Monday, April 19, 2010

Arguing the meaning of claim terms is difficult when the spec contains broadening language

Looking back: Last week I started a new series of arguing on appeal about the meaning of a claim term. The first post (here) highlighted a case where the Applicant won a narrower claim construction (and thus avoided the art) because the term of art used in the claim was not broadened by the spec. Today's case illustrates the dangers of using broadening statements in the spec.

Takeaway: Arguing for a narrower claim construction to distinguish over the art is difficult when the spec contains broadening language. Think very carefully about your claim terms when drafting the spec. Broad terms are great because they're more likely to ensnare infringers. But if you use nothing but broad terms, you may have trouble obtaining a patent to assert in the first place.

Ex parte Laxman
(Appeal 2008-281; Appl. No. 10/115,453; Tech. Center 2100)
Decided March 20, 2009

This application involved assigning addresses to network cards. As explained in the specification, each network card is originally assigned an address (a "MAC address") by the manufacturer. The claims in this application were directed to reprogramming the network card to use a MAC address assigned to the slot in which the card is located. Here is representative claim 1:

1. A system for assigning a Media Access Control (MAC) address to
a physical location in a network, comprising:
a slot having a physical location in a network;
a slot MAC address assigned to said slot, said slot for receiving a card having a card MAC address;
means for reprogramming the card MAC address with said slot MAC
address ... 

One issue on appeal was the meaning of "slot." The Examiner "broadly interpret[ed] the term slot to mean or be synonymous to 'hardware location' or 'physical location' of a network device in a network." The Applicant argued that the Examiner's claim construction was incorrect, but did not offer a particular construction. The Board characterized this as arguing for "some narrow but undefined meaning for 'slot'."

The Board looked to the specification to interpret the terms "card" and "slot."
Every hardware device or terminal (hereinafter referred to simply as a "card") connected to the network has its own unique address, commonly known as a Media Access Control address or "MAC" address. 
According to the invention, the MAC address is associated with a particular hardware location (e.g. slot) in the network rather than to the card itself. According to the invention, the MAC address is associated with a particular hardware location (e.g. slot) in the network rather than to the card itself. Thus, the card's MAC address assigned by the manufacturer is effectively ignored. Each slot is assigned its own MAC address. When a card is plugged into the slot for the first time it is initialized and reprogrammed with the MAC address of the slot.
Based on these passages, the Board made a Finding of Fact that a "card" was "a hardware device or terminal," and that a "slot" was "a device or terminal's physical interface at a particular hardware location in a network." Then the Board found that the reference did not use the terms "card" and "slot," but using this claim interpretation, the reference nonetheless taught the limitation at issue:
[The reference] shows components of a network device 100 .. whereby the communication address for each location is associated with the physical site location of the device, rather than the device MAC address.
My two cents: The Applicant attempted to expand claim coverage by using "slot" and "card" broadly in the spec. As a POSITA in this area of technology, I say that a slot really is a physical structure (not just a location), and a card is not exactly the same as a device. But the spec redefined "card" to mean "hardware device," and while the spec didn't actually redefine slot, it never explained how a "slot" differed from a "physical location." Without these statements, I believe the Applicant could have offered evidence as to what the terms at issue meant to a POSITA, and won the argument with that evidence.

Rather than writing the spec so that a term of art has broader coverage, maybe a better approach is to use a different word. Maybe use "card" and "slot" to describe one embodiment, and "device" and "physical location" to describe another embodiment. Even better, link the broad and narrow terms together so that [narrower] "card" is an example of [broader] "device."


  1. If the Examiner is using broadening language from applicant's spec for his "claim construction," doesn't he have to explicitly state the basis for his construction in the rejection? In other words, how do we know that the Examiner is relying on broadening language in the applicants' spec if he does not tell us? I don't think I have ever seen an Examiner cite broadening language in a specification to explain why he is interpreting a claim a certain way.

  2. >doesn't [the Examiner] have to explicitly
    >state the basis for his construction in the

    In short, No. Not *required* to do this in the Rejection or even in the Answer.

    Explicit claim construction is simply not a part of prosecution. It's quite common for the Board to decide a case that really turns on claim construction, without anything in the record from either side about how the term is being interpreted.

    In the Laxman case, the Examiner's Answer did explain how the Examiner was interpreting the terms at issue. And although the Answer didn't actually refer to a piece of the spec, the Answer did say "the term 'slot' as disclosed in the spec is an example of hardware location or physical location." Thus, the Answer definitely gave the Applicant a clue as to what the Examiner was relying on.

    But note that this explanation didn't appear until the Answer - until the case was *already on appeal*. If the Applicant understood the Examiner's interpretation earlier, he may we have chosen to amend rather than appeal.

    My two cents on this issue: Applicants who push the Examiner into stating on the record what his construction is have a better chance of either winning on appeal or realizing the claims should be narrowed.

    However, the best way to push the Examiner into claim construction is to affirmatively argue why the claims don't read on the art, which means you're implicitly performing claim construction yourself. Applicants are often hesitant to actually make distinguishing arguments, much less put an implicit claim construction on the record.