The following are the methods GDRI may use to determine works by a particular developer.
Thanks to a program developed especially for GDRI, we can now do code comparisons. This program can look at two different files (in this case, ROMs) and find what data is shared between the two. From there, we can search for this shared data/code in other ROMs.
Sometimes, this is not particularly helpful if there is a lot of generic code involved or there are drastically different programming teams. Other times, this can be a powerful tool (especially if it can be backed up by other evidence).
The aforementioned program is not available for download, as it is not in a distributable state.
GDRI scours the Internet, ROMs, and other sources to find game credits. We might even play through an entire game to get them. When we've gathered enough of them from various games, we can compare them and see what is shared between them.
As alluded to before, credits can be found in the ROMs. Usually, these are the same credits that can be seen by finishing the game. This is not to be confused with ROM text (described below), which is typically not meant to be seen by the general public.
You never know what you will find when you open up a ROM (which is as easy as opening it in Notepad). One might find the name of the developer, names of staffers, or other "secret" text strings not otherwise accessible by playing the game.
Company websites are great resources for information, especially if the company is open about the games it worked on in the past (thus eliminating a lot of legwork for us).
Failing that, a great resource is SIT Developer Table, a Japanese site that was the inspiration for this site. There, you'll find works lists for a multitude of developers. If we're interested enough in a developer listed, we might be inspired to do some of our own research.
Sometimes, information can be culled from message boards and discussion forums such as 2ch, the large Japanese Internet forum.
On rare occasion, GDRI is able to make contact with former staffers who are willing to help and share info with us. We just wish it would happen more often.
If you are a former staffer with one of the developers featured on GDRI and want to help us, please contact us at smsgenny [@] vgrebirth.org.