A Novel Federated Cloud Simulation Framework andits Key Techniques
Hongbo Sun, Wenhui Fan, Tianyuan Xiao
National CIMS Engineering Research Centre, Tsinghua University, Beijing 100084, China
hsun@ieee.org, fanwenhui@tsinghua.edu.cn, xty-dau@tsinghua.edu.cn

Abstract— In increasingly saturated markets, innovation andproduct development are essential conditions for the sale ofproducts. Adopting collaborative product development makes
full use of several independent systems, and enhances theirabilities at the same time. But as a matter of fact, collaborative
product development (CPD) systems are complicated andcomprise various systems for collaborative design, simulation,and optimization. It involves processes like CAD modeling,simulation and optimization, requires data and information like
CAD digital models, CAE analysis and optimization results from
distributed sources.
When simulation is added into a collaborative productdevelopment environment, there always exist several subsystems
in the same environment with independent design goals. Thesesubsystems may follow different design or management rules intheir respective engineering fields.
As a well-known modeling and integration standard of
distributed simulation, HLA (High level Architecture) has beensuccessfully adopted in various simulation systems, and been
extended to some other research areas. HLA defines a federation
as a named set of federate applications and a common Federation
Object Model (FOM) that are used as a whole to achieve somespecific objectives. Federates exist within a federation in the formof data abstraction, and federated integration keeps well theindependency of its participants. This kind of integration is moresuitable for and is widely used in distributed and loosely coupledsimulation integration. The owner of each participant does notneed to worry about exposing too much private information. The
federation only defines the interesting domains for given
objectives and the rules of their interoperations. It is a realloosely coupled integration solution. Within a federation,
subsystems collaborate in an indirect way so that the context ofinteroperation can be taken into consideration.
At the same time, due to their distributed and multiparticipant nature of CPD systems, web services are widely used
to provide interoperation functions and cloud computing is areasonable architecture choice. As one kind of cloud computing,cloud simulation is a model for enabling convenient, on-demand
network access to a shared pool of configurable simulation
resources (e.g. computers, simulators, physical equipment,simulation tools, platforms, open-resource code, models andservices) that can be rapidly provisioned and released withminimal management effort or service provider interaction. This
cloud model promotes availability in which simulation resources,
including hardware, software, and different kind of models, areavailable to provide as services. However, architecture of cloud
simulation varies according to different application objectives.
This paper proposes a novel federated cloud simulation
framework, in which cloud computing technique is adopted toextend HLA. This framework extends HLA into two levels:
resource management federation level and application federationlevel. Concerned key techniques are presented, including HLA
compatible access, virtual resources management and simulation
task automatic generation. This framework has great potential to
improve the efficiency and availability of distributed
collaborative simulations, and enhance the applicability andflexibility of collaborative product development systems (Figure1).
Collaborative Simulation Applications
Smart Phone

Personal Computer…… Other Device

Tele Vision

Condensation
AccessControl……

Transaction
ServiceDeclaration
Management

ObjectManagementOwnershipManagementSearching
SeviceTime
Management

Data Distribution
Management

Federation
ManagementApplication
Federation

Application
Federation

Simulation Task Intelligent Generation
Environment
ServiceApplication
Federation
MonitorServiceService
Description

Fault
Tolerance

ServiceComposition

ServiceRegistration……
ServiceSearching

Service
Discovery

MappingServiceNetwork
Service

Service
Matching

ServicePublication

Sublimation
Resource Management Federation
Virtualized Simulator
Virtualized Platforms

Virtualized Models

Algorithms

Virtualized Environments

Virtualized Open Source Codes Virtualized Storage ……
Virtualization
HLA Compatible Access

Simulation Resources
AccessSoftwareAccessEnvironment Computing Resources
AccessAccessKnowledge
Access……
……

ComputingResources

Open source codes

Platforms

Simulators

Environments

Templates

StorageServices
DataModels
EnginesFigure1 Federated framework for cloud simulation

In this framework, there are three processes related to thisfederated framework: virtualization turns related simulation
resources into virtualized resources; sublimation organizes
virtualized simulation resources in a cloud manner; andcondensation maps services in federation based cloud intoapplication scenarios.
Before virtualization, an HLA compatible access systemcollects simulation related resources to supporting futureapplications. These resources include computing resources,
platforms, environments, storage, data, engines, models, services,
templates simulators and open source codes. Computing
resources reflects computation execution and supporting
capability, such as CPU power. Engines are basic software
supporting some given operations, such as searching engine
supports service searching. Services are simulation related
services, which can be divided into two categories, basic services
and value-added services. Basic simulation services areindispensable services for a successful simulation application,such as time advance service, data distribution service, andownership service. Value-added services goes with basic services
and improves the quality of basic services, such as service
searching, service discovery, service composition, and service
matching. Environments reflects different platforms on whichapplications run, such as Windows, Linux, Symbian, Windows
Mobile, Android, Palm OS, BlackBerry and Snow Leopard. Data
gives history records to evaluate coming simulation transactions.
Data templates describe regulated registration or publication
formats, and sometimes service composition needs process
templates to introduce some basic skeletons. Models are essential
abstractions of some entities or processes.
As a virtual resources pool, resource management federation
saves information and access methods of resources gathered by
HLA compatible access system. The virtualized resources include
virtualized simulator, virtualized models, algorithms, virtualizedenvironments, virtualized platforms, virtualized open source
codes, and virtualized storage.
Federated framework for cloud simulation is composed of aset of well-organized services and one kernel, simulation task
intelligent generation system. The services include resources
related services and application related services. Resources
related services searching, organizing, manipulating and accessvirtualized resources in the form of services, such as environment
service, monitor service, fault tolerance service, mapping service,
network service, service description, service searching, service
discovery, service registration, service publication, service
composition and service matching. Application related services
serves simulation applications in a more direct manner, which
include declaration management service, user access control,transaction service, ownership management service, object
management service, content searching service, time management
service, data distribution management service and federation
management service. The simulation task intelligent generation
system provides (semi)automatic simulation task creation
functions to support different kinds of simulation tasks.
Collaborative simulation applications can be performed onany device that can access network. These applications include
collaborative design evaluation, collaborative simulation based
optimization and collaborative training.

The key techniques of proposed federated framework forcloud simulation include HLA compatible access technique,virtual resource management technique, simulation task
automatic generation technique, simulation task dynamic
adjustment technique and ubiquitous computing.
As an HLA compatible access technique HLA enabled
template is designed to facilitate transform actions of commercial
simulation models. In this HLA enabled template, DiyModel class,which is user defined model class, is a kernel part. DiyModel
encapsulated the virtual variable and event objects so that user
program can exchange data with other distributed models
without concerning about the data mapping process.
As a virtual resource management technique, resource
management federation (RMF) organizes, manipulates and stores
simulation related resources in a layered federation manner. Its
main ides is that every computer (node) that joins collaborative
simulation and every node’s resource are declared as themembers of “resource pool”, and RMF is responsible for themanagement of simulation resources.
Application federation is the result of simulation task
automatic generation technique and simulation task dynamic
adjustment technique. It fulfills different kinds of simulation
requirements in a flexible manner. This paper chooses a FCA likemethod to construct SOM ontology from scratches, and proposesa deterministic finite state automaton is built to automaticallytransform SOM file into an ontology based SOM. Compared withexisting ontology construction method, this method is easier toapply in HLA based CPD systems. It also maximally reuses
existing knowledge. For ontology based FOM auto generation,
this paper introduces ontology fusion method, which includes
three basic steps. Ontology mapping employs a top-down
mechanism to explore all bridge relations between two terms
from different ontologies on the base of bridge axioms anddeduction rules. Ontology alignment adopts a bottom-up
mechanism to discover implicit bridge relations between twoterms from different domain ontologies on the base of equivalentinference. And ontology merging generates new ontology fromfounded equivalent bridge relation. It adopts an axiom-based
reasoning ontology fusion strategy, and takes heavy-weighted
ontologies into consideration. It can find all the explicit andderived inter-ontology relations. As to collaboration task dynamicadjustment, this paper employs ontology maintenance todynamically adjust ontology based FOMs.
Ubiquitous computing enables end users access federated
framework for cloud simulation on any device that can accessInternet. To be brief, this part is not included in this paper.
The proposed federation-based cloud simulation frameworkextends HLA into two levels: resource management federationlevel and application federation level. The OMT of an application
federation in HLA can be configured dynamically by RMF, theshare and maintenance of distributed and heterogeneous
simulation models and physical nodes can be implemented asservices. It aims particularly in short-term-stable multi-objective
collaboration under incomplete coverage condition of control
domain and trust domain for heterogeneous simulation systems.
The further work includes some management functions of theframework, such as fault tolerance, intelligent update, consistentsustainment, and so on.