plugins/org.eclipse.bpel.help/html/Reference/Editors/structuredActivities.html - bpel/org.eclipse.bpel - Git at Google

 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml">
 <head>
 <meta content="text/html; charset=UTF-8" http-equiv="CONTENT-TYPE" />
 <link rel="stylesheet" href="../../book.css" type="text/css" />
 <title>Structured Activities</title>
 </head>

 <body>
 	<h1>Structured Activities</h1>

 	<p>
 		Structured activities can be thought of as containers that can hold
 		one or more activities. The <strong>Controls</strong> section of the <strong>Palette</strong>
 		contains all of the <em>structured activities</em>.
 		When you drag and drop one of these onto the drawing canvas, the BPEL
 		Designer will create a basic skeleton of the activity, and assign
 		default properties.
 	</p>
 	<p>
 		All structured activities will require some additional
 		configuration before they are considered valid. For example, BPEL does
 		not allow an empty Sequence activity. Invalid structured activities
 		will be decorated with an error icon similar to basic activities.</p>
 	<p>
 		Structured activities can be expanded and collapsed on the
 		drawing canvas by clicking the plus and minus buttons at the bottom of
 		the figure. Illustrated below is a collapsed and expanded Sequence:
 	</p>

 	<p><img src="../../..images/reference/BPEL_Designer_12.png" alt="Collapsed Sequence" /></p>
 	<p><b>Collapsed Sequence</b></p>

 	<p><img src="../../../images/reference/BPEL_Designer_13.png" alt="Expanded Sequence" /></p>
 	<p><b>Expanded Sequence</b></p>

 	<p>
 		The following sections describe the structured activities and
 		how each must be configured to be considered valid for BPEL.
 	</p>

 	<h5>If</h5>
 	<p><img src="../../../images/reference/BPEL_Designer_14.png" alt="If, ElseIf and Else" /></p>
 	<p><b>If, ElseIf and Else</b></p>
 	<p>
 		The If activity allows conditional execution of one or more
 		sequences of activities. It consists of a sequence of one or more
 		conditional branches defined by If and optional ElseIf elements. The
 		elements are evaluated in left-to-right order (or top-to-bottom if you
 		have selected horizontal layout). An optional Else branch will be
 		executed if none of the other conditions are true.
 	</p>
 	<p>
 		An If activity must define a condition (expressed as an XPath)
 		and an activity which is executed if the condition evaluates true. To
 		insert additional ElseIf and Else elements, right-click the If figure
 		and select the desired element from the context menu. The figure above
 		shows a complete If activity with optional ElseIf and Else elements.
 	</p>

 	<h5>Pick</h5>
 	<p><img src="../../../images/reference/BPEL_Designer_15.png" alt="Pick" /></p>
 	<p><b>Pick</b></p>
 	<p>
 		The Pick activity will cause the process to wait for one of any number
 		of messages to be received. An optional timer can be set to limit the
 		time to wait for receipt of these messages. Activities to handle
 		receipt of messages and timer expiration are defined in the Pick.
 		Message receipts are handled by OnMessage activities (
 		<a href="#Reference-Details_tab-OnMessage">OnMessage</a>), and timer expiration is handled by the OnAlaram
 		activity (<a href="#Reference-Details_tab-OnAlarm">OnAlarm</a>).
 	</p>

 	<h5>While</h5>
 	<p><img src="../../../images/reference/BPEL_Designer_16.png" alt="While" /></p>
 	<p><b>While</b></p>
 	<p>
 		The While activity repeatedly executes the contained activity as
 		long as a condition evaluates true at the beginning of each iteration.
 		A While activity must define a condition and must contain an activity.
 	</p>

 	<h5>ForEach</h5>
 	<p><img src="../../../images/reference/BPEL_Designer_17.png" alt="ForEach" /></p>
 	<p><b>ForEach</b></p>
 	<p>
 		ForEach is a looping activity that executes the activities
 		contained in its Scope a specified number of times. A counter
 		variable, defined in the ForEach property detail tab, is used to keep
 		track of the iterations. The ForEach properties must be configured
 		with starting and ending value expressions for this counter variable.
 		The counter is initially set to the starting value and activities in
 		the Scope are executed until the counter exceeds the ending value.
 	</p>
 	<p>
 		This activity can also be configured to execute all iterations
 		in parallel, meaning the enclosed Scope activity behaves as if
 		multiple Scopes are enclosed in a Flow activity.
 	</p>
 	<p>
 		An optional early termination value can be defined, which will cause
 		the loop to complete before the counter has reached its ending value.
 		The ForEach will complete when the counter is equal to this early
 		termination value for the sequential execution case. For the parallel
 		execution case, the early termination value is the number of completed
 		iterations. For example, the ForEach completes when at least
 		<em>some number</em> of <em>some action</em> have finished.
 	</p>

 	<h5>RepeatUntil</h5>
 	<p><img src="../../../images/reference/BPEL_Designer_18.png" alt="RepeatUntil" /></p>
 	<p><b>RepeatUntil</b></p>
 	<p>
 		The RepeatUntil activity repeatedly executes the contained
 		activity as long as a condition evaluates true at the end of each
 		iteration. A condition must be defined for a RepeatUntil, and it must
 		contain an activity.
 	</p>

 	<h5>Sequence</h5>
 	<p>
 		A Sequence is a container for one or more other activities,
 		which are executed in sequential order and (unlike Scope and Flow
 		activities), has no other special characteristics. Because the
 		conditional activities ( If, While, RepeatUntil and ForEach) can have
 		only one activity as the target of their execution, a Sequence is
 		typically used to execute multiple activities.
 	</p>
 	<p>For example, the If shown below contains only a single Assign activity:</p>

 	<p><img src="../../../images/reference/BPEL_Designer_19.png" alt="Sequence" /></p>
 	<p><b>Sequence</b></p>
 	<p>
 		If it were necessary to perform an assignment and then invoke
 		another web service, the Assign and Invoke could be contained within a
 		Sequence. The Sequence would then become the target of the If:
 	</p>

 	<p><img src="../../../images/reference/BPEL_Designer_20.png" alt="Sequence" /></p>
 	<p><b>Sequence</b></p>

 	<h2>Note</h2>
 	<p>
 		The BPEL Designer will automatically create a  Sequence if you drag-drop a second
 		activity into any of the conditional activities.
 	</p>

 	<h5>Scope</h5>
 	<p><img src="../../../images/reference/BPEL_Designer_21.png" alt="Scope" /></p>
 	<p><b>Scope</b></p>
 	<p>
 		A Scope provides a context for its enclosed activity. This
 		context includes variables, partner links, message exchanges,
 		correlation sets, event handlers, fault handlers, a compensation
 		handler and a termination handler. These Scope contexts can be nested
 		hierarchically where the root context is provided by the process
 		itself.
 	</p>
 	<p>
 		A Scope can be thought of as a compartmentalized sub-process. If the
 		Scope is declared as being <em>isolated</em> , then the variables and
 		partner links shared with the process are locked to prevent other
 		concurrent Scopes from altering them while a Scope is executing. Scope
 		may also be nested to any depth and all variables, partner links and
 		others defined in a Scope, are inherited by its children. Refer to
 		<a href="#Reference-BPEL_Designer-Structured_Activities-Flow">Flow</a> for
 		a discussion of concurrent execution.
 	</p>

 	<p>
 		To be valid, a Scope must have a single activity. The typical
 		use of a Scope activity is to invoke a service and wait for a response
 		message or timeout. In the above figure, the Scope has defined a
 		message variable and a partner link used to interact with the invoked
 		service.
 	</p>

 	<h5>Flow</h5>
 	<p>
 		The Flow activity allows multiple activities to be executed in
 		parallel. All activities or Sequences of activities that are contained
 		in a Flow, are executed (or begun) at the same time by the BPEL
 		engine. A Flow completes when all of its enclosed activities have
 		completed.
 	</p>
 	<p>
 		Parallel processing is typically used to save time by doing more than
 		one thing at a time and as a result, speed up the process. However, in
 		many situations several tasks can be started at the same time, but one
 		or more tasks may depend on the successful completion of other tasks.
 		This task dependency sequencing is called <em>synchronization</em> and
 		is achieved using Links.
 	</p>
 	<p>
 		For example, a process that handles purchase orders for material
 		goods needs to:
 	</p>

 	<ol>
 		<li><p>Calculate the total order price</p></li>
 		<li><p>Calculate shipping costs for the order</p></li>
 		<li><p>Send a customer invoice</p></li>
 	</ol>

 	<p>
 		All of these activities can be started at the same time, however
 		the shipping cost must be finalized before the total order price can
 		be determined, and the invoice can be sent.
 	</p>

 	<p>
 		To create a Link, right-click on the activity that must be completed
 		first (the activity that is the <em>source</em> of the dependency) and
 		select <strong>Add Link</strong> from the context
 		menu. Next, move the mouse to the activity in the Flow that depends on
 		this one (the <em>target</em>) and click the left mouse button to
 		create the link.
 	</p>
 	<p>
 		A Link is identified by a name that must be unique within the
 		Flow. The BPEL Designer generates a reasonable default name, but you
 		can change this in its properties. You can also add a test to the Link
 		that defines the conditions for considering an activity to be
 		complete. For example an activity in a Flow may require two pieces of
 		information, provided by other services, in order to continue.
 		Consider the process Flow shown below:
 	</p>

 	<p><img src="../../../images/reference/BPEL_Designer_22.png" alt="Flow example" /></p>
 	<p><b>Flow example</b></p>
 	<p>
 		In this example, the <em>Billing</em> department can begin preparation
 		of a customer invoice, but it needs to know if sufficient stock is on
 		hand to fulfill the order and if an outside vendor needs to provide
 		the additional quantities ordered. The following condition would
 		enable the Link so that execution can continue for the price
 		calculation and customer invoicing:
 	</p>

 	<p><img src="../../../images/reference/BPEL_Designer_23.png" alt="Link example" /></p>
 	<p><b>Link example</b></p>

 	<p>
 		This process is only partially complete though as it does
 		not consider the number of outside vendors, or if the total
 		quantity being ordered can ever be filled.
 	</p>
 </body>
 </html>
	<?xml version="1.0" encoding="UTF-8"?>
	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
	<html xmlns="http://www.w3.org/1999/xhtml">
	<head>
	<meta content="text/html; charset=UTF-8" http-equiv="CONTENT-TYPE" />
	<link rel="stylesheet" href="../../book.css" type="text/css" />
	<title>Structured Activities</title>
	</head>

	<body>
	<h1>Structured Activities</h1>

	<p>
	Structured activities can be thought of as containers that can hold
	one or more activities. The <strong>Controls</strong> section of the <strong>Palette</strong>
	contains all of the <em>structured activities</em>.
	When you drag and drop one of these onto the drawing canvas, the BPEL
	Designer will create a basic skeleton of the activity, and assign
	default properties.
	</p>
	<p>
	All structured activities will require some additional
	configuration before they are considered valid. For example, BPEL does
	not allow an empty Sequence activity. Invalid structured activities
	will be decorated with an error icon similar to basic activities.</p>
	<p>
	Structured activities can be expanded and collapsed on the
	drawing canvas by clicking the plus and minus buttons at the bottom of
	the figure. Illustrated below is a collapsed and expanded Sequence:
	</p>

	<p><img src="../../..images/reference/BPEL_Designer_12.png" alt="Collapsed Sequence" /></p>
	<p><b>Collapsed Sequence</b></p>

	<p><img src="../../../images/reference/BPEL_Designer_13.png" alt="Expanded Sequence" /></p>
	<p><b>Expanded Sequence</b></p>

	<p>
	The following sections describe the structured activities and
	how each must be configured to be considered valid for BPEL.
	</p>

	<h5>If</h5>
	<p><img src="../../../images/reference/BPEL_Designer_14.png" alt="If, ElseIf and Else" /></p>
	<p><b>If, ElseIf and Else</b></p>
	<p>
	The If activity allows conditional execution of one or more
	sequences of activities. It consists of a sequence of one or more
	conditional branches defined by If and optional ElseIf elements. The
	elements are evaluated in left-to-right order (or top-to-bottom if you
	have selected horizontal layout). An optional Else branch will be
	executed if none of the other conditions are true.
	</p>
	<p>
	An If activity must define a condition (expressed as an XPath)
	and an activity which is executed if the condition evaluates true. To
	insert additional ElseIf and Else elements, right-click the If figure
	and select the desired element from the context menu. The figure above
	shows a complete If activity with optional ElseIf and Else elements.
	</p>

	<h5>Pick</h5>
	<p><img src="../../../images/reference/BPEL_Designer_15.png" alt="Pick" /></p>
	<p><b>Pick</b></p>
	<p>
	The Pick activity will cause the process to wait for one of any number
	of messages to be received. An optional timer can be set to limit the
	time to wait for receipt of these messages. Activities to handle
	receipt of messages and timer expiration are defined in the Pick.
	Message receipts are handled by OnMessage activities (
	<a href="#Reference-Details_tab-OnMessage">OnMessage</a>), and timer expiration is handled by the OnAlaram
	activity (<a href="#Reference-Details_tab-OnAlarm">OnAlarm</a>).
	</p>

	<h5>While</h5>
	<p><img src="../../../images/reference/BPEL_Designer_16.png" alt="While" /></p>
	<p><b>While</b></p>
	<p>
	The While activity repeatedly executes the contained activity as
	long as a condition evaluates true at the beginning of each iteration.
	A While activity must define a condition and must contain an activity.
	</p>

	<h5>ForEach</h5>
	<p><img src="../../../images/reference/BPEL_Designer_17.png" alt="ForEach" /></p>
	<p><b>ForEach</b></p>
	<p>
	ForEach is a looping activity that executes the activities
	contained in its Scope a specified number of times. A counter
	variable, defined in the ForEach property detail tab, is used to keep
	track of the iterations. The ForEach properties must be configured
	with starting and ending value expressions for this counter variable.
	The counter is initially set to the starting value and activities in
	the Scope are executed until the counter exceeds the ending value.
	</p>
	<p>
	This activity can also be configured to execute all iterations
	in parallel, meaning the enclosed Scope activity behaves as if
	multiple Scopes are enclosed in a Flow activity.
	</p>
	<p>
	An optional early termination value can be defined, which will cause
	the loop to complete before the counter has reached its ending value.
	The ForEach will complete when the counter is equal to this early
	termination value for the sequential execution case. For the parallel
	execution case, the early termination value is the number of completed
	iterations. For example, the ForEach completes when at least
	<em>some number</em> of <em>some action</em> have finished.
	</p>

	<h5>RepeatUntil</h5>
	<p><img src="../../../images/reference/BPEL_Designer_18.png" alt="RepeatUntil" /></p>
	<p><b>RepeatUntil</b></p>
	<p>
	The RepeatUntil activity repeatedly executes the contained
	activity as long as a condition evaluates true at the end of each
	iteration. A condition must be defined for a RepeatUntil, and it must
	contain an activity.
	</p>

	<h5>Sequence</h5>
	<p>
	A Sequence is a container for one or more other activities,
	which are executed in sequential order and (unlike Scope and Flow
	activities), has no other special characteristics. Because the
	conditional activities ( If, While, RepeatUntil and ForEach) can have
	only one activity as the target of their execution, a Sequence is
	typically used to execute multiple activities.
	</p>
	<p>For example, the If shown below contains only a single Assign activity:</p>

	<p><img src="../../../images/reference/BPEL_Designer_19.png" alt="Sequence" /></p>
	<p><b>Sequence</b></p>
	<p>
	If it were necessary to perform an assignment and then invoke
	another web service, the Assign and Invoke could be contained within a
	Sequence. The Sequence would then become the target of the If:
	</p>

	<p><img src="../../../images/reference/BPEL_Designer_20.png" alt="Sequence" /></p>
	<p><b>Sequence</b></p>

	<h2>Note</h2>
	<p>
	The BPEL Designer will automatically create a Sequence if you drag-drop a second
	activity into any of the conditional activities.
	</p>

	<h5>Scope</h5>
	<p><img src="../../../images/reference/BPEL_Designer_21.png" alt="Scope" /></p>
	<p><b>Scope</b></p>
	<p>
	A Scope provides a context for its enclosed activity. This
	context includes variables, partner links, message exchanges,
	correlation sets, event handlers, fault handlers, a compensation
	handler and a termination handler. These Scope contexts can be nested
	hierarchically where the root context is provided by the process
	itself.
	</p>
	<p>
	A Scope can be thought of as a compartmentalized sub-process. If the
	Scope is declared as being <em>isolated</em> , then the variables and
	partner links shared with the process are locked to prevent other
	concurrent Scopes from altering them while a Scope is executing. Scope
	may also be nested to any depth and all variables, partner links and
	others defined in a Scope, are inherited by its children. Refer to
	<a href="#Reference-BPEL_Designer-Structured_Activities-Flow">Flow</a> for
	a discussion of concurrent execution.
	</p>

	<p>
	To be valid, a Scope must have a single activity. The typical
	use of a Scope activity is to invoke a service and wait for a response
	message or timeout. In the above figure, the Scope has defined a
	message variable and a partner link used to interact with the invoked
	service.
	</p>

	<h5>Flow</h5>
	<p>
	The Flow activity allows multiple activities to be executed in
	parallel. All activities or Sequences of activities that are contained
	in a Flow, are executed (or begun) at the same time by the BPEL
	engine. A Flow completes when all of its enclosed activities have
	completed.
	</p>
	<p>
	Parallel processing is typically used to save time by doing more than
	one thing at a time and as a result, speed up the process. However, in
	many situations several tasks can be started at the same time, but one
	or more tasks may depend on the successful completion of other tasks.
	This task dependency sequencing is called <em>synchronization</em> and
	is achieved using Links.
	</p>
	<p>
	For example, a process that handles purchase orders for material
	goods needs to:
	</p>

	<ol>
	<li><p>Calculate the total order price</p></li>
	<li><p>Calculate shipping costs for the order</p></li>
	<li><p>Send a customer invoice</p></li>
	</ol>

	<p>
	All of these activities can be started at the same time, however
	the shipping cost must be finalized before the total order price can
	be determined, and the invoice can be sent.
	</p>

	<p>
	To create a Link, right-click on the activity that must be completed
	first (the activity that is the <em>source</em> of the dependency) and
	select <strong>Add Link</strong> from the context
	menu. Next, move the mouse to the activity in the Flow that depends on
	this one (the <em>target</em>) and click the left mouse button to
	create the link.
	</p>
	<p>
	A Link is identified by a name that must be unique within the
	Flow. The BPEL Designer generates a reasonable default name, but you
	can change this in its properties. You can also add a test to the Link
	that defines the conditions for considering an activity to be
	complete. For example an activity in a Flow may require two pieces of
	information, provided by other services, in order to continue.
	Consider the process Flow shown below:
	</p>

	<p><img src="../../../images/reference/BPEL_Designer_22.png" alt="Flow example" /></p>
	<p><b>Flow example</b></p>
	<p>
	In this example, the <em>Billing</em> department can begin preparation
	of a customer invoice, but it needs to know if sufficient stock is on
	hand to fulfill the order and if an outside vendor needs to provide
	the additional quantities ordered. The following condition would
	enable the Link so that execution can continue for the price
	calculation and customer invoicing:
	</p>

	<p><img src="../../../images/reference/BPEL_Designer_23.png" alt="Link example" /></p>
	<p><b>Link example</b></p>

	<p>
	This process is only partially complete though as it does
	not consider the number of outside vendors, or if the total
	quantity being ordered can ever be filled.
	</p>
	</body>
	</html>