View source for Mission monitor sequencer

===Introduction===

This plug-in implements a a language that is a mixture of a rule-based and a sequential based language. The idea is that a number of situations need permanent - or semi permanent - monitoring to get a good situation awareness for the root, and at the same time a large number of the robot tasks are better described by a sequential language.

This implementation attempts to cover this gab.

===Language===

An example function could look like this:

 <?xml version="1.0" ?>
 <plan name="CrossRoad">
    <init>
        odoPose.tripB = 0
        nearRoad = false // define local variable
        <plan name="maxOdoDist" if="odoPose.tripB > 250"> 
            print("Driven too far on odo " odoPose.tripB "m") // print message
            break CrossRoad // failed to cross road - could trigger a relocalization
        </plan>
        <plan name="closeToRoad" if="hypot(utmPose.poseY - 6174307, utmPose.poseX - 707873) &lt; 15" >
            print("Cose to road slowing down) // print message
            smr.speed=0.5  // set the desired maximum speed in mrc interface module
            nearRoad = true  // set flag
            disable  // disable this rule (plan)
        </plan>
        <plan name="turn">
            <parameter angle="pi" dist=1.0/>
            <commands to="smr.send">
              # construct commands to MRC using the smr.send command
              'drive @v ' smr.speed ' : ($drivendist > ' dist ')'
              'turn ' angle
              'drive : ($drivendist > ' dist ')'
            </commands>
        </plan>
    </init>
    print("started")
    enable maxOdoDist    // should have found road by now
    enable closeToRoad   // active until disabled.
    roaddrive.right(0.75) : nearRoad // follow road 75cm from edge until near road
    // more stuff missing here to detect traffic etc.
    ...
    turn() // turn back - using a call to a plan
    success=true
    <post>
        print("finsihed crossRoad - success=" success)
    </post>
 </plan>

A number of these plans can be started (enabled) simultaniously, an can in principle be total independant. I.e.one can control the robot arm whele another controls the navigation.

===Language definition===

The language definition is:

====Plan====

planBlock ::= planOpenTag   planBody   planCloseTag

planOpenTag ::= '<plan' 'name=' planName [runAttribute] [ruleCondition] '>\n'

planName ::= '"' symbol '"'

runAttribute ::= 'run="default"'  (there may come more values later)

ruleCondition ::= 'if="' expression '"'

planCloseTag ::= '</plan>\n'

planBody ::= [parameters] [description] [planInitBlock] planMainBlock [planPostBlock]

parameters ::= '<parameters ' [symbol '="' [paramDefaultValue] '"']* '/>\n'

paramDefaultValue ::= constantValue

description ::= '<description>\n' xmlText '</description>\n'

xmlText ::= any 7-bit characters except '\0', '&' and '<', the last two must be coded as &amp; and &lt;

planInitBlock ::= '<init>\n' [declarationStatement]* '</init>\n'

declarationStatement ::= planBlock | executableStatement

planMainBlock ::= [statement]*

planPostBlock ::= '<post>\n' [statement]* '</post>\n'

====Statements====

statement ::= executableStatement | controlStatement 

executableStatement ::= assignment | procedureCall | blockStatement | 
breakStatement | enableStatement | ifStatement | emptyStatement

controlStatement ::= proceureCall ':' expression [remark] '\n'

assignment ::= [symbol.]* symbol '=' expression [remark] '\n'

procedureCall ::= [symbol.]* symbol '(' [expression [',' expression]* ')' [remark] '\n'

blockStatement ::= '<block>\n' [statement]* '</block>\n'

breakStatement ::= ('break' [symbol] | 'continue' ) [remark] '\n'

enableStatement ::= ('enable' | 'disable') [symbol] [remark] '\n'

ifStatement ::= 'if (' expression ')' [remark] '\n' statement [remark] '\n' [elseStatement]

elseStatement ::= 'else' [remark] '\n' statement [remark] '\n'

emptyStatement ::= [remark] '\n'

remark ::= ('#' | ';' | '//') xmlText except '\n'