Source: s3://data.kl3m.ai/documents/govinfo/USCOURTS/USCOURTS-ca13-18-02276/USCOURTS-ca13-18-02276-0/pdf.json

Nature of Suit Code: 830
Nature of Suit: Patent
Cause of Action: 

---

NOTE: This disposition is nonprecedential.

United States Court of Appeals 

for the Federal Circuit ______________________

MIRROR WORLDS TECHNOLOGIES, LLC,

Plaintiff-Appellant

v.

FACEBOOK, INC.,

Defendant-Appellee

______________________

2018-2276

______________________

Appeal from the United States District Court for the 

Southern District of New York in No. 1:17-cv-03473-JGK, 

Judge John G. Koeltl.

______________________

Decided: January 23, 2020

______________________

MARC AARON FENSTER, Russ August & Kabat, Los Angeles, CA, argued for plaintiff-appellant. Also represented 

by BRIAN DAVID LEDAHL, JAMES S. TSUEI, BENJAMIN T.

WANG; CHARLES R. MACEDO, Amster Rothstein & 

Ebenstein LLP, New York, NY. 

 HEIDI LYN KEEFE, Cooley LLP, Palo Alto, CA, argued 

for defendant-appellee. Also represented by DENA CHEN,

LOWELL D. MEAD, MARK R. WEINSTEIN; PHILLIP EDWARD 

MORTON, Washington, DC. 

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2 MIRROR WORLDS TECHNOLOGIES v. FACEBOOK, INC.

 ______________________

Before PROST, Chief Judge, TARANTO and STOLL, Circuit 

Judges.

TARANTO, Circuit Judge.

Mirror Worlds Technologies, LLC owns U.S. Patent 

Nos. 6,006,227, 7,865,538, and 8,255,439, which describe 

and claim systems and methods for presenting and storing 

data in time-ordered streams on a computer system. Mirror Worlds brought the present action against Facebook, 

Inc., alleging that Facebook’s making, selling, using, and 

other actions involving various Facebook systems infringed 

the ’227, ’538, and ’439 patents. Facebook filed a motion 

for summary judgment of non-infringement before discovery ended, and the district court granted it. Mirror Worlds 

appeals. 

We agree with Mirror Worlds that the district court’s 

judgment must be reversed. The district court relied for its 

decision on an erroneous conclusion that there is no genuine dispute about certain facts. Facebook defends the summary judgment on alternative grounds. We will not affirm 

on those alternative grounds. We reverse the court’s judgment and remand for further proceedings.

I

A

The ’227 patent issued from an application filed in June 

1996. The ’538 and ’439 patents are descendants of the ’227 

patent through a series of continuation applications, with 

an intervening continuation-in-part application. The ’227 

patent is representative for the purposes of this appeal. 

The patent states that, as of its priority date, conventional computers used certain kinds of hierarchical directories to store and organize data. ’227 patent, col. 1, lines 

21–30. Under the conventional system, a user created a 

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new document by naming the document and choosing a 

storage location. Id. According to the patent, requiring 

such operations has disadvantages: specifically, the operations involve needless overhead; file names are often meaningless to a user; and a user of such a system must 

remember not just the file name but where the document 

is stored. Id., col. 1, lines 40–59. The ’227 patent describes 

an alternative: storing documents in a chronologically ordered “stream.” Id., col. 1, lines 4–6. 

A “stream” is “a time-ordered sequence of documents 

that functions as a diary of a person or an entity’s electronic 

life. Every document created and every document sen[t] to 

a person or entity is stored in a main stream.” Id., col. 4, 

lines 6–10. Past documents are contained in the tail of the 

stream, id., col. 4, lines 10–12, and new documents are

added to the present time point in the stream, id., col. 4, 

lines 35–43. Besides containing documents from the past 

and present, a stream may contain “documents allotted to 

future times and events, such as[] reminders, calendar 

items, and to-do lists.” Id., col. 4, lines 18–21. “A document 

can contain any type of data,” including “pictures, correspondence, bills, movies, voice mail and software programs.” Id., col. 4, lines 16–18. 

A user may create “substreams” by filtering the main 

stream. Id., col. 4, lines 48–61. Describing preferred embodiments, the patent characterizes a substream as dynamic and persistent in the following sense: if a user filters 

for “all emails from Smith,” a substream containing all 

emails from Smith will collect any such emails as they are 

added to the main stream, and the substream will continue 

to exist “until destroyed by the user.” Id., col. 4, line 62, 

through col. 5, line 13. A substream is a subset of the main 

stream, in that each substream document is in the main 

stream, though a particular document may be in multiple 

substreams. Id., col. 5, lines 14–19.

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4 MIRROR WORLDS TECHNOLOGIES v. FACEBOOK, INC.

Claim 13 of the ’227 patent is representative for the issues on appeal:

13. A method which organizes each data unit received by or generated by a computer system, 

comprising the steps of:

generating a main stream of data units and at least 

one substream, the main stream for receiving 

each data unit received by or generated by the 

computer system, and each substream for containing data units only from the main stream;

receiving data units from other computer systems;

generating data units in the computer system;

selecting a timestamp to identify each data unit;

associating each data unit with at least one chronological indicator having the respective 

timestamp;

including each data unit according to the 

timestamp in the respective chronological indicator in at least the main stream; and

maintaining at least the main stream and the substreams as persistent streams.

Id., col. 16, lines 9–25. Each of the asserted claims contains 

a “main stream” or “main collection” limitation and a “substream” or “subcollection” limitation.

The parties agree that the “main stream” has two properties: first, it includes every data unit received or generated by the “computer system”; second, it is a time-ordered 

sequence of data units.1 While Facebook contends that 

 

1 The ’538 and ’439 patents use the term “documents” rather than “data units.” Although the parties 

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“main stream”—used in the ’227 and ’538 patents—and 

“main collection”—used in the ’439 patent—are synonymous, Mirror Worlds disagrees. Mirror Worlds admits, 

however, that any difference is immaterial to the resolution of Facebook’s summary judgment motion.

B

Facebook provides a popular social networking service. 

Several features of Facebook’s service are relevant to this 

appeal. According to Facebook’s description in this case, 

the “News Feed” for a Facebook user displays a variety of 

items that Facebook has “deemed to be relevant” to that 

user. J.A. 1104. “Timeline,” Facebook says, “focuse[s] on a 

particular Facebook user,” showing “basic information 

about that user, as well as actions taken on Facebook by or 

directed toward that user.” Id. And “Activity Log” provides 

“a list of activities that occurred on Facebook that pertain 

to a particular user.” J.A. 1106.2 

Generally, the content Facebook users see is an amalgamation of “objects” and “associations,” which are two 

classes of data. Users, pictures, and comments are types of 

objects, while associations describe the relationship between objects. For example, if user “Alice” posts a comment 

on Facebook, an “authorship” association would connect Alice and the comment. 

In providing content to users, both News Feed and 

Timeline rely on certain “front-end” hardware and software. The evidence—when understood most favorably to 

Mirror Worlds, as required when considering summary 

judgment—indicates that these front-end components 

 

disagree about whether those terms are synonymous, any 

difference is immaterial to our decision in this appeal.

2 At least two of the three patents at issue here have 

expired. Nevertheless, following the parties’ usage, we use 

the present tense in describing the accused services. 

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include a user’s desktop computer, smartphone, or comparable device and its resident software, together with certain “web” technologies, including a PHP layer. See, e.g.,

J.A. 1483–85, 1488, 1550, 2117–18, 2132, 2422, 2599. The 

two services also rely on certain “back-end” computing 

equipment and associated software to which the user’s device is connected over a network such as the Internet. The 

back-end infrastructure for News Feed is called “Multifeed.” The “Timeline back-end system” supports both the 

Timeline and Activity Log features. In the summary-judgment proceedings, Mirror Worlds asserted that those two 

back-end systems were the “computer system[s]” for purposes of the claims.

Multifeed has several components, of which three have 

been featured in this appeal: Leaves, Tailer, and Aggregator.3 Facebook describes Leaves as a collection of databases of information about user actions and objects. Tailer, 

in turn, writes user actions and objects to Leaves. Aggregator retrieves information from Leaves and applies an aggregation algorithm to create a list of stories that may be 

shown on a particular user’s News Feed.

The Timeline back-end system includes the TimelineDB database and an Aggregator. TimelineDB has a list 

of all actions performed by a user. Similar to the Multifeed

Aggregator, the Timeline Aggregator serves as an intermediary between the front end and the database. When a user 

views Timeline, the front end passes parameters to the 

Timeline Aggregator, which then retrieves information 

 

3 For simplicity, and to maintain parallelism with 

the other relevant components, we will refer to “Leaves” in 

the singular as a unit, though the evidence sometimes refers to “the Leaves” in the plural. The parties have not 

identified any way in which such treatment alters the analysis relevant to our decision.

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from TimelineDB that is used to create (or render) the image on the user’s screen.

Neither Multifeed nor the Timeline back-end system 

contains all the information necessary to produce the features they support. The News Feed and Timeline features 

rely in part on another Facebook system known as “TAO,” 

which stands for “The Associations and Objects.” Facebook 

describes TAO as a “data store that provides access to objects and their associations with other objects.” J.A. 1111. 

Retrieving objects such as photographs or comments to display on a user’s News Feed or Timeline uses, respectively, 

Multifeed Leaves or TimelineDB, but those back-end components contain pointers to the objects, not the objects 

themselves. It is TAO that is called on to deliver up-to-date 

versions of the objects to which Leaves and TimelineDB 

point. Those objects then become part of the News Feed or 

Timeline viewed by the user.

C

In May 2017, Mirror Worlds filed this action against 

Facebook in the District Court for the Southern District of 

New York, alleging that Facebook infringed the asserted 

patents by, e.g., using its servers—including TAO—to provide features such as News Feed, Timeline, and Activity 

Log to Facebook users. In its first set of interrogatories, 

Facebook asked Mirror Worlds to identify what elements of 

the accused Facebook services that it was alleging meet the 

“main stream” and “substream” limitations. J.A. 2472–73. 

Facebook did not ask Mirror Worlds to identify what “computer system[s]” it was accusing. Id. Mirror Worlds responded in early December 2017. J.A. 2473. Mirror Worlds 

identified, as meeting the “main stream” limitation, “the 

user-related information in at least Facebook’s Social 

Graph, MemCache, TAO, Multifeed Leaf Servers and Aggregators, Timeline Databases and Aggregators, Channel 

Servers and RTGW Messaging Bus, and servers, databases 

or aggregators from which Facebook’s Events, Activity Log, 

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8 MIRROR WORLDS TECHNOLOGIES v. FACEBOOK, INC.

Graph Search, and search features obtain information for 

Facebook users.” J.A. 2473. Mirror Worlds identified, as 

meeting the “substream” limitation, “the user-related information that appears in at least Facebook’s Newsfeed, 

Timeline, Events, Activity Log, Graph Search, and search 

features.” J.A. 2473.

Fact discovery was not due to close until September 

2018. See J.A. 1045–46, 1057, 1061. But in April 2018, 

after completion of the briefing on claim construction—but 

before significant expert or other factual discovery had occurred—Facebook filed a letter with the court, asking permission to file a motion for summary judgment. J.A. 1015–

17. At a status conference, Facebook argued that it had a 

simple, case-ending point to make, while Mirror Worlds asserted that contention interrogatories cannot be filed under 

local rules until the close of fact discovery, that it was not 

accusing Facebook as a whole but had identified the two 

back-end systems separately from TAO, and that the record did not even include expert disclosures or depositions. 

The court granted Facebook leave to file a motion for summary judgment and set out a schedule for responses, while

allowing discovery to continue. J.A. 1065–66.

In its motion for summary judgment of non-infringement, Facebook made essentially just one point. See 

J.A. 1095–97. It contended that Mirror Worlds had failed 

to provide evidence that there was an accused Facebook 

“computer system” that contained a “main stream” in 

which all data created or received by the system is stored 

in a time-ordered sequence. In support of that contention, 

Facebook argued, simply, that Mirror Worlds had included 

TAO in the accused “computer system[s],” J.A. 1087–89,

and that the evidence established that “TAO does not store 

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all of its data items in any kind of time-ordered sequence,” 

J.A. 1095.4 

In response, Mirror Worlds explained principally that 

Facebook’s motion misunderstood what the accused “computer system[s]” were. Specifically, it argued that it is the

News Feed back-end system, Multifeed, and the Timeline 

back-end system specifically that are the systems accused 

of coming within the asserted patent claims. See, e.g.,

J.A. 1422 (“[t]he Multifeed and Timeline backend systems”), 1439 (“the Multifeed system”), 1440 (“the Timeline 

backend system”). Mirror Worlds contended that within 

the Multifeed system, Leaves meets the “main stream” limitation, and that within the Timeline system, TimelineDB 

meets the limitation. See, e.g., J.A. 1421, 1438–40. According to Mirror Worlds, both Leaves and TimelineDB include 

every data unit received by their respective computer system and store those data units in a time-ordered sequence. 

J.A. 1438–40 (asserting inclusion of “every data unit”); see 

J.A. 1421, 1427, 1434, 1436, 1439, 1440 (asserting inclusion of every action and object in the respective systems, 

citing evidence). It does not matter how TAO stores its 

data, Mirror Worlds argued, because TAO is separate from 

Multifeed and the Timeline back-end system. J.A. 1421–

22.

In reply, Facebook argued that Mirror Worlds had 

failed to identify the relevant “computer system[s]” to 

which Leaves and TimelineDB belong. J.A. 2508–09. Facebook emphasized that both Leaves and TimelineDB consist primarily of pointers used to find corresponding data 

in TAO and that News Feed and Timeline as seen by users 

 

4 Facebook mentioned, as a descriptive matter, that 

the substream and sub-collection data must be drawn from 

the main stream and main collection, but it made no separate argument that evidence was missing as to the substream/sub-collection limitations. J.A. 1095–97. 

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include data from TAO. J.A. 2509–11. In a footnote, Facebook cited certain evidence as assertedly showing that, in 

the Multifeed system, the Aggregator “retrieve[s] data 

units from the non-accused TAO data store.” J.A. 2508–

09 n.4. On those bases, Facebook contended, Leaves and 

TimelineDB cannot meet the “main stream” limitation. 

J.A. 2511–12. Facebook did not dispute that Leaves and 

TimelineDB store their data units in a time-ordered manner.5

The court allowed Mirror Worlds to file a surreply. In 

that filing, Mirror Worlds reiterated its contentions that 

Multifeed and the Timeline back-end system were the relevant “computer system[s],” and Leaves and TimelineDB 

met the “every data unit” requirement for being “main 

streams” for those systems, even if information from other 

systems might be necessary to create the News Feed and 

Timeline features seen by users. J.A. 2675–77. It also asserted that, contrary to Facebook’s footnote suggestion, the 

evidence showed that the Aggregators do not receive the 

TAO data at issue, which, rather, is obtained by the (unaccused) front-end PHP feature. J.A. 2676 n.4 (citing 

J.A. 2604, 2610 (also appearing at 2430)).

When it granted Mirror Worlds leave to file a surreply, 

the district court instructed Facebook that it should “resist 

the urge to file further papers in response to Mirror 

Worlds’[] sur reply brief.” J.A. 2673. Instead, the court assured the parties that it would “consider all of the arguments raised . . . at oral argument.” Id. At the oral 

argument, Facebook argued that Mirror Worlds still failed 

to show that the Facebook systems meet the “main stream” 

limitation. One of its arguments—the one originally suggested in its Reply footnote (discussed above)—was that

 

5 Facebook added a new argument about Mirror 

Worlds’ failure to show that the “substream” and “sub-collection” limitations are met. J.A. 2512–13.

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the Aggregators receive data from TAO, not just TimelineDB or Leaves. Facebook also argued that the Aggregators receive data from certain sources that Facebook had 

never mentioned until the oral argument. J.A. 60–61, 119–

20. 

The district court granted Facebook’s motion for summary judgment on August 11, 2018. The court determined 

that the record established conclusively—so that there was 

no genuine issue of fact about the proposition—that neither 

TimelineDB nor Leaves (which Mirror Worlds identified as 

the accused main streams) contains all the data received or 

generated by their respective computer system. The court 

reasoned that the Aggregators are parts of the accused 

“computer system[s]” and concluded that it was beyond 

reasonable dispute on this record that the Aggregators 

(hence the systems) receive data from TAO that does not 

enter TimelineDB or Leaves. Because there is data received by the accused systems that is not included in TimelineDB or Leaves, the court held, TimelineDB and Leaves 

cannot be main streams. Mirror Worlds Technologies, LLC 

v. Facebook, Inc., 320 F. Supp. 3d 538, 547 (S.D.N.Y. 2018).

The court entered judgment on August 16, 2018. Mirror Worlds timely appealed. We have jurisdiction under 28 

U.S.C. § 1295(a)(1). 

II

We review a “grant of summary judgment of non-infringement under the law of the relevant regional circuit.” 

Clare v. Chrysler Grp., 819 F.3d 1323, 1326 (Fed. Cir. 

2016). The Second Circuit reviews a grant of summary 

judgment de novo. Rojas v. Roman Catholic Diocese of 

Rochester, 660 F.3d 98, 104 (2d Cir. 2011). “The court shall 

grant summary judgment if the movant shows that there

is no genuine dispute as to any material fact and the movant is entitled to judgment as a matter of law.” Fed. R. 

Civ. P. 56(a). “[S]ummary judgment will not lie if the dispute about a material fact is ‘genuine,’ that is, if the 

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evidence is such that a reasonable jury could return a verdict for the nonmoving party.” Anderson v. Liberty Lobby, 

Inc., 477 U.S. 242, 249 (1986). When determining whether 

summary judgment is appropriate, a court must resolve all 

ambiguities and draw all reasonable inferences against the 

moving party. Matsushita Electrical Industrial Co. v. Zenith Radio Corp., 475 U.S. 574, 587 (1986).

A

The district court rested its summary-judgment ruling 

on a single basis—its determination that one fact could reasonably be found only in Facebook’s favor. Mirror Worlds 

challenges that determination. Specifically, Mirror Worlds 

argues that the district court erred in concluding that the 

record would require a reasonable jury to find that the Aggregators in Multifeed and in the Timeline back-end system receive data from TAO—data that is not included 

within Leaves or TimelineDB. We agree that the district 

court erred in so concluding.

1

Regarding News Feed and its back-end system, Multifeed, the district court concluded that the record required 

a finding that the Aggregator “draws the actual content 

that is indexed by the ‘Multifeed Leaves’ from ‘TAO,’ and 

receives information from ‘TAO.’” Mirror Worlds, 320 F. 

Supp. 3d at 546. The court relied on a declaration of 

Dr. Bronson, a Facebook engineer, and the testimony of 

Dr. Vickery, another Facebook engineer. Id. But that evidence does not establish that the Multifeed Aggregator receives content from TAO that is not in Leaves.

The Bronson declaration states that “when News Feed, 

Timeline, [and] Activity Log . . . seek to retrieve objects 

such as photos and comments from Facebook’s data store, 

it is TAO that retrieves and delivers an up-to-date version 

of those objects to those features.” J.A. 1111–12 (emphasis 

added). The quoted statement does not say that TAO 

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delivers content to the Multifeed Aggregator (in the backend system). It states only that the content is delivered to 

the front-end features, including News Feed. The statement is consistent with Mirror Worlds’ theory of the case, 

and it does not establish that the identified data from TAO 

is received by the accused “computer system” (the back-end 

system), which is the premise of the district court’s determination that Leaves, in the back-end system, cannot be a 

main stream (because that TAO data is not included in 

Leaves).

A similar conclusion is required as to Dr. Vickery’s testimony. Dr. Vickery said that “the aggregators combine together metadata that’s received from the leaves into 

another list of metadata that has several steps such as querying TAO . . . to fetch additional information that is required to render someone’s News Feed.” J.A. 2595. Dr. 

Vickery also said that “one of the most important things in 

generating someone’s News Feed is their list of friends and 

the pages that they follow. And that information is queried 

from TAO.” J.A. 2599. Those statements, like Dr. Bronson’s statement discussed above, do not establish that the 

referred-to data from TAO enters the Aggregator or, therefore, the only accused system for News Feed, i.e., Multifeed. 

In another statement, Dr. Vickery said that the 

“[a]ggregators combine together information from multifeed leaf servers as well as other sources in order for—as 

the next step in preparing someone’s News Feed.” 

J.A. 2595 (emphasis added). But that testimony does not 

clearly state that the Multifeed Aggregator retrieves the 

cited information from TAO. It is not enough to remove the 

issue from genuine dispute, especially in the face of evidence suggesting otherwise. See, e.g., J.A. 2014 (Facebook’s Dr. Bronson indicating it is the “application layer” 

that “queries TAO using [the] backend identifiers”), 2030 

(Dr. Bronson discussing certain “trace” tests: “My recollection is that all the TAO queries that—that were initiated 

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as, like, directly in response to rendering my News Feed 

came from the—the PHP application layer.”). 

In fact, other testimony from Dr. Vickery suggests that 

TAO is queried by a part of the front-end system called the 

PHP layer (PHP being a scripting language). For example, 

Dr. Vickery testified that “the list of story identifiers that 

the aggregator returns back to PHP contains pointers 

which can be used, perhaps through a series of steps, to 

fetch the set of information that will be rendered in the final story” and the returned list of story identifiers “determines what queries to TAO will be run in order to generate 

those stories.” J.A. 2604. Additional testimony of Dr. Vickery further suggests that the PHP layer, not the Aggregator, queries TAO. J.A. 2602–04.

We conclude that, on the current record evidence, the 

district court erred in concluding that a reasonable jury 

would have to find that the Multifeed Aggregator receives 

data from TAO that is not in Leaves. That erroneous conclusion was the sole basis for the grant of summary judgment as to News Feed.

2

Our conclusion regarding Timeline is similar to our 

conclusion regarding News Feed. The district court concluded that a reasonable jury would have to find that the 

Timeline Aggregator receives data from TAO that is not in 

TimelineDB. Mirror Worlds, 320 F. Supp. 3d at 546–47. 

The court cited the declaration of Dr. Bronson; Mirror 

Worlds’ response to Facebook’s statement of material facts; 

and the testimony of Jeffrey Huang, a Facebook engineer. 

Id. at 546. We conclude, to the contrary, that the record 

evidence, as presented to the district court and identified 

to us, does not compel a reasonable jury to find that the 

Timeline Aggregator receives the asserted data from TAO.

As for Dr. Bronson, the district court relied on the 

statement by Dr. Bronson we addressed above in 

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discussing the News Feed aspect of the case. As discussed, 

Dr. Bronson’s statement does not show that the Timeline 

Aggregator receives the cited data from TAO.

Mirror Worlds’ response to Facebook’s statement of 

material facts also does not show, as Facebook contends,

that the Timeline Aggregator receives the relevant data 

from TAO. In the paragraphs cited by the court, Mirror 

Worlds discussed only querying of the TimelineDB, not of 

TAO, by the Timeline Aggregator. J.A. 1464–67. Facebook 

has not pointed to anything in the Mirror Worlds’ response 

that supports the district court’s crucial determination 

about interaction between the Timeline Aggregator and 

TAO.

Mr. Huang’s testimony is similarly insufficient. Mr. 

Huang testified that “[i]n order to actually show anything 

on Timeline, you need to take those IDs you get from the 

TimelineDB and go to TAO to actually fetch the content.” 

J.A. 2587. Like Dr. Bronson’s testimony, Mr. Huang’s testimony does not show that the Timeline Aggregator is the 

element of Facebook’s infrastructure that receives the referred-to content from TAO. Mr. Huang’s testimony is consistent with the theory that front-end systems receive that

content without the content having first gone through the 

accused (back-end) system. Indeed, other testimony by Mr. 

Huang suggests that the front-end web layer retrieves that 

content: Mr. Huang testified that “it’s really the web tier 

that I consider the frontend that then, you know, needs to 

go to TAO to actually fetch any of the content.” J.A. 1910–

11. At least one internal Facebook document corroborates 

Mr. Huang’s testimony that the front end, including PHP, 

queries TAO. J.A. 2430.

We conclude that, on the current record evidence, the 

district court erred in concluding that a reasonable jury 

would have to find that the Timeline Aggregator receives 

data from TAO that is not in TimelineDB. That erroneous 

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16 MIRROR WORLDS TECHNOLOGIES v. FACEBOOK, INC.

conclusion was the sole basis for the grant of summary 

judgment as to Timeline.

B

Facebook asks us to affirm on grounds other than the 

ones relied on by the district court. We find neither of its 

two arguments to be a sound basis for affirmance here.

First, citing Celotex Corp. v. Catrett, 477 U.S. 317 

(1986), Facebook argues that it is entitled to summary 

judgment under Federal Rule of Civil Procedure 56 on the 

ground that Mirror Worlds failed to provide evidence that 

would permit a jury to find that Leaves or TimelineDB contains every data unit received or generated by, respectively, 

Multifeed or the Timeline back-end system. The Second 

Circuit has explained that “when a defendant moves for 

summary judgment, it is the defendant who must show entitlement to judgment, notwithstanding that, at trial, the 

plaintiff will have the burden of proving every element of 

its claim.” Nick’s Garage, Inc. v. Progressive Casualty Ins. 

Co., 875 F.3d 107, 115 (2d Cir. 2017). “The mere assertion 

by a defendant moving for summary judgment that the 

plaintiff ‘has not produced any evidence’ to support an essential element of the plaintiff’s claim does not satisfy the 

burden that Rule 56(a) imposes.” Id. “[U]nless the moving 

defendant cites portions of the record that show its entitlement to judgment, an assertion by the defendant that the 

plaintiff ‘has not produced any evidence,’ without more, 

does not show that the plaintiff has insufficient evidence.” 

Id. at 115–16. 

Facebook, in its summary-judgment motion, did not 

show that Mirror Worlds “cannot produce admissible evidence to carry its burden” to show that Leaves or TimelineDB contains every data unit. Fed. R. Civ. P. 56(c) 

advisory committee’s note to 2010 amendment. “A plaintiff 

is under no obligation to ‘produce’ its evidence prior to trial, 

unless such an obligation arose in response to a discovery 

demand (or a court order) requiring the plaintiff to set forth 

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the evidence supporting its claim.” Nick’s Garage, 875 F.3d 

at 115. As far as we have been shown, Facebook has not 

made a discovery demand that Mirror Worlds identify all 

its evidence for the “every data unit” limitation. Given that 

discovery is still open, Mirror Worlds may still muster evidence to prove its claim. Facebook has not otherwise 

shown that sufficient evidence cannot be produced.

When Facebook moved for summary judgment, having 

been allowed to file such a motion even before discovery 

closed, its attempt to “show” entitlement to summary judgment rested on one assertion: that TAO does not store information in a time-ordered sequence. J.A. 1095–97; 

J.A. 1092–94. Facebook did not assert that the record 

lacked evidence of infringement even if TAO is not part of 

the “computer system.” Mirror Worlds, in arguing that the 

accused “computer system[s]” do not include TAO, met the 

ground asserted by Facebook, and the district court did not 

conclude otherwise. Mirror Worlds, in fact, went further. 

As recounted above, it identified the accused “systems,” it 

described (with evidentiary support) how those systems 

work, and it asserted based on that description that Leaves 

and TimelineDB meet the “every data unit” requirement

and hence are “main streams.” Although the district court 

concluded that Mirror Worlds’ response failed in one particular respect, that conclusion is erroneous, as already discussed. On this record, we are not required, and we do not 

think it appropriate, to declare on appeal that Mirror

Worlds’ opposition was categorically insufficient to withstand summary judgment.

Second, Facebook points to certain information that it 

argues is received by the two back-end systems that is not 

included in Leaves or TimelineDB: information from Adfinder and Ego for Multifeed; certain query criteria for the 

Timeline back-end system. But although Facebook mentioned these points at the oral argument before the district 

court, see J.A. 119–20, it did not present them in its motion 

or even its reply in the district court, leaving Mirror Worlds 

Case: 18-2276 Document: 101 Page: 17 Filed: 01/23/2020
18 MIRROR WORLDS TECHNOLOGIES v. FACEBOOK, INC.

without a fair opportunity to address them. And the district court did not address these points, which raise questions about, among other things, whether this information 

comes within the relevant claim terms, e.g., “data units,” 

under a proper construction.

In these circumstances, we will not adopt Facebook’s 

alternative arguments for affirmance. Our ruling is without prejudice to otherwise-appropriate consideration of 

non-infringement contentions on remand, especially once 

the record is fully developed.

C

To the extent that the district court’s construction of 

“main collection” and “subcollection” apply beyond Facebook’s summary-judgment motion, Mirror Worlds asks us 

to vacate those constructions. We do not read the court’s 

opinion as having construed the terms with any such effect. 

The district court stated that, despite the parties’ dispute, 

the terms “main collection” and “subcollection” “present 

identical issues for purposes of this motion” as the terms 

“main stream” and “substream,” respectively. Mirror 

Worlds, 320 F. Supp. 3d at 543–44. We understand that 

statement to go no further than indicating that any difference between those terms does not matter given the ground 

on which the court decided the case. We have reversed that 

ground for summary judgment. The claim-construction issue is open on remand.

III

For the foregoing reasons, we reverse the district 

court’s summary judgment of non-infringement. We remand the case for further proceedings.

Costs awarded to Mirror Worlds.

REVERSED AND REMANDED

Case: 18-2276 Document: 101 Page: 18 Filed: 01/23/2020