Application Integration with XProc

Vojtech

Toman

Principal Software Engineer

EMC Corporation

Overview

XProc basics

Application integration with XProc

Q/A

XProc: An XML Pipeline Language

W3C Candidate Recommendation

http://www.w3.org/TR/xproc/

Language for describing operations to be performed on XML

documents

Declarative, XML-based, extensible

XProc Status

XProc processor implementations

Calabash (http://xmlcalabash.com)

Calumet (http://developer.emc.com/xmltech)

…more in development

XProc.org

Informal website about XProc and its use

http://xproc.org

XProc Test Suite

http://tests.xproc.org

Validate/XQuery/Transform Pipeline

Validate

XQuery

XSLT

XProc Basics

StepPerforms a well-defined task

Validate, XSLT, XInclude, identity transformation, rename elements, …

Three main step types:Atomic, compound, and built-in language constructs

PipelineSequence (possibly non-linear) of steps

Is a step itself

Built-insFor-each, choose, try/catch, …

XPath as expression language

Anatomy of an XProc Step

Step declarationType, input ports, output ports, options

When used in a pipeline, a step

is a black box thatExpects zero or more XML documents on

its input ports

Produces zero or more XML documents

on its output ports

Step

result

source

Step Declaration –

Atomic Steps

Standard XProc step: p:add-attribute

<p:declare-step type="p:add-attribute"

xmlns:p="http://www.w3.org/ns/xproc">

<p:input

port="source"/>

<p:output

port="result"/>

<p:option

name="match" required="true"/>

<p:option

name="attribute-name" required="true"/>

<p:option

name="attribute-value" required="true"/>

</p:declare-step>

Step Declaration –

Compound Steps

Pipeline that applies the p:add-attribute step

<p:declare-step>

<p:input

port="source"/>

<p:output

port="result"/>

<p:add-attribute match="book"

attribute-name="foo"

attribute-value="bar"/>

</p:declare-step>

Extensibility of XProc

Custom steps

Step libraries & import functionality

Extension attributes

Implementation-defined mechanisms

I/O extensibility

Security

…

Application Integration with XProc

XProc as the XML processing layer

Integration using standard XProc facilities

Interoperable

Integration using extensions

Implementation-dependent

Limited interoperability

XProc –

Enabling Technology

Some XML standards depend on

XML processing capabilities

XForms

The XRX architecture

XForms/REST/X......

End-to-end XML model

XProc is a natural fit

XForms

XProc

NativeXML DB

HTTP

XML

XML

Validate/XQuery/Transform Pipeline

XProc itself integrates multiple XML technologies

Easy to use, robust

Focus on WHAT, not on the low-level HOW

Better maintainability and customizability

p:validate-

with-xml-

schema

p:xquery p:xslt

Validate/XQuery/Transform Pipeline

<p:for-each>

<p:validate-with-xml-schema>

<p:input

port="schema">...</p:input>

</p:validate-with-xml-schema>

</p:for-each>

<p:xquery>

<p:input

port="query">...</p:input>

</p:xquery>

<p:for-each>

<p:xslt>

<p:input

port="stylesheet">...</p:input>

</p:xslt>

</p:for-each>

Executing external programs

p:exec

Program to execute

Command-line arguments

Working directory

Standard input/output

Support for non-XML data

Error handling

p:exec

cmd

Executing external programs –

Example

Pipeline that counts the words in the input document

<p:declare-step>

<p:input

port="source"/>

<p:output

port="result"/>

<p:exec

command="/usr/bin/wc"

source-is-xml="false"

result-is-xml="false"/>

</p:declare-step>

Integration with REST Web Services

p:http-request

Request URL

Request method

Authentication

Headers

Multipart messages

p:http-request

RESTService

Request

ResponseHTTP

Integration with REST Web Services –

Example

Pipeline that retrieves the Twitter public timeline

<p:declare-step>

<p:output

port="result"/>

<p:http-request>

<p:input

port="source">

<p:inline>

<c:request

method="GET"

href="http://twitter.com/statuses/public_timeline.xml"/>

</p:inline>

</p:input>

</p:http-request>

</p:declare-step>

Custom Atomic Steps

Custom step that provides the

integration logicImplementation in the processor’s host

language

Step declaration + import

Potentially not interoperablep:step-available() XPath function

EXProc.orghttp://exproc.org

ext:custom-

step

Custom Atomic Steps –

Example

Custom step that triggers a workflow (xproc-wf.xpl)<p:declare-step type="wf:trigger-workflow"

xmlns:wf="http://example.com/ns/xproc-wf">

<p:input

port="source"/>

<p:option

name="workflow-type" required="true"/>

</p:declare-step>

Usage:<p:declare-step xmlns:wf="http://example.com/ns/xproc-wf">

<p:input

port="source"/>

<p:import

href="xproc-wf.xpl"/>

<wf:trigger-wf

workflow-type="translate"/>

</p:declare-step>

Integration on the I/O level

Resource access in XProc is URI-based

XProc processors should support file and http(s)

Support for other URI schemes is implementation-defined

Transparent support for additional storage models/systems

p:load p:store

Storage system

Integration on the I/O Level -

Example

Pipeline that loads a document from a native XML database

<p:declare-step>

<p:output

port="result"/>

<p:load href="xhive:/books/book24.xml"/>

</p:declare-step>

Other Types of Integration

XML data model integration

Persistent DOM-based native XML databases

Integration via other XML languages

XSLT and XQuery extensions

Conclusions

XProc deals with composing XML processes

Extensible by nature

Easy to integrate with external world

Declarative code easier to develop and maintain

Questions and Answers

Vojtech Toman

toman_vojtech@emc.com

http://www.emc.com

http://developer.emc.com/xmltech