5. Análisis bivariado
5.2. Análisis bivariado de una variable cuantitativa y una cualitativa: Prueba t Student
A t times, the default behavior of toolkit widgets was not the best user interface behavior in the specific context of our application . Sometimes no existing widgets provided the functionality we needed. Thus, in certain cases, we had to write our own widgets or borrow w idgets from other develop ment groups. In other cases, we had to find ways to override the toolkit widgets' default behavior. Two particular cases of this were in the text widget's
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handling of word \Vrapping, :1nd the d ialog box widget's hanc.lling of navigation with the Tab key. Line Wrapping The DECwindows text widget sup ports automatic wrapping of l ines when the cursor reaches the right edge if the word wrap resource is set. Because this setting eliminates the need for the user to hit a return at the end of each line, it w:1s enabled as a default for the Create-Send window in DECwindows mail. However, the wrapping was done on the screen only. The text sent by the mail application only contained t he hard returns entered by the user. Jn general, there was no problem as long as the mail message was read with DEC windows VMS mail . The word wrap is set in the Read window as well, and the lines are w rapped to fit the reader's window width. However, if the reader were using VMS mail, the paragraph would be displayed as a single line with only the first 80 characters visible. Also, if the paragraph was very long, the VMS mail protocol record length restrictions would prevent transmission of the message.
We considered two options to solve the word wrapping problem because we did not have a direct way to obtain the wrapped text from the text widget. First, we could e l iminate the default word wrap and require users to enter a return at the end of each line. The other possibility was to insert returns at an arbitrary point near the end of each line, e.g . , the last white space previous to the 80th character of each l ine. However, in read ing the sources for the text widget, we found that it might be possible to query the text widget indirectly to find where it had wrapped the text on the screen. Word wrapping was achieved by using undocu mented text widget calls and data structures and forcing the text widget to move through the entire message text one screen at a time.
Tab Navigation According to the XU! Style Guide, the Tab key navigates from one text field to the next one within the same window and selects the field's entire contents for pending delete. In other worc.ls, the next keystroke automatically inserts itself after deleting the selected text . This feature was designed for dialog boxes containing several short text fields, but was less appropriate for DECwindows VMS mail Create-Send window's message area. I n fact, it cre ated problems. For example, if a user pressed t he
Tab key while in the message area, the cursor would move to the personal name field, which is the first text field in the window A tab character could not
be inserted into a text widget , even a widget being used more as a text editor than a text field .
A more serious problem was that o f selection for pending delete. When users would tab to the message area and begin typing, the first keystroke would wipe out the previous contents. Since the text widget provides no practical way to undo such changes, the user could not recover from a simple and common error. We had to override the dialog box's t ranslation for tab and reimplement t he nor mal processing to fix the problem. In this case, normal processing means process as normal for envelope text widgets and insert the tab for the mes sage area.
Summary
DEC w indows VMS mail was one component in the integrated development effort of the DECwindows system. The problems we faced and solved and those which still need to be addressed, reflect many of the problems of developing integrated systems in an environment in which some components are constrained by external standards, the compo nents interact in potentially complex ways, and many components are under active development . Our experiences in developing DECwindows VMS mail have left us better prepared to deal with the continuing trends toward software integration.
Acknowledgments
We would l ike to thank everyone who has worked on and helped with DECwindows VMS mail during its development. This includes the members of the
XUI toolkit team, the VMS DECwindows team, as well as the many people throughout Digital who used and helped test mail. In particular we would like to thank Terry Weissman , the U LTRIX system based DECwindows mail developer, for his help and cooperation throughout the project , and the engi neers, writers, and managers who were directly involved in the development of DECwindows VMS mail : Pam Bantis, Roger Brinkley, Mike Daugherty, Elaine Egolf, Eric Hansen, Gerry Hornik, Debbie Huffman, Craig jackson, Lorri Menard, Cheryl Mrozienski, Linda Nallctt, Kel l y Sol inas, and Duane Smith.
References
I .
CCI1'T
Data Communication Networks .Message Handling Systems RecommendationsX. 40()
X. 430,
Volume VIII - Fascicle YJ!I .7, CCITT,ISBN 92-6 1 -0236 1 -4 .
Digital Tecbnicaljournal
Vol. 2 No. 3 S11mmer /')')()
The Development of DEC windows VMS Mail
2 . P. Mierswa, "The Evolution of the MAILbus," Digital Technical journal, vol. I , no. 9 (June
1989): 37-43.
3 .
XU!
Style Guide (Maynard: Digital Equipment Corporation, Order No.AA
-MG
20A
-T
E, 1988).4 . R. Scheifler et a l . , " Introduction" and "Introduc t ion to Xlib," X Window System, C Library' and Protocol Reference (Bedford : Digital Press, Order No. E
Y
-67
37 £
-DP
, 1988).5. R. Travis,
" CDA
Overview," Digital Technical journal, vol. 2 , no. 1 (Winter 1990): 8- 1 5 . 6. W . Laurune and R . Travis, "The Digital Document Interchange Format," Digital Tee/mica/ journal, vol . 2 , no. I (Winter 1990): 16-27. 7. D. Rosenthal, X Window System, Version 11-
/nterclient Communication Conventions Man u.al Version
1.0.
8. B . Cheung and N. Jacobson, " lnterapplication Access and Integration," Digital Technicaljour nal, vol . 2 , no. I (Winter 1990): 49-59.
Dinesh Mirchandani