Okay, SW:TOR has a fairly complicated crafting system, with all sorts of variants to existing plans that you can discover. Instead of going crazy wondering if I've got it all, I found an expert.

Here's the main forum thread explaining it all. As new things are discovered it should get updated:

And here's a graphic that summarizes it all:

It's kind of confusing, but examining the key brings it mainly into focus. It's a great guide to what's going on, but doesn't really explain it all. So here's my summary of it all:

First off, you can purchase plans, create items, 'reverse engineer' them, and get improved plans to create more advanced items.

The grades of items in SW:TOR are:
Low-quality (gray)
Common (white)
Premium (green – WoW 'uncommon')
Prototype (blue – WoW 'rare')
Artifact (purple – Wow 'epic')

Custom (orange – closest to WoW 'legacy')

Non-equippable items (Mods, barrels, stims, etc) are straightforward. You get a plan for a green item, you reverse-engineer it, and get a plan for a blue item that is directly better than it, you reverse engineer that, and get a plan for a purple item that is a direct upgrade to that.

Equippable items (chest, gloves, earpeice, lightsabers, etc…) are more complex. First, there are plans for sale for green, blue and purple (and orange!) items out there. Here's the sequence for a purchased green plan:

Craft green item and reverse engineer it a few times, and you get a plan for a blue item. This will have a higher rating (which controls armor or damage), but none of the bonus stats will change (like they would on an improved Mod). Instead it will get a new bonus stat, and the name of the item will have a prefix which tells you which attribute it is.

There are three possibilities: Critical {item name} (+Crit), Overkill {item name} (+Power), and Redoubt {item name} (+Defense). [The community seems to be adopting the term "Tier 1" to refer to an item with this bonus attribute. I wish they'd picked a different term.]

If you start reverse engineering one of these, you will eventually get the plans for a purple version, with a second bonus stat. [An item with both bonus stats is being referred to as "Tier 2".] There are five different bonus attributes this time around (Accuracy, Alacrity, Presence, Surge, Shield), and they can appear with any of the first three bonus stats, creating fifteen different possibilities for the bonus attributes attached to the new plan (well, fourteen, actually, so far no one has seen a +Defense +Alacrity item).

So if you're wondering, "am I done finding new plans from this item yet?", you're looking for three variations of the base plan, and then four/five variations for each one of those.

If you look at the chart, you can see the same thing happens if your initial purchase is for a blue item plan, but both of the "Tier 1" and "Tier 2" variants will be purples. Reverse engineering purple purchased item plans does not seem to ever generate new item plans. Also, orange items cannot be reverse engineered at all (except for a bug which may be fixed by now).

And finally, a note on suffixes:

It is possible to get a critical success while crafting an equippable item, which will add an Augmentation slot to it. A green item with this will have the suffix "[Exceptional]" added to the item name. Actually, any item that does not have bonus attribute (and accompanying prefix) will have this added to it, including blue and purple items where the plan was leaned directly from a trainer or schematic.

An item that has one bonus attribute will gain the suffix "[Advanced]" if it has a Augmentation slot.

A purple with both bonus attributes gains the suffix "[Superior]" (this is how you can tell these from the purples that have one or no reverse-engineering derived bonus attributes–well that and the prefix name).

A purple with both bonus attributes and the Augmentation slot has the suffix "[Mastercraft]".