Diistributed Data Management DDM in HLA. Distributed Data Management HLA by default does one sort of...
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Transcript of Diistributed Data Management DDM in HLA. Distributed Data Management HLA by default does one sort of...
Diistributed Data Management
DDM in HLA
Distributed Data Management
HLA by default does one sort of interest management: functional. Your federate can express interest (subscribe to) instances of particular classes and their attributes
Only those class attributes will be sent to you when they are updated
This is actually somewhat sophisticated, or can be, depending on the (black box) RTI implementation
Just as with DIS we may want to limit distribution of object information to a specific area
Geographic Interest Management
Region 1
Region 2 Region 3
GeographicThe overall space is divided up into smaller
regions, and individual federates can listen to a subset of the total geographic space
This is called a “routing space”. A routing space is simply a list of attributes along with minimum and maximum values
Normally the attributes define an area or volume, but this isn’t a restriction on the concept. You can use any bounded variable
Routing SpacesA routing space is defined in the FOM(spaces (space <name> (dimension <name>) (dimension <name>))There is a default routing space provided
if you don’t define one
Creating RegionsYou can dynamically create regions in the
routing space with a call to the RTIAmbassador createRegion(). You get back a handle for that newly created region, and can set the extent of the region with setLowerBound(), etc.
Each federate knows only of the regions it creates; there is no way to share regions between federates. Regions are not globally known to the federation execution
AttributesAn object attribute is tied to a routing
space in the fed file(spaces (space TestSpace (dimension TestDimension) ))…(class A (attribute aa reliable timestamp TestSpace) (attribute ab reliable timestamp TestSpace))
Attributes and RoutingThe name for the routing space dimension
is not tied to class attributesIf you have a tank with attributes (lat, lon)
defined in the FOM, this does not necessarily have any link to the routing space dimensions of (lat, lon)
The producing federate must associate object updates with regions
AttributesAn “attribute instance” is one attribute of
one object instance (vs. the class attributes)
You can tie attribute instances to a region with associateRegionForUpdates() on particular object instances
Attribute instances can be associated with only one region at a time
SubscribingSuppose you want to learn of all class
attribute updates in region XMake call to
subscribeObjectClassAttributesWithRegion()
Associates the given attributes from the given class with a region, so any updates to attributes in other federates will result in a notification to your federate
Similar mechanism for interactions
Management Object ModelThe MOM refers to metainformation about
HLA itself--the federates, the RTI, the federation execution, etc
We want to learn about what is going on in the simulation at runtime
HLA uses HLA to find out about itself at runtime
MOMSuppose we want to find out about the
other federatesThe RTI can maintain information about
this in an object, and if that is the case, why not make it an HLA object?
That is the basic insight of MOM--HLA objects are used to describe the state of the simulation