Computer-assisted data extraction from the
Jim Diederich*, Renaud Fortuner**, and Jack Milton*
*Department of Mathematics, University of California, Davis, CA 95616, USA
**11, place de la Frézellière, 86420 Monts sur Guesnes, France. Correspondant du Muséum National d'Histoire Naturelle, Paris, France. email@example.com
Key words: biological character data, computer-assisted data extraction, published data, identification, biology, nematodesJim Diederich
This paper may be cited if a proper reference is given:
Diederich, J., Fortuner, R. & Milton, J. (1999). Computer-assisted data extraction from the taxonomical literature. Virtual publication on web site: http://math.ucdavis.edu/~milton/genisys.html.
This article presents some problems associated with the acquisition of morphological data from printed descriptions of taxa and our solution to these problems.
An electronic tool, the Terminator, was used in 1993 for testing our approach. After an article has been scanned into electronic form and run through OCR processing, the Terminator aids the operator to identify all the characters present in the description, record them in a standard format, and store them prior to the creation of a database. Some difficulties one can expect in the creation and the population of such a database are discussed. The prototype has been implemented primarily for use with descriptions of plant-parasitic nematodes. The complexity of our set of characters, which necessitated new concepts to handle the set, has required changes to the tools originally built to create and manage the set. When this task is completed, the Terminator will have to be modified accordingly, and it will be reformulated into a generic tool, as we see no inherent reasons that it cannot be adapted for other biological domains.
We have previously (Diederich et al., 1997a) proposed a representation of morpho-anatomical characters based on a decomposition of traditional systematic characters into: i) a biological structure (taken in a hierarchy from the whole organism to systems, organs, tissues, cells, cell organites, and molecules); ii) the aspects of this structure that is being described (taken from a list of about 20 basic properties, see Diederich, 1997); iii) and the state or value taken by the basic property in a particular species or individual.
Once a character set has been created for a particular biological group using this representation, it can be used to create a morpho-anatomical database that will house the descriptions of taxa (species, genera, families, etc.) in this group. The question remains as to how to populate this database. This article proposes a possible approach that has been prototyped and tested with a set of nematode descriptions.
Creating a character database
New data vs. published data
The first question to be answered is whether we should create a character
database from new data gathered for this purpose or rely on published data.
The first option would solve many problems such as those presented by missing data and format ambiguities. However, this would not be possible for taxonomic groups of more than a few species. Recording new data for, e.g., the 8,000 populations of plant-parasitic nematodes that have been described over the last hundred years would require, first, to conduct a worldwide sampling expedition, then to extract and process 8,000 samples (actually much more because it would take more than one sample to find each targeted population), then to record the data, to the tune of more than one day per sample. This is just not an option for practicing nematologists.
The alternative is to use published data. Existing published data are far from perfect, but they exist. While problems raised by missing data and differences in format are unavoidable, a great amount of published data has been recorded by some of the best (i.e., reliable) past or still active taxonomists. We cannot be certain that our new data would be more accurate. Some of the data from the literature is probably better than anything a systematic worldwide survey would provide, depending on the expertise of the surveyors.
The creation of a general database with published data is the only practical option, but the question remains as to how to do it . This can be done by hand with the operator reading the data directly from the printed documents and entering it in the proper place in existing forms, or data extraction and entry can be assisted by computer, using several possible methods discussed below.
This article describes the approach we propose for the creation of such a database, as well as some difficulties we can expect to encounter during this task. The task remains daunting, but we have designed electronic tools to help in this endeavor. While ours is by no means an automated system, it makes the task at least possible.
The tools were prototyped a few years ago during the NEMISYS project (Nematode Identification System), but they are of a sufficiently general nature that we see no major problems in extrapolating them to other biological domains. We have therefore begun the GENISYS Project (General Identification System), which makes the construction of similar databases in other areas closer at hand.
Possible approaches to published data acquisition
There are two basic methods that can be used to acquire the data: manual
data entry, and electronic data entry via a scanner and optical character
recognition (OCR) processing. With the second option, one has three options:
(i) store only the text without trying to extract and store character data
in a database, (ii) use natural language processing to aid placement of
the data in the database, or (iii) use some other means short of natural
Manual data entry
Manual entry can be cost effective if the amount of data to be entered
is reasonably small. Even if the amount is substantial it can be entered
manually if it can be done in a very systematic way by entering data for
the same few characters repeatedly. Furthermore, if the data is simple,
the errors can probably be kept to a minimum, though one cannot escape
the tedium of the continual typing. Another advantage of manual entry is
that it eliminates the need for any pre processing such as scanning, but
the saving would not be great, as most of pre-processing can be done by
Unfortunately, these conditions are rarely met in biological descriptions. The descriptions, outside of a few basic measurements, are not written in any systematic fashion and so one must often jump from one character to a much different character to enter the data. A typical nematode description contains about 50 to 80 characters out of a list of over 5,000 characters that currently exist in our system. A few characters are found in all descriptions, but others were used only by one or a few authors. The data are complex, often involving measurements, thus making it likely there will be entry mistakes. With a vast literature the list of known characters is not stable, and more characters must be added to it with each processed description, particularly early in the task. The general morphological database we are proposing to construct will be so large that manual data entry would likely be made, not by a taxonomist but by a data entry operator, i.e., someone who would be unfamiliar with the domain and who would not be able to make expert judgments about biological data. However, some character names may not be easy to find in the published descriptions, and only experts may be able to decide exactly what character is being described. This would make it impossible to entrust to a data entry operator who is not a taxonomist the task of extracting the characters directly from a printed description. The creation of a general data matrix (i.e., one that includes all possible characters for all existing species in a large group) is an almost impossible task using manual entry, which probably explains why nobody has ever succeeded in such an endeavor.
Scanning published descriptions
Using the method of electronic scanning and OCR processing presumes
a large amount of data, enough to warrant the investment in a scanner and
OCR software, although the costs are quite low. This initial part of the
process can be done by persons without any scientific training, if they
are given explicit scanning instructions. OCR processing will introduce
errors into the text, either spelling errors or scanning errors in measurements,
such as substituting the letter l or o for the digits one or zero, or missing
or adding decimals, but there are ways for handling such problems. The
time required to scan, process OCR, and spell-check is quite reasonable,
as discussed below. It should be noted that an ever increasing amount of
taxonomic descriptions are already available in an electronic form from
the author or the publisher, which will simplify the process for such new
After the text of the description has been transferred to an electronic medium, the three electronic options for data extraction listed above are available, and the choice depends to some extent on the intended use of the data.
Full text storage
The first option (simply storing and retrieving the electronic text)
only requires correcting errors introduced by the OCR. Spelling errors
can be corrected through a word processor, and this requires only that
a list of terms from the application domain have been entered in the user
defined dictionary. Correcting the numerical errors could be tedious without
some preprocessing software with a good interface to help make the corrections.
The corrected text could then be retrieved by keyword methods (Salton, 1989), or in the future by text-based intelligent systems (Jacobs, 1992) when they have been significanlty developed. However, for uses of the data for such purposes as identification this would be of limited value and would be very inefficient unless the user had already guessed the probable identity of the organism and needs only to check the description of the corresponding species. The user would still have to retrieve all of the articles containing a description of the candidate species and then locate the descriptions in each article. For many uses the data are required in a structured form, for example for similarity comparisons, and full text would insufficient for such a tasks.
It would be much more difficult to retrieve descriptions with specific values for particular characters. For this kind of search, keyword methods in themselves do not work very well without some kind of enhancement. Some data is extremely cryptic, and it is unlikely that searching the descriptions would find the desired data. For example, published descriptions of nematode species often include abbreviations. For example, in nematology, the traditional character Ratio a (the ratio of length to width of Body) often is represented simply by the letter a. It is unlikely that text retrieval systems could differentiate between the article a and the ratio a and find the latter in descriptions. Also, distributing the copies of a published article raises copyright concerns. Copyright protection for data is a hotly debated topic (Samuelson, 1992; 1996).
Natural language processing
The second option is to use some natural language processing (NLP Ð
see Special Issue on NLP, 1996) to help place the characters in a database.
NLP has moved in this direction in recent years due to the hugh quantities
of available on-line text which needs to be processed to be useful as there
is too much information available to be read in detail. This work is done
under the rubric of Information Extraction (IE) (Cowie & Lehnert, 1996)
and the general thrust of this work is to summarize text for the intended
audience such as news reports and financial reports and transactions (Jacobs,
The preparation of the text after scanning would be the same as in the first option, though it could be assumed that the spell checker would rely on the terms already entered in the lexicon prepared for NLP. However, the time and expertise required to create a lexicon and knowledge base for the terms in a domain would be considerable, the lexicon would have to be updated as new articles were processed, and new terms would have to be added. Though NLP can do well in restricted domains, it is unclear how well they could do in handling biological descriptions. The output would have to be checked carefully by a domain expert, since reading articles requires a lot of expert judgment. New lexicons would have to be built for each additional biological domain or for processing descriptions in other languages. It is unclear what later savings in time would result from building a lexicon. We are unaware of any inexpensive systems that could be used for NLP, and it is unclear that the necessary enhancements to such a system, discussed below, would be included if such a package becomes available.
Use of a schema
The last option is based on the schema, i.e., a formal list of morphologicalcharacters and related information organized for use in a database system. This schema originates from the character set created according to the principles and guidelines set by Diederich (1997) and Diederich et al. (1997a). The schema is used as the launching point for acquiring the data itself. The schema, as we have defined it in the previous two references, contains great deal of the word combinations one expects to find in the descriptions, a significant part of the form information takes in the sciences (Harris et al, 1989).
This approach requires the text of the descriptions to be transferred
to an electronic medium, but the terms for the spell checker would be available
from the schema and many of the problems with handling OCR errors with
measurements can be finessed. Given that a lexicon is not constructed,
the system would have to be keyword based. This makes the transition from
one biological domain to another or from one language to another easier
than with NLP systems. While basic keyword systems may need some enhancements
to give reasonable performance, the developers of NLP systems readily admit
"they are fast, portable, relatively inexpensive, and relatively easy
to learn" while "By contrast, natural language processing can
be slow brittle, and expensive" (Jacobs, 1992). Also,it is crucial
that the interface is well designed to make alternative actions quick and
efficient when the keyword approach fails. It is this option that we describe
in this paper, and we feel that it is a reasonable balance between options
one and two. Perhaps the main point here is that a well constructed list
of characters and a good interface provide a solid foundation for data
aquisition requiring otherwise fairly simple concepts for processing.
The Terminator: a tool for semi-automated data extraction
The Terminator, so named because it is based on key words, or terms,
is a set of tools for (i) reading electronic versions of descriptions and
aiding with the decomposition of characters and the placement of the data
in records, (ii) reading tables of data after having been rearranged in
a simpler format, (iii) reviewing, changing, and recovering the data, and
(iv) storing the data in a form that can be used to import the data into
a commercial DBMS. In conjunction with these activities, a schema tool
assists in the creation and management of the schema. The schema creation
and management functions are of critical importance, as without a good
schema the data would be nearly useless: fraught with redundancy, lacking
uniform structure and meaning, and containing information that cannot easily
be found and used. At this point neither a biological database management
system nor a biological knowledge base management system is commercially
available to support the complex relationships among biological characters
needed in a large identification system. However, we have taken an important
step in this direction by building the prototype of a schema tool to manage
large sets of characters.
Prototypes of the Terminator and the schema tool were built in the early 90's and used for testing our approach in 1993 (see below). However, full size tools have not been prepared, not because of any intrinsic problem with our concepts, but because the size of our schema is so large and the difficulties so fundamental that we have spent the time since then working on concepts and practical considerations to solve these (Diederich, 1997; Diederich et al., 1997a; 1997b).
Extracting data from the printed literature using the Terminator includes several main steps: (i) retrieving the appropriate articles from the literature, (ii) scanning them electronically using commercial optical character recognition (OCR) software, (iii) spell-checking, (iv) dividing the text into blocks (normally one block consists of the description of one population), and (v) running the Terminator tools to extract the data either from text or from tables. The domain expert identifies the appropriate articles, and then steps i, ii, and iii can be done by operators with very little knowledge of the domain. Steps iv and v should be done by a trained domain expert, at least in the present state of the prototype.
The Terminator Interface, Processing text
Since interface design is a critical element in creating a usable and
efficient system, it is important to give some idea of how the Terminator
operates. Indeed, throughout the development of the Terminator prototype,
interface considerations proved to be a very important driving element
of the overall design of the system (Diederich & Milton, 1993). User
interactions also help to illustrate additional information which must
be captured in the course of processing species descriptions. What is described
here provides the essential elements of a specification of the system.
It must be noted that the description below is based on the 1993 prototype,
as no current version of the tool exists. The future version of Teminator
will integrate new concepts defined since 1993 and its operating principles
and interface will be somewhat different but the 1993 prototype gives a
good illustration of the principles and philosophy we put into the tool.
Figure 1 shows the window for the Terminator. The scanned text appears in pane 12. To begin to process this text, the operator clicks the mouse with the cursor on the button labeled Next in the collection of buttons numbered 11. The Terminator proceeds through the text in chunks (roughly sentences or phrases separated by punctuation within a sentence), as this or other buttons are repeatedly pushed. The chunk highlighted in pane 12 reads spermatheca round with round sperms. Following suggested interpretation by the Terminator, a list of the suggested candidate characters appears in pane 10. The best candidate character (Spermatheca, shape, round) has been highlighted by the system. It happens to be the correct character in this example. Once a candidate character is highlighted, pushing the Accept button 11 causes it to appear in pane 7 as an accepted character. The operator can also proceed to the next chunk by pushing the Accept/next button which both accepts the current choice and moves to consider the next chunk. During description processing, a majority of the operations performed by the operator involve the accept/next button alone.
If a chunk is related to more than one character the Terminator usually comes up with suggestions for all characters, and they are displayed in the list in pane 10. The operator can accept as many as are appropriate. There is no limitation, and several records can be created from a single chunk.
Sometimes the Terminator will not find the correct character at all.
For example, during the processing of the chunk incompletely areolated
on tail (Figure 2), the system was
unable to find the correct character. However, two of the candidates, Areolations/kind
on tail/irregular areolations and Areolations/kind on whole body/irregular
areolations, do include the correct structure, Areolations.
If item 1 in pane 10 is selected, a menu item for that pane called Get
path causes a path through the hierarchy to be highlighted in panes
1 through 5: Exoskeleton, to which Areolations belongs, is highlighted
in pane 1; the main structure, Cuticle, is highlighted in pane 2; the Areolations
itself is highlighted in pane 3; and the list of corresponding properties
appears in pane 4. The operator can scroll the list of those properties,
select the correct one (kind on tail in this case), and finally
select the correct state (irregular areolations in this case)
from pane 5.
Sometimes the characters appearing in pane 10 are too far from the mark and do not even include the correct structure name. In this case the operator can highlight a word in the chunk, e.g., part of a structure, and use the Find command. The system finds all places where this word appears in the schema and produces a list. When the operator selects one of the characters in the list, it is displayed in panes 1 through 5 and it can be accepted as previously. If all else fails the operator has the option of scrolling and selecting the correct biological system in pane 1, structure in pane 2, substructure in pane 3, property in pane 4, and state in pane 5 or value in pane 6. This happens very infrequently.
Pane 6 is used to handle numerical values found within a chunk when problems arise, e.g., when there has been a scanning error. The operator uses pane 6 to enter a new set of values or modify an existing one.
The biological structure, basic property, and state/value panes have some menu items that assist in understanding the schema, such as definitions or synonyms for the biological structures and basic properties in the schema. The status panes (panes 8 in Figure 1) are used to record important information about the data, such as the stage being described (female, male, juvenile, cyst, etc.), the type of specimens (holotype, paratypes, syntype, etc., or non-type material), the errors, if any, in the original description (not valid), the difficult characters that the operator wants to be checked by the expert (review), the diagnostic characters, and general remarks made by the operator. Qualifiers that are found in the text (sometimes, usually, often, rarely, etc.) can also be entered.
The Terminator Interface, Processing tables
Some articles contain data in tables. Tables cannot be processed in
the same way as text, because (i) the chunks are not free-flowing and are
not delimited by commas, which requires a different approach to processing,
(ii) in a scanned document converted to ASCII the rows and columns often
do not line up, which makes them difficult to read, (iii) sometimes different
columns represent different populations that must be kept separate, (iv)
character names and other information in the headers often are more cryptic
than in written text, which requires additional interpretation, and (v)
there are many different formats for tables, with headers as different
populations, different species, or characters, although characters are
the row headers in most tables.
We resolved some of these problems during the scanning stage and others with modifications to the Terminator prototype, although tables are handled in the current version of Terminator by doing more manual work than would be ideal. For example, delimiters are entered manually to indicate the beginning of each header and character. Also, all of the various formats found in the literature are reduced manually during pre-processing to the single format that is most commonly found (columns = populations; rows = characters). This means that, at the expense of some manual processing, the current Terminator can be used to extract data from tables. The Terminator must accommodate the fact that each column refers to a different population or a different species, but at least the rows are most often characters.
Description Processing by the Terminator
In this section we discuss how the Terminator determines the list of
characters to propose in the Suggested pane in the window (pane
10 of Figure 1). Again, this is based on the protptype version of 1993
and the operating principles of a future updated version may be somewhat
When the text is first processed, the system attempts to determine where the true periods are that mark the end of sentences, as opposed to periods that appear in measurements, in abbreviations, or as stray marks misinterpreted by the OCR as periods. Once a sentence is identified it is decomposed into chunks, phrases that are separated by commas and semicolons. Some errors in measurements can be automatically corrected, whereby l's and o's (ells and ohs) can be converted to 1's and 0's (ones and zeros).
The system uses what is primarily a keyword approach. The keywords are those that appear in the hierarchical schema of structures along with their properties and states. However, the schema does not have to have a hierarchy of structures and substructures to work. A flat schema would work as well. Common words such as articles and prepositions can easily be eliminated from the list of keywords by creating a fairly small list of common words to be excluded.
Our approach does not rely on exact word matching, nor does it require that roots of words be specified. For example, the words annulus, annuli, annule, annulated, and annules are all sufficiently close that it is not necessary to specify or determine whether annul is a root. Terms that do not match closely enough can be put into a global list of synonymous terms for explicit matching. Also, synonyms are allowed in the schema, so many synonyms are automatically handled in the hints, as discussed below. It is useful for a few variations in spelling, such as oesophagus vs. esophagus, to have a global list of synonyms so that they do not need to be listed as synonymous everywhere in the schema where one or the other appears.
Keyword matching alone does not work particularly well. Generally, proposed enhancements to keyword-based systems include means for weighing and ranking the selected candidates and statistical methods for associating terms in a dictionary. We have found that we get reasonable performance using keywords with just some simple heuristics.
One of the main features used in the system is a set of hints, which are automatically generated by the system after the schema is created. (While the hints comprise the main elements used by the system, other information in the schema plays a role, such as whether the property is quantitative or qualitative so that quantitative properties are not considered if measurements are not found in the sentence.) A hint has the form [word, pattern, schema-element]. For example, ['tail', ('tail' 'end' 'mucro'), <structure element>] is one hint for the word tail when it is encountered in a sentence. The pattern consists of the words comprising the name or a synonym of the name of the schema-element, e.g. ('tail' 'end' 'mucro') in this example. The <structure element> is a structure, property of a structure, or state of a property of a structure that is specific to this hint. Likewise ['tail', ('tail' 'end' 'annuli'), <structure element>] is also a hint for the word tail.
For each sentence, the system attempts to determine which biological structures are possible candidates before treating individual chunks. This is done by first selecting those structure hints whose first entry, i.e., the word, matches sufficiently well with some word in the sentence. Some of the hints selected are then discarded if their patterns fail to match other words in the sentence sufficiently well. For example, the sentence: The end of the tail is rounded generates several hints, including the two hints in the example above, because words in the sentence match two of the three words in their pattern. In this particular case, however, the two resulting <structure element>s would be rejected due to other criteria discussed below. No other words in this example hint at other structures. For example, the word rounded does not match any structure names, but it does match several state names, and it will be used at a later stage when chunks are processed. The surviving hints for the structure elements are used to form a hierarchy of nodes for the sentence. The nodes of the hierarchy represent structures and substructures of those elements well matched with the words in the sentence. The system then proceeds with the analysis of each chunk of the sentence.
Each chunk within the sentence inherits a copy of the hierarchy of nodes for the sentence. Then, the system selects hints for properties and states that match words within the chunk sufficiently well. If the corresponding properties and states are associated with structures already in the hierarchy of nodes for the sentence, they are added as nodes below their respective structures. The other hints are discarded, unless they belong to substructures of other structures in the hierarchy. For example, for the chunk Lip region rounded, ... the original hierarchy of nodes includes a node for the structure Lip region. In the schema, the property state rounded is associated with a structure named Outline that is not in the original hierarchy of nodes because it does not appear in the sentence. However, Outline is a substructure of the structure Lip region, which is a node in the hierarchy. Consequently, the hint associated with the state rounded is used to add a node for Outline to the hierarchy for the given chunk.
A number of simple strategies are used to compensate for the system's lack of linguistic knowledge. The example in the previous paragraph shows how the system deals with implicit references. Another strategy is to designate some words as must words. For instance, in the examples of hints previously given, the words mucro and annuli are designated as structure words that must appear in the sentence for the hint to be added to the hierarchy of nodes for the sentence or a chunk of the sentence. It is easy for the domain expert to establish a list of structure names that are must words, that is, words that one expects to see in most situations when the corresponding structure is discussed. Must words are also given for character states. For example, in lemon- shaped, the word lemon is a must word, while shape is not. The net effect is to eliminate hints like ['tail', ('tail' 'end' 'mucro'), <structure element>] if the must word mucro is absent from a sentence or chunk, as in The end of the tail is rounded, but to retain it if mucro is present. If a word like end, which is not a must word, is absent from the sentence the hint would not automatically be discarded, but would be evaluated for overall matching as previously discussed.
After all the nodes that have matched sufficiently well have been added to the chunk's hierarchy the lowest level elements in the hierarchy become possible candidates. A candidate may consist of a structure, one of its properties, and a state, e.g., Body, posture, weak C. Some structures and properties may match well, but it may happen that the system does not find any state hint if the state used in the description is not currently in the schema. For example, in a sentence such as The body posture is a widely open C, if widely open C is not yet part of the schema we would still want to maintain Body, posture as a candidate. Each candidate is scored on how well it matches at each level in the node hierarchy and these scores are combined to form an overall score. The candidates are rank-ordered, first by simple heuristics, and then by their scores within a given rank. For example, candidate characters having hints for states or values are ranked above those that do not. If two states for the same property are candidates, only the one with the highest score is maintained in the list.
There are a few other elements in the system, such as Exact Hints and Table Hints, which help in specific expected situations. For example, measurements are often given in the form <character abbreviation>= <measurement>, such as a = 12.4, which gives the value for ratio a. If the same character appears in a table, the row header might simply be the letter a. A special table hint would allow the system to recognize this character.
In this section we examine the efficiency of the various activities
associated with the extraction of published data, from pre-processing the
printed text (i.e., scanning the document, optical character recognition
(OCR), and spell checking) through extracting the data (i.e., running the
Terminator), paying particular attention to how much time it takes to accomplish
each step, according to tests made in 1993. We did not try to conduct formal
replicated tests with different operators. In fact, the operator can take
many different courses of action with a highly interactive system like
the Terminator, and the time to carry out some actions is very much dependent
on a complex context that is difficult to characterize. For example, a
schema change may take only a few seconds when it requires only a simple
action (e.g., adding a state or a basic property to an existing structure)
or it may require a lengthy study of a complex situation by the domain
expert. Our goal in 1993 was to demonstrate proof of concept, that is,
that this is a practical tool for the job of building this type of database.
We tested the system on sixteen descriptions as part of an initial effort to obtain data for approximately fifty species of plant-parasitic nematodes of interest to the California Department of Food and Agriculture. The descriptions were scanned and spell-checked by a student assistant and the Terminator was used to process 16 description blocks, representing 12 text blocks and 4 table blocks. The descriptions were not processed with the idea of obtaining the fastest possible times, and they reflect the nematologist (RF) working efficiently but carefully as time allowed over several weeks to obtain error-free data.
On the average it took 12 minutes per page (with a range of 7 to 28 min/page) to pre-process descriptions (16 min/page for data presented in tables) prior to data extraction by the Terminator. The average description (text block) was 1.3 pages long. This pre-processing time included scanning the article, sometimes rescanning in case of a poor scan, running the OCR processing, and spell checking using a word processor. It should be noted that the time needed for OCR processing (using AccutextTM software) varied greatly depending on whether a training function (the Verifier) was on or off, with the verifier taking significantly more time than straight OCR operations (i.e., after training is completed and the verifier is off). Since we were processing from different journals, the verifier was often on, which slowed the process. Descriptions that included data arranged in tables took longer because of the need to reduce the various formats used for printed tables into the single format that can be read by the Terminator.
Data Extraction Times
Tables 1 and 2 give the times for data extraction from 16 descriptions
using the Terminator. Table 1 gives
the results for processing descriptions without any data tables (12 descriptions),
and Table 2 gives results for 4 data
tables processed separately. The processing time included the time the
Terminator takes to process the text as well as the interactive time the
operator takes to accept or input the data. The number of characters extracted
from the description and the number of schema changes were also recorded.
On average for the 16 descriptions, there were 64 characters per description and approximately 3 characters were processed per minute. The average time was 21.5 minutes per description. Processing the descriptions without data tables (Table 1) took 26.3 minutes per description, with 2.80 characters per minute and 74 characters per description. The schema had to be modified 4.9 times per textual description. This rather large number is probably due to the fact that the tests were made at a time when the concepts of schema building were not fully developed and the nematode schema used included many missing characters and improperties. Changes would be far less extensive with the current schema. The number of schema changes and the time for processing the text was greater than for tables.
The pre-processing operator was paid $5.58/hr and the scientist extracting the data was paid $25/hr, which means that it cost about $12.50 to completely extract the data from one description. It would cost about $100,000 for extracting the data from the 8,000 published descriptions of plant parasitic nematodes, a sizable sum but well within funding possibilities of large organizations.
In addition to processing times, we also recorded the qualitative performance
of the Terminator by checking how well it found the correct characters
on its own (without the help of the operator) in one of the descriptions,
(i.e., Table 1, line 2) selected at random. Since the test involved running
the Terminator a second time on a description that had already been processed,
there were no characters missing from the schema. Therefore, this gives
a better indication of the Terminator's performance when the schema is
nearly complete (i.e., it includes all the characters that are present
in the description being processed). It should be noted that the Terminator
was tested at a time when we were still grappling with problems associated
with the decomposition and representation of traditional characters. Solutions
described in Diederich (1997) and Diederich et al. (1997a) will make it
much easier to build an initial and partially complete schema, even before
starting with description processing.
In this test, if the correct candidate character, i.e., correct structure, property, and state/value, appeared in the display (among the first five suggested candidates), we called this a perfect match. In such cases, the operator only had to accept the character, possibly after selecting the correct one from among the displayed list of five candidates. Since these are very fast operations, we gave them the maximum score.
If the correct structure and/or property appeared in the first five characters but had the wrong state or value, we called this an incomplete match. In this case the operator had to select the candidate, get a path through the schema hierarchy, select the correct state/value or input the correct value, and accept the character from the hierarchical display. These are fast operations too, but not as fast as accepting the correct character directly from the initial pane.
Finally, in some cases, the state/value was missing because of our design decision to display only one candidate among all those that have the same property but different states and to print only the first measurement with each candidate even when there are multiple measurements in a chunk. In other cases, the data were missing because the Terminator takes a conservative approach to numerical problems introduced by the scanner. For example, the measurement I 8 (I7-2o) would not be corrected to 18 (17-20) and recognized as an average and range. Instead the Terminator recognizes the range and the number 8 as separate values and the operator needs to enter the correct values in pane 6.
We called it a mismatch when the correct candidate was not among the first five candidates. When this happens, the operator had to do a Find on a selected word to get to the correct character. An alternative would be to scroll through the list of other candidates. Choosing one method over another is a question of personal preference. Doing a Find and accepting from the path is approximately as fast as scrolling, while scrolling is more demanding because it requires reading through the candidates.
The results of this test were as follows. For measurement characters, usually simple and easier to recognize, the system achieved a perfect match 67% of the time, an incomplete match 25% of the time, and a mismatch the remaining 8% of the time, to yield an overall score of 76%. Even with the more difficult descriptive characters the Terminator did quite well, as the percentages were 55, 31, and 14, respectively, for a score of 71% on the descriptive characters only.
It should be noted that, even in those cases in which the Terminator did not find the correct character on its own, the alternative actions described above allowed the operator to process the data. In this sense, the overall success rate for the tool together with its human operator was 100%.
The Terminator offers a viable means of capturing and supplying data
from the published literature for use in populating general morphological
databases for any biological group. It may also be useful in other areas,
perhaps outside biology. This is an important advance, since other approaches
either would not work at all (e.g., when manual data extraction and entry
is not a practical option) or would require extensive effort with the resulting
costs possibly outweighing the benefits. As we indicated, natural language
processing in biological domains might require considerable independent
effort in each domain. Not only was the Terminator successfully used to
extract data in nematology, but it proved to be fast, easy, flexible, and
reliable. Much of this is due to its interface and related functionality.
The Terminator would also be particularly well suited to the concept of an electronic journal as an on-line database. Electronic publication is making progress, but the electronic journals we have seen implemented or tested so far propose full-text materials, that is, materials in which the data are not formatted and are embedded in extraneous material. This makes queries difficult and many types of direct use virtually impossible. A typical keyword search often returns unwanted elements resulting from query string mismatches, which represents a down side of this approach. Alternatively, an electronic journal could consist of one or several on-line databases. Authors would use Terminator to represent their data in the format of these general databases prior to adding the formatted data to the general pool of descriptions.
The Terminator interface has been refined and tuned many times, not only to make actions fast, but to make the layout and the nature of the actions easy on the operator to perform tasks, considerably reducing the fatigue factor. Easy usage relies first and foremost on both obvious and subtle aspects of the interface that require a great deal of tuning. Though we have not fully used the concept of Visual plan (Diederich & Milton, 1993), which relies on the arrangement of the various panes in the tool for suggesting the most likely course of action, it has influenced our design. It has made how to use this complex tool relatively easy to remember, even when one has not used it for a considerable time.
Easy usage helps with reliability too, since the operator can then be more attentive to the data that is being entered. However, smooth operation can actually be a problem in that it can lull the operator into a false sense of security. Fortunately, warnings such as those we have implemented for the change of type and stage will help overcome this potential problem. A tool is also available that is used to review the results, review data that has been tagged by one or more of the various indicators discussed earlier, and show which chunks have not had any data accepted yet in a description.
Another aspect of the tool is that it allows the operator ways to handle unusual or difficult situations. Without such capabilities it might become difficult to manage large sets of descriptions. Just keeping track of what needs to be reexamined could be troublesome. For example, there may be problems in deciding where to place a piece of data. In Globodera pallida the live females are white, but after they die they become dark brown cysts full of eggs. In the chunk Some populations pass through a four to six week cream stage before turning brown, it is not clear whether the cream color should be attributed to the female or to the cyst. The Terminator solution to this type of problem is to rely on the flexibility built in the schema and in the knowledge base that will be attached to it. In case of ambiguous statements or characters, the operator chooses one of the options (e.g., cyst, color) and explains the nature of the ambiguity in a memo attached to the character. Later, appropriate relationships will link the two characters so that an entry in one can be compared to an entry in the other.
The Future Version of Terminator
As indicated above, the 1993 prototype is no longer available and funding
is being seeked to create a new version of the tool. The major changes
and principals we determined for designing the characters will necessitate
reformulating the design of the terminator from the top to the bottom.
For example, the prototype showed that even a relatively simple Terminator
could be used to do the job but it did not try to "learn" from
the data it had processed. The new one would.
Obviously, it is too early to indicate what this tool will be, how it will operate, and what its interface will be. These points will be defined in the design phase of the implementation of the tool, once it is funded. At this moment, we can only indicate some avenues we will explore.
The interface : easier to use and more intuitive
We will try to implement fully the visual plan concept.
The data : uniform representation
We will integrate the new concepts defined since the time the prototype was built: basic properties, structures, views. For example, the prototype top 5-panel display will be replaced by a 3-panel display with structures-basic properties-states/values.
Extraction and formatting engine : smarter
Operating principles will take advantage of the new concepts. For example, the search of terms in the prototype put on the same footing all the terms in the schema. As a consequence, the list of suggestions at times was quite wrong. For example, if the text included "Tail round", the tool would also propose "Spermatheca/shape, round", because of the similarity in shape. The final version will give priority to structures over basic properties and values.
This work was supported in part by grant of the California Department of Food and Agriculture, Exotic Pest Research N° 3498.
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