US 5402527

I'll search for this specific patent number to check current status and any litigation.

Let me check for any litigation or court records involving this patent.

Summary of U.S. Patent No. 5,402,527

Bibliographic data

Source: Google Patents, US5402527A — https://patents.google.com/patent/US5402527/en (fetched 2026‑09‑24).

Abstract

There is provided a printing system for producing prints from a print job written in one of a plurality of page description languages, the print job assuming the form of a print job stream. The printing system includes a plurality of page description language analyzing units for sampling the print job stream, each analyzing unit outputting an information signal which provides information regarding the print job stream. A filter, which receives the information signals, processes the information signals and outputs a filtered signal which indicates the page description language in which the print job is written.

Independent claims in plain language

The patent has two independent claims — claim 1 (system) and claim 10 (method) — with dependent claims 2–9 and 11–15 respectively.

Claim 1 – Printing system
A printing system that prints a job written in one of several page description languages (PDLs), where the job arrives as a data stream. The system has:

• Multiple PDL analyzing units that sample the print job stream, each producing an information signal about the stream; and
• A filter that receives all those signals, processes them, and outputs a filtered signal identifying which PDL the job uses.

Two details distinguish this claim:

• The filter uses a set of rules to arbitrate the information signals conjunctively (i.e., weighing them together rather than in isolation).
• That rule set is dynamically configurable by a printing system user: the filter has a control line, and when the user transmits a control signal across it, the filter changes its rules so that the filter is given enhanced predictive capability.

Claim 10 – Method
A method of determining the PDL of a print job (again, a stream written in one of several PDLs), comprising:

• Communicating the print job stream to a plurality of PDL analyzing units;
• Generating a plurality of information signals from those units, each providing information about the stream;
• Transmitting the signals to a filter; and
• Processing the signals with the filter to produce a filtered signal indicating the PDL.

As in claim 1, the processing step involves arbitrating the information signals conjunctively using a set of rules that is dynamically configurable by a printing system user, where the filter receives a control signal and changes the rule set in response, giving it enhanced predictive capability.

Selected dependent claims worth noting: claim 2 adds a print server that interprets the PDL; claim 4 covers recognition of a representative operator; claims 5–6 cover a certainty factor that varies with an operator-distribution frequency and with the PDL version; claim 7 covers recognition of a characteristic PDL signature; claim 8 covers a binary filter that reports the percentage of binary characters to avoid mis-identifying a job (e.g., avoiding reporting PostScript when the stream is not predominantly binary). Method claims 11–15 mirror these themes (translation, certainty factor, versions, signature, binary-character percentage).

Regarding USPTO / CAFC 2026 docket checks

I searched for this specific number and for litigation/docket activity involving it. Based on those searches:

• No CAFC 2026 docket or pending litigation tied to US 5,402,527 was found. The Xerox-related patent suits surfaced in the results (e.g., Monument Peak Ventures v. Xerox, MASA cases) assert entirely different patents (the '425, '582, '415, '149, '336, '890, '573, '966, '090, '375, '795, '255 patents) and are not directed to the '527 patent.
• The patent has been expired since April 23, 2013, which is consistent with the absence of current enforcement activity.

Uncertainty note: I could not confirm a live entry in the USPTO Patent Center / Patent Trial and Appeal Board or an official CAFC docket for this number directly from the search results; my bibliographic and status information above is drawn from the Google Patents record and corroborating listings (e.g., uspto.report/patent/grant/5402527, the EPO family listing showing US 5402527 A as a family member of EP 0621530). I did not find any authoritative source indicating 2026 court activity for this patent. Also note that search results reference related family/later Xerox filings (e.g., EP 1006430, EP 1006431, EP 1006432) describing a "PDL guesser" — these are separate, later applications, not this patent, and should not be conflated.

I'll research litigation involving US patent 5402527 across patent litigation databases.

Initial results show no litigation. Let me check dedicated patent litigation databases.

No litigation matches yet. Let me check additional specialized litigation databases.

Litigation Search: US Patent 5,402,527

Bottom Line

No litigation involving US Patent 5,402,527 was found in the sources I was able to search.

I ran multiple targeted searches across general web indexes that surface patent litigation content — including queries aimed at Unified Patents' litigation portal, Docket Alarm, Justia Patents, RPX Insight, CourtListener, and CAFC opinion databases — using the exact patent number in both raw ("5402527") and comma-formatted ("5,402,527") forms, plus variants combining the number with the patent title, the assignee (Xerox), and the inventors (Bigby, O'Brien, Brindle). None returned a district court, ITC, PTAB, or Federal Circuit proceeding naming this patent as an asserted or challenged patent.

Important Caveat on Methodology

I want to be transparent rather than overstate confidence:

• Direct database access was limited. I could not open the Unified Patents case list (portal.unifiedpatents.com/litigation/caselist), Docket Alarm's case page for this patent, or PACER directly. My conclusion rests on indexed/web-searchable coverage of those databases, not on an authoritative docket query. A PACER or Docket Alarm search by patent number would be the definitive verification step.
• Several of my later queries hit a tool step limit and returned no usable content, so coverage was not exhaustive.

Negative-Indication Analysis (Why "No Litigation" Is Plausible)

Independent evidence from the patent record supports the absence of litigation:

1. The patent expired long ago. Google Patents lists an "Anticipated expiration" of 2013-04-23 (20 years from the 1993-04-23 priority/filing date), with legal status "Expired - Lifetime." A patent that lapsed in 2013 is an unlikely target for assertion during the busiest NPE years that followed.

2. The assignee is the original operating company. The patent was assigned to Xerox Corporation at filing and remained with Xerox throughout; the only recorded reassignment events are security interests (Bank One, 2002; JPMorgan Chase, 2003) and a 2022 release of that security interest. There is no record of assignment to a litigation-focused entity (NPE/PAE), which is the typical precursor to assertion campaigns for a patent of this vintage.

3. The "cited by" litigation records belong to unrelated patents. My searches surfaced numerous cases citing a "'527 patent," but on inspection these are different patents and must not be conflated with US 5,402,527:

   • The Western Digital / MediaTek ITC and district court matters (e.g., the Section 337 investigation resolved in the 2005 Federal Register notices) involve a different '527 patent concerning IDE/ATA disk-drive controller circuitry — not a page description language patent.
   • Merck v. Mankind (ANDA litigation) asserts a pharmaceutical '527 patent (listed alongside a '733 patent).
   • Display Solutions Inc. v. Daktronics (1997) construes yet another unrelated '527 patent (a matrix lamp bank display).
   • IP Bridge / Western Digital references to U.S. Patent 8,514,527 are a different number entirely.

   Per your instruction to interpret identifiers literally and not auto-correct, I am treating each of these as distinct from US 5,402,527 and excluding them.

What I Cannot Confirm

I cannot rule out:

• A short-lived or sealed case that never generated a searchable opinion, docket entry, or press mention.
• An ITC Section 337 investigation in the 1990s–2000s, which sometimes lack easily indexed complaint-level detail.
• Class-action or antitrust matters that referenced the patent in passing without asserting it.

These would only be definitively excluded via a direct PACER/Docket Alarm patent-number query, which I was unable to complete.

Recommendation

For an authoritative negative, run a patent-number search directly in:

• PACER (District Court and ITC dockets) — search "5402527" or "5,402,527"
• Docket Alarm — https://www.docketalarm.com (patent case database)
• Unified Patents litigation portal — https://portal.unifiedpatents.com/litigation/caselist
• RPX Insight — https://insight.rpxcorp.com

If any of these surfaces a case, the number to give me is the exact case number and court, and I can then research the parties, filing date, and disposition. Based on everything currently available, however, the best-supported answer is that no litigation involving US 5,402,527 is known.

Sources consulted:

• Google Patents, US5402527A — https://patents.google.com/patent/US5402527/en (legal status, assignment history, citations)
• Justia Patents — https://patents.justia.com/patent/5402527
• Federal Circuit opinion database — https://www.cafc.uscourts.gov/opinions-orders
• CourtListener / RECAP search results
• govinfo.gov Federal Register volumes (2005 ITC determinations — confirmed unrelated patents)

I'll verify the structured block's default against live sources before concluding.

Let me run additional targeted checks to rule out proceedings that might be indexed under related entities or sibling patents.

Let me check for post-grant review/reexam activity and any litigation asserting this patent, since that context shapes the defensive posture.

PTAB Proceedings Report — US 5,402,527

Patent: "Apparatus and method for determining the page description language in which a print job is written"
Patent Owner: Xerox Corp (original assignee, 1993-04-23)
Inventors: Bigby, O'Brien, Brindle · Filed: 1993-04-23 · Granted: 1995-03-28 · Legal status: Expired – Lifetime (anticipated expiration 2013-04-23)

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Proceedings overview

Total AIA trial proceedings on file: 0 — zero active, zero claims invalidated, zero claims sustained, zero settled, zero institution denials. The USPTO Open Data Portal structured block reports no AIA trial proceedings for US 5,402,527, and I could not surface any on live web search either (queries run against PTAB E2E document text, Google Patents' "Cited By" and PTAB sections for the patent, and general web search for "5,402,527" / "5402527" paired with IPR/PGR/CBM terms). The bottom-line defensive posture is therefore "nothing has been canceled, nothing has been sustained, and nothing has been tested" — the patent stands as granted, claims 1–15 untested at the Board. That sounds like bad news for a defendant, but on this particular patent it isn't: the real defensive strength is expiry, not PTAB precedent. An IPR-based defense has no roadmap to copy, so the operative defenses are the § 286 damages bar and the absence of any live infringement window.

Null-result caveat (as instructed): the default is "no PTAB activity on file." One nuance makes the null result unsurprising rather than suspicious — AIA trials only became available on 2012-09-16, and this patent expired 2013-04-23. Any assertion campaign on a 1995-issued printing patent would have played out largely before the IPR regime existed (the only post-issuance review then was ex parte reexamination, and from 1999 inter partes reexamination — neither is an AIA trial). I found no evidence of a reexamination either, but I cannot rule one out from search alone; confirm against USPTO Patent Center's "Reexam" tab for this patent number.

Proceedings

None. No proceeding numbers exist to report, and I will not manufacture any.

For completeness, the statutory doors that were (or were not) open to a challenger:

• IPR — technically available even against an expired patent (the Board can institute on a lapsed patent), and no § 315(b) one-year clock ever started because there is no record of a complaint for infringement being served on anyone. Theoretically still fileable today.
• PGR — unavailable. PGR reaches only patents whose claims have an effective filing date on or after 2013-03-16. The '527's effective filing date is 1993-04-23.
• CBM — never applicable. The '527 claims an apparatus/method for analyzing a data stream to identify a page description language — a technical printing invention, not a "financial product or service" as the CBM statute requires. The CBM program also sunset on 2020-09-16 and no such petition could be filed now in any event.

Verification sources for the null result: Google Patents US5402527A (no PTAB/litigation proceeding table), USPTO PTAB E2E, CourtListener.

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Strategic summary

Claim status. Every claim of the '527 is UNTESTED, not sustained — an important distinction. No claim has been canceled at the Board, and no claim has been upheld at the Board. As issued, the claim set comprises apparatus claims 1–9 (claim 1 = analyzing units plus a rules-based arbitration filter; claim 8 = the binary-filter guard against false-positive PDL identification) and method claims 10–15 (claim 10 = the method counterpart of claim 1; claim 15 = the binary-character-percentage informing step). Dependent claims 5–6 and 12–13 are the "certainty factor" / PDL-version claims; claim 7 covers signature recognition. If a demand letter quotes any of these, there is no FWD to point at saying the claim is dead — the claims are live in form, and the attack has to come from somewhere other than PTAB precedent.

Estoppel landscape. Because no IPR/PGR was ever instituted, § 315(e)(2) estoppel is a non-issue: no petitioner, and no petitioner's privies, are barred from raising anything. Every printed-publication and patent ground is available to a defendant today, and so are the grounds that an IPR cannot reach at all — § 101, § 112 (written description/enablement/indefiniteness), and § 102(b) on-sale or public-use art. That last category may be the richest vein here: the '527's own prosecution history is unusually thin on documentary prior art, and Google Patents' citation table lists only 24 examiner citations, of which a meaningful share are Xerox's own internal UI/network patents (Beard, Pajak, Paradise, etc.) rather than intervening printing-system art.

The denominator that actually matters. The patent expired on 2013-04-23 (20 years from the 1993-04-23 filing; ODP confirms "Expired – Lifetime"). That means: (i) there can be no ongoing or post-2013 infringement; (ii) damages are limited to the six-year lookback under 35 U.S.C. § 286, so the recoverable window runs at most from six years before service of the complaint to the 2013 expiry — meaning a complaint served after roughly mid-2019 recovers nothing at all; and (iii) anyone who was never served within six years of their last allegedly infringing act is now time-barred outright. A demand letter citing this patent today is very likely aimed at a historical (pre-2013) accused product, and the § 286 math is the first thing to run.

Pattern signals. No recurring petitioner, no defensive aggregator (no Unified Patents, RPX, or similar) anywhere in the chain, and no Federal Circuit appeal implicating this patent. Xerox, as patent owner, has been on the losing end of IPRs on other, much newer patents (e.g., US 8,489,599, invalidated in consolidated IPRs brought by Snap/Meta/X and affirmed on appeal; see PTAB E2E and CAFC coverage), but that has no bearing on the '527. What it does signal is posture: Xerox is a large, sophisticated owner that litigates and appeals — it is not a non-practicing entity susceptible to pressure. Note also the family's second-generation members, which are the more assertion-exposed assets if the demand is really about PDL-guessing technology: EP 0621530 B1, JP H0749754A, BR 9401573 B1 (same family), and the 1998 Xerox continuations EP 1006430 / EP 1006431 / EP 1006432 and US 6,525,831 ("Non-format violating PDL guessing technique"). Those have their own, later expiries.

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Recommended next steps

1. Lead with § 286, not IPR. Because the patent expired 2013-04-23, establish (a) the date the demand letter or complaint was served and (b) the date of the last accused act. If service post-dates the last accused act by more than six years, the claim is time-barred and no PTAB filing is needed. There is no FWD to quote for this patent — the disposition you cite is the expiry date itself and the ODP "Expired – Lifetime" status at patents.google.com/patent/US5402527A.

2. Confirm the reexam/reexam-certificate record. My searches surfaced no reexamination of the '527, but this is the one gap in my record. Pull the patent's full file wrapper and the "Reexam" tab on USPTO Patent Center before finalizing any invalidity opinion — a hidden reexam certificate could have canceled or amended claims without appearing in the AIA-trial data.

3. Check whether the assertion is really about a later family member. The '527's PDL-guessing concept was carried forward into Xerox's 1998-era continuations (EP 1006430/6431/6432; US 6,525,831). Those patents are separately expiring and separately failable; if the demand letter's claim charts map to automatic PDL detection rather than the '527's specific "multiple analyzing units + rules-based arbiter" architecture, the asserted patent may not be the '527 at all.

4. If an IPR is still on the table, understand what it buys you. An IPR on an expired patent can still yield a cancelation (useful for a declaratory posture or a collateral estoppel/covenant-not-to-sue outcome), and it faces no § 315(b) time bar here because no prior complaint was served. But with no damages exposure, an IPR is often a poor trade unless a pending or threatened suit makes cancelation independently valuable. There is no statutory trial deadline to track because no trial exists — no institution decision deadline, no oral hearing date, no one-year FWD due date is running.

5. Flag anything I missed. If you have actual knowledge of an unindexed proceeding, a pre-2012 reexamination, or an ITC/district court action on this patent, surface it — the ODP ingest may simply lag. Until then, the accurate statement is: no AIA trial activity on file for US 5,402,527, and the defense should be built on expiry and the § 286 bar rather than on PTAB precedent.

I'll research the assignment record for US 5,402,527 starting with the USPTO Assignment Center and related sources.

Let me pull the assignment records from uspto.report and Google Patents' legal events for this specific patent.

I found Xerox-related security agreement data. Let me pull the specific INPADOC legal events for US 5,402,527 and the assignment records.

Assignment / Ownership Analysis — US 5,402,527

Analyst note on sourcing. I was able to corroborate the parties, dates, and conveyance types for every post-issuance recording from the Google Patents legal-events record embedded in the authoritative patent text, and I corroborated the Xerox portfolio security-agreement reel/frames from a sibling Xerox patent's INPADOC record (US 5,608,023). I was not able to retrieve the actual Assignment Center abstract-of-title page for US 5,402,527 itself, so the patent-specific reel/frame numbers and the correspondents of record are marked as not independently confirmed. I do not fabricate reel/frame numbers or attorney names; gaps are flagged as gaps.

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Inventors

All three executed an "ASSIGNMENT OF ASSIGNORS INTEREST" to Xerox Corporation recorded on the filing date, 1993-04-23, indicating employee-inventor assignments (standard Xerox practice). No inventor is listed on any later conveyance.

Unusual-pattern check: No evidence of any inventor departing Xerox within 12 months of filing, and no evidence that any inventor later appears as an assignor, assignee, or principal in a spinoff/NPE. I cannot confirm departure timing from the sources available — this is a gap, not a negative finding. There is no fire-sale-precursor pattern here.

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Original assignee

Xerox Corporation (Stamford, Connecticut), assignee on the issued patent per the 1993-04-23 assignment.

• Primary line of business: Document technology — xerographic printers/copiers, production printing, and managed print/document services.
• Did they ship a product embodying the claims? Yes. The patent's own specification ties the claimed PDL-determining arrangement to the Xerox DocuTech Network Server and the Xerox Production Print Services System (Media Server + Network Server), and to a DocuTech print engine with a Xerox 4045-type decomposer. Xerox's own later filings in the same family line (EP 1 006 430 / 431 / 432, "page description language guesser" with analyzing units 702-1…702-N and an arbiter 704) explicitly cite EP 0 621 530 (this patent's European counterpart) as prior art and re-implement the claimed architecture in a spooler — strong corroboration of productization. (Note: do not conflate the later EP '430/'431/'432 applications with this patent itself; they are separate, later Xerox filings.)
• Current status: Operating. Xerox Corporation remains a subsidiary of the publicly traded Xerox Holdings Corporation (NASDAQ: XRX). Caveat: I cannot verify 2025–2026 corporate-control developments from the sources available and will not guess; verify against current SEC filings.

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Assignment timeline

Interpretation caveat / flagged contradiction. Google Patents renders the 2002 and 2003 entries as "Assigned to BANK ONE, NA" and "Assigned to JPMORGAN CHASE BANK, AS COLLATERAL AGENT." This wording is misleading — both are collateral security interests (liens), not ownership transfers. Control and beneficial ownership never left Xerox; the banks held only a security interest, which was later released. Treat these as encumbrances on the timeline, not as assignments of title.

• 1993-04-23 (executed) / recorded 1993-04-23 — Reel not retrieved

  • Conveyance: Assignment of assignors' interest
  • Assignor: Bigby, Bruce W.; O'Brien, Mark D.; Brindle, Edward E.
  • Assignee: Xerox Corporation
  • Correspondent: not retrieved (Xerox's own IP/patent department of record; not confirmed from an Assignment Center abstract for this patent)
  • Context: Ordinary employee-inventor assignment to employer on the filing date.

• 2002-06-28 (recorded) — Reel 013153/0001 (reported for the Xerox portfolio batch; confirmed via sibling Xerox patent US 5,608,023 INPADOC; not independently confirmed for the '527)

  • Conveyance: Security Interest (secured financing)
  • Assignor: Xerox Corporation
  • Assignee: Bank One, NA, as Administrative Agent
  • Correspondent: not retrieved (bank's counsel of record)
  • Context: Securitization — collateral grant under a Xerox credit facility; lien only, no ownership change.

• 2003-10-31 (recorded) / effective 2003-06-25 — Reel 015134/0476 (same sourcing caveat as above)

  • Conveyance: Security Agreement
  • Assignor: Xerox Corporation
  • Assignee: JPMorgan Chase Bank, as Collateral Agent (successor collateral agent to the Bank One facility)
  • Correspondent: not retrieved (bank's counsel of record)
  • Context: Internal re-organization of the same secured financing; consolidation of the collateral agent role. Lien only.

• 2022-09-07 (recorded) — Reel not retrieved

  • Conveyance: Release by Secured Party
  • Assignor: JPMorgan Chase Bank, N.A. (as successor-in-interest administrative and collateral agent to JPMorgan Chase Bank)
  • Assignee: Xerox Corporation
  • Correspondent: not retrieved
  • Context: Termination of the secured facility and discharge of the lien — restores clean title in Xerox. (Timing is ~9 years post-expiration and is loan-driven, not patent-driven.)

Other legal events (not assignments): application filed 1993-04-23; patent granted 1995-03-28; anticipated expiration 2013-04-23; status Expired – Lifetime.

If the Assignment Center returns additional records beyond the four above, they were not surfaced by my sources — verify directly.

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Timeline diagram

timeline
    title Ownership of US 5402527
    1993 : Inventors assign to Xerox
         : Application filed 23 Apr 1993
    1995 : Patent issued 28 Mar 1995
    2002 : Security interest to Bank One NA
    2003 : Security agreement to JPMorgan Chase
    2013 : Patent expires 23 Apr 2013
    2022 : JPMorgan releases lien to Xerox

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NPE / troll-pattern signals

1. Shell-entity transfer — Not present. No assignee bears an "IP / Patents / Licensing / Holdings / Ventures" suffix. The only named assignees are Xerox Corporation, Bank One, NA, and JPMorgan Chase Bank, N.A. There is no single-purpose Delaware/Texas LLC anywhere in the chain (reels 013153/0001 and 015134/0476, 2002–2003).

2. Known asserter in the chain — Not present. No assignee matches the Acacia / Marathon / IV / IPNav / Wi-LAN / Mosaid-Conversant / Vringo / Pendrell / Innovatio / MPHJ / Lumen View / Round Rock / Document Generation Corp / Spangenberg lists. Xerox, Bank One, and JPMorgan are not high-frequency patent plaintiffs.

3. Repeat correspondent across the chain — Unclear / not determinable. I could not retrieve the correspondents of record for any of the four recordings from the sources available, so recurrence cannot be assessed. This is a research gap, not an absent signal. Recommend a manual pull of each PDF on the Assignment Center page to capture the correspondent attorney/firm per reel/frame before finalizing.

4. Cascading transfers — Not present. Four recorded events span 29 years (1993 → 2022), and consecutive events are ~15 months apart at the closest (2002-06-28 → 2003-10-31) but are parts of a single financing, not chained LLC assignments. No shared-principal LLC chain exists.

5. Pre-litigation transfer — Not present. No infringement suit naming US 5,402,527 was found, and the patent expired 2013-04-23. There is no pre-suit transfer.

6. Bankruptcy fire-sale — Not present. Xerox never filed Chapter 7/11; its IP was never sold in bankruptcy proceedings. The 2002 Bank One and 2003 JPMorgan recordings are secured-financing liens (reels 013153/0001, 015134/0476), not asset sales. (Xerox's early-2000s financial stress motivated secured borrowing — it did not produce a bankruptcy estate.)

7. Privateering — Not present. No NPE received the patent, and there is no evidence of a covert assertion campaign on Xerox's behalf.

8. Defensive aggregator (anti-NPE) — Not present. The chain does not terminate at RPX, AST, LOT, Unified Patents, or OIN. It terminates back at the original operating company, Xerox Corporation, per the 2022-09-07 release.

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Verdict

Insufficient data (ownership-wise this is a one-assignment chain; no NPE verdict is supportable).

The only assignment of ownership in the entire record is the 1993-04-23 inventor-to-Xerox assignment; the 2002 Bank One (reel 013153/0001) and 2003 JPMorgan (reel 015134/0476) entries are collateral security interests and the 2022-09-07 entry is their release — none of which moved title. Because there is no transfer to any asserting entity, every NPE/troll signal above is either not present or (for the correspondent-recurrence signal) unassessable from available sources. On substance, the patent is a dormant, never-asserted, operating-company-held asset that expired in 2013 — the opposite of an NPE pattern; the "assigned to BANK ONE / JPMORGAN" labels on Google Patents should not be read as ownership changes.

Verify directly:

• USPTO Assignment Center: https://assignmentcenter.uspto.gov/
• Legacy Assignment Search (same records): https://assignment.uspto.gov/patent/index.html (search patent 5402527)

Recommended next step: pull the four recording PDFs on the Assignment Center page to capture the correspondent of record for each reel/frame, which I could not confirm here, and to confirm the patent-specific reel/frame numbers for the 1993 assignment and the 2022 release.

I'll research this systematically — first confirming the patent record, then digging into each cited reference to assess § 102 anticipation potential.

Good material so far. Let me investigate the remaining key citations to complete the prior-art picture.

Prior-Art Analysis — U.S. Patent No. 5,402,527

1. USPTO record confirmation (number verified, not normalized)

The record for 5402527 resolves to a single granted U.S. patent — no other patent or application shares that number:

Source: Google Patents, us5402527A — https://patents.google.com/patent/[US5402527A](/patent/US5402527A) ; corroborated at https://uspto.report/patent/grant/5402527 and the EPO family record of EP 0621530B1 (which lists US 5402527 A, BR 9401573, JP 0749754 as family members).

Critical date for § 102: the 1993-04-23 filing date sets the § 102(b) one-year bar at 1992-04-23. Anything publicly available before that date is § 102(b); U.S. patents/applications with an effective date before 1993-04-23 but not yet public qualify as § 102(e) art.

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2. Methodology and a candid threshold point

The task asks which cited reference "potentially anticipates" which claim under 35 U.S.C. § 102. Anticipation requires a single reference disclosing every element of the claim as issued (not merely a similar concept). Two features sit in both independent claims (claim 1 and claim 10) and are the crux of the patent:

"…a set of rules for arbitrating conjunctively the information signals, the set of rules being dynamically configurable by a printing system user, said filter having a control line … in response to receiving the control signal across the control line, said filter changing the set of rules so that said filter is provided with enhanced predictive capability."

No reference cited on the face of the '527 patent — and none of the family-cited art I located — discloses user-driven, dynamic reconfiguration of the arbitration rules over a control line. That element is what distinguishes the patent, and it means that, strictly read, none of the cited references fully anticipates claim 1 or claim 10 (and therefore none anticipates the dependent claims, which incorporate all parent limitations). The cited art is nevertheless highly probative as § 103 obviousness art against the broad concept (multi-unit sampling + arbitration/filtering to identify a PDL), and several references are the closest § 102 candidates but for the dynamic-configurability element. I map both below and flag where I am uncertain.

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3. The 24 patent citations of US 5,402,527 (complete list, literal dates)

Note: the Google Patents "Citations (24)" list for the '527 record enumerates the 24 items above (I have de-duplicated two Beard-family entries and cross-checked against the fetched document). Where I could not re-verify a description in this session, I flag it below.

Separately, the '527 Google Patents page carries a "Family Cites Families (2)" pair that is the most material art and is not in the numbered 24 — I treat it as Tier 1 below:

• US 5,293,466 — Bringmann / QMS, Inc. — filed 1990-08-03, issued 1994-03-08.
• US 5,392,419 — Walton / Hewlett-Packard — priority 1992-01-23, filed 1992-11-01, issued 1995-02-21.

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4. Reference-by-reference § 102 assessment (most relevant first)

Tier 1 — Directly on point for "determine the PDL of an incoming stream"

US 5,293,466 — Bringmann, "Method and apparatus for selecting interpreter for printer command language based upon sample of print job transmitted to printer" (QMS, Inc.; filed 1990-08-03; issued 1994-03-08; EP 0 469 974).

• Disclosure: A printer that buffers a sample (64–512 bytes) of the start of each print job and, using a resident algorithm plus statistically derived "characterizing data sets," identifies the printer control language; it then selects the correct interpreter. The data sets are n-gram weighted-pattern vectors with thresholds; scores are compared and the best-matching language wins. Source: https://patents.google.com/patent/US5293466 and EP 0469974A3.
• § 102 relevance: This is the single closest reference. It discloses sampling the stream, plural analyzing mechanisms/data sets, and a decision function that selects the language — i.e., elements (a)–(d) and the "conjunctive" scoring of claim 1, plus the "operator/frequency" concepts of claims 4–5. It does not disclose dynamically user-configurable rules over a control line with enhanced predictive capability (elements (f)–(i)). It is § 102(e) art as to the '527 (effective date 1990-08-03 < 1993-04-23) and § 102(a)/(b) via its EP 0469974 publication.
• Anticipation verdict: Would anticipate claim 1 and claim 10 only if elements (f)–(i) were read out of the claims; as issued, it is best characterized as anticipating the subject matter of the pre-characterizing portion and as strong § 103 art against claims 1/4/5/10.

US 5,392,419 — Walton, "Language identification system and method for a peripheral unit" (Hewlett-Packard; priority 1992-01-23; issued 1995-02-21; EP 0 558 804).

• Disclosure: A printer on a LAN identifies an incoming language using plural voter modules (one per expected language — PCL, PostScript, etc.) whose outputs feed a decider module. Each voter counts "For"/"Against" keys, multiplies counts by skews, accumulates tallies, tests for uncertainty, and resolves ties on further syntax. Source: https://patents.google.com/patent/[US5392419A](/patent/US5392419A).
• § 102 relevance: This maps almost element-for-element onto the architecture of claim 1 — multiple analyzing units (voters) + a filter (decider) that arbitrates their signals conjunctively. The "key × skew ⇒ tally/uncertainty resolution" is squarely the "operator / certainty factor / distribution" subject matter of claims 4–6. It is § 102(e) art (effective 1992-01-23 < 1993-04-23). It does not disclose user-driven dynamic rule reconfiguration via a control line.
• Anticipation verdict: Closest prior art on the apparatus architecture; would anticipate claims 1/4/5/10 but for the dynamic-configurability + control-line + enhanced-predictive-capability limitation. Strong § 103 art.

US 5,165,014 — Vassar, "Method and system for matching the software command language of a computer with the printer language of a printer" (Hewlett-Packard; filed 1990-09-12; issued 1992-11-17).

• Disclosure: Senses the "nature, character and frequency" of the data stream, using parallel character counters (Early-Percent, Escape, Left-Bracket, Right-Bracket) and a comparator + "language determinator" to auto-select the matching printer or conversion card. Source: https://patents.google.com/patent/US5165014.
• § 102 relevance: Discloses multiple analyzing units + a determinator = filter outputting a language signal, and operator/frequency detection (claims 3–4). Fully § 102(b) art (published 1990/1992, before 1992-04-23). No user-configurable rules; the counters are fixed.
• Anticipation verdict: Relevant principally to claims 4 and 5 (operator/frequency), and as a secondary § 103 combination with US 5,293,466. Does not anticipate claims 1/10.

US 5,222,200 — "Automatic printer data stream language determination" (Lexmark; filed 1992-01-08; issued 1993-06-22). (Family-cited; not in the numbered 24.) Determines PDL from a data-stream sample; § 102(e) art. Included here because it is materially on point and any "most relevant prior art" survey of this patent should not omit it — but treat as unverified in this session.

Tier 2 — Related printing-system / language-handling art cited for background

US 5,226,112 — Mensing et al., Xerox (Ser. No. 07/898,045), filed 1992-06-12, issued 1993-07-06. Sibling Xerox work on context-file swapping between PDL interpreters. It assumes the PDL is already known (the job ticket identifies it) and does not determine it from the stream. Relevance: § 102(e)/(a) art only as to the environment; describes the same architecture the '527 improves upon (the specification expressly says the '527 is "an improvement over" the '045 work). Does not anticipate any claim.

US 5,228,118 — Brother Kogyo, filed 1991-06-29, issued 1993-07-13. Selects a printer driver based on which interpreters are available on the printer — host/printer negotiation, not stream analysis. § 102(e) art. Not anticipatory.

US 4,968,159 — Brother Kogyo, filed 1987-03-04, issued 1990-11-06. Printer that adapts to the host computer's operation mode based on received control codes. § 102(b) art. Conceptually related to language detection; I could not re-verify its full disclosure in this session. Not anticipatory of claims 1/10.

US 4,992,957 — Aoyama et al., Seiko Epson, filed 1988-03-17, issued 1991-02-12. Printer that distinguishes character codes and control codes (interpretation of embedded commands). § 102(b). Background only.

US 5,075,874 — Steeves et al., Eastman Kodak, filed 1989-04-10, issued 1991-12-24. Communications interface for a computer output printer, supporting multiple emulations via input ports. § 102(b). Background; relevant only to the general "multi-emulation printer interface" concept.

US 5,050,098 — Lexmark, filed 1989-08-25, issued 1991-09-17. Printer initialization system. § 102(b). Background only.

US 5,113,555 — Nomura, Fuji Xerox, filed 1990-10-10, issued 1992-05-12. Printer control system. § 102(b). Background only.

US 4,651,278 — Herzog et al., IBM, filed 1985-02-11, issued 1987-03-17. Interface process for an all-points-addressable printer. § 102(b). Background only.

Tier 3 — Cited for the network/server/UI context (no PDL-determination content; cannot anticipate)

These disclose Xerox-style workstation/network and copier infrastructure and were cited to frame the "network printing system" background of the '527:

• US 3,597,071 (Burton/Xerox, 1968/1971) and US 4,623,244 (Andrews/IBM, 1976/1986) — modular/scanned-input printer architectures.
• US 3,920,895 / US 3,958,088 (Vieri/Xerox, filed 1974, issued 1975/1976) — selective facsimile output systems.
• US 4,947,345 (Paradise/Xerox) — print/fax queue management.
• US 5,133,048 (Parsons/Xerox) — ordered-stock printing; US 5,170,340 (Prokop/Xerox) — printer state controller (the '527 relies on the Prokop engine, so this is the printing apparatus reference, not prior art on PDL determination).
• The Beard/Bly/Pajak/Henderson/Mackey “8000/ViewPoint” family (US 4,899,136; 4,937,036; 4,939,507; 5,008,853; 5,065,347; 5,072,412; 5,113,517; 5,153,577) — network, UI, display-object, and font/greyscale patents. None touches page-description-language identification.

Verdict for Tier 3: these are background/§ 102(b) "analogous art" citations only; none has a claim, element, or disclosure directed to sampling a print stream to identify a PDL, and none anticipates any claim of the '527.

Non-patent literature cited (all § 102(b) printed publications)

• PostScript® Language Reference Manual, 2nd ed., Addison-Wesley, 1990.
• PCL 5 Printer Language Technical Reference Manual, 1st ed., Hewlett-Packard, 1990.
• Harrington, S. J. & Buckley, R. R., Interpress: The Source Book, Simon & Schuster, 1988 (the source for the "Interpress signature/header" concept discussed at col. relating to claims 7).
• Currid & Gillett, Mastering Novell® NetWare®, SYBEX, 1990.
• LeComte, "The Xerox DocuTech® Production Publisher," BIS CAP International, Oct. 1990.

These teach the PDL formats themselves (and thus support claims 4–7's "operator," "distribution," and "signature" concepts as known PDL features) but disclose no determining apparatus; they cannot anticipate.

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5. Consolidated § 102 mapping — which reference reaches which claim

Bottom line: The most relevant prior art for US 5,402,527 is US 5,293,466 (QMS/Bringmann) and US 5,392,419 (Hewlett-Packard/Walton) — both squarely on "sample the stream, run parallel analyses, decide the language" — with US 5,165,014 (HP/Vassar) and (family-cited) US 5,222,200 (Lexmark) as close supporting art. Under a strict § 102 reading, none of these anticipates claims 1 or 10 as issued, because no cited reference discloses the dynamically user-configurable rule set, the control line, and the resulting "enhanced predictive capability." The realistic exposure, had this patent been litigated, would have been § 103 over US 5,293,466 or US 5,392,419 alone or in view of US 5,165,014.

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6. Two flags worth recording

1. Possible claim/specification gap (not a prior-art issue). The phrase "enhanced predictive capability" — present in both claim 1 and claim 10 — does not appear in the specification text I retrieved. The specification describes the arbiter's programmable configuration file, the "client rules / server rules / client over-ride / server over-ride" inputs, and "tunability" of the arbiter, but never uses the "enhanced predictive capability" language. If reproduced accurately, this suggests the as-issued independent claims were amended during prosecution to add the dynamic-configurability/control-line limitation (consistent with the patentee distinguishing over the fixed-data-set art such as US 5,293,466). Flagging as an apparent inconsistency between claims and description, per your cross-reference rule.

2. Verification caveat. Full-text re-verification of every one of the 24 citations could not be completed in this session (tool step limit reached while opening the remaining Brother/Seiko Epson/Kodak/Lexmark records). Descriptions for US 4,968,159, US 4,992,957, US 5,050,098, US 5,075,874 and the Tier-3 Xerox family are drawn from the Google Patents citation record and general knowledge and are stated with lower confidence. The bibliographic data for US 5,402,527 itself and the disclosures of US 5,293,466, US 5,392,419, US 5,165,014 and US 5,226,112 are directly grounded in the fetched sources cited above.

I'll research the key prior-art references cited in this patent to ground the obviousness analysis.

Let me get more detail on the HP language-identification reference and the co-pending configuration-file application.

Obviousness Analysis — U.S. Patent No. 5,402,527 under 35 U.S.C. § 103

Analysis date context: system date 2026-10-01; task states April 26, 2026. Because the '527 application was filed April 23, 1993, the pre-AIA version of § 103 governs. My analysis therefore uses the Graham v. John Deere framework (scope/content of prior art, differences, PHOSITA level, secondary considerations) as refined by KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007).

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1. The claim-1 / claim-10 element breakdown

From the previously generated claim summary, the independent claims reduce to four functional requirements:

Elements A–C are squarely met by the prior art. Element D — the dynamically user-reconfigurable arbitration rule set — is the only genuinely distinguishing feature, and it is met by a co-pending Xerox disclosure that the '527 specification itself incorporates.

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2. The prior-art references (all from the '527 record / family citation list)

Note on dates: US 5,392,419's priority (1992-01-23) and filing (1992-01-24), US 5,293,466's filing (1990-08-03), and US 5,166,014's filing (1990-09-12) all predate the '527 filing (1993-04-23) and its earliest claimed invention date, so they qualify as prior art under § 102(b)/(a)/(e). US 5,226,112 issues after the '527 filing but was filed 1992-06-12, so it is available as § 102(e) prior art (and is separately in the specification as the incorporated '045 application). Ser. No. 07/936,477 was filed 1992-08-28, before the '527 filing, and is likewise available at least as § 102(e) art if it matured to a patent.

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3. Primary ground of rejection: US 5,392,419 in view of US 5,293,466

This combination renders independent claims 1 and 10 obvious.

Element A — plurality of analyzing units sampling the stream. US 5,392,419 discloses "a plurality of voter modules 34, 36 and 38, each of which is specifically assigned to analysis of an expected printer language" (voter 34 → PCL, voter 36 → PostScript, etc.), operating on "a 256-byte block of data received from one of PC's 10, 12 or 14." This is structurally the claimed "plurality of page description language analyzing units for sampling the print job stream." US 5,293,466 reinforces the sampling concept ("sampling a portion, say from 64 to 512 bytes, of the print job").

Element B — each unit outputs an information signal. US 5,392,419: each voter module returns "a single number … indicating a value of either 0 to +127 … or −1 to −128" to the decider. These are per-unit information signals in exactly the claimed sense. Each module internally uses three independent accumulations ("a count of both positive and negative key weights …; a weighted sum …; and For and Against tallies"), i.e., per-unit information about the stream.

Element C — a filter receiving the signals and outputting a filtered signal identifying the PDL. US 5,392,419's decider module 40 "receives outputs from each of voter modules 34, 36, and 38 and decides, based upon those voter module inputs, the most likely identity of the received language," then "instructs CPU 20 to access … the decided-upon language." That is precisely the claimed "filter, receiving each of the information signals … and outputting a filtered signal which indicates the page description language." The specification's own glossary equates the "filter" to the "arbiter"/"best-guess arbiter" (Fig. 6, element 204), so the decider is the corresponding structure.

Element D (part 1) — "a set of rules for arbitrating conjunctively the information signals." The decider in US 5,392,419 is a rule-driven combination of multiple independent votes. The reference expressly states the process "employs three separate and simultaneous accumulations of analytical data to decide upon a language's identification," combining (i) positive/negative key-weight counts, (ii) a weighted sum, and (iii) contextual For/Against tallies. Combining several signals into one decision is conjunctive arbitration. US 5,293,466 supplies an alternative/more elaborate rule engine — weighted pattern vectors, thresholds, a tree of linear discriminants, tie-handling and "cannot decide" handling.

Element D (part 2) — rule set dynamically configurable by the user via a control line, providing "enhanced predictive capability." Two routes:

• US 5,392,419's architecture is expressly modular and extensible: "the arrangement of the decision process into a separate decider module, with a separate voting module for each language, enables the system to be modified to accommodate additional languages that are not contemplated at the outset." The skew values in the weight tables (Figs. 5a/5b) are parameters, and the reference contemplates tie-breaking "specified by the user." A POSITA would recognize that editing these tables/votes to add or modify a rule is dynamic reconfiguration of the rule set.
• More directly, the Hower '477 configuration-file teaching (incorporated by the '527 specification itself; see §4) supplies a hierarchical, programmable configuration file by which rules are displayed, deleted, replaced, and re-prioritized.

Why a PHOSITA would combine. Both references address the identical problem — automatically determining an incoming print stream's control/PDL language so the correct interpreter is invoked, without manual switches or proprietary job headers (US 5,293,466 Background; US 5,392,419 addresses the same "periodic language selection errors"). They are analogous art in the same field of endeavor (networked printers/servers). A POSITA seeking higher accuracy would naturally combine the modular multi-voter/decider architecture of '419 (which improves reliability by aggregating independent votes) with the statistical n-gram scoring of '466 (which improves reliability on short samples and pure-text cases). KSR makes this a textbook "predictable variation": arranging known, individually effective language-identification techniques into a single aggregating decision stage yields nothing more than the expected improvement in identification accuracy. The '527 specification concedes the point — it says the invention "is an improvement over the foregoing in that the characteristics of a stream of data may be analyzed for determining whether it contains one of a plurality of PDLs," i.e., aggregation of known analyses.

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4. Ground for element D as an independent feature: Hower '477 (and the Xerox UI references)

If the examiner/analyst treats "dynamically configurable by a printing system user … changing the set of rules so that said filter is provided with enhanced predictive capability" (claim 1) and claim 9 ("adding a rule … or modifying a rule") as requiring a distinct teaching, the co-pending application Ser. No. 07/936,477 (Hower Jr. et al.) supplies it. The '527 specification itself says the configuration file "assumes a hierarchical form of the type shown in U.S. patent application Ser. No. 07/936,477," and that "through use of the rules lines a client user or a server administrator can display the current rules … and selected rules can be deleted and replaced with other desired rules," and that "the client user or server administrator may set printing priorities and/or precedents." That is § 103 material because:

• It predates the '527 filing (filed 1992-08-28) and, as a commonly owned Xerox filing, is available at least under § 102(e) (and, if issued, as a printed publication/patent).
• It discloses the mechanism recited in the claim — a configurable rule store plus a control line by which a user adds/modifies/replaces rules, with conflict resolution — which is the substance of claim 1's "control line … control signal … changing the set of rules."
• The motivation to combine is explicit and near-tautological: the Hower system configures a print job's option set from the same client-server job ticket that travels with the job (the '527 Fig. 3 job ticket carries %XRXsourceFile and %XRXdestination), so a POSITA would use the same job-ticket/config-file mechanism to carry a language-identification preference/override to the filter. The '527 specification's own examples — a user overriding a PS job to print as non-interpreted text for diagnostics; a server admin adding a rule to fault any Interpress-RES job the decomposer can't process — are the routine, expected uses of the Hower rule mechanism.

Accordingly, Ground 1 + Hower '477 renders claims 1, 9 and 10 obvious.

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5. Ground for the server claims: add US 5,226,112

Claims 2–3 and 11 add "a print server … for interpreting the page description language," which "includes said plurality of page description language analyzing units and said filter," and a "print job translating unit."

US 5,226,112 (Mensing, Xerox) discloses a print server having a host processor 72 and accelerator coprocessor 74 with swappable PDL interpreter context files 94 that translate PS/HP-PCL into Interpress. A POSITA would place the identifying units/arbiter of '419/'466 in that server because (a) the server is where the interpreter decision must be made and where the interpreters are swapped (US 5,226,112, Fig. 4; US 5,166,014 expressly performs language matching at a "network print serving station"); and (b) US 5,293,466 and US 5,392,419 both note that identification must occur before interpreter selection. Combining the '419/'466 identifier with the '112 server is the "predictable use of prior-art elements according to their established functions."

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6. Dependent-claim disposition

Caveat on claims 8 and 15. I do not see an express disclosure of a "binary filter … reporting a percentage of binary characters" in the four references I retrieved. US 5,293,466 comes closest: it distinguishes "pure text" from encoded languages and builds its data sets from character-content statistics, and US 5,166,014 counts control/non-printable ASCII characters (Escape = character 27). A POSITA could implement a binary-character-percentage gate as a straightforward statistical refinement within the '466 framework (and the '527 specification itself describes the binary filter as merely preventing a false PS positive — a defensive design choice). But because I could not confirm an explicit teaching, claims 8 and 15 should be asserted with less confidence than the others; a secondary reference (e.g., a printer-language-detection reference discussing binary vs. ASCII PostScript) would be desirable. I cannot state with high confidence that claims 8/15 are obvious on this record alone.

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7. Motivation-to-combine summary (KSR factors)

1. Same field, same problem. '419, '466, '014 and '112 all address auto-selecting the correct printer/PDL interpreter on a shared or networked printer — the exact problem the '527 Background recites.
2. Teach-teach-suggest. '419 teaches aggregating independent per-language votes into a decider; '466 teaches statistical operator scoring with thresholds and tie handling. Both are improved by the other's technique; neither teaches away.
3. Design incentive / market demand. The '527 Background documents the industry need (small printers handle one PDL; PC users want high-speed multifunction printers) and the DocuTech server context. LAN printing demanded automatic language determination, so there was strong pressure to make identifiers accurate — which drives aggregation of multiple analyzers.
4. Modularity motivation. '419 expressly says its voter/decider split "enables the system to be modified to accommodate additional languages," i.e., it invites rule-level reconfiguration — bridging directly to claim 1's "dynamically configurable" rule set and the Hower configuration file.
5. Predictable result. Combining known identification techniques to raise accuracy is a "predictable variation"; the '527 spec claims only an "improvement" over the aggregation concept, and the conjunctive-arbitration + user-configurability additions are routine engineering in the configuration-file art.

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8. Counter-considerations / candor notes

• The genuine novelty pole is element D's "dynamically configurable … enhanced predictive capability." Independent claims 1 and 10 were apparently allowed over the '419-style modular voter/decider art precisely because of this limitation. The strongest § 103 case therefore depends materially on the Hower '477 configuration-file teaching (or equivalent user-configurable rule store). If that application is not effective as prior art (e.g., it never published/issued with the relevant disclosure, or the relevant passages post-date the '527 invention), the "dynamically configurable by a user" limitation may survive on this record.
• "Conjunctively" and "enhanced predictive capability" are largely functional/result language. Under § 103 these add little weight beyond the mechanisms already taught by '419's decider and '466's scoring.
• No litigation/validity challenge is on record (per the earlier litigation section), so there is no court or PTAB construction to rely on for how broadly these terms read.
• Interpreter/identifier date nuance: the '527 specification's own incorporated '045 application issued as US 5,226,112 after the '527 filing; I have used it as § 102(e) art, which is the correct treatment for a pre-AIA case, but this should be confirmed against the actual prosecution record.
• I did not retrieve claim-by-claim text for US 4,968,159, US 5,228,118, US 5,050,098 or US 5,075,874, so I have characterized them only by title/abstract; they are cumulative rather than load-bearing.

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9. Bottom line

• Claims 1 and 10 are obvious over US 5,392,419 in view of US 5,293,466, and further in view of the Hower '477 configuration-file disclosure for the "dynamically configurable rule set" limitation.
• Claims 2, 3 and 11 are obvious with the addition of US 5,226,112.
• Claims 4–7 and 12–14 are obvious over the same combination given '419's keys/tallies, '466's statistical scores, and '014's parallel character counters.
• Claims 8 and 15 are the only limitations for which I lack an explicit prior-art teaching on this record and should be treated as a qualified, not confident, obviousness position.

Sources consulted (grounding the prior art):

• US 5,392,419 / EP 0 558 804 A2 — https://patents.google.com/patent/[US5392419A](/patent/US5392419A)/en ; https://patentimages.storage.googleapis.com/fe/a2/54/011e1a77419290/US5392419.pdf
• US 5,293,466 / EP 0 469 974 B1 — https://patents.google.com/patent/US5293466 ; https://lexdana.ai/patent/[5293466](/patent/5293466) ; http://www.everypatent.com/comp/pat5293466.html
• US 5,166,014 — https://patents.google.com/patent/[US5165014](/patent/US5165014) ; https://uspto.report/patent/grant/[5165014](/patent/5165014)
• US 5,226,112 / EP 0 574 222 B1 — https://patents.google.com/patent/US5226112
• The '527 record itself — https://patents.google.com/patent/[US5402527](/patent/US5402527)/en (citation lists, family citations, specification references to Ser. Nos. 07/898,045 and 07/936,477)