Another key point: Walmart isn't rating, grading, or ranking companies, let alone products. It hasn't established a set of criteria or set a bar for performance. This isn't an eco-labeling scheme. Rather, it is a means for providing transparency about companies, allowing them and others to compare companies to one another, showing how each performs. The information will be one of many factors it will use to assess companies. It may be a tiebreaker, all other factors (price, quality, availability, etc.) being equal.

Walmart doesn't plan to say which companies are "good" and which aren't. Its plan is to put the information out there and hope that transparency foments competition. But that won't ensure that any company will necessarily be "good." If, for example, all of the companies in a given sector are doing poorly, but one is doing a little less poorly, the least-bad one will rise to the top, though it may be far from a "good" company. Once again, this is clever on Walmart's part. While it can honestly say it is rewarding good behavior, it isn't really setting a benchmark.

As for the 15 questions. Well, they're a start. Taken together, they set a fairly middling bar, the kinds of things that some leadership companies have been doing for a decade or more. And because they deal with the company, and not its products, they omit some fairly critical details. Among them: they don't mention toxic materials used in manufacturing or in the products themselves. They don't talk about the energy efficiency of products or their recyclability or other disposition at the end of their useful lives. One need only compare Walmart's Index to Nike's Considered Index, which goes deep into product details, to see how relatively primitive it is. There are equally good examples from several other companies.

Do such shortcomings render the Walmart Sustainability Index as greenwash? No. This is a solid first effort. It's important to note that over the past year, Walmart engaged some 20 universities, a handful of environmental activist groups, associations like Business for Social Responsibility, many of its key suppliers, and a small army of consultants. Patagonia's iconoclastic founder, Yvon Chounaird, has played a role. It's gone through a great deal of thinking and more than a few iterations. (You can download a backgrounder on a slightly earlier iteration of the Index here -- PDF, that contained 16 questions.) This was not some slap-dash effort.

Walmart acknowledges the iterative process. Some of its staff have told me privately, and quite proudly, that this is a "ready-fire-aim" exercise -- that the company wanted to get something out there, however imperfect, and improve it as it got real-world use. That's admirable, albeit risky, but that strategy underscores how the company has been addressing most sustainability issues over the past three years: set a big goal, rally the best minds (and persuade them to do a tremendous amount of work at their own expense), make some choices, put it out there, and refine. Hey, that's pretty much how Google made it big.

Much like Google, this effort will likely head down many innovative pathways. For example, Walmart already is talking with Microsoft about creating an open-source database and tools to make information about companies and products accessible; no doubt, for consumers there will eventually be an app for that.

And Walmart has made it clear that they don't want to own this. They want it to live within some credible entity that will continue to develop and deploy the Index. (The company isn't beyond starting its own nonprofit if it isn't able to find one that suits its needs.) And the company is working to bring in other companies -- Best Buy, Costco, Kroger, and Target have been part of the conversation -- to adopt the Index, too, creating even more purchasing power in the marketplace.

It's definitely a bold move, one that stands to raise the bar on sustainability and transparency, empowering both retailers and consumers to leverage their buying power to affect change. It stands to spur innovation in products and processes. And it appears to be around for the long haul. Walmart has gone well beyond talking the talk here. It's changing the game. How quickly and dramatically the game really changes will be something we'll all be watching, very closely.