XML pipeline

For instance, given a two transformations T₁ andT₂, the two can be connected together so that an input XML document is transformed by T₁ and then the output of T₁ is fed as input document to T₂. Simple pipeline like this one are called linear, as a single input document always goes through the same sequence of transformation to produce a single output document. Non-linear pipelines can include:

• Conditionals — where a given transformation is executed if a condition is met while another transformation is executed otherwise
• Loops — where a transformation is execute on each node of a node set selected from a document
• Tees — where a document is fed to multiple transformations potentially happening in parallel
• Aggregations — where multiple documents are aggregated into a single document

Pipeline languages

XML Pipeline languages are used to define pipelines. The definition can understood by a pipeline engine that given a pipeline definition can create the processes, connect them together and execute the pipeline. Existing pipeline languages include:

• W3C XML Pipeline Definition Language is specified in a W3C Note and Sun provides an implementation.
• Cocoon sitemap allows the declaration of linear pipelines
• XPL is the OXF XML Pipeline Language. It allows the declaration of complex pipeline with conditionals, tees and aggregations.

External links

• W3C XML Pipeline Definition Language (http://www.w3.org/TR/xml-pipeline/Overview)
• Sun's XML Pipeline Definition Language Controller Implementation (http://wwws.sun.com/software/xml/developers/pipeline/)
• Cocoon sitemap (http://cocoon.apache.org/2.0/userdocs/concepts/sitemap)
• XPL (http://www.orbeon.com/oxf/doc/processors-pipeline)