LEAP - Features & Changes

LEAP - Features & Changes

Beta Release 0.10

Last revised, 7th March 1996

This page contains a brief summary of the features in LEAP. Also included is the change history of LEAP over the last year.

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Features

LEAP, in summary, offers the following:

A relational algebra query language. Examples taken directly from major DBMS texts (such as C.J.Date) are included in the examples.
Complete support of the structural and behavioural components of the relational model.
Multiple data types.
A rudimentary data dictionary.
Multiple databases, including example databases based on published text examples.
Online help.
Operator timing, enabling the execution time of queries to be compared and evaluated.
Extensive documentation/user manual.

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B0.9a -> B0.10 - 5th March, 1996

Multiple data types supported.

Duplicate tuples are not permitted, and this is enforced internally.

Hash tables are built for each and every relation, and stored between runs. All operators have been made more efficent as a result of this, previously they built their own hash tables. Should make for much more efficent operators and execution.

An iterative, two stage query parser can be used, which is much faster, and will eventually facilitate a query optimiser.

Data files are character delimited, rather than space delimited. Space delimited files are still supported, but all new relations are created with the new format.

Multiple databases are supported.

A completely rewritten user manual/instruction guide.

A "create database" operator is supported.

A small data dictionary is now utilised by LEAP.

Duplicate attributes are handled consistently.

A relation/Attribute rename operator is implemented.

Far fewer file handles are required.

An optional data cache is implemented.

Case sensitivity is available.

Implemented a "duplicate" operator.

Capitalised data has been removed.

Fixed a problem with the DISPLAY operator.

Infix expressions are the default format. Prefix are still supported (for now)

A form for feedback is included in the distribution.

LEAP has a new home page: http://www.brookes.ac.uk/cms/students/richard_leyton/leap.html

B0.9 -> B0.9a - September 1995

Minor documentation changes to reflect a change in contact details.

B0.8 -> B0.9 - July 1995

Infix expressions are fully supported.
The parser is more robust, and should no longer crash with malformed expressions.
Context sensitive help is available on all operators within LEAP, and on key relational concepts.
The help file can be changed to suit users needs. eg. Customised for teaching, changed for language.
CTRL-C no longer crashes the program at a prompt.
Screen is returned to 80x25 mode at the end and when NORMAL is entered. Earlier versions returned to the same mode as at startup, which did cause problems after a crash.
Status information available.
Timing information is available, and may be switched on/off within LEAP.
US Time format is supported, and can be switched on/off within LEAP.
Output copy file can be disabled if required.
Debug information can be switched on/off within LEAP.
Wildcards no longer valid in relation names when relation created.
LEAP no longer crashes if one of the relation files is missing.
Removed irratating ---> before source files when listed.

A0.7 -> B0.8 - May 1995

Polite error message if important files not found.
<> added to expressions.
Nesting allows the DISPLAY command to print relations.
Helpfile brought into line in a couple of places.
"Christened" as LEAP, executable filename changed to tally.
Documentation.

A0.6 -> A0.7 - April/May 1995

Nesting of commands supported.
Relations can be created within the program.
Tuples can be added to relations within the program.
No longer bombs out if unknown relation specified in an operator
Screen size can be adjusted to EGA/VGA 43/50 lines.
General tidyup of some output
Memory leaks have been resolved.
$TEMPDIR$\RARDBMS.TMP file created, mirroring output to screen
Irratating "Press any key" removed.
Debug information added to reporting.

->0.6 - September 1994 - March 1995

Purely internal revisions. Version A0.6 was the first version released onto the internet, and provided full operators, but limited flexibility.

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E-Mail richard_leyton@mail.amsinc.com