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XPath Functions and Operations in the BPEL Mapper

Contributed and maintained by VictoriaZhukovskaya and Alyona Stashkova
December 2007

The BPEL Mapper is a tool for visual work with XPath expressions. The BPEL Mapper allows you to work with expressions, copying variables, XSD elements, and XSD attributes. This tool enables you to work with predicates and use XPath functions.
The XPath expressions editor is used for work with some business process elements. The following allowed expressions are defined for each element: either copy expressions, condition expressions, or time functions usage.

Content on this page applies to NetBeans IDE 6.0

User Interface
Functions and Operators Used in BPEL Mapper
Summary
See Also

User Interface

The BPEL Mapper features an easy-to-use intuitive user interface. The BPEL Mapper window appears when you select a BPEL diagram element that can contain XPath expressions. The BPEL Mapper is used for the following business process elements: Assign, If, ElseIf element of If, ForEach, RepeatUntil, While, and Wait. Every element has allowable expressions, which include copy expressions, condition expressions, time function usage. Condition expressions are defined for the If, ElseIf element of If, While, and RepeatUntil elements. Copy expressions are defined for the Assign element. Duration expressions are defined for the Wait element. And condition expressions with parameters are defined for the ForEach element. Using the BPEL Mapper interface you can make calculations by assigning XPath operations and functions listed above to local and global variables, XSD elements and attributes, and parts.

Every business process element listed above has the Show BPEL Mapper item in the context menu in the Design view of the BPEL Designer. The context menu is available when you closed the BPEL Mapper window. You can also open the XPath expressions editor window by choosing Window > BPEL Mapper from the main menu.

You can edit XPath expressions in the source text of a BPEL file as shown in Figure 1. The BPEL Mapper displays the correct modifications as shown in Figure 2.

Figure 1: Source View of the BPEL file

Click to enlarge

Figure 2: Addition Operation for Assign1

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Functions and Operators Used in the BPEL Mapper

The BPEL Mapper supports version 1.0 of the XML Path language (XPath 1.0). The XPath language is a key part of the XML platform. The XPath language developed by the W3C consortium is a language that addresses the structural parts of an XML document. The language has functions for manipulating strings, numbers, and boolean values. The main syntactic construct of XPath is an expression. As a result of processing an expression, an object that falls into one of the following four fundamental types will appear:

node-set - unordered set of nodes without duplicates
boolean - true or false
number - number with a floating dot
string - sequence of UCS symbols

The XPath language supports number expressions, equality and comparison operations, and boolean expressions. The BPEL Mapper supports part of XPath operations and functions.

Numerical Expressions and Operations

The Operator menu of the BPEL Mapper appears as shown below.

Figure 3: The BPEL Mapper Operator Menu

Numerical Expressions

Numerical expressions are used for performing arithmetic operations over numbers. Equality operations are used to check the equality of two values. Any number in the XPath language has a representation with a floating point. A number can take on any value in the 64 bit format of IEEE 754 DP. This includes a special "Not-a-Number" (NaN) value, positive and negative infinities, and positive and negative nulls.

Table 1: Operators Used in Numerical Expressions

Operator	Description	Sample	Result
+	Addition of two numbers	2 + 3	5
-	Subtraction of a number from another one	5 - 2	3
*	Multiplication of a number by another number	2 * 5	10
div	Division of a number by another number	10 div 2	5
mod	Remainder from division of a number by another number	11 mod 3	2
-	Unary minus	-2	-2

Equality Operations

Notice that length equal to 5.50 is initial data for the table below.

Table 2: Operators Used in Equality Operations

Operator	Description	Sample	Result
=	Equality operation	length=5.50	`true`
!=	Inequality operation	length!=5.50	`false`

Comparison Operations

Notice that length equal to 5.50 is initial data for the table below.

Table 3: Operators Used in Comparison Operations

Operator	Description	Sample	Result
<	Less	length<5.50	`false`
<=	Less or equal	length<=5.50	`true`
>	Greater	length>5.50	`false`
>=	Greater or equal	length>=5.50	`true`

Note: If none of the objects subject to comparison is a node-set, and if the operator is either <=, <, =>, or >, the compared objects are first converted into numbers and then compared.

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Boolean Expressions and Functions

The Boolean menu of the BPEL Mapper is shown below.

Figure 4: The BPEL Mapper Boolean Menu

Boolean Expressions

answer = true

Table 4: Operators Used in Boolean Expressions

Operator	Description	Sample	Result
or	Returns `true` if at least one of the Boolean operands is equal to `true`	false() or answer	`true`
and	Returns `true` if both the Boolean operands are equal to `true`	true() and answer	`true`

Boolean Functions

Notice that answer equal to true and the language of the xml:lang="en" context node are initial data for the table below.

Table 5: Boolean Functions Usage

Name	Description	Sample	Result
boolean	Converts a argument to a boolean type	boolean(2)	`true`
false	Returns `false`	false() or answer	`true`
true	Returns `false`	true() or answer	`true`
not	Returns negation	not(false())	`true`
lang	Returns `true` or `false` depending on whether the context node language defined in xml:lang attributes is the same language (or sublanguage) as the one defined in the attribute string	lang('en')	`true`

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Numerical Functions

The Number menu of the BPEL Mapper is shown below.

Figure 5: The BPEL Mapper Number Menu

Table 6: Numerical Functions Usage

Name	Description	Sample	Result
round	Rounds off to the nearest integer	round (3.14)	3
ceiling	Function returns the smallest integer that is greater or equal to the argument	ceiling (3.14)	4
floor	Function returns the biggest integer that is less than or equal to the argument	floor (3.14)	3
number	Converts an argument to a number	number(length)	Numerical value of the `length` element
sum	Function converts every node from a node-set to a number and sums them up	sum(/apple/count)	Sum of all `count` nodes
Number Literal	Number ( in XPath a number has a representation with a floating point)	1.2	1.2

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String Functions

The String menu of the BPEL Mapper is shown below.

Figure 6: The BPEL Mapper String Menu

Table 7: String Functions Usage

Name	Description	Sample	Result
string	Converts an argument into a string	string(3.14)	'3.14'
string-length	Returns the string length	string-lenght('MyString')	8
substring	Returns the part of the first argument string that starts with the position set by the second argument and has the length set in the third argument	substring('1234',2,3)	'234'
substring-after	Returns the part of the first argument string that follows the first occurrence of the second argument string	substring-after('20-30','-')	'30'
substring-before	Returns the part of the first argument string that precedes the first occurrence of the second argument string	substring-before('14-30','-')	'14'
contains	Returns `true` if the first string contains the second one	contains('XPath','X')	`true`
starts-with	Returns `true` if the first string starts with the second one	starts-with('XPath','X')	`true`
concat	Returns concatenation of two strings	concat('String1 ','String2')	'String1 String2'
normalize-space	Returns the argument string with normalization of space symbols	normalize-space(' 1 2 ')	'1 2'
translate	Returns the first argument string where symbols set in the second argument string are replaced by the symbols of the third argument string in a corresponding position	translate('black','kcalb','etihw')	'white'
String Literal	String constant; strings are formed by a sequence of null and more symbols defined in XML reference	'String'	'String'

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Node-Sets Functions

The Nodes menu of the BPEL Mapper is shown below.

Figure 7: The BPEL Mapper Nodes Menu

The following code is a sample of a SOAP message.

Code Example 1: SOAP Message Sample

<soapenv:Envelope
xsi:schemaLocation="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:syn="http://xml.netbeans.org/schema/SynchronousSample">

  <soapenv:Body>
    <syn:typeA>
      <syn:paramA>String1</syn:paramA>
      <syn:paramA>String2</syn:paramA>
      <syn:paramA>String3</syn:paramA>
      </syn:typeA>
  </soapenv:Body>
</soapenv:Envelope>

Table 8: Node-Set Functions Usage

Name	Description	Sample	Result
count	Returns the number of nodes set in the argument	count($inputVar.inputType/xs:paramA)	3
last	Returns the number of the last element in a multitude	$inputVar.inputType/paramA[last()]	String3
position	Returns the position of an element in a multitude
local-name	Returns the name of the first tag in a multitude without namespace	local-name($inputVar.inputType/xs:paramA)	paramA
name	Returns the full name of the first tag in a multitude	name($inputVar.inputType/xs:paramA)	syn:paramA
namespace-uri	Returns a reference to the url that defines the namespace	namespace-uri($inputVar.inputType/xs:paramA)	http://xml.netbeans.org/schema/SynchronousSample

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Functions for Working with Date and Time

The BPEL Mapper allows you to set constants and use time functions with the help of a graphical interface.

The Datetime menu of the BPEL Mapper is shown below.

Figure 8: The BPEL Mapper Datetime Menu

Table 9: Functions for Working with Date and Time Usage

Name	Description
current-time	Returns current time
current-date	Returns current date
current-dateTime	Returns current date and time
Duration Literal	String; allows for setting the time interval in the 'P1Y2M3DT4H5M6S' format.

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Summary

Graphical representation offers easy analysis and seeing of XPath expressions. The BPEL Mapper is a tool that allows you to create and edit XPath expressions in a visual mode. The BPEL Mapper graphical interface allows you to set constants, use time functions, and work with predicates. The BPEL Mapper interface enables you to perform calculations using XPath operations and functions that are listed in this article over local and global variables, XSD elements and attributes, and parts.

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