XQuery/Google Chart Bullet Bar

Motivation To display a Bullet Chart to display the current value of a system parameter with its safe and danger ranges. Bullet Bars This is one of the chart types supported by the now deprecated " Google Chart API which constructs the chart from URL parameters. Sample URL http://chart.apis.google.com/chart?cht=bhs&chs=150x30&chd=t:70&chm=r,ff0000,0,0.0,0.5|r,ffff00,0,0.5,0.75|r,00A000,0,0.75,1.0|r,000000,0,0.8,0.81&chco=000000&chbh=10 Sample Screen Image Image:Bullet-bar-screen-image.png frame|center|terms used in dashboard gauge Declarative XML Representation An XML representation of the chart design might be: <chart > <type>bar-gauge</type> <height>30</height> <!-- in pixels --> <width>150</width> <!-- in pixels --> <danger-threshold>50</danger-threshold> <!-- end of danger level --> <danger-color>ff0000</danger-color> <warning-threshold>75</warning-threshold> <!-- end of warning level --> <warning-color>ffff00</warning-color> <ok-threshold>100</ok-threshold> <!-- end of ok level --> <ok-color>00ff00</ok-color> <target-value>90</target-value> </chart> Google Chars Representation Which, when supplied with a current value, must be transformed into the following URL: http://chart.apis.google.com/chart? cht=bhs& chs=150x30& chd=t:70& chm=r,ff0000,0,0.0,0.5| r,ffff00,0,0.5,0.75| r,00A000,0,0.75,1.0| r,000000,0,0.8,0.81& chco=000000&chbh=10 Sample XQuery Function This function takes the specification of the chart and the current value, and generates the corresponding Google Chart URL. Note that the width of the danger, warn and ok bars (red, yellow and green) are expressed as a percentage digit from 0 to 100. declare function local:bullet-bar($spec,$current-value) { let $danger-width-percent := $spec/danger-threshold div 100 let $warn-width-percent := $spec/warning-threshold div 100 let $ok-width-percent := $spec/ok-threshold div 100 let $target-width-percent := $spec/target-value div 100 let $target-plus-one := $target-width-percent + 0.01 return concat( 'http://chart.apis.google.com/chart?cht=bhs&chs=', $spec/width, 'x', $spec/height, '&chd=t:',$current-value, '&chm=r,',$spec/danger-color,',0,0.0,', $danger-width-percent, '|r,',$spec/warning-color,',0,', $danger-width-percent, ',', $warn-width-percent, '|r,',$spec/ok-color,',0,', $warn-width-percent, ',', $ok-width-percent, '|r,000000,0,', $target-width-percent, ',', $target-plus-one, '&chco=000000&chbh=', round($spec/height * 0.6) ) }; Generating a bullet bar let $current-value := 70 let $url := local:bullet-bar($bar-spec,$current-value) return <div> <h2>Example bullet bar</h2> <div> <img src="{$url}"/></div> </div> [/visualization/bullet-chart.xq Execute]