Potential Direct-Revision-Inconsistency and WWR Interleaving-Inconsistency 79

public class Bird { boolean canFly;

Bird(){

canFly = false;

...

}

public boolean fly(){

return canFly;

}

… }

public class Bird { boolean canFly;

Bird(){

canFly = true;

...

}

public boolean fly(){

return canFly;

}

…

… }

public class Penguin extends Bird {

Penguin(){

} ...

}

Time

Mary

Mary Tom

Figure 6.11: CSWMS effectiveness - Illustrating example for the

C

D2

E1

E2 B

A

D1

Figure 6.12: Example of a potential Direct-Revision-Inconsistency detected by CSWMS.

A: CSW Manager window of admin2. B: The ShowBirdProperty CSW of admin2. C:

admin2 is modifying the Bird class using Eclipse IDE. D1 & D2: Warning for Direct-Revision-Inconsistency appears in CSW Manager and Eclipse IDE of admin2. E1: Con-tents of the changes causing the potential Direct-Revision-Inconsistency are shown in Eclipse IDE of admin2. E2: The F lyM ethod CSW of admin is viewed by admin2 to understand the context of the inconsistency.

A

C B

D1

D2

E2

E1

Figure 6.13: Example of a potential WWR Interleaving-Inconsistency detected by CSWMS. A: CSW Manager window of admin. B: The F lyM ethod CSW of admin.

C: admin is coding the P enguin class using Eclipse IDE. D1 & D2: Warning for WWR Interleaving-Inconsistency appears inCSW Managerand Eclipse IDE ofadmin. E1: Con-tents of the changes causing the potential WWR Interleaving-Inconsistency are shown in Eclipse IDE of admin. E2: The ShowBirdProperty CSW of admin2 is viewed by admin to understand the context of the inconsistency.

First, Mary, whose username is admin, defines the FlyMethod CSW for implementing the change request that represents the ability to fly of birds. Because she does not have a clear plan for what she will do, she definesFlyMethod with one activity only, theFlyofBird activity, and executes it. She adds the fieldcanF ly to denote the ability to fly of birds. In the constructor of the Bird class, she sets the default value of canF ly tof alse, because she thinks that this helps specify the bird species more conveniently. With flying birds, for example Eagle, one needs to describe more information about this ability such as speed.

Therefore, one can change the value of canF ly to true in the constructor, and override the f ly() method to add more information. With flightless birds, for example Penguin, one can ignore this function. Because she has an appointment with a customer for lunch, she finishes the current activity. To not forget the ongoing work after coming back from lunch, Mary adds to the FlyMethod CSW a new activity, the P enguin&F ly activity, as a successor of the FlyofBird activity, before leaving the office.

Direct-Revision-Inconsistency warning for Tom: While Mary is having lunch with the customer, Tom, whose username is admin2, implements the change request for displaying the common properties of birds. He defines theShowBirdP roperty CSW with one activity, the View Common Properties of Bird activity, first and starts it. When he adds the new methods to theBirdclass, for example theprintBirdProperty() method, he recognizes that the fly() method returns thefalse value, because thecanFly field is set to false in the constructor of Bird. In his opinion, most birds can fly. Therefore, he changes the value of canFly to true. As a result, a warning of Direct-Revision-Inconsistency is shown. If he opens the warning, CSWMS will show him the context of the potential inconsistency which includes the ShowBirdP roperty CSW of his, the F lyM ethod CSW of Mary, and the source codes of the changes causing the potential inconsistency (Fig.

6.12). By examining it, Tom can recognize that his changes may affect Mary’s work.

He can delay his changes after discussing with Mary, or keep his opinion but add more explanations about his work to his CSW to help Mary understand his intention. Assuming that Tom ignores the warning. He finishes his activity before Mary returns to the office.

Direct-Revision-Inconsistency and WWR Interleaving-Inconsistency warn-ings for Mary: Coming back from lunch, Mary continues her work. There is a warning about Indirect-Revision-Inconsistency at the bottom of her CSW Manager. If she inves-tigates the warning, she can realize that the change of Tom affects her work, and she can adjust her implementation plans to make the system work correctly. Assuming that she continues her work without paying attention to the warning. Persisting with her original intention, she starts the P enguin&F ly activity and begins coding the P enguin class. When she is editing its constructor, a warning of WWR Interleaving-Inconsistency appears. If she does not ignore it again, she could understand what is happening by examining the context of the potential inconsistency (Fig. 6.13). She can solve the sit-uation by setting the value of the field canFly to false in the constructor of Penguin, or negotiating with Tom to change the value ofcanFly in the constructor ofBird tofalse as her original intention.

6.8 Summary

We have presented the development and implementation of CSWMS that realizes our approach to solve the inconsistency problem in collaborative software development.

CSWMS has the advantage of warning workers as early as possible (potential) in-consistencies to help the workers prevent or solve them before their effects go further.

CSWMS can detect exactly Intra|Inter-Direct-Conflicts and the potential cases of the re-maining patterns of the patterns of inconsistency. However, in the case of the semantic inconsistencies, CSWMS cannot ensure the detected potential inconsistencies will lead to real inconsistencies or not. Since the semantics of the changes are difficult to express in a formal way, the detection of such problems is challenging and requires the intervention of the workers involved. In the case of a false warning, it interrupts the workers from their work and takes time to examine the falsely reported inconsistency. However, by applying the fine-grained analysis, we can reduce the false warnings. Moreover, by supplying the workers with the CSWs of the changes that cause the reported inconsistency, we can help them understand the context of the inconsistency and skip the false alarm quickly and easily. In addition, even if an inconsistency does not happen, the warnings of potential inconsistencies still contribute to increasing the awareness of a worker about the works of his co-workers. This directs the worker to make correct changes and avoid unexpected impacts on the changes of other workers.

Chapter 7

Performance Evaluation and Discussion

In this chapter, we first make a comparison between our work and the related studies toward the inconsistency problem in collaborative software development. We then evalu-ate performance of the inconsistency detection algorithm to examine its scalability. Some discussions about the effectiveness of our research and the challenges in evaluating its effectiveness are also given.