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A Discussion of the Pinpoint vs. Amazon Case

I'm integrating a number of updates into this page. For those who care, the earlier version may be found here. In general, updates are integrated into this text and significant ones are announced on my blog. So, you may want to check my blog if you're interested in the subject. Also, we have set up a mailing list for discussion of the Pinpoint patents. If you're interested in the list send an email to with the following in the body:
subscribe cfpatents


A lawsuit has been issued against Amazon involving their collaborative filtering (a.k.a. "recommendation engine") technology:my
Pinpoint, a company that says it holds several e-commerce patents, sued on Thursday for allegedly violating its business-method patents. The suit, filed in the United States District Court in Chicago, also named six of Amazon's affiliated retail partners, including Borders Group, Target, Toys "R" Us and CDNow. The lawsuit claims that Amazon violated Pinpoint's personalization technology patents--a service popularized by Amazon that allows e-commerce retailers to recommend related products or newer items to shoppers based on their purchase history at the site. []
The present article will discuss those patents, including relevant prior art from the 1980's, some of which originated with the present writer.

The patents being used against Amazon in the lawsuit are 5,754,939, 5,758,257, 5,835,087, and 6,088,722. (That information is not available a news article I have seen to date, but the docket at the Federal Court in Chicago is available through a paid service.) Pinpoint lists their patent collection here.

Click on these links for my notes on specific patents: 5,754,939, 5,758,257, 6,088,722, and 5,835,087.


The earliest of the Pinpoint patents used in this lawsuit was filed on November 29, 1994 and the rest are continuations-in-part derived ultimately from that one. Further details can be obtained by by purchasing "file wrappers" of the prosecution history of the patents.

Amazon has been doing collaborative filtering for a number of years. In fact I had a few conversations with Jeff Bezos about it around 1995 because I thought Amazon might be interested in licensing my own CF technology, but not much later they made a deal with Net Perceptions to supply CF. If anyone has any dates on when specific recommendation-related features were added to the Amazon site, and/or the sources of those features, please let me know. I will be collecting information on the case and posting updates here. My impression is that Amazon is now building its own CF technology in-house. Update: One of the people commenting on this piece on Slashdot is Patrick Tuft, who apparently is responsible for Amazon's "customers who shopped for this item also shopped for ..." technology.

In order to be useful against Amazon in U.S. court of law, the patentees must have an earliest provable date of invention earlier than Amazon's, or earlier than that of whoever may have licensed the technology to Amazon.

The concept of "earliest provable date of invention" is a bit complicated. In the U.S., it isn't the date on which the application was filed. It goes back, under ideal circumstances, to the date the invention was conceived of. But several things have to line up properly. After concieving of the idea, the inventor must have been diligent in "reducing the invention to practice." This term refers either to "actual reduction to practice," which means building and testing the invention, or "constructive reduction to practice" which takes the form of simply filing a patent application.

Under some circumstances is possible to keep an invention secret for years after an actual reduction to practice and before filing a patent application, and still keep the date of conception as the date of the invention, as long as the patent is applied for within one year of the invention becoming public.

Given all the above, it may be impossible to determine from publicly available documents, including the file wrapper, what actual date of invention Pinpoint will claim. That may only by determined in court, when the parties involved in a lawsuit put all their cards on the table in order to make their cases.

However, there is some prior art that is very highly likely to come before any date of invention they will be able to claim. First of all, there is my own 212-ROMANCE project from the mid-1980's. That project used techniques that seem fundamentally the same as the basic principles used in the Pinpoint patents. For instance consider claim 1 of the '939 patent

  1. A method for providing a user with access to selected ones of a
     plurality of target objects and sets of target object characteristics that
     are accessible via an electronic storage media, where said users are
     connected via user terminals and data communication connections to a
     target server system which accesses said electronic storage media, said
     method comprising the steps of:
       automatically generating at least one user target profile interest summary
         for a user at a user terminal, each of said user target profile interest
         summary being indicative of ones of said target objects and sets of target
         object characteristics accessed by said user; and
       storing said at least one user target profile interest summary in a memory.
212-ROMANCE had "a method for providing a user with access to selected ones of a plurality of target objects and sets of target object characteristics" namely, recorded personals ads together with certain characteristics of them that we used for recommendation purposes. These were "accessible via an electronic storage media, where said users [were] connected via user terminals [touch-tone telephones] and data communication connections [phone lines] to a target server system [an IBM AT] which access said electronic storage media [the AT's hard drive]". 212-ROMANCE further fulfilled the tasks of "automatically generating at least one user target profile interest summary for a user at a user terminal, each of said target profile interest summary being indicative of ones of said target objects and sets of target object characteristics accessed by said user." Then it fulfilled the task of "storing at least one user target profile interest summary in a memory" prior to using that information to determine which recorded personals ads were most likely to appeal to a particular user.

There could conceivably be some quibbling about whether a touch-tone telephone is a user terminal, but no reasonable court would say that pressing the keys of a computer keyboard is a non-obvious leap over pressing the keys of a touch-tone keypad. Moreover, the '939 patent's specification explicitly makes the connection to "telephone transmission by means of text-to-speech system" so that should end any debate about whether a phone may be used as a terminal or whether a phone line is a "data communication connection" in the sense of the claim.

Since I have been involved in the collaborative filtering field since that time, and have been aware that people might try to get broad patents that could potentially preclude me from doing my work, I have kept the relevant source code around ever since as proof of my date of invention. On a bookshelf in an adjoining room from where I am typing this, I have ancient paper printouts and 8-inch CP/M floppies in a manila folder containing that code.  They date from 1986. (I have the files on more durable storage media as well.)

From a legal point of view, it may be of interest that the hardcopies were printed by a colleague using laser printers he had access to and I did not have access to (they were a rare commodity at the time), and were automatically dated by the software running those printers, and my colleague would be able to attest to the integrity of the process that included the automatically printed dates.

This prior art may have already proven useful. John Hey filed patent applications in 1987 and 1989 that basically did the same thing as described above but using different mathematical calculations for determining which users "have common interests." These patents, 4,870,579 and 4,996,642, were subsequently purchased by a company called LikeMinds, Inc. The CTO of LikeMinds posted a message on the Collaborative Filtering Mailing List in 1997 which mentioned LikeMinds' supposed "broad patent" in the field of collaborative filtering. Some perceived this as a veiled threat to eventually sue infringers. (It wouldn't do them much good to have purchased, rather than merely licensed, the patents if they had no ambition to ever use it offensively).

So I mentioned my prior art in a reply on the same list, and a fairly lengthy private email exchange ensued between me and the CTO in which he grilled me for details about 212-ROMANCE, and I had the distinct impression he was trying to find nontrival ways to differentiate the Hey patents from 212-ROMANCE. I further had the impression that he felt that he had failed in that effort. Eventually, the email exchange fizzled out, and I never again saw any public mention of those patents.

With respect to the Pinpoint case, the Hey patents are yet another source of prior art; almost certainly the 1994 original patent application behind the stream of continuations was not based on prior art dating back to before 1987 or even 1989.

Also, the Hey patent could be easier prior art to make use of in court than the 212-ROMANCE service, at least for the claims it applies to, because no one can possibly argue that the filing date wasn't the one on the patent. In contrast, someone might argue that someone doctored the file creation dates on my disks, or argue that that feature wasn't in the live 212-ROMANCE at the time it was in the software (admittedly an improbable argument), etc. The latter is relevant because it doesn't matter what software someone had in his computer at a given date if it wasn't publicly used. It's the public use that makes it prior art. (Actually, the CTO mentioned above pointed out that he found in his own research that there's yet another complication -- if it was publicly used, but the technology was a trade secret, that may not count -- the case law isn't fully resolved on the issue. 212-ROMANCE's collaborative filtering wasn't a trade secret, but this is another fuzzy area.)

One fact that I find highly interesting is that the Pinpoint patents don't list the Hey patents as references. This leads me to the conjecture that the patent examiner didn't find them in his prior art search. If that is the case, the broad aspects of the Pinpoint claims may fall apart as soon as Hey's patents are mentioned in court.

Now, I am not saying that these items of prior art would completely invalidate the Pinpoint patents. But that's not necessary in any case. The inventors associated with these patents have a right to patent whatever unique (and unobvious) ideas they have come up with. And they have plenty of technology described in those hundreds of pages; some of it is, no doubt, unique. But based on what I've seen of the patents so far, and based on my knowledge of CF technology in general, it does not seem likely in the light of the prior art that these patents would be defensibly broad enough to include Amazon's recommendations technology. That is, when awareness of the prior art causes the legal system to cut out the broader claims, the claims that are left may not be enough to be a problem for Amazon. I am basing that tentative judgement on the visible aspects of Amazon's technology, which could be accomplished any number of ways under the covers.

I should mention a major caveat with respect to the above discussion. At present we do not know exactly what infringement Pinpoint is claiming against Amazon. That makes it impossible to make any conclusive statements. And even once that information is out, there is always a random element to the legal system that makes it impossible to know how things will turn out.

The larger fear, of course, is that Pinpoint will go on to sue other companies in the CF space. Luckily, Amazon has been sued first, and has deep enough pockets to defend itself quite effectively. Hopefully, the Amazon team will be very aggressive and seek to have the Pinpoint patents overturned as being overly broad.

However, there is a danger we should be aware of. Pinpoint may have the following strategy in mind: Amazon can afford to pay a relatively small license fee without breaking into a sweat, so maybe it will just do so rather than fight. The financial details, of course, would not be made public. Then, the precedent of having appeared to be able to force a settlement out of Amazon would give Pinpoint a psychological edge when they subsequently go after smaller practicioners in the CF field, who do not have Amazon's resources to defend themselves.

From a purely business sense, Amazon would the following reason not to go along with the strategy above: if it settles in this case there may be hundreds of other companies and individuals "waiting in line" to sue (as one lawyer who emailed me regarding this article put it). Alternatively Amazon could go a step further and simply purchase Pinpoint and its patent portfolio. I don't need to descibe the danger of a company with Amazon's resources having such patents in its back pocket. Even if the prior art mentioned above would be a powerful weapon in combating lawsuits based on those patents, small companies may simply not have the financial resources to avoid simply being overwhelmed by Amazon's legal resources.

Update: someone on Slashdot mentioned Ringo. The problem with Ringo as prior art is that Upendra Shardanand's paper, like the earliest Pinpoint patent, is also from late 1994, and as discussed above, the filing date is not the same as the invention date. The invention date will be earlier, and that is what counts in U.S. patent law. So, at this point the question of whether Ringo can serve as prior art is unknowable.

Full disclosure: I have a couple of patents of my own in the CF space. However, these patents are for highly specific mathematical techniques and are of no interest to anyone using different mathematical techniques, of which many are freely available. Update: there have been some comments of Slashdot about these patents. One person read the Abstract and thought it looked like one of those ridiculously broad mindless patents the PTO keeps awarding. I admit that that the Abstract does look exactly like that -- I had other things I needed to do and let the lawyer put in some meaningless gobbledegook because it had no legal relevance, and I didn't care and had no reason to think the patents would ever be examined by anyone without a strong interest in the very specific underlying mathematics. These are EXTREMELY narrow patents when you look at the claims and specifications. They will not effect anybody's work unless they want to use my particular brand of arcane statistical mathematics, which took a very long time and a lot of effort for me to work out. BTW, if you have an interest in looking at them for some reason, only look at the later one, beginning at column 20, line 59. The rest was written while I was still trying to figure stuff out, but stuff starting in column 20 is pretty good IMHO. :) Also, suggestions were made that a) these patents of mine could serve as prior art to Pinpoint (unlikely due to being later than the root of Pinpoint's continuations) and b) that my 1980's prior art should invalidate my own patents (not true because my later patents are very narrow and do involve substantial mathematical improvements over my 1980's work).

Comments on specific Pinpoint patents

So far I've only had a chance to look at one of the patents in a non-trivial way, still withot reading the whole thing. I may never read the whole things, in fact, because I have no interest in these patents beyond figuring out what they are trying to protect.


This ptent has been discussed in the main text above. As far as I can tell, Claim 1 of this patent, filed for in 1995 exactly mimics 212-ROMANCE's collaborative filtering feature from 9 years earlier, and also mimics an embodiment described Hey's 1989 patent (search for the words "remote user" to find the network-related embodiment). In other words, a lawyer should begin preparing a case to put this patent to rest. It's very hard to imagine how Pinpoin could defend it in light of this very solid prior art.

However, in lieu of such action to invalidate the patent, it is hard to see how Amazon would not infringe on the broadest claims such as Claim 1. The named inventors have described the basic functionality of a network-based recommendation engine in this patent. But the patent was filed for a number of years after it had been first used publicly and a number of years after at least one other person had received patents describing the same idea.


This patent concerns using recommendation engine technology to schedule the times people will view particular video programming (or be presented with other objects such as retrieved text).

It appears that, depending on what happens "under the covers" at Amazon, their Gold Box (which appears to be based on scheduling) and home-page recommendations may infringe on this patent.

Also, it appears that John Hey's patents do not necessarily provide prior art, because his patents don't involve scheduling.

However, 212-ROMANCE involved sequencing the recorded audio ads so that users would hear them in a particular temporal order. Indeed the scheduling aspect was the main motivator for the collaborative filtering in the product.

A voice-mail based personals ad system had obvious advantages over printed ones in newspapers, such as being able to hear the voice of the advertiser and being able to respond immediately by voice mail. But it has disadvantages too. Printed newspaper personals ads can be visually scanned quite quickly. Audio ones have to be listened to and it takes substantial time, even when there is a "skip-forward" feature such as 212-ROMANCE had.

So, I was strongly motivated to find a way to play the ads the user was mostly like to respond to first. The collaborative filtering element in 212-ROMANCE accomplished that.

While the aim of the '257 patent isn't purely to save time but to maximize enjoyment, the resulting solution is essentially the same: use recommendation engine technology to make the items available first that the user is most likely to respond to positively.

So 212-ROMANCE is a source of prior art with respect to the broader claims of this patent. For example, Claim 2 seems to be completely anticipated by 212-ROMANCE with the exception that it mentions video rather than audio content -- a difference that no rational court would consider to be "non-obvious" enough to be patentable over that prior art, particularly since the specification explicitly broadens the notion beyond video: "The present invention is thus designed to help the customer of video and other data services to receive, with minimal effort, the information he or she is most interested in." (Emphasis mine.)


This patent seems to have the intention to refine the '257 patent, which it continues-in-part. But again, it involves the scheduling of content based on a recommendation engine, and, for instance, Claim 1 appears to be totally anticipated by 212-ROMANCE.


This patent focuses on the recommendation engine of the '257 patent, extended so that it automatically creates a hierarchical menu of desirable items. I'm not sure, specifically, what features of Amazon pinpoint has in mind. Neither 212-ROMANCE or John Hey's patents discuss this hierarchical aspect.

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Last update: 1/30/06; 2:48:13 PM.
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