在運用ＣＯＲＢＡ技術當作我們分散式驗證系統的基礎的過程中，我們馬上遭遇到一些設計上的困難與問題。其中之一就是ＣＯＲＢＡ並不提供一個標準的負載平衡服務。更精確的說ＣＯＲＢＡ的制作標準中保留了特定的機制來擴充並把這個工作留給了各廠商及使用者。通常這種問題有兩種解決方式：不按標準來實作或技巧性的迴避此問題。兩種方式都會帶來負面影響，如程式無法移殖或增加設計的困難度。在此篇論文中，我們會參考和評估許多來自廠商和開放軟體專案的解決方式（例如ＴＡＯ、ＭＩＣＯ、Ｖｉｓｉｂｏｒｋｅｒ）並指出它們的優缺點。我們主要的貢獻在於提供一個新的機制來解決上述的問題。我們能讓使用者使用數個相同的物件當作一個物件群組，並且在不使用非標準機制的方式下讓使用者通透的使用物件，也提供使用者一個新的負載平衡機制。我們採取的方法是結合命名服務和攔截並重導向要求。我們使用前者來註冊、註銷並收集物件然後分派要求給這些物件。這兩種方式均按照ＣＯＲＢＡ標準來實現，因此而逹成了可移稙性。最後，我們提供了一個獨立的、可移稙並易於使用的負載平衡器，它不僅可當作我們分散式驗證器的基礎也可以應用於其它的需要負載平衡的領域。

In trying to apply the Common Object Request Broker
Architecture (CORBA) technology as an infrastructure for the
distributed architecture of our SGM model checker, we
immediately face some design problems and issues. One of them is
CORBA's lack of standard Load Balancing mechanism. More exactly,
the CORBA specification preserves certain mechanisms to scale up
and leave this issue to vendors and users.
There are two popular philosophies to resolve the problem: extend
the specification or use tricky methods, either way will cause
penalties like non-portable applications or increase design
complexity. In this Thesis we will review and study several
solutions from vendors and open-source projects (such as Borland
Visibroker, TAO, MICO) and point out their limitations and
disadvantages.
Our major effort is on providing a new mechanism to solve the
above issue, we let user to create an object cluster consisting of
several CORBA objects of the same kind and use it transparently as
a single one without introducing new function calls or complex
design schemes. This approach benefits users by saving design
efforts, through our implementation of the novel load balancing
scheme.
The adopted strategy is a combination of the Naming service and the redirection of object requests wring the Interceptor
pattern. We use the former to register, unregister, and collect
CORBA objects and dispatch the request with latter one. Both of
them were implemented by following the CORBA standard mechanism
and implicitly provide portability.
Finally, we will provide a stand-alone, portable, and easy-to-use
CORBA-based load balancer. Not only can it be used as a building
block for distributed SGM tool, but can also be applied to other
application fields where such a load balancing service is needed.

1 Introduction 1
1.1 Background
1.1.1 Model Checking and the SGM Tool1.1.2 AGR-based parallel verication
1.2 Motivation
1.3 Thesis Organization
2 PreviousWork
2.1 CORBA Architecture
2.1.1 Object Model
2.1.2 Interoperable Object Reference
2.1.3 POA 2.1.4 Servant Manager of POA
2.1.5 Object Groups
2.1.6 Naming Service
3 The Mechanism and Analysis of Load Balancing of CORBA products
3.1 TAO
3.1.1 Component Structure
3.1.2 Mechanism and Analysis
3.1.3 Remarks
3.2 MICO 3.2.1 Mechanism and Analysis
3.2.2 Remarks
3.3 Borland Visibroker
3.3.1 Mechanism and Analysis
3.3.2 Remarks
4 The Implementation of DSGM 30
4.1 Design Guidelines
4.2 System Component Structures
4.2.1 Implementation of the SGM Core and Client Program
4.2.2 Middle Layer
4.3 Load Balancing of DSGM
4.3.1 Service Registering and Deregistering
4.3.2 Servant Locator and Load Balancing Strategies
4.4 System Deployments
5 Example
6 Conclusion and FutureWork
Bibliography

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