Issue 17203: Bug in ForkedToken::withdraw when the baseToken is a ForkedToken (fuml-rtf)
Source: Model Driven Solutions (Mr. Ed Seidewitz, ed-s(at)modeldriven.com)
Nature: Uncategorized Issue
Severity: 
Summary: Specification: Semantics of a Foundational Subset for Executable UML Models (fUML) (formal/2011-02-01)

Subclause: 8.5.2.2.10 ForkedToken

 

ForkedToken::withdraw calls isWithdrawn() to check if its baseToken is withdrawn, and then withdraws it if that is false. The intent is that baseToken.withdraw() only be called once. However, if the baseToken is itself a ForkedToken, then calling withdraw() may only decrement the remainingOffersCount of that token, with isWithdrawn() only becoming true if this count goes to zero. This means that additional calls to withdraw() on the first ForkedToken may result in additional calls to withdraw() on its baseToken, prematurely reducing the remainingOffersCount for the baseToken.

 

This can be avoided by adding an explicit baseTokenIsWithdrawn flag to ForkedToken that is set when the baseToken is withdrawn and then checked to avoid further withdraws.


Resolution: agreed
Revised Text: In Subclause 8.5.2.2.10, and in Figure 8.27, add the attribute 
•	baseTokenIsWithdrawn: Boolean.
Indicates whether withdraw() has been called on the base token.
In the withdraw operation, replace:

if (!this.baseToken.isWithdrawn()) {
	this.baseToken.withdraw();
}
with:

if (!this.baseTokenIsWithdrawn & !this.baseToken.isWithdrawn()) {
	this.baseToken.withdraw();
		
	// NOTE: This keeps a base token that is a forked token from being
	// withdrawn more than once, since withdrawing a forked token may
	// not actually remove it from its fork node holder.
	this.baseTokenIsWithdrawn = true;
}

Actions taken:
February 28, 2012: received issue
January 7, 2013: closed issue
Discussion: 

End of Annotations:=====

m: Ed Seidewitz <ed-s@modeldriven.com>
To: "issues@omg.org" <issues@omg.org>
Subject: Bug in ForkedToken::withdraw when the baseToken is a ForkedToken


Specification: Semantics of a Foundational Subset for Executable UML Models (fUML) (formal/2011-02-01)

Subclause: 8.5.2.2.10 ForkedToken

 

ForkedToken::withdraw calls isWithdrawn() to check if its baseToken is withdrawn, and then withdraws it if that is false. The intent is that baseToken.withdraw() only be called once. However, if the baseToken is itself a ForkedToken, then calling withdraw() may only decrement the remainingOffersCount of that token, with isWithdrawn() only becoming true if this count goes to zero. This means that additional calls to withdraw() on the first ForkedToken may result in additional calls to withdraw() on its baseToken, prematurely reducing the remainingOffersCount for the baseToken.

 

This can be avoided by adding an explicit baseTokenIsWithdrawn flag to ForkedToken that is set when the baseToken is withdrawn and then checked to avoid further withdraws.