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.
<FORM ACTION="url"> ... </FORM>
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 theInside aMETHODof typePOSTwith the NCSA HTTPd you will need to get version 1.0a5 or later.
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.
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:
NAME are grouped into
"one of many" behavior)
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.
<FORM> ... </FORM>, 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:
<SELECT NAME="a-menu">
<OPTION> First option.
<OPTION> Second option.
</SELECT>
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.
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.
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:
<TEXTAREA NAME="foo" ROWS=4 COLS=40></TEXTAREA>
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.").
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.
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.
METHOD="POST", use
ACTION="http://hoohoo.ncsa.uiuc.edu/cgi-bin/post-query"
METHOD="GET", use
ACTION="http://hoohoo.ncsa.uiuc.edu/cgi-bin/query"
query and post-query
programs is distributed with NCSA HTTPd, in the
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.
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).
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).
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.
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:
ISINDEX document; this provides that
very cleanly.
METHOD=POST.
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.
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