[Extensive Reading] 4 papers on Web Service Replication

Introduction to replication:
"Replication is the process of sharing information so as to ensure consistency between redundant resources, such as software or hardware components, to improve reliability, fault-tolerance, or accessibility." (Wikipedia)
The purpose of replication technology is to improve the dependability of distributed systems (such as distributed objects, databases, and file systems), rely on redundant resources, and maintain consistency between these resources.
The copied objects can be divided into two types: Data Replication and computation replication.
There are two implementation methods: active replication and passive replication.
See http://en.wikipedia.org/wiki/Replication_ (computer_science)

Thesis (1)
Osrael J, froihofer L, goeschka K m. what service replication middleware can learn from object replication middleware [c] // Proceedings of the 1st Workshop on middleware for service oriented computing. melbourne, Australia: Association for Computing Machinery, 2006: 18-23
(1) In this paper, we believe that replication in the so system is still in its infancy. At the architectural level, we compare some existing service replication middleware with the object replication middleware.
The result is that replication middleware in the so system has a lot in common with replication middleware in the distributed object system. Some differences are caused by the granularity of the replicated entity and different transaction models.
(2) Existing so replication Middleware
A) Primary-Backup replication middleware: "Fault Tolerant Web Service"
B) active replication middleware: "WS-replication: A Framework for highly available Web Services", "a middleware for replicated Web Services"
(3) the replication of stateless service is relatively simple, and the main difficulty lies in the replication of stateful service.
(4) six types of repeated tural units (applicable to object and service replication middleware) are extracted ):
Multicast Service
Monitoring Service
Replication manager
Replication Protocol Unit
Invocation Service
Transaction Service (optional)
(5) independent from WSC; only dependent on dependability, independent from QoS

Thesis (II)
Liang D, Fang c l, Chen C et. al. fault Tolerant Web Service [c] // Proceedings of the tenth Asia-Pacific Software Engineering Conference (apsec ). washington, DC: IEEE Computer Society, 2003: 310-319
GS: 32
(1) A Fault Tolerant Web Service (FT-soap) is proposed to intercept user requests at the message layer (SOAP). If the requested ws fail, will be automatically redirected to the backup ws. the layout of this article is messy.
(2) stateful WS is not involved; WSC and QoS are not involved; fault tolerant for a single service is used; replication manager is used to generate backup services, and dynamic discovery of services is not supported.

Thesis (III)
Ye X, Shen Y. A middleware for replicated Web Services [c] // IEEE International Conference on Web Services (ICWs). Los Alamitos: IEEE Computer Society, 2005: 631-638
(1) an active replication-based middleware that supports reliable Web Service is proposed. This middleware maintains the status of replicas.
With this middleware, the existing single-thread ws can be copied to different sites without changing the implementation.
Each replica includes two entities: proxy service site (pwss) and common web service site (WSS). When a user sends a request through pwss, pwss maintains the consistency and error handling of the corresponding WSS.
(2) does not involve WSC QoS

Thesis (IV)
Salas J, PEREZ-SORROSAL F, PATINO-MARTINEZ M, et. al. WS-replication: A Framework for highly available web services [c] // Proceedings of the 15th International Conference on World Wide Web (WWW ). edinburgh, Scotland: Association for Computing Machinery, 2006: 357-366
(1) This paper proposes the WS-replication architecture (infrastructure) for ws replication in the WAN environment.
The purpose of WS-replication is to make ws highly availability, so as to meet the requirements of mission critical system.
This architecture is based on group communication WS, WS-multicast. WS-Multicast Transmission is based on soap and relies on WS for cross-organizational interaction.
WS-replication adopts the active replication method.

The four papers are rough, but I have a rough understanding of the work of the paper, but I have not read the full text. After reading it, I have the following impressions on WS replication:
1. Web services as replica are generally implemented in the same copy, and maintenance is required.CodeConsistency with status
2. ws are not dynamically discovered
3. It is not discussed in the WSC scenario. It mainly targets ws reliability and does not involve other QoS
4. Both Support Web Service Replication through Middleware
5. You need to consider the location of replica