¯ [1]    Info on Lexa Desk


Lexa Desk

The idea behind Lexa Desk is to offer users a platform for loading individual
programmes of the Lexa group. Each option of a menu activates one of the pro-
grammes. After completion of this programme you return automatically to Lexa
Desk. Note that some programmes require that you enter information in the form
of command line options before loading.

Programmes of your own can be loaded via Shift-F1 or F5. You exit to DOS with
Alt-F4 or F7. Lexa Desk and any programmes called must be accessible via the
DOS path variable (usually specified in the startup file AUTOEXEC.BAT).

Bear in mind that when Lexa Desk is first loaded it executes the batch file 
_PRELUDE.BAT which you can use to customize the environment for the Lexa
programmes. This is especially useful if Lexa Desk is called from within
Microsoft Windows with which it is fully compatible.

N.B. You may also use Lexa Control to launch programmes. There is furthermore
a user-configurable shell available, Lexa Shell.

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¯ [2]    Introduction to Lexa 

A few words to begin with...

Let me remind users of the present software that the first matter they have to
decide before using the programmes is just what goal they are trying to attain
with the corpus data they intend to process. The task of tagging a corpus or
portion of it is carried out by the main programme, called simply Lexa. It may
well be, however, that this is not what one wishes to start with. Equally, if
not more common, is the wish to retrieve information from an available corpus,
tagged or not. In this case one should precede to the second menu 'Retrieval',
see comments in relevant help text.

You may wish to convert textual data into a database for more accurate stat-
istical processing. In this case choose the menu 'Databases'. If you have not
acquainted yourself with database management you might try doing so with the
database processing software of Lexa. By using this programme type you can
arrive at results not possible with text editing software.

It should be mentioned at this point that the Lexa suite does not constitute
natural language processing software in the sense of programmes which make
decisions on the grammatical status of input data. This must be done by the
user of Lexa in advance (for instance when tagging a corpus or part of one).
Lexa can only recognize categories which have been conveyed to it by the user.

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¯ [3]    Primary data processing 



What is a text and how is it processed?

The primary input data for Lexa are texts. At its simplest, a text is a series
of lines, each of which ends with a pre-defined pair of characters. Corpora
such as those of the ICAME Collection of English Language Corpora distributed
by the University of Bergen are shipped in simple text form. Such texts can be
processed directly by the programmes listed in the first menu. Tasks such as
tagging (automatic, manual or a combination of both), concordance generation,
making lexical density profiles, transferring of text to a database environment
are achieved by the main programme Lexa (first option).

The other programmes of the first menu allow one to edit texts directly, to
compare versions with one another, to gain relevant information on the struc-
ture of texts, or to view a supplied sample corpus with a comfortable interface.

If you just want to see what type of tasks the Lexa suite can be used for you
might care to try out the demonstration programme, Lexa Demo (choose option
'Run demonstration' in first menu).

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¯ [4]    Retrieving information


What kinds of information retrieval are there?

In the Lexa suite three main types of information retrieval are possible. The
first is the simplest: you are looking for a string and want to know what 
files it occurs in (use: Lexa Search). The second is much more powerful: you
wish to find all strings which match a partially specified input where you
may also set a number of search parameters (use: Lexa Pat). Thirdly there
is a programme which will allow you to search for syntactic contexts (use:
Lexa Context). Here you specify a frame by entering an initial string (or
part of one) and a terminal string and set various parameters such as where
the frame is expected (line or sentence) how large it can be maximally, manual
confirmation of potential finds, etc.

Retrieval involves texts in the main. However it is equally possible to carry
out similar operations with databases. Furthermore retrieval can include the
option of replacing finds with some user-specified string(s).

Information gleaned from texts can be sensitive to the parameters and their
values contained in Cocoa-style text file headers as provided for by the
Helsinki corpus, for example.

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¯ [5]    Using databases

How to make the most of databases

Most linguists involved in corpus processing will have experience with a word
processor and hence be oriented towards data in textual form. The potential to
manipulate data within the confines of a text are quite limited so that it is
strongly recommended that users of corpora consider the option of transferring
part if not all of their data to a database environment for further processing.

Transfer to a database can be achieved most easily by availing of the inbuilt
options in the programme Lexa (first option in first menu). It allows you to
extract all unique word forms from a set of texts, keep a track of their fre-
quencies, generate a reverse dictionary and carry out a variety of grammatical
analyses specified by the user on the basis of formal criteria applying to the
data contained in the output database.

Bear in mind the following rule of thumb: if you have large quantities of data
which are structurally similar and which you wish to expand on and still have
quick access to and to manipulate easily, then you should maintain this data
in a database environment. You can sort, extract, combine and filter data sel-
ectively in database form. And you can always re-export data back into a text
environment if you want to (use database managers: DbStat and/or DbTxt).

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¯ [6]    File management

Looking after your files and your hard disk

Last but not least, users of corpora should pay attention to the maintenance
of their data in file form on the hard disk of the computer. This is of part-
icular relevance if one makes temporary copies of files (as one should) when
experimenting with them or indeed if one is engaged actively in the task of
corpus compilation. You should store different kinds of data in different
directories on the hard disk and be careful to name files in a sensible manner
so that one can later recognize from their operating system name what their
contents are.

For your convenience, the Lexa suite puts at your disposal a number of power-
ful tools for file management. First and foremost one should mention the
file manager Lexa File, one of the major programmes of the group. You can use
it for all file maintenance and as a launching pad for processing tasks if you
wish. To move around directories use Lexa Dirs and to gain a quick overview
of the contents of a disk, use Lexa Browse. When locating files is an urgent
need, use Lexa Find. Lastly remember that there is a configurable shell in
the Lexa suite with which you can customize the type of operations you wish to
carry out on your corpus data, the programmes you want to use, etc. (use: Lexa
Shell).

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