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日期:2020-10-30 10:59

Robotic Process Automation

RPA is an emerging technology that allows organizations to automate repetitive clerical work by executing

software scripts (RPA scripts) that support executions of sequences of fine-grained interactions with Web and

desktop applications. An example of such repetitive clerical work is transferring data across information

systems, for instance, from a spreadsheet into a Web form (refer to Figure 1).

A common approach to eliciting RPA scripts

nowadays is through observing workers or

interviews, which is time-consuming. Alistair and

Artem would like to start a business, called A&A

RPA, which will offer a new product to the market.

This product will aim to automate the process of

identifying routines, i.e., sequences of interactions

with User Interfaces of information systems that

lead to the same effect. For example, in the context

of Figure 1, a routine is a procedure for transferring

data from a row in sub-figure (a) to the Web form

in sub-figure (b) and clicking the “Save” button. As

the first

step, we developed a tool that records a trace

of consecutive actions, where an action

captures information about user interaction

with an infor-

(a) Student records spreadsheet (b) New Record creation form

Figure 1: Extract of spreadsheet with student data that needs

to be transferred to a Web form; https://bit.ly/2SPet3u.

mation system. Examples of actions include selecting

a cell in a spreadsheet, copying the content of a cell, and clicking a button in a Web form. An action is

characterized by a precondition and effect, each captured as a collection of Boolean variables.

For example, the precondition of clicking the “Save” button action in the Web form in Figure 1(b) may be

that variables FirstNameEntered, LastNameEntered, and CountryOfRresidenceEntered are all set to true, and

variable InternationalStudentSelected is set to false. The effect of this example action may be that variable

NewStudentEntryCreated is set to true, and all the precondition variables are set to false.

As the next step, we would like to develop a tool that given a trace and a candidate routine, both specified

as sequences of actions with preconditions and effects, identifies all sub-sequences of actions in the trace that

generate the same cumulative effect as the candidate routine. Candidate routines that lead to identifying many

such sub-sequences can be recommended for implementing in RPA scripts. Note that the identified subsequences

may, in general, be different as, for example, a user may be transferring content from the

spreadsheet cells to the form in different orders for different students (first name then last name, or vice versa).

Your task is to implement a tool for checking candidate routines.

Input Data

Your program should read input from stdin. The input starts by listing names of Boolean variables, one per line,

that must be set to true in the initial state, where the initial state is defined by values of all the Boolean

variables before a trace gets executed. All the other variables must be set to false in the initial state. An input

line with a single character ‘#’ denotes the end of input of the initial state. The lines that follow define actions,

one action per line. Each action is defined as a quintuple. The first two elements of an action list its precondition,

i.e., variables that must be set to true and false to enable the action. The third element is the name of the

action. The last two elements of an action specify its effect, i.e., variables that are set to be true and false after

the action is executed. Another input line with a single character ‘#’ denotes the end of the action definition

section of the input. The subsequent input characters encode a trace, each referring to the name of the action

executed in the corresponding position of the trace. All the lines of the input, except the last line, are not empty.

The following file test0.txt defines the initial state, three actions, and a trace executed from the initial state

(the numbers in italics show line numbers and are not part of the input file).

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1 a 4 y 7 ab:c:X:cf:b 2 b 5 z 8 f::V:pq:

3 x 6 # 9 fpq:b:U::pq

10 #

11 XVUVU

12

Boolean variables are denoted by characters ‘a’, ‘b’, ..., ‘z’ (lower-case Latin alphabet letters), while action

names are referred to as ‘A’, ‘B’, ..., ‘Z’ (upper-case Latin alphabet letters). Hence, the above input specifies the

initial state in which variables a, b, x, y, and z are set to true, while variables c, d, ..., w are set to false. The

input trace consists of five actions, see line 11. From the initial state, the trace commences by executing action

X, followed by an execution of action V, followed by action U, followed by another occurrence of V, and

concludes by another occurrence of action U. Actions U, V, and X are defined at lines 7–9 of the input. The five

components of each action are delimited using the colon character ‘:’. For example, the action defined at line

7 of the input has name X. This action can occur in a state where variables a and b are set to true, and variable

c is set to false. Once this action is executed, variables c and f are set to true, while variable b is set to false.

Stage 0 – Reading and Analyzing Input Data (8/20 marks)

The first version of your program should read the input from stdin, ensure that the input trace is valid, and

print out some basic information so that you can be sure you have read the inputs correctly. A valid trace is

composed of actions that occur in states that satisfy their preconditions; otherwise, the trace is invalid. The

required output from this stage generated for test0.txt file shown above is the summary shown below on the

left.

mac: ass2-soln < test0.txt

==STAGE 0===============================

Number of distinct actions: 3

Length of the input trace: 5

Trace status: valid

---------------------------------------

abcdefghijklmnopqrstuvwxyz >

11000000000000000000000111

X 10100100000000000000000111

V 10100100000000011000000111

U 10100100000000000000000111

V 10100100000000011000000111

U 10100100000000000000000111

mac: ass2-soln < test1.txt

==STAGE 0===============================

Number of distinct actions: 3

Length of the input trace: 5

Trace status: invalid

---------------------------------------

abcdefghijklmnopqrstuvwxyz >

11000000000000000000000111

X 10100100000000000000000111

V 10100100000000011000000111

U 11100100000000000000000111

V 11100100000000011000000111

The basic information printed by your program should specify the number of distinct actions, length of the

trace, and the status of the trace read from the input, which are 3, 5, and valid, respectively, for input file

test0.txt. This information should be followed by a delimiter line, followed by the detailed specification of the

trace given as a table of ASCII characters. The columns in this table refer to variables, while rows specify states

and executed actions. A state is encoded as a sequence of ‘0’ and ‘1’ characters, where ‘0’ indicates that the

corresponding variable (specified in the column header) is set to false and ‘1’ indicates that the variable is set

to true. The first printed state, denoted by character ‘>’ in the left-most column, specifies the initial state. Each

subsequent line prints the next executed action, followed by the sequence of zeros and ones that encodes the

state one achieves after executing the action. For instance, the execution of action X in the example input trace

flips the values of variables b and f in the initial state.

If the input trace is invalid, your program should report the corresponding status of the trace and print its

valid prefix. For example, if line 9 in file test0.txt is changed from “fpq:b:U::pq” to “fpq:b:U:b:pq” to obtain file

test1.txt, then your program should produce the output shown above on the right. In this case, the second

occurrence of action U cannot take place as its precondition requires that variable b is set to false. However, b

is set to true after the execution of the first four actions of the trace.

All inputs will follow the format specified in the Input Data section. No input action will specify that a

variable is equal (or should be set) to true and false simultaneously, e.g., “a:a:X:b:b”. Also, no input action will

set a value of a variable as in the precondition, e.g., “a:b:Y:a:b”. Your program will not be tested on erroneous

inputs. Refer to the input files distributed with this specification for the exact formatting of inputs.

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Stage 1 – Check Basic Routines (16/20 marks)

Extend your program from Stage 0 to perform a basic check of a candidate routine by identifying all trace

subsequences that produce the same effect. All of the Stage 0 output should be retained. If the input proceeds

with a line with a single character ‘#’, your program should generate Stage 1 output, which starts with this line:

==STAGE 1===============================

For each subsequent input line containing a candidate routine specified as a sequence of action names,

discover and print non-overlapping sub-sequences of consecutive actions of the trace that produce the same

cumulative effect as the candidate routine. Proceed from left to right in the trace. Once the shortest subsequence

with the desired effect is identified, record it and restart searching from the next position in the trace.

The cumulative effect of a routine or sequence of actions is determined as all the values (true and false)

set to the Boolean variables as effects of the actions executed in the order they appear in the routine/sequence.

Considering input file test0.txt, candidate routine VU generates the cumulative effect of setting variables p and

q to false. First, action V sets p and q to true. Next, action U updates them to be false. Hence, would input file

test0.txt be modified to contain a single character ‘#’ at line 12 and string “VU” at line 13 to encode a candidate

routine followed by the new line character, Stage 1 output should proceed by printing these lines:

Candidate routine: VU

1: VU

3: VU

Here, the first line specifies the candidate routine and the two subsequent lines refer to two sub-sequences

that start at positions 1 and 3 of the input trace (counting positions from zero); trace positions are printed

using the formatting string “%5d”. These two sub-sequences generate the same cumulative effect as the

candidate routine.

Each subsequent input line with a candidate routine should be processed in the same way, and its output

should be separated from the previous output by the delimiter line composed of ‘-’ characters, refer to Stage

0 specification above for examples of using the delimiter line. Consider input file test2.txt listed below.

The Stage 1 output for input file test2.txt is shown below on the left. Indeed, both sequences of actions D and

AB have the cumulative effect of setting variables x, y, and z to true, and are therefore identified. Subsequences

with smaller start positions should be printed first.

==STAGE 1=============================== ==STAGE 2===============================

Candidate routine: AB Candidate routine: D

0: D 0: D

2: AB 2: AB

---------------------------------------- 5: ACGHE

Candidate routine: D ----------------------------------------

0: D Candidate routine: AB

2: AB 0: D

2: AB

5: ACGHE

==THE END===============================

Stage 2 – Check Advanced Routines (20/20 marks)

Extend your program from Stage 1 to perform further checks for the input candidate routines. All of the output

from Stages 0 and 1 should be retained. If your input after Stage 1 continues with a single character line of ‘#’,

process subsequent input lines with candidate routines (one routine per line). This time, an identified subsequence

of actions in the input trace should be allowed to modify the values of variables not set by the

candidate routine. However, in this case, once all the actions of the identified sub-sequence are executed, the

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values of such variables must be set to the values they had before executing the sub-sequence. Note that this

knowledge of variable values can be obtained from the preconditions of the trace actions.

For example, the sub-sequence of actions ACGHE in the trace of input file test2.txt sets values of variables

i, j, x, y, and z. Note that, to execute, action G requires that i and j are both set to false, and sets them to true.

However, next, action H sets them to false, which are their original values at the start of the sub-sequence.

Hence, the cumulative effect of executing ACGHE is the same as that one of executing D or AB, i.e., setting x, y,

and z to true. The complete output of Stage 2 for input file test2.txt is proposed on the right of the listings

presented in the specification of Stage 1. If your program concludes with Stage 2, at the end, it should output

this line: ==THE END===============================

Important...

The outputs generated by your program should be exactly the same as the sample outputs for the

corresponding inputs. You should not assume the maximal allowed lengths for the input trace and candidate

routines and, thus, use malloc and linked lists to store them. Regardless of the algorithmic techniques you will

employ in this assignment, your program should run under 1 second on each sample input.


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