# developer.vapModifiers

Description: Autoplot vap references can have modifiers that apply tweaks to the vap files, and we are considering allowing xslt transforms to provide greater support for this.

Audience: autoplot power users

# 1. Introduction

Autoplot has always allowed modifiers to vap files, the primary use case being the one where an existing product is used to look at different timeranges. Suppose the file

http://autoplot.org/data/autoplot-applet.vap


looks at timeranges from 2003-05-01 through 2003-05-31, then

http://autoplot.org/data/autoplot-applet.vap?timerange=2003-05-10


would use the same vap, except just the day 2003-05-10 is shown.

What Autoplot does is to load the dom from the vap file, then any transformations following the question mark (?) are applied to the dom.

# 2. Allowing for XSLT transforms

Allowing for XSLT transforms would provide a useful way to create VAPs. For example, an empty template vap could be populated with URIs and labels. XML files that are configurations for other systems could be transformed into a vap file.

# 3. Syntax

Vap file modifier:

<vapFile>?xslt=<xsltFile>&<xsltFileArgs>



and <xsltFileArgs> is a list of ampersand-delimited arguments, for example:

color=yellow&background=black


Note in this case, the vapFile should be a valid vapFile. (Anything with a .vap extension ought to be a vap.)

Autoplot should be able to work without a vap file, where just the xslt is used to create the DOM.

<xsltFile>?<xsltFileArgs>


In this case, Autoplot will trigger off the .xslt extension to invoke its handling code. I would also suggest a couple of special named parameters, as with Autoplot URIs:

resourceURL is the name of a file to be transformed that is not a .vap file.
arg_i be the ith unnamed argument.


# 4. Examples

http://autoplot.org/data/autoplot.vap?xslt=http://autoplot.org/data/text.xslt&title='My+data"