense of accomplishment, some relief, and an opportunity to
clear their working memory of the details of the task in preparation for another.