Architectures for an Event Notification Service Scalable to Wide-area Networks
Architectures for an Event Notification Service Scalable to Wide-area Networks
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发表时间：
2000
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通讯作者：
A. Carzaniga;L. Baresi;G. Biondini;F. Cattaneo;Thorna O. Humphries;A. Klauser;P. Lanzi;Edoardo Marcora-Edoardo
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作者：
A. Carzaniga;L. Baresi;G. Biondini;F. Cattaneo;Thorna O. Humphries;A. Klauser;P. Lanzi;Edoardo Marcora-Edoardo
抽象用户定义类型：在这种情况下，事件服务将提供允许定义抽象数据类型的类型化编程语言的特征（例如，将过滤器扩展到用户定义的类型可以通过对过滤语言的简单扩展来完成，类似于面向对象数据库的查询语言，如O2 SQL或OQL。一个过滤器可能看起来像这样：person.birthday. CherterThan（Date“Dec 16”））;从应用程序程序员的角度来看，后一种解决方案最适合其增强的建模特性。然而，由于过滤器可能包含任意的用户定义代码，因此很难基于过滤器的静态分析进行优化。这将不可避免地影响可伸缩性。此外，在大规模上，假设系统的每个组件都能够理解面向对象语言可能是不合理的。从事件服务设计者的角度来看，第一个解决方案肯定是最容易实现的。它带来的编码问题更少
abstract user-defined types : in this case, the event service would pro-vide the features of a typed programming language that allows thedefinition of abstract data types (e.g., an object-oriented language).Extending filters to user-defined types can be done with easy exten-sions to the filtering language similarly to query languages for object-oriented databases like O2 SQL or OQL. A filter might look like this: person.birthday.greaterThan ( Date “Dec 16” )) ;From the viewpoint of the application programmer, the latter solutionwould be best for its enhanced modeling features. However, because filterscould contain an arbitrary user-defined code, it would be very difficult to per-form optimizations based on the static analysis of filters. This would severelyimpact on scalability. Also, on a largescale, it might not be legitimate to assumethat every component of the system is able to understand an object orientedlanguage.From the viewpoint of the designer of the event service, the first solutionis definitely the easiest one to implement. It poses less problems of encoding