Files are essential to the storage and
retrieval of information. Traditionally they are kept in some form of container
and include: text, numeric, and graphical information. Computers use data
stored in digitally coded files. This has resulted in a great deal of thought
and experimentation with various filing concepts, structures, organization,
etc. to improve storage and retrieval efficiency. Databases are
carefully structured files.
A principal function of a computer operating
system is to efficiently manage files of various types and sizes.
Filing systems provide a means of reliable
(safe) storage and retrieval. Essentially a file is an array of information.
This information is in some form of code arranged in some structure. Individual
file components are identified by file keys. Some files are referred to as
databases. Collections of files are often called volumes, and libraries.
Close examination of a traditional library
provides insight into the kinds of organization that are useful in developing
any filing system. Once a filing system is developed, and in active use, it is
hard to change, so great care should be taken during the initial structuring,
and implementation The disaster is the loss by one means or another of the
files once they have been established.
Files need to be maintained, supplemented,
cleaned, etc. during use. Any system must take the routine maintenance into
account. The costs will include use and maintenance.
FLAT and INVERTED (transposed ) FILES
A flat file can be thought of as an ij array
where the rows i are individual file components, and the columns j are items or
variables that apply to each component. A case by variable array is an example
of a flat file. The file may in fact be stored as a segmented string rather
than a rectangular or multidimensional array. Examples of a file of records:
This short example shows
three parts of a file component, the record identifier or
key, the information in the file, the location information.
A flat file can be inverted (transposed) so
that the information becomes the key, and the former key the
information. e.g. a partial inverted file from the above example is:
batch, 1002;
beam, 1001;
concrete, 1001 1002 1003;
design, 1003;
Note: the records that include 'concrete' are
identified as 1001, 1002, 1003 , and those that include 'batch' are 1002.
Therefore the records that include 'concrete beam' are the logical 'concrete'
and 'beam' or (1001 1002 1003)^(1002), where ^ is the logical and (APL
primitive), or record 1002.
A fairly extensive example of inverted files
are the local university library index.
^ [NUNET] * [Search Index * Files] * [About Files and Analysis
2. INFORMATION
4. Knowledge and Information,
Storage and Retrieval
6. Introductions to various TOPICS
included in MYSYS
7. Time Value and Engineering Economy
Topics
8. General List of Transportation
Topics
9. CE3201 Introduction to Transport
Engineering Course
End to date, ams 980122