British Telecommunications PLC v. Prodigy Communications Corp.

DECISION AND ORDER

OPINION AND ORDER FOLLOWING MARKMAN HEARING

On December 13, 2000, British Telecommunications (“BT”) filed suit against *105 Prodigy Communications Corporation (“Prodigy”) for infringement of the Sargent patent, U.S. Patent No. 4,873,662 (issued October 10, 1989) (“the ’662 patent”). Prodigy answered, asserting the defenses of non-infringement and invalidity. BT reduced the number of asserted claims from seven to five on June 22, 2001, and then from five to four on January 18, 2002. BT continues to assert independent claims 3 and 5 and dependent claims 6 and 7 of the ’662 patent against Prodigy.

Infringement analysis involves two phases. The proper construction of the disputed claims is determined in the first phase (the Markman phase) as a matter of law. In the second phase, issues of validity and infringement are determined as a matter of fact. Markman v. Westview Instruments, Inc., 52 F.3d 967, 976 (Fed.Cir.1995).

The parties exchanged proposed constructions for the patent claim terms to be interpreted, and a hearing was conducted by the Court on February 11, 2002, limited to issues of intrinsic evidence. This decision construes the disputed claims.

1. Background of the Sargent Patent

The original Sargent patent application, #814,922, was filed July 12, 1977. The Sargent invention resulted from research conducted at BT (then part of the Post Office, the provider of telephone service in the United Kingdom) on ‘videotex,’ a system developed in the early 1970s to provide users access to text-based information via a telephone network. (BT Br. at 1.)

The prosecution history of the Sargent patent extended over 13 years. It includes several successor patent applications, each with multiple claims. In order to aid recognition of the documents, a brief summary follows.

Application # 178,307 was filed August 15, 1980 as a continuation of the original application, #814,922, and #814,922 was abandoned. # 178,307 (“ the ’307 application”) was modified several times and by January 26, 1983 claims 1-18 had been canceled, leaving claims 19-22 before the patent examiner. On June 8, 1983, # 502,-114 (“the T14 application”) was filed as a divisional application of ’307, directed to the subject matter of the claims originally filed in application ’307 as claims 7-9. Amendments to T14 canceled 7-9 in favor of 12-15, and then claim 14 was canceled, leaving three claims. After the examiner issued a final rejection to both applications, the applicant appealed to the U.S. Patent Board of Appeals, which heard the appeals together on November 7, 1988. The Board reversed and the Sargent patent was granted on October 10, 1989. In the patent as issued, application ’307 claims 19-22 became patent claims 1-4, and application T14 claims 12, 13 and 15 became patent claims 5-7, of #4,873,662 (“the ’662 patent”).

The Sargent patent describes an improved way for multiple users, each located at a remote terminal, to access data stored on a central computer. Communication between the remote terminals and the central computer takes place over a telephone network. (See BT Br. at 2-3.)

The information accessed by the remote terminals is stored on the central computer in the form of blocks, each block identified by an address. The central computer uses the address to retrieve the associated block from storage when a user requests that block of information. Each block stored on the central computer is comprised of two parts: a first portion, which contains textual and graphical data for display (a display page), and a second portion, not intended for display, which contains the complete addresses of other blocks of *106 information that are linked to the current display page. (Id. at 2.)

In the asserted claims, the entire block is transmitted to the remote terminal where the first portion is displayed and the second portion is stored in the local memory of the remote terminal. The display page includes abbreviated addresses of particular blocks of information that can be accessed from the central computer. When the user selects one of the displayed abbreviated addresses, the terminal accesses its memory to determine the corresponding complete address. That complete address is then sent to the central computer to request the next desired block of information. (Id. at 1-3.)

BT’s description of the patent infers that the abbreviated address is the invention, (BT Br. at 2 (last sentence)), but the applicant acknowledged that use of an abbreviated address was recognized in the prior art. (Jan. 24, 1986 Appeal Br., Prodigy Br. Ex. 3 at 2; Jan. 6, 1987 Appeal Br., Prodigy Br. Ex. 14 at 2.) The innovation claimed by the Sargent invention is instead how the blocks of information are stored:

Ordinarily one would be inclined to astutely avoid storage of the address-linkage data on the disk store — where data access times are relatively long and where there necessarily must be competition for data accesses to obtain the display data itself. One typically seeks to reduce required accesses to the disk store.

Nevertheless, applicant teaches:

(a) dividing up the total address linkage data array into sub-portions associated only with the possible next screen selections to be made from a given screen;

(b) co-storing such sub-portions on the main store (e.g., a disk) contiguous with the said “given” screen data; and (c)only temporarily stripping off and storing in RAM those sub-portions which are associated with the screen then actively being accessed and viewed within the system.

(Jan. 24,1986 Appeal Br. at 3; Jan. 5,1987 Appeal Br. at 3.)

The applicant clarified that the “object of this invention ... is to enable the computer to service as many requests for data as possible with a given maximum delay time[.]” (Jan. 24, 1986 Appeal Br. at 10; Jan. 5, 1987 Appeal Br. at 16.) “[Thus the] invention overcomes a very real difficulty in the art of distributed digital information storage, retrieval and display.” (Jan. 24, 1986 Appeal Br. at 11; Jan. 5, 1987 Appeal Br. at 17.)

2. Claim Construction

The technique for construction of a disputed claim was set forth by the Federal Circuit in the Markman decision. 52 F.3d at 976-80. The meaning of a claim should be interpreted in light of the intrinsic evidence, comprised of the claims and the specification of the patent, and the prosecution history. Id. at 979. The intrinsic evidence constitutes the public record of the patent on which the public is entitled to rely. Id. Thus, if the intrinsic evidence is sufficient to resolve the meaning of a disputed term, then it is improper to resort to extrinsic evidence such as expert testimony or treatises. Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1583 (Fed.Cir.1996). Extrinsic evidence only should be relied upon where necessary to resolve an ambiguity in a disputed claim term. CVI/Beta Ventures, Inc. v. Tura, L.P., 112 F.3d 1146, 1153 (Fed.Cir.1997).

To define the scope of the patented invention, the Court must first look at the words of the claims themselves. *107 Vitronics Corp., 90 F.3d at 1582 (citing Bell Communications Research, Inc. v. Vitalink Communications Corp., 55 F.3d 615, 620 (Fed.Cir.1995)). Words in the claim are generally given their ordinary and customary meaning. However, “a pat-entee may choose to be his own lexicographer” and assign special definitions to the words in the claim, as long as those definitions are clearly stated in the patent specification or file history. Id. (citing Hoechst Celanese Corp. v. BP Chems. Ltd., 78 F.3d 1575, 1578 (Fed.Cir.1996)). Therefore, “it is always necessary to review the specification to determine whether the inventor has used any terms in a manner inconsistent with their ordinary meaning. The specification acts as a dictionary when it expressly defines terms used in the claims or when it defines terms by implication.” Id. (citing Markman, 52 F.3d at 979). The Federal Circuit has stated that “claims must be read in view of the specification, of which they are a part.” Id. (citing Markman, 52 F.3d at 979); see also Gart v. Logitech, Inc., 254 F.3d 1334, 1341 (Fed.Cir.2001) (“it is certainly correct that the specification and the prosecution history should be consulted to construe the language of the claims.”). Because the specification must contain a description sufficient to enable those of ordinary skill in the art to make and use the invention, the specification “is the single best guide to the meaning of a disputed claim term.” Id.

The court also may consider the prosecution history of the patent. Id. (citing Markman, at 980; Graham v. John Deere, 383 U.S. 1, 33, 86 S.Ct. 684, 15 L.Ed.2d 545 (1966)). The prosecution history is the complete record of the proceedings before the Patent and Trademark Office. During the course of these proceedings, the applicant may have made express representations regarding the scope of the invention, so the prosecution history is “often of critical significance to determining the meaning of the claims.” Id. (citing Markman, 52 F.3d at 980; Southwall Tech., Inc. v. Cardinal IG Co., 54 F.3d 1570, 1576 (Fed.Cir.1995)). Claim terms may appear to be plain language— as in this case, where most of the words have fairly straightforward definitions, or have passed over time into common usage. However, the prosecution history may demonstrate that the claims do not cover some matters that would otherwise be encompassed in the plain meaning of the words used. Prosecution histories often contain an analysis of the distinctions between the prior art and the applicant’s claims, providing the Court with clues to limitations of the claims. Id. at 1583; Autogiro Co. of America v. United States, 181 Ct.Cl. 55, 384 F.2d 391, 399 (1967). Furthermore, “the prosecution history limits the interpretation of claim terms so as to exclude any interpretation that was disclaimed during prosecution.” Southwall Tech., Inc., 54 F.3d at 1576. Even when the written description would otherwise support a construction, the prosecution history, which is generated after-wards, can relinquish any coverage of that claimed embodiment. Rheox, Inc. v. Entact, 276 F.3d 1319, 1325-27 (Fed.Cir.2002).

Prodigy’s claim construction arguments are primarily based on relinquishments allegedly made during the prosecution of the Sargent patent.

3. Means-Plus-Function

A means-plus-function element under 35 U.S.C. § 112, ¶ 6 is one that refers to a “means” for performing a given function, without specifying in the claim the structure for performing that function. Chiuminatta Concrete Concepts, Inc. v. Cardinal Indus. Inc., 145 F.3d 1303, 1307- *108 08 (Fed.Cir.1998). 1 The applicant is presumed to have used the word ‘means’ in a claim to state a means-plus-function limitation under 35 U.S.C. § 112, ¶ 6. York Prods., Inc. v. Central Tractor Farm & Family Ctr. and Custom Form Mfg., Inc., 99 F.3d 1568, 1574 (Fed.Cir.1996). Means-plus-function elements have additional claim construction rules. 35 U.S.C. § 112, ¶ 6.

In Lockheed Martin Corp. v. Space Systems/Loral, Inc., 249 F.3d 1314, 1324-25 (Fed.Cir.2001), the Federal Circuit set forth a three step process for construing the means-plus-function language. First, the court must identify the claimed function. Id. Once this function is identified, it must be construed using the ordinary principles of claim construction. Id. The function of a ‘means plus function’ claim must be construed to include the limitations contained in the claim language. Id. However, a claimed function may not be improperly narrowed or limited beyond the scope of the claim language. Id. Finally, the court must determine the corresponding structure disclosed in the patent specification for performing the function. Id.; see also Chiuminatta, 145 F.3d at 1307-08; Pennwalt Corp. v. Durand-Wayland, Inc., 833 F.2d 931, 934 (Fed.Cir.1987) (en banc).

Means-plus-functions limitations are construed to cover the corresponding structure described in the specification and any equivalents thereof. 35 U.S.C. § 112, ¶ 6. The structure includes any device that is identical or structurally equivalent to that structure described in the specification. Valmont Indus., Inc. v. Reinke Mfg. Co., 983 F.2d 1039, 1042-44 (Fed.Cir.1993). The structure disclosed in the patent specification must be clearly linked to the claimed function. B. Braun Medical Inc. v. Abbott Labs. and NP Medical, Inc., 124 F.3d 1419, 1424 (Fed.Cir.1997).

4. Means-Plus-Function Analysis

In their briefing, the parties agreed that “central computer means” and “remote terminal means” were not means-plus-function elements, while “keypad means,” “modem means,” “display means,” “local memory means,” “further memory means,” “means coupled to said memory means and to said keypad means,” “means responsive to information stored in the further memory means,” and “logic means” were means-plus-function elements. The Court questioned how this could be so at the Mark-man hearing, and the parties analyzed the terms both ways.

Claim 3 includes:

a central computer means in which plural blocks of information are stored at respectively corresponding locations each of which locations is designated by a predetermined address therein by means of which a block can be selected, each of said blocks comprising a first portion containing information for display and a second portion containing information not for display but including the complete address for each of plural other blocks of information ...

’662 patent, col. 6,11. 15-24.

The use of the word “means” in the claim (particularly as used in the phrase “means for”) raises a presumption that the means-plus^function limitation ap *109 plies. York Prods., Inc., 99 F.3d at 1574; Greenberg v. Ethicon Endo-Surgery, Inc., 91 F.3d 1580, 1584 (Fed.Cir.1996). The means-plus-function presumption may be rebutted, however, if the claim uses the word “means” but specifies no corresponding function for the “means,” or if the claim recites a function but also includes a definite structure to perform entirely the recited function. Sage Prods., Inc. v. Devon Indus., Inc., 126 F.3d 1420, 1427-28 (Fed.Cir.1997); Cole v. Kimberly-Clark Corp., 102 F.3d 524, 531 (Fed.Cir.1996). The Court must determine, as a matter of law, whether to apply the means-plus-function analysis.

Whether there is definite structure recited in the claim language may be evidenced by a lack of alternate structures disclosed in the specification. See Turbocare Division of Demag Delaval Turbomachinery Corp. v. General Electric Co., 264 F.3d 1111, 1120-21 (Fed.Cir.2001). In Turbocare, the Federal Circuit found that a claim including the term “compressed spring means” recited too much structure to be means-plus-fnnction. Id. Nothing in the specification disclosed anything other than a “spring” or a “compressed spring” to perform the function of the “compressed spring means.” Id. at 1121. This result differed from the court's prior decision in Unidynamics Corp. v. Automatic Prods. Int'l, Ltd., 157 F.3d 1311, 1319-22 (Fed.Cir.1988). In that case, the court found that the term “spring means” was written in the means-plus-function format. Id. The Federal Circuit decided that the use of the word “spring” did not preclude the means-plus-function limitation because the specification demonstrated that a “spring” was only one example of a “spring means.” Therefore, the Federal Circuit found that the phrase “spring means” was broader than a “spring” as generally recognized in the mechanical arts. See Turbocare, 264 F.3d at 1120 (distinguishing Unidynamics, 157 F.3d 1311).

Accordingly, I find that the “central computer means” is not a means-plus-function claim. The functions of the central computer are stated in the claim language, however, the claim recites the entire structure necessary to perform the claimed function. Sage, 126 F.3d at 1427-28. That structure is a computer.

The function of the central computer means as asserted in the claims is storing blocks of information. The computer also communicates with the remote terminals. The specification discloses a “computer” for performing these functions. The term “computer” is the only structure described in the specification, and there is no indication that the patentee wished the term “computer means” to be broader than a “computer.” If the term “computer” does not tell us what the computer is, then the claim would be indefinite. See S3 Inc. v. nVIDIA Corp., 259 F.3d 1364, 1367 (Fed.Cir.2001) (quoting In re Donaldson Co., 16 F.3d 1189, 1195 (Fed.Cir.1994) (“if an applicant fails to set forth an adequate disclosure, the applicant has in effect failed to particularly point out and distinctly claim the invention as required ... ”)). If possible, patents should be construed in order to preserve their validity. Modine Mfg. Co. v. United States Int’l Trade Comm’n, 75 F.3d 1545, 1557 (Fed.Cir.1996) (abrogated on other grounds). Therefore, I find that “central computer means” is not a means-plus-function.

The same is true of the phrase “remote terminal means” found in the following claim language:

plural remote terminal means, each including (a) modem means for effecting input/output digital data communications with said central computer means via the telephone lines of a telephone net *110 work, (b) local memory means for locally storing digital data representing at least the first portion of the selected block of information received via said modem means from the central computer and for processing' digital data, (c) display means for visually displaying such a locally stored first portion of a block of information and (d) keypad means connected to communicate data to at least said local memory means for manual entry of keyed digital data; and

further memory means being provided as part of said local memory means at each of said remote terminal means for receiving and storing said second portion of the selected block of information in response to the selection of the block and when its respective first portion is transmitted thereto, said local memory means utilizing keyed digital data of less extent than any one of said complete addresses for. another block of information but nevertheless uniquely indicative of one of the complete addresses contained in said second portion of the block of information which contains the first portion then being displayed for selectively accessing said further memory means and for supplying data to be transmitted by said modem means and indicative of the complete address of the next block of information which is to be retrieved and utilized for display purposes.

’662 patent, col. 6, 11. 25-66. The claim language discloses the structure of the remote terminal means. It describes the component parts of a terminal. The phrase starts “plural remote terminal means, each including ...” —in other words, the remote terminals are comprised of the component parts that follow that language. The function of the remote terminal means, although it is not stated in the usual means-plus-function format, is to store, retrieve and display at a remote site digital information obtained from the computer means. The explanation of these components contains sufficient structure to perform this function. Therefore, the claim language overcomes the means-plus-function presumption.

In Turbocare, the Federal Circuit found that “radial positioning means” in the following claim language was not a means-plus-function:

a radial positioning means comprising a compressed spring means biased against said ring segments to forcibly cause said segments to move to said large clearance position, while working fluid which is freely admitted to the annular space between said casing and said ring segments toward said small clearance position, whereby at low speed and small turbine loads the spring forces will predominate, while at high flows and high working fluid pressure the pressure forces will predominate.

264 F.3d at 1119. The structures for performing the function of positioning the ring segments were the compressed spring means and the working fluid. Id. Similarly, in the case at hand, I find that the component parts listed in the claim language describing the remote terminal means state its structure. Unlike in Tur-bocare, I have decided that some of these component parts are means-plus-function terms. However, I do not find that this distinction makes the meaning of the remote terminal means a means-plus-function where radial positioning means was not. The structure of the component parts is present — it is just found in a different part of the patent, in the specification, rather than in the claim language. Hence, I find that the phrase “remote terminal means” is not a means-plus-function.

For the same reason, I have also concluded that “modem means” is not *111 means-plus-function terms. There is no structure disclosed in the specification for this claim term other than a “modem.”

I do agree with the parties, however, that display means, keypad means, local memory means, further memory means, means coupled to said memory means and to said keypad means, means responsive to information stored in the further memory means, and logic means are all means-plus-function terms.

CLAIM 3 2

A digital information storage, retrieval and display system comprising:

a central computer means in which plural blocks of information are stored at respectively corresponding locations each of which locations is designated by a predetermined address therein by means of which a block can be selected, each of said blocks comprising a first portion containing information for display and a second portion containing information not for display but including the complete address for each of plural other blocks of information; plural remote terminal means, each including (a) modem means for effecting input/output digital data communications with said central computer means via the telephone lines of a telephone network, (b) local memory means for locally storing digital data representing at least the first portion of the selected block of information received via said modem means from the central computer and for processing digital data, (c) display means for visually displaying such a locally stored first portion of a block of information and (d) keypad means connected to communicate data to at least said local memory means for manual entry of keyed digital data; and

further memory means being provided as part of said local memory means at each of said remote terminal means for receiving and storing said second portion of the selected block of information in response to the selection of the block and when its respective first portion is transmitted thereto, said local memory means utilizing keyed digital data of less extent than any one of said complete addresses for another block of information but nevertheless uniquely indicative of one of the complete addresses contained in said second portion of the block of information which contains the first portion then being displayed for selectively accessing said further memory means and for supplying data to be transmitted by said modem means and indicative of the complete address of the next block of information which is to be retrieved and utilized for display purposes.

’662 patent, col. 6,11. 13-56.

A. Central Computer Means

A computer is a device that receives, processes and presents data. In this patent, the computer is a single device, in one location. It is referred to as “central” because it is connected to numerous physically separate stations called, “remote terminals,” by the telephone lines of a telephone network. So there is one computer, connected to many remote terminals. The central computer means in this patent thus serves as the hub of a digital information storage, retrieval and display sys *112 tem — and all of the remote terminals connect to it.

The central computer stores information. The central computer contains a “main store.” In the context of this patent, the main store is a mass information storage or memory device. An example of a main store is a magnetic disk, which is a rotating circular plate having a magnetizable surface on which information may be stored as a pattern of polarized spots on concentric recording tracks. Now, a magnetic disk is not the only thing that qualifies as a main store — that term also includes such things as a Cartridge Disc (which is a type of disk storage device consisting of a single disk encased in a compact container which can be inserted in and removed from the disk drive unit), a Magnetic Tape 9 track, and a paper tape recorder. But the main memory device does not include something called RAM — random access memory. RAM is a type of memory that is volatile, meaning that it loses its contents when the power is turned off. RAM cannot be used as the main store in the context of this patent.

The central computer contains an information database, which is “centralized” in the sense that all of the remote users can access it by accessing the central computer. This data is stored as something the inventor called “blocks of information.”

The central computer means communicates “via the telephone lines of a telephone network” with “plural remote terminal means.” The central computer means is the device “in which plural blocks of information are stored at respectively corresponding locations.” ’662 patent, col. 6,1. 15. The central computer means retrieves and sends at least a portion of the “block of information” associated with the requested “complete address” to the remote terminal from which the request originated. Id., 11. 26-28, 53-54.

1. The “central computer means” is a central computer in one location

Throughout the specification, the “central computer means” is referred to as a computer, defined as “a device that receives, processes, and presents data.” Dictionary of Scientific and Technical Terms 342 (Sybil P. Parker ed., McGraw Hill 3d ed.1984). 3 The word “central” modifies “computer” to describe the relationship between the device where the “blocks of information” are stored, and the “remote terminals” from which an operator may access the information. The term “central” therefore suggests that the computer is the hub of a “digital information storage, retrieval and display system.” This hub is in one central location, connected with many remote terminals.

BT’s proposed definition (a computer system that stores and transmits blocks of information) ignores the juxtaposition emphasized by the description of a “central computer” connected via the telephone lines of a telephone network to “remote terminals.” (emphasis added). As Prodigy points out, “all the limitations of a claim must be considered meaningful,” Unique Concepts, Inc. v. Brown, 939 F.2d *113 1558, 1562 (Fed.Cir.1991), and no claim language may be interpreted as mere sur-plusage. Texas Instruments, Inc. v. United States Int’l Trade Comm’n, 988 F.2d 1165, 1171 (Fed.Cir.1993). BT’s definition does not make it clear that the computer means is a “central one,” and thus is incomplete. BT responds that the term “central” is conveyed by the claim language that says that the remote terminals are connected “via the telephone lines of a telephone network.” While the remote terminals are indeed connected to the central computer means via the telephone lines, this does not give meaning to the term “central” in the phrase “central computer means.” Prodigy’s definition, which clarifies that the central computer is in one location, does.

According to the specification, “information is derived from a central computer at a remote point and transmitted via the public telephone network to terminal apparatus.” ’662 patent, col. 1, 11. 9-11. This indicates that there is one central computer at one point, or place. Throughout the specification, the “computer” is referred to as a singular device. The embodiments in the detailed description and diagramed by the figures are also consistent with this interpretation. While the inventor carefully describes how the computer and any remote terminal are connected (via telephone lines), the inventor never mentions connections between the parts of the “central computer means.” Therefore, I find that the specification confirms that the central computer is a single device, in one location.

2. The central computer contains a main store

The “central computer means” must have a “store” for storing data. The parties dispute whether the applicant specified a particular kind of store during the patent prosecution.

Several passages from the applicant’s appeal briefs discuss storage on the central computer means. The applicant’s communications with the patent office included references to a “store” (Jan. 26, 1983 Amend., Prodigy Br. Ex. 4, at 6-7), “a multi-address store” (Id. at 7), a “mass storage device” (Jan. 24, 1986 Appeal Br. at 1-2), a “central main ‘store’ or mass memory device such as a magnetic disk,” (Id. at 2), a “main store (e.g. a disk)” (Id. at 3; Jan. 5, 1987 Appeal Br., at 3), and a “main data storage device” (Jan. 24, 1986 Appeal Br. at 9). While the applicant did mention many kinds of “stores” during the course of the patent prosecution, the most compelling citation is located in two of the applicant’s appeal briefs where the applicant stated:

Ordinarily one would be inclined to astutely avoid storage of the address-linking data on the disk store — where data access times are relatively long and where there necessarily must be competition for data accesses to obtain the display data itself. One typically seeks to reduce required accesses to the disk store.

Nevertheless, applicant teaches:

(a) Dividing up the total address linkage data array into sub-portions associated only with the possible next screen selections to be made on a given screen;

(b) co-storing such sub-portions on the main store (e.g. a disk) contiguous with the said “given” screen data; and

(c) only temporarily stripping off and storing in RAM those sub-portions which are associated with the screen and then actively being accessed and viewed within the system.

In this manner, no extra disk access cycles are required (because the relevant co-stored address linkages are *114 fetched at the same time a given “screen” of data is fetched)' — and yet— the majority of the massive address linkage data is, at any given time, actually stored on the mass store (e.g. the disk)! The necessary size of RAM can be maintained within reasonable limits — and yet — the relevant portion of the address linkage array is always readily at hand for substantially immediate access in RAM.

(Jan. 24, 1986 Appeal Br., p. 3; Jan. 5, 1987 Appeal Br., p. 3 (italics added, underlining in original).) This reference is highly significant because it: (1) describes what the invention “teaches;” (2) distinguishes the invention over prior art with respect to the type of storage used; and (3) distinguishes between the “main store” (hard disk storage) and RAM.

BT argues that this citation to the prosecution history merely discusses the advantages of the technology of the Sargent patent, rather than distinguishes prior art. BT further argues that the file wrapper describes a number of different “stores,” and Prodigy improperly attempts to narrow the claim to only one of those descriptions.

However, BT is incorrect. “Teaches” is a term of art in the patent world — what the patent “teaches” is the invention. Therefore, the explanations in this passage relating to the way data is stored in the system are of particular significance. In this passage, the applicant notes that the manner of storing information is the distinction between his invention and prior art.

The parties are particularly concerned about whether this passage disclaims the use of RAM as a “main store.” This quote, found in two of the applicant’s appeal briefs, supports Prodigy’s contention that RAM has been disclaimed. The briefs open by describing the prior art in the world of “data base storage and retrieval system[s].” (Jan. 24, 1986 Appeal Br. at 1; Jan. 5,1987 Appeal Br. at 2.) The applicant acknowledges that the usefulness of “abbreviated keyed-in selection data is recognized in the prior art.” (Jan. 24, 1986 Appeal Br. at 2; Jan. 6,1987 Appeal Br. at 2.) In such systems (i.e., abbreviated keyed-in selection data systems), “Then one might store the necessary full address linkage data in RAM where it is readily accessible for use in translating a user’s keyed-in single digit ... into the full disk-store address of the next desired screen.” (Jan. 24,1986 Appeal Br. at 2; Jan. 5,1987 Appeal Br. at 2.) However, this “scheme” has its disadvantages “as more voluminous and complex data bases are considered.” (Jan. 24, 1986 Appeal Br. at 2; Jan. 5, 1987 Appeal Br. at 2.) These drawbacks, as stated by the applicant, are that more RAM must be used for this function, proper updating may become complicated, and inefficient use of RAM and disk storage may result.

The applicant explains that his invention flies in the face of the conventional wisdom regarding storage of the address linkage data. (Jan. 24, 1986 Appeal Br. at 3; Jan. 5, 1987 Appeal Br. at 2.) The accepted wisdom was to avoid storage on the disk store where data access times are too long. Applicant’s appeal brief argues that his invention instead creates a system where address information