Mosaic for X version 2.0 Fill-Out Form Support
Here are details about what we have implemented for fill-out forms in
help-on-version-2.0.html - Mosaic for X 2.0
The FORM Tag
The FORM tag specifies a fill-out form within an HTML document. More than one
fill-out form can be in a single document, but forms cannot be nested.
The attributes are as follows:
ACTION is the URL of the query server to which the form contents will be
submitted; if this attribute is absent, then the current document URL will be
used.
METHOD is the HTTP/1.0 method used to submit the fill-out form to a query
server. Which method you use depends on how your particular server works; we
strongly recommend use of (or near-term migration to) POST. The valid choices
are:
GET -- this is the default method and causes the fill-out form contents to be
appended to the URL as if they were a normal query.
POST -- this method causes the fill-out form contents to be sent to the server
in a data body rather than as part of the URL.
ENCTYPE specifies the encoding for the fill-out form contents. This attribute
only applies if METHOD is set to POST -- and even then, there is only one
possible value (the default, application/x-www-form-urlencoded) so far.
NOTE: If you want to use the METHOD of type POST with the NCSA httpd you will
need to get version 1.0a5 or later.
Inside a FORM you can have anything except another FORM. Specifically, INPUT,
SELECT, and TEXTAREA tags are used to specify interface elements within the
form.
Forms are not automatically visually differentiated from the rest of a
document. We recommend using the HR (horizontal rule) tag before and after a
form to cleanly differentiate it from surrounding text and/or other forms.
The INPUT Tag
The INPUT tag is used to specify a simple input element inside a FORM. It is
a standalone tag; it does not surround anything and there is no terminating
tag -- i.e., it is used in much the same way as IMG.
In Mosaic for X, various types of INPUT tags are instantiated as Motif widgets
(text entry fields, toggle buttons, pushbuttons, etc.).
The attributes to INPUT are as follows:
TYPE must be one of:
"text" (text entry field; this is the default)
"password" (text entry field; entered characters are represented as asterisks)
"checkbox" (a single toggle button; on or off)
"radio" (a single toggle button; on or off; other toggles with the same NAME
are grouped into "one of many" behavior)
"submit" (a pushbutton that causes the current form to be packaged up into a
query URL and sent to a remote server)
"reset" (a pushbutton that causes the various input elements in the form to be
reset to their default values)
NAME is the symbolic name (not a displayed name -- normal HTML within the form
is used for that) for this input field. This must be present for all types
but "submit" and "reset", as it is used when putting together the query string
that gets sent to the remote server when the filled-out form is submitted.
VALUE, for a text or password entry field, can be used to specify the default
contents of the field. For a checkbox or a radio button, VALUE specifies the
value of the button when it is checked (unchecked checkboxes are disregarded
when submitting queries); the default value for a checkbox or radio button is
"on". For types "submit" and "reset", VALUE can be used to specify the label
for the pushbutton.
CHECKED (no value needed) specifies that this checkbox or radio button is
checked by default; this is only appropriate for checkboxes and radio buttons.
SIZE is the physical size of the input field in characters; this is only
appropriate for text entry fields and password entry fields. If this is not
present, the default is 20. Multiline text entry fields can be specified as
SIZE=width,height; e.g. SIZE=60,12. Note: the SIZE attribute should not be
used to specify multiline text entry fields now that the TEXTAREA tag is
available.
MAXLENGTH is the maximum number of characters that are accepted as input; this
is only appropriate for text entry fields and password entry fields (and only
for single-line text entry fields at that). If this is not present, the
default will be unlimited. The text entry field is assumed to scroll
appropriately if MAXLENGTH is greater than SIZE.
The SELECT Tag
Inside , any number of SELECT tags are allowed, freely
intermixed with other HTML elements (including INPUT and TEXTAREA elements)
and text (but not additional forms). In Mosaic for X, SELECT tags are
instantiated as Motif option menus and scrolled lists.
Unlike INPUT, SELECT has both opening and closing tags. Inside SELECT, only a
sequence of OPTION tags -- each followed by an arbitrary amount of plain text
(no HTML markup) -- is allowed; for example:
The attributes to SELECT are as follows:
NAME is the symbolic name for this
SELECT element.
This must be present, as it is used when putting together the
query string for the submitted form.
SIZE: if SIZE is 1 or if the SIZE attribute is missing, by default the SELECT
will be represented as a Motif option menu. If SIZE is 2 or more, the SELECT
will be represented as a Motif scrolled list; the value of SIZE then
determines how many items will be visible.
MULTIPLE, if present (no value), specifies that the SELECT should allow
multiple selections (n of many behavior). The presence of MULTIPLE forces the
SELECT to be represented as a Motif scrolled list, regardless of the value of
SIZE.
The attributes to OPTION are as follows:
SELECTED specifies that this option is selected by default. If the SELECT
allows multiple selections (via the MULTIPLE attribute), multiple options can
be specified as SELECTED.
The TEXTAREA Tag
The TEXTAREA tag can be used to place a multiline text entry field with
optional default contents in a fill-out form. The attributes to TEXTAREA are
as follows:
NAME is the symbolic name of the text entry field.
ROWS is the number of rows (vertical height in characters) of the text entry
field.
COLS is the number of columns (horizontal width in characters) of the text
entry field.
TEXTAREA fields automatically have scrollbars; any amount of text can be
entered in them.
The TEXTAREA element requires both an opening and a closing tag. A TEXTAREA
with no default contents looks like this:
A TEXTAREA with default contents looks like this:
<TEXTAREA NAME="foo" ROWS=4 COLS=40>
Default contents go here.
</TEXTAREA>
The default contents must be straight ASCII text. Newlines are
respected (so in the above example there will be a newline both
before and after "Default contents go here.").
Form Submission
For Method = GET
When the submit button is pressed, the contents of the form will be assembled
into a query URL that looks like this:
action?name=value&name=value&name=value
("action" here is the URL specified by the ACTION attribute to the FORM tag,
or the current document URL if no ACTION attribute was specified.)
Strange characters in any of the "name" or "value" instances will be escaped
as usual; this includes "=" and "&". Note: This means that instances of
"=" that separate names and values, and instances of "&" that separate
name/value pairs, are not escaped.
For text and password entry fields, whatever the user typed in will be
the value; if the user didn't type anything, the value will be empty
but the "name=" part of the query string will still be present.
For checkboxes and radio buttons, the VALUE attribute specifies the value of a
checkbox or radio button when it is checked. An unchecked checkbox is
disregarded completely when assembling the query string. Multiple checkboxes
can have the same NAME (and different VALUEs), if desired. Multiple radio
buttons intended to have "one of many" behavior should have the same NAME and
different VALUEs.
For Method = POST
The contents of the form are encoded exactly as with the GET method (above),
but rather than appending them to the URL specified by the form's ACTION
attribute as a query, the contents are sent in a data block as part of the
POST operation. The ACTION attribute (if any) is the URL to which the data
block is POSTed.
Test Servers
If you wish to write a prototype fill-out form and test it against a
query server that simply shows you what you submitted (with name/value
pairs decoded and itemized), you can use the following:
For METHOD="POST", use
ACTION="http://hoohoo.ncsa.uiuc.edu/htbin-post/post-query"
For METHOD="GET", use
ACTION="http://hoohoo.ncsa.uiuc.edu/htbin/query"
C source code for the query and post-query programs is distributed with NCSA
httpd, in the ftp://ftp.ncsa.uiuc.edu/Web/httpd/Unix/ncsa_httpd/cgi/cgi-src
directory.
The fill-out form examples listed below use these query servers as
their back ends, so you can see them in action and know what to
expect with your own forms.
Important note: If you use the GET method in your form, you will notice that
the example GET server will choke if too much data (more than a couple hundred
bytes) is submitted at a time -- the server is passing the data to the form-
processing module via a shell command line, and the maximum shell command line
length is being exceeded. This problem does not exist with the POST method
and server.
Things To Note
Some things in the HTML+ spec aren't yet supported. In particular, mailto
URLs aren't supported as actions yet, and also the Mosaic 2.0 support only
includes a subset of the allowable types of input fields (obviously "text" can
also serve as "url", "int", "float", and "date" but without intrinsic
range/error checking).
A "submit" element is necessary in all forms except those containing only a
single INPUT element of type TEXT (in which case Return in the text entry area
submits the form) or at least one INPUT element of type IMAGE (in which case a
click in the image submits the form).
Mosaic has a stealth feature: if a single text field is in a form and the NAME
of the text field is "isindex", then the submitted query will be just like you
are used to getting with ISINDEX -- "url?querystring" (i.e., not
"url?isindex=querystring"). This allows you to use simple fill-out forms in
your documents to point to existing query servers (including Gopher and WAIS
servers!). This of course assumes that the POST method is not specified for
such forms.
There seems to be a bug under IRIX 5.1.0.1 and 5.1.1 (at least) that causes
text entry fields in forms to only be half as (physically) big as they should
be. This is not a bug in Mosaic -- the fields are the correct size on all
other X servers we have seen, and this general geometry problem afflicts other
programs running under IRIX 5.1.0.1/5.1.1 also (e.g. Marc's Epoch windows come
up half as big as they should, etc.). There's nothing we can do until SGI
fixes the bug in their X server.
ISINDEX Handling
Now that we have this fancy fill-out form support, we're supporting the
ISINDEX tag differently. Instead of having a browser-interface method (dialog
box or text field) for entering a query, an instance of ISINDEX is
instantiated as a preloaded fill-out form suitable for entering a query; the
form is inlined at the location of the ISINDEX tag itself in the document.
Justifications for change:
Consistent approach to query mechanisms inside Mosaic.
Allow code and interface complexity to be reduced.
A few nasty problems were hitting the "popup text entry field" approach
attempted for prerelease 2; notably, lots of unavoidable flashing when field
popped up and down and intermittent but crippling Motif geometry management
problem. This change removes those problems.
Everyone wants the ability to enter a query (and the corresponding widgets) to
be present only when the document is actually an ISINDEX document; this
provides that very cleanly.
This solves existing problem of when to retain contents of search field --
since search field now exists on a per-document basis, this is very clean.
Encourage experimentation with fill-out forms by presenting an example for
existing query engines.
Examples
Twelve examples are available. All of the examples now use METHOD=POST.
Example 1 -- a ludicrously simple fill-out form.
Example 2 -- three text entry fields.
Example 3 -- text entry fields and checkboxes.
Example 4 -- changing the default values of text entry fields and checkboxes.
Example 5 -- changing various attributes of text entry fields.
Example 6 -- multiple, independent forms in a single document.
Example 7 -- radio buttons, "one of many" behavior.
Example 8 -- password entry fields.
Example 9 -- option menus.
Example 10 -- scrolled lists with single and multiple selections.
Example 11 -- multiline text entry areas.
Example 12 -- image maps in forms.
Example 13 -- forms with hidden elements.
Writing Your Own Fill-Out Form Query Engine
If you want to set up one or more query engines corresponding to fill-out
forms that you create for database accesses or other purposes, you may want to
take a look at http://hoohoo.ncsa.uiuc.edu/docs/Overview.html - NCSA httpd
1.0. One of the example programs included with NCSA httpd is a sample fill-
out form server (the same server used in the examples above, actually) and
will provide a good model for writing your own servers.
We strongly, strongly recommend use of the POST method with fill-out forms.
One reason: with the GET method, given the way many servers (e.g. NCSA httpd)
pass query strings from URLs to query server scripts, you run an excellent
chance of having the forms contents truncated by hardcoded shell command
argument lengths. With POST (again, e.g., with NCSA httpd) you should be able
to do a total end run around such problems.
NCSA httpd 1.0 (the official release) should be out shortly and will contain
an example POST fill-out form server.
Fill-Out Forms in the Real World
Here are some fill-out forms in use in the Real World(tm). For up-to-date
examples, search on "form" in ../whats-new.html - What's New.
http://cea-ftp.cea.berkeley.edu/Registration.html - Registration form.
http://www.cm.cf.ac.uk/Movies/moviequery.html - Cardiff's Movie Database
Browser
http://web.nexor.co.uk/archieplex-info/archieplexform.html - ArchiePlex forms
interface.
http://south.ncsa.uiuc.edu:8241/Free.html - Free For All
http://rs560.cl.msu.edu/weather/getmegif.html - weather map "order form".
http://doccenter.com/doccenter/home.html - Document Center is a hard copy
document delivery service specializing in government and industry
specifications and standards. Document Center has the complete Department of
Defense (DoD) Index of Specifications and Standards collection available, as
well as the complete collection of the American Society for Testing Materials
(ASTM). The Center also has additional industry (ANSI, SAE, IPC, IEEE, EIA)
and govenment (NASA, DLA, FAA) documentation at its Silicon Valley location.
Another http://marvin.physik.uni-oldenburg.de/Docs/net-serv/archie-gate.html -
Archie gateway at Oldenburg.
Comments?
Please send mail to mosaic-x@ncsa.uiuc.edu.