<PowerForms Syntax>

PowerForms extends standard html syntax with the following xml syntax. As PowerForms uses xml syntax all attribute values must be enclosed in single (') or double quotes (").

Syntax

Semantics

Assigning formats to fields

• <format [form=form] field=field>

  Declares that fields named field must satisfy the format. If no fields are named field the declaration has no effect. The optional attribute form is used to state to which form the declaration applies.

  If no form attribute is supplied and only a single form is declared on the html page then the format applies to field on the single form. If more than one form is declared and the format declaration occurs inside some form then the format applies to field on the enclosing form. Otherwise an error is reported.

  If a field has a format that is the <empty/>-regexp, then that field is valid no matter what the value is. See an example of the use of <empty/>: personal.

  Additional attributes

  Three extra attributes are allowed in the format-tag:

  • help: a short help message to aid the user in filling the field correct
  • warning: a short message to tell the user that the field contains incomplete input
  • error: error message to show the user if he tries to submit the form when the field contains invalid data

  Note: due to browser incompatibilities these attributes are currently ignored until a submit error occurs.

Formats

• <format id=id>

  Defines the format for future reference by the name id.

• <format idref=id>

  Evaluates to a previously declared format with name id.

• <if>

  If boolexp evaluates to true this format evaluates to the format given inside <then> . . . </then>. Otherwise it evaluates to the format inside <else> . . . </else>.

Boolean expressions

• <match [form=form] field=field >

  Evaluates to true if and only if one value of field on form matches the regular expression (if field is a set of checkboxes it can have more than one value). Otherwise the result is false.

• <matchall [form=form] field=field >

  Evaluates to true if and only if all values of field on form matches the regular expression. Otherwise the result is false.

• <equal [form=form] field=field value=value >

  Evaluates to true if and only if one value of field on form is equal to value. Otherwise the result is false.

• <and>

  Evaluates to true if and only if all the boolean expressions in evaluates to true. Otherwise the value is false.

• <or>

  Evaluates to true if and only if one of the boolean expressions evaluates to true. Otherwise the value is false.

• <not>

  Evaluates to true if and only if all the boolean expressions evaluates to false. Otherwise the value is false.

If the page contains only a single form, then the form attribute is optional for both match and equal.

Regular expressions

It is assumed that the reader is familiar with regular expressions and below is a brief description of the semantics of the PowerForms constructs for regular expressions.

• <empty>, <anychar>, and <anything>

  Generates the languages consisting of respectively no strings (not even the empty string), all strings of length 1, and all strings.

• <const value=value />

  Generates the language containing the string value.

• <charset value=value />

  Generates the language containing all strings of length 1 containing characters from value.

• <charrange low=low high=high />

  Generates the language containing all strings of length 1 lexicographically between low and high, which both must be of length 1.

• <interval low=low high=high />

  Generates the language consisting of integers between low and high. If low or high start with a leading 0 (ignoring leading `-') both values must have the same number of digits, and the language generated consists of integers with leading 0's to make them the same length as low and high (ignoring leading `-').

• <intersection>, <concat>, and <union>

  Respectively, the intersection, concatenation, and union of the regexps.

• <star> <plus>

  Respectively Zero or more, or one or more repetitions of the regexp.

• <optional>

  Zero or one occurence of the regexp.

• <repeat count=count >

  count consecutive occurences of the regexp.

• <repeat low=low high=high >

  Between low and high occurences of the regexp. At least one of low or high must be specified. If low is absent it defaults to 0. If high is absent it defaults to "infinity".

• <complement>

  The complement of the regexp.

• <regexp pattern=pattern >

  The regular expression encoded in pattern. The syntax allowed in pattern is a subset of that known from perl and flex. See PowerForms regular expression syntax for more specific information.

• <regexp id=id >

  Defines the regexp for future reference by the name id.

• <regexp idref=idref >

  Evaluates to a previously declared regexp with name id.

• <regexp url=url >

  Import of a regular expression from url. See Format of external regular expressions.

Submit

• <submit >

  The submit element provides the same functionality as an input element with type "submit", but with a more flexible layout. [DET ER FAND'ME EN DÅRLIG FORMULERING!!!]

  The type attribute can have two values, "button" and "anchor" (the default), which are described below.

  • type="button": The submit element is rendered as a button. The label on the button is the plain text-value of the body if it is non-empty. Otherwise the label is given by the value attribute of the submit element.

  • type="anchor": The submit element is rendered as an anchor containing the body of the submit element.

  As with submit-buttons only the name of the activated submit element is sent to the server in the query string. The submitted value is that of the value attribute if it is present. Otherwise it is the empty string.

  Example: . . .

Other

• <powerforms >

  The powerforms-tag is used to control e.g. the appearence of the status images. The following attributes are recognized:

  • na, red, yellow, and green: The values of these attributes decide the urls of the status images used to signal errors in input fields. The default values are: na.gif, red.gif, yellow.gif, and green.gif, respectively. Relative urls are interpreted relative to miscurl [see below]. When changing the images it must be assured that they all have the same size to avoid distorted images.

  • errortitle: the value of this attribute is displayed in the titlebar of the error window when a user tries to submit a form containing invalid data.

  • miscurl: this is the base url from which images and generic javascript code is included in the generated html file. The default value is http://www.brics.dk/bigwig/powerforms/misc/.

• <include url=url >

  Replaces the include element with the content of url.

bigwig@brics.dk
Last updated: October 10, 2001