Fluid Visualization Of Spreadsheet Structures (Page 6 of 8) in pdf

patterns such as those shown in Figure 8. This section

describes our approach of constructing these regular

structures

graphically

using

induction.

current

spreadsheets, the user must use the “$” symbol to specify

=A$1 =B$1 =C$1

=$C$1 =$C$1 =$C$1

absolute references, and then correctly perform fill

operations to construct the desired dataflow patterns. The

$ symbol indicates that the following parameter is invariant

throughout the fill operation, while other parameters change

=$A2+$B$1

according to the relative position of the filled cells. For

=$A3+$B$1

=$A4+$B$1

example, if the formula for B2 is =$A2*B$1 and the user

filled the region of B2-D4 with this formula, the formula for

D4 becomes =$A4*D$1.

Figure 8. Regular patterns of cell

This scheme fails for a number of useful patterns, such

referencing . It is difficult to encode these

as those shown in Figure 8. Even in simple cases it is very

patterns using $ symbols. In fact, the fourth

difficult to construct and understand correct formulas using

example cannot be expressed using

$ symbols. Hendry proposed a programming-by-example

$ symbols.

technique to solve the problem [11]. His approach is to have

the user key in the first two formulas, specify the region for

filling, and run a menu command to initiate the fill. He

showed that two examples are sufficient to express common

spreadsheet structures. Formulas for the filled cells can be

Select

automatically inferred from the relative position of the cells

“Fill” on a

and the difference of parameter values between the two

region

examples. Although he doesn’t use this term, he has

b) The default second

a) Initial state. The

essentially proposed filling formulas using induction on the

example generated by

current cell refers to

The user edits

the system.

structure of the first two formulas.

two incoming cells.

the second

Our interactive graphical induction technique extends

This will be used as

example

the first example.

his approach by using graphical examples [7] instead of

textual formulas for the induction. The system allows the

user to edit the two examples graphically, and then visually

presents the result of the fill operation. Our current

implementation works as follows:

1. Key in a formula in the cell that starts the fill region.

2. Select the fill region and run the fill command.

Press OK

3. The system presents a graphical proposal of the

button

second step of the induction, which can be graphically

d) Result of the inductive fill

c) The second example

manipulated into the correct state.

operation based on a) and c).

specified by the user.

4. Press the confirm button to perform the fill operation.

Figure 9. Interactive graphical induction .

The key idea is in step 3: the system prompts the user to

The system automatically infers the cell

specify the second example graphically. As a result of this

referencing for the filled cells based on

interactive approach, the user no longer needs to prepare the

induction from the first two graphical

textual formulas carefully before the fill operation. All the

examples. The first example is given by the

user has to do is to answer the system’s request for

user. The system generates the default second

confirmation, by very naturally moving the graphical boxes

example and asks the user to adjust it.

to the correct locations. In addition, the graphical

representation of the first two examples and subsequent filled

cells also helps the understanding of the resulting structure of

8 Related work

the dataflow graph. Figure 9 shows examples of dataflow

structures created using this graphical induction mechanism.

The success of the spreadsheet as an easy-to-use

Both position and size of regions are correctly inferred

computational environment [8, 12, 22] has led to several

because the system applies induction for the row and column

end-user programming systems based on spreadsheet-like

numbers of both the upper-left and lower-right cells of the

interfaces. ACE [13] extended the basic idea of spreadsheets,

fill regions.

a tabular layout enhanced by textual notations, and applied it

Fluid Visualization Of Spreadsheet Structures Page 6

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