What is usage of package interface?

Question

Hi Experts:
                Who knows what the usage of package interfce is？ How to use it in development.

Answer 1

Use
From the outside, a package looks like a "black box." To make packages visible from the outside so that they can be used, you define package interfaces. Only those package elements that have been added to an interface can be used by other packages. Packages make their services available to other packages using interfaces.
Prerequisites
You have opened the relevant package in the Package Builder.
Procedure
To create a package interface:
Make sure you are in Change mode.
Choose the Package interfaces tab.
Choose Add.
The system displays the Create package interface dialog box.
Enter a name and short description for the interface.
Choose  to confirm your entries.
Save your entries ().
In the dialog box that appears, assign a transport request.
Result
You have created an interface for the package. Each interface you create is an independent transport object, separate from the package.
You can also add package elements to the interface to make the elements in it visible to other packages.
package inerfaces play a important role in advanced ABAP technogies
such as
ABAP OBJECTS
DYNPRO
for  detailed information packages interfaces
follow thelink
https://www.sdn.sap.com/irj/sdn/go/portal/prtroot/docs/library/uuid/6066fbe8-edc4-2910-9584-a9601649747d
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Edited by: Alvaro Tejada Galindo on Feb 22, 2008 2:39 PM