On Lexical Cohesive Behavior of Heads of Definite
Descriptions: A Case Study
Beata Beigman Klebanov and Eli Shamir
School of Computer Science and Engineering,
The Hebrew University of Jerusalem, 91904, Israel,
Abstract. This paper uses materials from annotation studies of lexical cohe-
sion (Beigman Klebanov and Shamir, 2005) and of definite reference (Poesio
and Vieira, 1998; Vieira, 1998) to discuss the complementary nature of the two
processes. Juxtaposing the two kinds of annotation provides a unique perspective
for observing the workings of the reader’s common-sense knowledge at two lev-
els of text organization: in patterns of lexis and in realization of discourse entities.
1 Introduction
Introducing the notion of cohesion of a text, Halliday and Hasan [6] detail numerous
ways in which textual elements connect with each other, providing the perception of the
unity of the text. Among other kinds of texturizing devices, they cite lexical cohesion
use of words with related meaning, and referential cohesion the tendency of a text to
refer repeatedly to the same set of entities.
Subsequent research discovered that whereas the cohesive devices are often identi-
fiable on the basis of their form, the patterns they form with each other – what connects
to what are by no means easy to establish by some systematic, algorithmic resolution’
procedure [4,10,12]. Readers were thought to do it effortlessly; however, reader-based
studies show cases of disagreement and difficulty [9].
In this paper, we will attempt to analyze the relationship between lexical and refer-
ential cohesion: whether and when they reinforce each other, and what can be learned
from their divergence. Human-annotated data is used to provide information about each
of the phenomena: The Wall Street Journal 1989 article ’Computers Start to Get Per-
sonal’ (shown as appendix A) was used both in Poesio and Vieira’s seminal annotation
study regarding referential behavior of definite noun phrases [9,11] and in Beigman
Klebanov and Shamir [1–3] lexical cohesion annotation experiment.
In what follows, we introduce the two annotation schemes, and sketch out our pre-
dictions of the interaction between the two types of cohesion (sections 2, 3). We then
proceed to testing the prediction on the basis of the annotated data.
2 Lexical Cohesion through Anchoring
In Beigman Klebanov and Shamir’s rendering, lexical cohesion between items in a text
arises on the basis of stereotypical, common-knowledge-based connections between the
We will use another annotated text which will be introduced in due course.
Shah H. (2006).
Chatterbox Challenge 2005: Geography of the Modern Eliza.
In Proceedings of the 3rd International Workshop on Natural Language Understanding and Cognitive Science, pages 109-119
DOI: 10.5220/0002505001090119
relevant concepts [1–3]. Sensitive to text dynamics, their question to the subjects was:
”For every concept first mentioned in the text, which previously mentioned concepts
help the easy accommodation of the current concept into the evolving story, if indeed
it is easily accommodated, based on the common knowledge as perceived by the sub-
ject” [3]. The preceding helper concept is called an anchor, and the relation is marked
Only first mentions of every lexical item in the text were subjected to anchoring
annotation. There were no limitations on the number of anchors per item or on the
textual distance between the anchored item and its anchor. Subjects were made aware
of the notion of referential cohesion through examples, and were asked not to mark
connections solely on the basis of identity of reference in the given text.
Beigman Klebanov and Shamir’s experiment resulted in 10 texts annotated for an-
choring relations by 22 readers. Detailed statistical analysis of the data identified 2 out-
liers, and set annotator agreement thresholds that ensure high degrees of reliability [1].
In particular, an item is reliably anchored if it was given some anchor by at least 13
out of 20 non-outliers
; an anchoring pair ab is core, or strong, if the anchored item
a is reliably anchored, and the specific anchor b features in at least 6-7 annotations.
Examples will be given during case-study presentation; also see [2].
3 Definite Reference
The phenomenon of definite reference concerns both the text and the reader’s general
knowledge; it is thus particularly interesting to investigate its relationship with anchor-
ing. We will concentrate on one type of definite references - noun phrases quantified
by ’the’. Other definite references include demonstratives and possessives; however,
Poesio and Vieira’s study [9] only considered ’the’-definites.
According to the discourse analysis literature, ’the’-definites are used to mention
entities that should be uniquely identifiable by the hearer/reader on the basis of the
nominal alone in her mental representation of the current discourse augmented with her
general knowledge, as construed by the speaker/writer [5,8].
Unique identifiability is a cognitive status commanding an intermediate degree of
givenness in the following hierarchy [5]: In Focus > Activated > Familiar > Uniquely
Identifiable > Referential > Type Identifiable.
The sources for this degree of givenness are variable, and include linguistic context,
situational context, and general knowledge:
Linguistic: My sister has two children, a boy and a girl. The boy is an excellent student.
Situational: The boy sitting in the front row is misbehaving.
General Knowledge: When John came home, he saw that the door was already open.
In Poesio and Vieira’s study [9], definite descriptions were classified according to
the following taxonomy:
The gist of the example was that if in a given story a child’s father went out to the sea because
he is a sailor, then sailorsea, but not sailorfather.
This corresponds to 99% reliability threshold.
The exact threshold depended on the text.
ENTITY referred to by a definite description
linked to previous mention
new in the text
mentioned before
new but based on text
presumably known to the average reader
(larger situation)
presumably new to the average reader
Fig.1. Poesio and Vieira’s classification of Definite Descriptions. Category descriptions are
shown according to Vieira’s [11] summary of instruction given to the annotators. Additional
category titles shown in parenthesis are used by Poesio and Vieira in their article, highlighting
the correspondence with other concepts commonly employed in studies of the phenomenon.
3.1 ’D’-type definites
Given the position of definites in the givenness hierarchy, the D type (no previous
knowledge of the entity) is not expected to be abundant. However, about 20% of the
definite descriptions annotated in Poesio and Vieira’s study belong to this type [11]. A
cursory inspection of cases unanimously classified as D yields numerous examples of
long definites with lexically rich post-modifiers of the head:
the class of asbestos including crocidolite
the unit of New York-based Loews Corp that makes Kent cigarettes
the fact that New England proposed lower rate increases
In these cases, the reader probably does not know about the aforementioned classes,
units, and facts, but the rich description given on this first mention is sufficient for secur-
ing the unique identifiability. Thus, the identifiability is not based on either knowledge
or prevoius linguistic information, but on linguistic information within the NP itself.
In terms of lexical anchoring, we expect heads of D definites to be left un-anchored,
as they are judged to be new and not based on previous text. This is even more so for
the ’heavy-tail’ definites, where identifying information follows the head.
3.2 ’=’ type Definites
Definites that repeat an already mentioned entity constitute less than half of all ’the’-
definites in Poesio and Vieira’s study. A repeated mention of an entity can be done with
the same lexical head (as in ...a boy ...The boy ... ), or with a different lexical head (as
in ...a boy . ..the kid ...). In the first case, anchoring information will not be available,
as the relevant item would constitute a lexical repetition.
In the different-head case where the current head is first mentioned within the given
definite, we ask whether this head is anchored at all, and if yes, whether the anchor coin-
cides with the previous mention of the same entity (this would be the case if kidboy in
the last example). In such cases, lexical and referential cohesion would go hand-in-hand,
intensifying the connectedness between the two items. Cases of divergent anchoring and
reference annotations would constitute examples of the item’s different positioning at
the two planes of textual structure.
3.3 ’R’ type Definites
These are cases where the entity is new but based on text, or, as Poesio and Vieira’s
guidelines [9] elaborate, ”based on, dependent on, related to some other idea or thing
in the text”, exemplifying by ”The Parks wanted to buy an apartment but the price
was very high”, where the price should be classified as R with an apartment as its
trigger/antecedent. This class is the smallest in their data, only 6-11% of all definites.
This class often termed bridging references, or indirect anaphora bears the most
similarity to anchoring. We point out that in reference annotation, the trigger/antecedent
itself is taken to be a noun phrase,
whereas anchoring is at the word, rather than phrase,
level, and the part-of-speech of the anchor is not constrained in any way.
Furthermore, anchoring guidelines allowed multiple anchors, whereas reference
guidelines ask for the previous related mention”, i.e. a single antecedent. Indeed, some
cases of annotator disagreement were due to different choices of antecedent [9].
Poesio and Vieira note that this was by far the most difficult category to distinguish
from the rest. A point of interest is whether the difficulty was in the initial judgement
of relatedness to something, or in pinpointing a previous noun phrase that functions as
the relevant previous item. In the first case, anchoring annotators might have a similar
difficulty; in the second, we expect to find robust anchoring decisions often going to
something other than the head of the triggering/antecedent noun phrase.
3.4 ’K’ type Definites
K definites refer to an entity that ”was not mentioned in the text, not related to something
in the text, but it refers to something which is part of the common knowledge of the
writer and readers in general” [9]. This class covers 20-25% of definites.
Similarly to R type, non-relatedness is likely to be understood as non-relatedness to
some other entity mentioned in the text. Hence, K class is not necessarily exclusive of
anchoring, as long as the anchor is not a head of a noun phrase.
Alternatively, K definites could be references to entities that come-out-of-the-blue
as far as the text is concerned, but have a natural reference point in the reader herself,
as in Poesio and Vieira’s example: ”During the last 15 years housing prices increased
nearly fivefold.” In such cases, the text would not provide any material for anchoring.
Table 1 summarizes prediction of anchoring according to reference classification.
4 Reference vs. Anchoring - A Case Study
In the article ”Computers Start to Get Personal” henceforth, PC-text, there are 6
examples of LINK-ENTITY (=/R) and 10 examples of NO-LINK (K/D) definites.
Poesio and Vieira speak about ”...the head noun of the definite description and the head noun
of its antecedent”, p. 200, our italics.
Table 1. Predicted relationship between referential and anchoring behavior.
Anchored Anchor Identity
= (Coref) Same Head
Other Head Yes Possibly same as coreferent
R (Bridging) Yes Same or other than the trigger/antecedent
K (Knowledge) Yes Not a head of an NP
D (Unfamiliar) No
In our analysis of LINK-ENTITY definites, we expand the data with coreferential
definites from a NYT article ”Inspectors: TWA Explosion Did’t Originate Near Cock-
pit” (appendix B) henceforth, TWA-text. This text was annotated for coreference
chains within MUC initiative [7], and used for anchoring annotation as well.
4.1 LINK-ENTITY Definites
Out of the 6 LINK-ENTITY definites in PC-text, 4 are unanimously classified as re-
peated reference. However, we do not get a chance to see anchoring at work, since in
none of the 4 cases is the head a newly introduced lexical item.
Table 2. LINK-ENTITY definites with lexically new heads. The heads are boldfaced. An-
tecedents are in square brackets. We show cases with majority =/R classification. The last column
shows the head’s anchors produced by the parenthesized number of people (out of 20).
Definite NP P&V class Anchors
the Homebrew D hobbyists (6) homebrew (1) garage (1)
Computer Club R [hobbyists]
= [hobbyists]
the world leader in = [ibm] pioneer (4) led (3) world (3) new (2) ibm (2)
computers = [ibm] chairman (1) team (1) owners (1) after (1)
D example (1) triggered (1) market (1)
The two cases with judgement variability are shown in table 2. The definites are em-
bedded in a larger NP with which they co-refer: an appositive (IBM, the world leader
in computers) and a list construction with a single member (for hobbyists such as the
Homebrew Computer Club). There is an uncertainty in reference annotations - some
annotators marked embedded NP as coreferential with the whole of the appositive/list
construction, whereas others apparently decided that the embedded NP does not consti-
tute a second mention, but rather is part of the ongoing first mention of the entity (D);
the single R annotation seems to hit the middle ground between the two solutions.
There is no reliable anchoring of the head of the definite, contrary to our prediction
for =/R types. In one case there is a tendency to anchor the head in its antecedent’s head
(clubhobbyists by 6 people), which is virtually nil in the other case (leaderibm by 2
people). In the latter case, there are better anchors which are not heads of noun phrases:
pioneer is a modifier inside the NP many pioneer PC contributors, and led is a verb.
For additional information on coreference and anchoring behavior of definites, we
turn to the TWA-text, and seek coreference chains that include coreferential definites
with first-mention heads. There are four such chains; the relevant heads are boldfaced:
Crash-chain: the crash – the accident – the crash – the plane crash
Plane-chain: Trans World Airlines Flight 800 the Boeing 747 the jet the plane
– the plane – plane – Flight 800 – plane – the airplane
Day-chain: Tuesday–the 20th day since Flight 800 exploded in midair off Long Island
Man-chain: James K. Kallstrom–the assistant director of the FBI’s New York office
Table 3 presents the anchoring data. Let us consider the last two chains first. For
day and director, the situation is similar to leader in PC-text: the items are embedded
in a coreferential appositive construction. Day shows negligible anchoring; director has
a stronger anchoring pattern, though it misses the core-reliability threshold.
Table 3. Anchoring behavior of coreferential definites, TWA-text.
Same-chain Anchoring Patterns
lexical heads Within the Chain Outside the Chain
crash – accidentcrash (17) accident explosion (11) catastrophic (9)
– accident wreckage (7) survived (4) destroyed (2)
flight 800 – boeing flight (15) boeing airlines (14) twa (11) cockpit (11)
– Boeing 747– jet flight (17) boeing/747 (16) jet airlines (16) cockpit (12) twa (9)
– jet – plane jet (17) flight (15) plane airlines (12) cockpit (12) twa (10)
– plane – boeing/747 (16)
– airplane airplane plane (19) jet (18) airplane airlines (10) cockpit(9) twa(7)
boeing/747 (11) flight (10) transportation (3) hangar (3) altitude (2)
Tuesday–day day tuesday (2)
Kallstrom – director chairman (7) assistant (4)
– director board (3) vice chairman (2) senior (1)
While the agreement on the best anchor for director is not high, chairman is the
preferred choice. This case shows clearly the distinction between referential and lexical
structures: the NP headed by chairman is not related referentially to the one headed by
director, as they refer to different people in different organizations. However, the direc-
tor is the second senior official named and quoted in this short article, so the items form
a pattern, for some readers. On the other hand, director is not cohesive anchoring-wise
with Kallstrom, as, presumably, this name does not feature in the readers’ knowledge.
We now turn to the crash- and plane-chains in table 3. None of the 7 definites in
question is embedded in its coreferent NP. Their behavior is radically different: all items
are anchored, with numerous strong anchors. Thus, accident in strongly anchored in its
coreferent’s head crash, but also in other items.
The pattern in the second chain is interesting: each member of the chain is strongly
anchored in each of the preceding members; all members of the chain
are strongly
anchored in the same additional items: airlines, cockpit, twa. We note that within-
chain anchors tend to be somewhat stronger than out-of-chain ones; this might mean
that coreference intensifies the perceived lexical connectedness. The anchoring support
given to the referential structure makes it different from Kallstrom–director chain, in
that the latter is an accidental referential connection, whereas the items in plane-chain
have a lot of associative commonality. Anchoring also shows additional ’networking’
of the chain in the given text, connecting it to other aviation-related things.
To summarize the analysis of LINK-TYPE entities with respect to our predic-
tions: heads of coreferential definites that are not embedded within their coreferent NP
confirm our expectation – they are anchored, and there is substantial anchoring texture
accompanying the coreference links. Anchoring provides additional information, show-
ing common-knowledge-based connection with items outside the coreference structure.
For heads of definites embedded in their coreferent NP, the anchoring support tends
to be weak or lacking. These are cases with an explicit syntactic construal of co-
referentiality, through an appositive. In the Gricean framework, this means that the
reader is not likely to be able to work out the connection without the explicit help;
Kallstrom-director is a good example. Hence, in terms of the involvement of the reader’s
knowledge, these cases are akin to D-definites – self-identifying lexically elaborate in-
troductions of unfamiliar entities. In fact, in both such cases in PC-text, there was a mi-
nority D annotation. The anchoring behavior of these definites matches what we would
expect of D-types, and is quite unlike that of other coreferential definites.
4.2 NO-LINK Definites
Table 4 shows the K/D definites from PC-text. Let us consider the 5 cases of majority K
annotations. Apart from Journal, all other items are reliably anchored, and have at least
one very strong anchor: century centennial, office business, drives computers,
drives disk, telephone modems.
It is predicted that anchors should not be nominal heads in the text, so they are
not perceived as discourse entities. Centennial is an adjective; business and disk are
non-head noun modifiers. However, computers and modems are NP heads. It seems that
reference and anchoring are at odds regarding the relatedness of the entity to the text.
The definite the telephone is embedded in ’the internal modems that allow PCs to
share data via the telephone’, headed by the anchor modems. This is reminiscent of
the problem with embedded appositives – perhaps the annotators thought that an entity
which is still being introduced could not be used as a basis for an R-type connection.
The annotators knew about the disk drives for PCs, but took them to be unrelated
to previously discussed computers. Indeed, the three computers launched in 1977 did
not have disk drives, as the text implies (’could store about two pages of text in their
memories’ carries a scalar implicature that they could not store more). From the modern
perspective, these are rather non-typical computers. Perhaps, the reference annotators
assumed the 1977 perspective from which disk drives were a new development, whereas
including flight, which is not listed as it was not introduced inside a coreferential definite NP
Table 4. NO-LINK definites. The heads are boldfaced. For minority =/R annotations, the an-
tecedent is in square brackets. Dots ... indicate 3 additional anchors, each marked by 1 person.
Definite NP P&V class Anchors
1 The Wall Street Journal K K K wall street (5)
2 the past century K K K centennial (19) year (7) past (2)
3 the face of personal computing K D D personal (1) changed (1)
4 the Apple II R [three computers] computers (17) ...
5 the home and office K K K business (11) computers (5) home (4)
pcs (2) desktop (4) owners (2) ...
6 the Altair = [b.-f.-kit types] pcs (1) types (1) apple ii (1)
K D commodore (1) tandy (1)
7 the team that developed D D D led (2) chairman (1)
the disk drives for PCs
8 the disk drives for PCs K K K computers (10) disk (9) keyboards (2)
pcs (2) data (2) technology (2) .. .
9 the internal modems that K/D D D computers (19) pcs (10)
allow PCs to share data keyboards (6) disk (4) technology (4)
via the telephone screens (4) drives (3) . ..
10 the telephone K K K modems (14) television (4)
technology (3) computers (2) .. .
anchoring annotators took their own current perspective, judging disk drives generally
related to computers. One difficulty for this explanation is the perspective of the text: it
mentions current, i.e. 1989, computers, which, presumably, did have disk drives.
Turning to the 3 cases where D type predominates, we note that two of them items
3 and 7 bear out our prediction of lack of anchoring. Additionally, case 6, coming from
’earlier built-from-kit types such as the Altair, Sol and IMSAI’ is a by now familiar case
of a definite embedded inside a NP with overlapping reference; the reference annotation
shows confusion, but the lack of anchoring places this case firmly in ’D’-type company.
Case 4 also shows uncertainty regarding reference. Apple II is one of the three
computers mentioned in the preceding sentence. The anchoring pattern is extremely
strong, suggesting that (some) computers are the entity to which Apple II is related. A
minority vote indeed opts for R; the K/D decisions are puzzling.
However, perhaps the most surprising case is that of modems (case 9): A robust D
type reference-wise, with an overwhelming anchoring connection to computers. The
discussion of perspective taken by annotators is possibly relevant here: The three com-
puter brands repeatedly mentioned in the text did not have modems. Still, surely the
connection between modems and computers is of readers’ knoweldge!
We suggest that the solution in the wording of instructions to reference annotators:
”...the D[efinite]D[escription] is self-explanatory or it is given together with its own
identification. In these cases it becomes clear to the general reader what is being talked
about even without previous mention in the text or without previous common knowl-
edge of it” [9]. Thus, D-types are not necessarily unfamiliar to the reader; rather, the
reader does not have to use the familiarity in order to achieve unique identification. In
this case, the 12-word definite headed by modems is squarely within this category, even
though the common knowledge could be in place, too. The mere existence of cases like
this is surprising Grice-wise, as they seem to provide superfluous information that the
reader could have recovered on the basis of her knowledge. Modems are introduced as
an important invention of the past, as are disk drives; however, there is no elaboration
about what disk drives are. Possibly, the ’modems’ case is slightly over-indulging for
an up-to-date 21st-century reader; perhaps modems were still a rarity in 1989.
We thus see that D-class is not homogenous with respect to the role of knowledge:
it contains elements that are unfamiliar, so the reader has to use the material inside the
definite to reach the unique identifiability, and elements that are in fact quite familiar in
the reader’s common knowledge, but their presentation in the text is such that the reader
does not have to use her knowledge to interpret them.
In contrast, anchoring sides completely with the reader’s knowledge: a putative con-
nection is either supported by it or not, irrespective of what the text says about each en-
tity. This is because anchoring asks for intuitive stereotypical judgment, for the shallow
but robust load brought into the text by the mere use of a word, like modems. Anchoring
is meant to uncover how such ’loads’ organize into structures in the text, below the level
of the discourse-entity-based who-did-what-to-whom stories where reference operates.
5 Conclusion
This paper reported a case study of the relationship between referential behavior of
definite NPs and lexical anchoring of their heads, on the basis of juxtaposed relevant
annotations of two texts.
We observed a tendency for definites whose referent repeats or relates to some pre-
vious textual entity (=/R) to be anchored in their antecedents, as well as in other things,
providing additional text-based connections (plane vs. airlines, cockpit).
Even when an entity is judged to be referentially unrelated to the text, but of reader’s
knowledge (K-type), the anchoring pattern shows what could have triggered the relevant
knowledge earlier in the text (diskcomputers, centurycentennial). Often, the anchor
is not a nominal head, although we saw cases of heads as well.
When the entity is judged new in the text (D-type), we discerned two sub-types.
In case the entity is genuinely unfamiliar, the lexical anchoring texture for the head
is indeed meager. In case the entity is familiar, but in the current case could as well be
uniquely identified by the current description, the anchoring pattern reveals the familiar-
ity. Such discrepancies could be interesting from a historical perspective, as, assuming
Gricean cooperative framework, they detect potential knowledge mismatches between
text-creation-time and current audience.
In the other direction, lack of anchoring tends to corresponds to D-class, but also to
cases where the definite is embedded, through an appositive or a list structure, inside
an NP with overlapping reference. These cases often show disagreement in reference
type classification, possibly reflecting confusion as to the availability of a referent-in-
the-making as an antecedent. There is usually a minority D annotation in these cases.
Clearly, additional parallel annotation is needed to check out these trends. Such
work is promising in exposing the intricate, multi-level workings of the reader’s knowl-
edge upon the text: not only does it help to consolidate the plot of the story by tracing
repeated and related referents, but also to prepare subtle, associative ground for intro-
duction of new things and ideas, and to strengthen the perceived unity of the text by
enriching the network of connections between its elements.
We thank Renata Vieira for giving us access to definite description annotations.
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Appendix A: PC text
Computers Start to Get Personal, 1977
Wall Street Journal
(During its centennial year, The Wall Street Journal will report events of the past century that
stand as milestones of American business history.)
Three computers that changed the face of personal computing were launched in 1977.
That year the Apple II, Commodore Pet and Tandy TRS-80 came to market. The computers
were crude by today’s standards. Apple II owners, for example, had to use their television sets as
screens and stored data on audiocassettes. But Apple II was a major advance from Apple I, which
was built in a garage by Stephen Wozniak and Steven Jobs for hobbyists such as the Homebrew
Computer Club. In addition, the Apple II was an affordable $1,298.
Crude as they were, these early PCs triggered explosive product development in desktop
models for the home and office.
Big mainframe computers for business had been around for years. But the new 1977 PCs
unlike earlier built-from-kit types such as the Altair, Sol and IMSAI – had keyboards and could
store about two pages of data in their memories. Current PCs are more than 50 times faster and
have memory capacity 500 times greater than their 1977 counterparts.
There were many pioneer PC contributors. William Gates and Paul Allen in 1975 developed
an early language-housekeeper system for PCs, and Gates became an industry billionaire six
years after IBM adapted one of these versions in 1981. Alan F. Shugart, currently chairman of
Seagate Technology, led the team that developed the disk drives for PCs. Dennis Hayes and Dale
Heatherington, two Atlanta engineers, were co-developers of the internal modems that allow PCs
to share data via the telephone.
IBM, the world leader in computers, didn’t offer its first PC until August 1981 as many other
companies entered the market. Today, PC shipments annually total some $38.3 billion world-
Appendix B: TWA text
Investigators: TWA explosion didn’t originate near cockpit
New York Times News Service
After picking apart some of the wadded remains of the cockpit of Trans World Airlines Flight
800, investigators concluded Tuesday that the catastrophic explosion that destroyed the Boeing
747 most likely did not originate inside the cockpit or in the electronics bay beneath it.
They were partly persuaded by a surprising discovery found in the ton of wreckage that had
been the jet’s cockpit: The circles of glass that cover many of the cockpit dials, and even a light
bulb above a staircase that led to the plane’s upper deck, had somehow survived the crash intact.
“You have this mass of wreckage and yet things from that area are relatively the way they
were before the accident, said Robert Francis, vice chairman of the National Transportation
Safety Board. “There is no indication at this point of anything in that area that would give cause
for concern in terms of something having initiated there.
A senior investigator who looked at the cockpit wreckage Tuesday said that one of the plane’s
altimeters instruments that show the plane’s altitude was frozen with a reading of 13,100
feet. Altimeters are mechanically driven instruments that do not depend on electricity to work,
so the finding suggests that the mechanics continued working for several seconds after the initial
explosion, at about 13,700 feet.
Federal investigators continued their search for the cause of the crash Tuesday, the 20th day
since Flight 800 exploded in midair off Long Island and plunged into the Atlantic Ocean, killing
all 230 people on board. On the seas and on the shore, investigators said they made a modest
amount of progress, though they still have not determined if the plane crash was caused by a
bomb, a missile attack or a mechanical malfunction.
At the former Grumman hangar in Calverton, investigators on Tuesday began piecing to-
gether the fractured parts of the airplane. They also pulled about one-third of the cockpit wreck-
age off the one-ton ball of metal, essentially unwrapping it.
James Kallstrom, the assistant director of the FBI’s New York office, said he had sent many
agents who had been working in Suffolk County back to their home offices, mostly in New York
City. Criminal investigators are anxious for the cause to be determined, he said, adding: “We are
in a bit of a waiting pattern.