Dynamically changing the process control file (Remote) location   

I have the following requirement - As part of the practice followed at the customer, all the xsl file will be moved to a Http server, so these files will be referred from within the actions, like http://myserver:port/mystyle.xls. Here the problem is that, when the application gets promoted to other environments, the location of the server and port will change or I can say everything except the xls file name can change. To accommodate this change, I have to open every policy and every action and update the process control file location with the new url. This is hectic and a very bad practice, and I'm sure that there should be an easy way there. Please let me know what your thoughts are - like reading from a config file and translate the url to the right one, or using some context variable or any other easy and efficient solution. This may be a very simple requirement - but I started learning the DP only a week back... help!!!!

For this kind of thing I put a XML file on the device, and the first action in my rules is a custom XSL that sets up context vars, that will be used by downstream actions.

If I follow as you suggested, how to do an implementation like this. Assume that for an action if I'm giving the process controll file as http://host:port/myxsl.xsl, and the I'll provide a configuration entry in the xml file some thing like <config>http://myserver:port/version/v1/</config>. And I want to have the final result like http://myserver:port/version/v1/myxsl.xsl. I hope you understand my point. I don't want to provide the comple url of each of the xsl file in the xml file, but I can provide the commmon part which is being used in the configuration file. As shown, I can give upto http://myserver:port/version/v1/ in the configuration file, which should be appended with the xsl file name, in tult in his case myxsl.xsl - which will result in http://myserver:port/version/v1/myxsl.xsl.

Sounds like you have a situation where not only can the IP address, Port change from environment to environment, but you are also using a versioning system built around directory paths.

One way to do it is to create a config file which resides on the device, and on each environment.

Perhaps something like:

<xsl_lookup>
<globals>
<prefixes>
<prefix id="v1">http://load-balancer/version/v1</prefix>
<prefix id="v2">http://load-balancer/version/v2</prefix>
</prefixes>
</globals>
<entries>
<entry id="aa.b" version="v1">filename.xsl</entry>
<entry id="cc.d" version="v2">another-file.xsl</entry>
<entries>
</xsl_lookup>

Then in your processing policy, you do two things:

(1) Set a context variable, perhaps var://context/xsl-lookup/id to "aa.b" or "cc.d" as the case may be
(2) Write an XSL file which takes that variable and config xml into account and derives the correct endpoint URL from it
(3) Transform the input context using the identified XML

Points (2) and (3) could be combined into a single re-usable rule.

If you wanted, you could even generalize this function into its own lookup service. Set an HTTP header to a particular identifier value and POST it this service, perhaps a loopback xmlf, and return the transformed result. Depends on how complex your requirements are -- but you have a lot of different options.