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