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<p><a class='wikilink' href='../Main/HomePage.html'>Main</a> > <span class='wikitrail'><a class='wikilink' href='Main.html'>Reference Manual</a> > <a class='wikilink' href='Modeling.html'>Modeling</a> > <a class='selflink' href='ModelingFlow.html'>Flow</a></span>
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<p class='vspace'>Flows are used to model the consumption and production of material from buffers.
</p>
<p class='vspace'>Two types of flows exist:
</p><ul><li>FLOW_START: Flows that consume material at the start of an operationplan.
</li><li>FLOW_END: Flows that produce material at the end of an operationplan.
</li></ul><div class='vspace'></div><h2>Fields</h2>
<table border='1' width='100%' ><tr><td width='20%' valign='top'><strong>Field</strong>
</td><td width='20%' valign='top'><strong>Type</strong>
</td><td width='60%' valign='top'><strong>Description</strong>
</td></tr><tr><td valign='top'>buffer
</td><td valign='top'>buffer
</td><td valign='top'>
<p>Buffer from which material will be moved or transferred into.<br />This is a required field.
</p></td></tr><tr><td valign='top'>operation
</td><td valign='top'>operation
</td><td valign='top'>
<p>Operation to which the material flow is associated.<br />This is a required field.
</p></td></tr><tr><td valign='top'>quantity
</td><td valign='top'>double
</td><td valign='top'>
<p>Material quantity being consumed or produced per unit of the operationplan.
</p></td></tr><tr><td valign='top'>effective_start
</td><td valign='top'>dateTime
</td><td valign='top'>
<p>Date after which the material consumption is valid.<br />Before this date the planned quantity is always 0.
</p></td></tr><tr><td valign='top'>effective_end
</td><td valign='top'>dateTime
</td><td valign='top'>
<p>Date at which the material consumption becomes invalid.<br />After this date (and also at the exact date) the planned quantity is always 0.
</p></td></tr><tr><td valign='top'>priority
</td><td valign='top'>integer
</td><td valign='top'>
<p>Priority of the flow, used in case of alternate flows.<br />The default is 1. Lower numbers indicate more preferred flows.
</p></td></tr><tr><td valign='top'>name
</td><td valign='top'>non-empty string
</td><td valign='top'>
<p>Optional name of the flow.<br />A name is only useful when using alternate flows. Otherwise leave it empty to save some memory.
</p></td></tr><tr><td valign='top'>alternate
</td><td valign='top'>non-empty string<br />or<br />flow
</td><td valign='top'>Name of the flow of which this is an alternate.<br />When using the Python API the argument can be a flow or a string.<br />When using the XML data format the argument is a string.
</td></tr><tr><td valign='top'>search
</td><td valign='top'>string
</td><td valign='top'>
<p>Defines the order of preference among the alternate flows.<br />The valid choices are:
</p><ul><li>PRIORITY<br /> Select the alternate with the lowest priority number.<br /> This is the default.
</li><li>MINCOST<br /> Select the alternate which gives the lowest cost.<br /> The cost includes the cost of all upstream operations, resources and buffers.
</li><li>MINPENALTY<br /> Select the alternate which gives the lowest penalty.<br /> The penalty includes the penalty of all penalties incurred in the upstream plan along the flow.
</li><li>MINCOSTPENALTY<br /> Select the alternate which gives the lowest sum of the cost and penalty.<br /> The sum is computed for the complete upstream path.
</li></ul></td></tr><tr><td valign='top'>action
</td><td valign='top'>A<br />C<br />AC (default)<br />R
</td><td valign='top'>
<p>Type of action to be executed:
</p><ul><li>A: Add an new entity, and report an error if the entity already exists.
</li><li>C: Change an existing entity, and report an error if the entity doesn't exist yet.
</li><li>AC: Change an entity or create a new one if it doesn't exist yet.
</li><li>R: Remove an entity, and report an error if the entity doesn't exist.
</li></ul></td></tr></table>
<div class='vspace'></div><h2>Example XML structures</h2>
<ul><li>Defining a flow
</li></ul><pre> <plan>
<flows>
<flow xsi:type="flow_start">
<buffer name="buffer component"/>
<operation name="operation B"/>
<quantity>-2</quantity>
</flow>
</flows>
</plan>
</pre><div class='vspace'></div><ul><li>Defining a flow nested in an operation structure.<br /> A quantity 2 of component A OR 3 of component B are consumed, and 1 unit of the end item is produced.
</li></ul><pre> <plan>
<operations>
<operation name="operation B">
<flows>
<flow xsi:type="flow_start">
<buffer name="buffer component A"/>
<quantity>-2</quantity>
<name>group1</name>
<priority>1</priority>
</flow>
<flow xsi:type="flow_start">
<buffer name="buffer component B"/>
<quantity>-3</quantity>
<alternate>group1</alternate>
<priority>2</priority>
</flow>
<flow xsi:type="flow_end">
<buffer name="buffer end item"/>
<quantity>1</quantity>
</flow>
</flows>
</operation>
</operations>
</plan>
</pre><div class='vspace'></div><ul><li>Defining a flow nested in a buffer structure
</li></ul><pre> <plan>
<buffers>
<buffer name="buffer component">
<flows>
<flow xsi:type="flow_start">
<operation name="operation A"/>
<quantity>-2</quantity>
</flow>
<flow xsi:type="flow_start">
<operation name="operation B"/>
<quantity>-1</quantity>
</flow>
</flows>
</buffer>
</buffers>
</plan>
</pre><div class='vspace'></div><ul><li>Deleting a flow
</li></ul><pre> <plan>
<flows>
<flow action="R">
<buffer name="buffer component"/>
<operation name="operation B"/>
</flow>
</flows>
</plan>
</pre>
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