FF and SF Relationships

I finally got around to committing my patch to add Finish to Finish and Start to Finish relationships to Planner. In order to keep the scheduling sane, I ended up forbidding many combinations of relationships:

• FF and SF can't be combined with any other relationship
• FF and SF can't be combined with a 'Start No Earlier Than' constraint
• 'Must Start On' constraint can't be combined with any relationship
• SF can't have a predecessor that starts on the project start date (this would force the task to begin before project start)

Finally, since there was no good way to totally protect the user from ending up with a task that would begin before project start, I added logic in FF and SF scheduling to set the start date to project start if it otherwise would end up starting before project start. This could happen if you have a FF relationship with a task that starts close to the project start date, and a long duration on the successor task.



In this screenshot, task t2 has a FF relationship with t1, and task t3 has a SF relationship with t2.

Tax Time

Well, its our favorite time of the year. Time to file those tax returns, and close to the one remaining reason to boot Windows. I was going to try out the online version of Tax Cut this year from my Fedora system, but the site didn't recognise my system configuration (Firefox running on Linux doesn't compute).

The other thing - probably more important is the idea of those Tax Cut people having all my financial info in their database. Now that's just begging for trouble! I'm sure the company (H&R Block) has a privacy policy and won't explicitly share my info with any telemarketers, but companies employ individuals, and all it takes is one individual with access to the data and a lack of scruples to foul things up for a lot of people.

Maybe I'll go back to pen and paper (yikes!).

Impossible Relationships

As I began looking at adding finish-finish (FF) and start-finish (SF) relationship handling to Planner, I started to think about how to handle combinations of relationships. For instance, you could say that task C is dependent on tasks A and B, and this is fine so long as both are finish-start (FS) relationships.

Things start to get complicated if you try to combine relationship types, though, so I decided to have a look at MS Project to see what it allowed, and how it handled relationships that shouldn't work. Here's the result of my test, which became quite amusing after just a few minutes. See if you can follow the Gantt:



Now, this was MS Project 2000, so I don't know if they've corrected this behavior in more recent versions. Still, there's nothing like seeing this sort of thing in MS to boost your confidence level. Looks like whatever I decide to implement can only be an improvement.