1 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 2 <html xmlns="http://www.w3.org/1999/xhtml"><head> 3 <meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type" /> 4 5 <title>Template Design</title><meta name="generator" content="amaya 8.1a, see http://www.w3.org/Amaya/" /> 6 <link href="styles.css" rel="stylesheet" type="text/css" /></head> 7 <body> 8 <h1>Template Design</h1> 9 <p>The template is a central concept in the XSLForms toolkit: each 10 template defines the structure of the XML document information being 11 processed by an application (or a resource within an application), and 12 each template presents that document information in a form readable by 13 an application's users.</p><h2>Defining a Structure</h2><p>The relationship between the defined structure and the template itself is described in the <a href="data.html">"Creating Applications: Design the Structure of the Form Data"</a> 14 document. Typically, one will have in mind a particular structure to be 15 presented and made editable by the template, and one will begin the 16 template design process with this structure in mind, although the 17 structure definition is likely to be modified by decisions made in the 18 design process and when testing the user interface by using the 19 application itself.</p><h2>Defining the Presentation</h2><p>Given a 20 document structure, one has to think about the most suitable ways of 21 representing the information in the user interface. The most common 22 medium for presentation is HTML and its derivatives, and we consider 23 here the different HTML elements available to present different 24 "patterns" in a document structure.</p><h3>General Template Structure</h3><p>Templates based on HTML usually have the following general structure:</p><pre><?xml version="1.0"?><br /><html xmlns="http://www.w3.org/1999/xhtml"<br /> xmlns:template="http://www.boddie.org.uk/ns/xmltools/template"><br /><head><br /> <title>Some title</title><br /></head><br /><body template:element="structure"><br /><br /><!-- The interesting part goes here... --><br /><br /></body><br /></html></pre><p>Since we will want to edit the data produced by such a template, an HTML <code>form</code> element is usually necessary within the <code>body</code> element:</p><pre><body template:element="structure"><br /><form action="" method="POST"><br /><br /><!-- The interesting part goes here... --><br /><br /></form><br /></body></pre><p>We usually define the <code>method</code> as <code>post</code> in order to minimise complications with handling the data in the XSLForms toolkit.</p><h3>Static Elements</h3><p>Static 25 elements, as opposed to collection elements, are elements in the 26 form data document structure which maintain some kind of organisation or grouping 27 within a document, but whose presence cannot be edited by the user of 28 an application. For example, in the <a href="XSLForms-resource.html">"Using the XSLFormsResource API"</a> document the following example is given:</p><pre><div template:element="hard-disks"><br /> <input template:selector-field="add-hard-disk,hard-disk" type="submit" name="..." value="Add hard disk"/><br /> <p template:element="hard-disk"><br /> ...<br /> </p><br /></div></pre><p>Here, the <code>hard-disks</code> element is present to group <code>hard-disk</code> 29 elements together. We can insist that elements are treated as static 30 elements in the document initialisation process by adding the <code>template:init</code> attribute to the annotated template element:</p><pre><div template:element="hard-disks" template:init="yes"><br /> ...<br /></div></pre><p>See the <a href="reference.html">"Template Attribute Reference"</a> document for more information on the <code>template:init</code> attribute.</p><h3>Collection Elements</h3><p>Collection 31 elements are elements in the form data document structure which represent a 32 collection of items or objects and whose presence may be edited by the 33 user of an application. In the following example, <code>hard-disk</code> elements are collection elements:</p><pre><input template:selector-field="add-hard-disk,hard-disk" type="submit" name="..." value="Add hard disk"/><br /><p template:element="hard-disk"><br /> ...<br /></p></pre><p>Whether 34 elements are treated as collection elements in the document 35 initialisation process depends on the presence or absence of the <code>template:init</code> attribute on the annotated template element: if the <code>template:init</code> attribute is present, the value of that attribute will determine whether such elements (named in the <code>template:element</code> 36 attribute) will be created automatically (and thus behave like static 37 elements) or created dynamically (and thus behave like collection 38 elements); if the <code>template:init</code> attribute is absent, 39 the way such elements are treated will depend on other factors, notably 40 the presence of selectors referring to such elements.</p><p>In the above example, the selector field (see below and in the <a href="reference.html">"Template Attribute Reference"</a> document for more details) mentions the document structure's <code>hard-disk</code> 41 element; thus, the element is treated as a collection. If we did not 42 have such a selector in the template, we could also have used a <code>template:init</code> attribute to have the same effect:</p><pre><p template:element="hard-disk" template:init="no"><br /> ...<br /></p></pre><p>Generally, 43 collection elements do have selector fields providing operations on the 44 collection, and so the extra annotation is not usually necessary.</p><h3>Selectors</h3><p>As described in the <a href="selectors.html">"Creating Applications: Add Selectors"</a> 45 document, selectors provide a means to select elements in collections 46 and to request that some operation be performed on those selected 47 elements. Two common selector types are those concerning the addition 48 and removal of elements.</p><h4>Selectors as Buttons</h4><p>In the collection elements example above, we saw the usage of a selector which could be used to add elements to a document:</p><pre><input template:selector-field="add-hard-disk,hard-disk" type="submit" name="..." value="Add hard disk"/></pre><p>This would produce the following HTML form control:</p><p><input name="..." value="Add hard disk" type="submit" /> </p><p>As described in the <a href="XSLForms-resource.html">"Using the XSLFormsResource API"</a> document, the above selector (with the name <code>add-hard-disk</code>) 49 could be obtained and the associated collection of elements used to 50 insert new elements within the specified elements. Similarly, a 51 selector which could be used to remove elements from a document could 52 be specified as follows:</p><pre><input template:selector-field="remove-hard-disk" type="submit" name="..." value="Remove hard disk"/></pre><p>This would produce the following HTML form control:</p><p><input name="..." value="Remove hard disk" type="submit" /></p><p>Again, such a selector could be obtained and its associated elements removed from the document.</p><h4>Selectors as Checkboxes</h4><p>Whilst 53 selectors can be modelled conveniently with buttons, since they may 54 cause an immediate update to the form data with feedback from the 55 operation occurring immediately, other form controls can be used to 56 communicate the selection of form data. For example:</p><pre><input template:selector-field="select-hard-disk" type="checkbox" name="..." value="..."/></pre><p>This would produce the following HTML form control:</p><p><input name="..." value="..." type="checkbox" /></p><p>Such 57 a checkbox could be used to mark a particular element in the form data 58 document as being selected, with the application left to determine what 59 kind of operation should be applied to the selection.</p><h3>Attribute Values</h3><p>A 60 simple attribute value is defined to be a value, freely editable set in 61 an attribute on some element in a document. For example, in an XML document:</p><pre><element attribute="value"/></pre><p>The 62 following sections describe ways in which the value can be viewed, 63 edited or changed through the presentation of the attribute in the 64 template.</p><h4>Editable Fields</h4><p>If we are to permit an attribute value to be edited, we might choose the following template representation:</p><pre><input template:attribute-field="attribute" name="..." value="..." type="text"/></pre><p>This would produce the following HTML form control:</p><p><input name="..." value="..." /></p><p>Note 65 that the element on which the attribute is defined is not declared in 66 the above example, although we could also add such an annotation to 67 the <code>input</code> element (as described above and in the <a href="reference.html">"Template Attribute Reference"</a> document).</p><h4>Read-only Values</h4><p>Where attribute values are only displayed, we can use non-form HTML elements to display them:</p><pre><span template:attribute-area="attribute">some text to be replaced with the value</span></pre><p>This would insert the value of the attribute in the document within the defined <code>span</code> template element.</p><h4>Hidden Values</h4><p>Where 68 attribute values are to be retained and submitted again by the 69 user, but probably not edited, we need to include them as hidden 70 elements:</p><pre><input template:attribute-field="attribute" name="..." value="..." type="hidden"/></pre><p>This 71 keeps the contents of the document intact, but it should be noted that 72 such values are only uneditable in the way they are presented to 73 the user, and that a determined user could easily find a way to change 74 such values and send them in to the application.</p><h4>Checkboxes</h4><p>Sometimes, 75 attributes are used to retain particular values that correspond to a 76 boolean state. Such values can be modelled as follows:</p><pre><input template:attribute-button="attribute,true,checked" name="..." value="..." type="checkbox"/></pre><p>This would produce the following HTML form control:</p><p><input name="..." value="..." type="checkbox" /></p><p>If selected, the checkbox would when submitted cause the attribute to contain the value <code>true</code> 77 in the form data document. Moreover, the presence of the attribute with 78 such a value would cause the checkbox to appear selected when the form 79 data is presented to the user again.</p><h4>Radio Buttons</h4><p>Unlike 80 checkboxes, radio buttons typically offer a means to select a value 81 from a number of alternatives. However, like checkboxes the selected 82 value would be stored on a single attribute in the form data document. 83 For example:</p><pre><input type="radio" template:attribute-button="attribute,some-choice,checked" name="..." value="..." /></pre><p>This would produce the following HTML form control:</p><p><input name="..." value="..." type="radio" /></p><p>If 84 selected, the radio button when submitted would cause the attribute to 85 contain the stated value in the form data document, which would be <code>some-choice</code> 86 for the button in the above example. Should a different button 87 associated with the same attribute be pressed, the value stated in the 88 definition of that button would be stored in the attribute. Like the 89 checkbox, the selected radio button would remain selected when the form 90 data is presented to the user again.</p><h3>Attributes Set from Lists of Choices</h3><p>Certain 91 attributes may have a list of acceptable values associated with them, 92 and whilst such attributes typically reside in the form data document 93 carrying a single, currently set value, the representation of the 94 document processed by the template must somehow incorporate the list of 95 acceptable values; this was covered in the <a href="multiple.html">"Creating Applications: Adding Multiple-Choice Fields and Values"</a> document, and involved adding new elements, each carrying a single acceptable value for the attribute concerned.</p><h4>Single Selection Menus</h4><p>In 96 certain situations, it makes more sense to present acceptable values 97 for an attribute in a menu-like representation in the final output 98 presented to the user. With the element on which the attribute resides 99 now containing a list of sub-elements with each carrying an acceptable 100 value in an attribute, a form control can be defined as follows:</p><pre><select template:multiple-choice-field="-,attribute" name="..."><br /> <option template:multiple-choice-value="element-enum,value,selected" value="..."></option><br /></select></pre><p>This would produce the following HTML form control:</p><p><select name="..."><option>First</option><option>Second</option><option>Third</option></select></p><p>Note that the element on which the attribute is defined is not declared 101 in the above example, although we could modify the <code>template:multiple-choice-field</code> annotation on 102 the <code>select</code> element (as described in the <a href="reference.html">"Template Attribute Reference"</a> document) and replace the <code>-</code> with a name such as <code>element</code>.</p><h4>Multiple Selection Lists</h4><p>In 103 other situations, where many values can be chosen, a single attribute 104 on a single element is not sufficient to hold all such values. 105 Consequently, a collection of elements is employed, each with an 106 attribute defined to hold a single value. With each value-bearing 107 element now containing a list of sub-elements with each carrying 108 an acceptable 109 value in an attribute, a form control can be defined as follows:</p><pre><select name="..." template:multiple-choice-list-field="-,element-enum,attribute" multiple="multiple"><br /> <option template:multiple-choice-list-value="element-enum,value,selected" value="..."></option><br /></select></pre><p>This would produce the following HTML form control:</p><p><select multiple="multiple" name="..."><option>First</option><option>Second</option><option>Third</option></select></p><p>Note that unlike the single selection menu example, an additional parameter is present in the <code>template:multiple-choice-list-field</code> annotation, but the first parameter is given as the placeholder value <code>-</code> (and is regarded as not having been stated). However, had the first parameter been stated (as opposed to being given as <code>-</code>) 110 the consequence would merely have been that upon submission of the 111 form, the elements in the collection would have been enclosed 112 within a single named element. In the above example, we assume that a 113 suitable element has already been defined in a template element and 114 that the above <code>select</code> element resides within that template element, thus providing the necessary enclosure (as recommended in the <a href="advice.html">"Creating Applications: Recommendations and Advice"</a> document).</p></body></html>
