157
TABLE UCH (The characteristic of the user)
QTYPE
NOE
NOU
DATE
Q1
14
56
12-04-90
Qn
10
74
20-04-90
QTYP
the type of a query
NOE
the number of errors
NOU
number of times queiy used
DATE
date of last addition to NOU
Q1
"SELECT"
Q2
"INSERT", etc
Figure 1. Structure of the database
’’The characteristic of the user"
The sequence of operations which
perform this procedure is as follows:
a. The user introduces a query.
b. The system checks the query for
correctness in relation to the language rules.
c. If an error has occurred, the procedure for
identification and correction of errors is
activated. In the database "the characteristic of
the user" is stored the information about the
error made by that user.
d. If no error has been detected the
information about the use of the query is stored.
e. On the basis of the frequency of errors,
the appropriate level of the help message is
displayed.
f. The user continues execution of the
corrected query.
In this implementation of quasi-
intelligent "help" three levels of the help
messages have been introduced: Level 1 will be
displayed if p (the frequency of the error) > 0.3,
level 2 if 0.1 =< p =< 0.3 and level 3 if p < 0.1. The
boundary of the intervals do not have any
theoretical background since they are
empirically derived based on tests. The
experiments have shown that the effectiveness
and the ease of operation of a system equipped
with a such quasi-intelligent help are much
higher than where traditional "help" is
employed.
3.3 A Procedure for Identification and
Execution of the Typical Tasks.
Work with a GIS can be consider as a
sequence of queries. In almost all cases, each
particular user performs individual type(s) of
task(s). This means that in each work session
he/she will use typically the same, sequence of
queries, the difference being only in the data sets
employed. Such an approach is not efficient if
lengthy periods are spent inputting information
via the keyboard. Formulation of identical
sequences of queries in each session can be
utilised to improve the effectiveness and speed of
operation of the system. This can be achieved by
the following procedure.
(i) For each "new" user the system creates a
database which we call "YOUR_JOB" (Figure
2).
TABLE YOUR.JOB
(The database of typical tasks)
SQNO SQSTR
1 Ql...Qi...Qn
N Qi...Qj...Qk
SQNO sequence number
SQSTR sequence structure
and associated TABLE QBASE
(The database of queries structure)
QTYPE QSTR
Q1 "SELECT FROM..."
Qn "DELETE ...FROM..."
QTYPE the type of a query
QSTR the structure of a query
Figure 2. Structure of the database
"YOUR_JOB".
(ii) During several work sessions, the
system introduces to the database the sequence of
queries used in each session.
(iii) Then the system makes a decision in
regard to its mode of operation.
(iv) The user is informed that a sequence or
sequences of queries, which will be considered