DPML Programs

The DPML language supports the construction and sequencing of active: URI requests using an XML based syntax.

A quick introduction to the DPML Programming Language and a DPML By Example tutorial are provided elsewhere, so a brief introduction here will describe the essential concept.

A DPML script program is defined within an idoc XML fragment. The seq element contains a sequence of instr elements:

Each instr element equates directly to an active: URI and an associated SOURCE and SINK pair of requests. The following active: URI

active:xslt+operator@ffcpl:/src/style.xsl+operand@ffcpl:/context.xml

Is coded in DPML as

The target element specifies the URI for a SINK request. The DPML fragment executes the XSLT transform by issuing a SOURCE request and then requests a SINK request on the target using the returned representation.

DPML can be used to chain service calls together as can be done in Unix using the Unix pipe operator ("|"). For example, the following DPML program

First copies the content of a file to a temporary variable in the var: namespace and then uses the as the operand parameter in the XSLT tranform service.

DPML script programs are themselves resources. A DPML script is run using the following active: URI request:

active:dpml+operator@ffcpl:/src/script.idoc

XML is selected for the DPML syntax because XML is a first-class resource within NetKernel. This means that DPML programs could be created from for example, simple XSLT transforms or other XML operators.