【正文】 questor): The software entity that calls a service provider. Traditionally, this is termed a “client”. A service consumer can be an enduser application or another service. – Service locator: A specific kind of service provider that acts as a registry and allows for the lookup of service provider interfaces and service locations. – Service broker: A specific kind of service provider that can pass on service requests to one or more additional service providers. Interfacebased design ? In both ponent and service development, the design of the interfaces is done such that a software entity implements and exposes a key part of its definition. ? Therefore, the notion and concept of “interface” is key to successful design in both ponentbased and serviceoriented systems. ? The following are some key interfacerelated definitions: ? Interface: Defines a set of public method signatures, logically grouped but providing no implementation. An interface defines a contract between the requestor and provider of a service. Any implementation of an interface must provide all methods. ? Published interface: An interface that is uniquely identifiable and made available through a registry for clients to dynamically discover. ? Public interface: An interface that is available for clients to use but is not published, thus requiring static knowledge on the part of the client. ? Dual interface: Frequently interfaces are developed as pairs such that one interface depends on another。 add, update, delete investment portfolios。 ? System engineering support: SOA application architecture has the SOSE supports, it is denoted with SY. On the contrary if an SOA application architecture has no SOSE support, it is denoted with SN. SOA Architecture Classification ? (S,N,FN,SN) Architecture ? Once the application is deployed, it cannot be changed or reposed. ? (D,N,FN,SN) Architecture ? Services are connected to the shared munication backbone. ? These services are loosely coupled such that an individual service does not need to know the details or even the existences of other services. ? The dynamic position as well as orchestration will be managed by Application Composition Manager. ? The workflow specification defines the execution sequence of services to deliver the desired functionalities. SOA Architecture Classification ? (D,R,FN,SN) Architecture ? In this way, after the application is deployed, the Data Collection service will keep on monitoring the behaviors of the participating services and collect data at runtime. ? The data collected will be continuously analyzed to decide if it is necessary to trigger a reconfiguration. ? If a reconfiguration is triggered, the application specification including the workflows and participating services will be dynamically updated according to the reconfiguration policy. ? (D,R,FC,SN) Architecture ? The control center is now more plex as it not only needs to keep track of the status of participating services, but also needs to check itself continuously to ensure the control center can tolerate its own faults. SOA Architecture Classification ? (D,R,FB/FC,SN) Architecture ? In the previous architecture, the control center is fault tolerant, but failures occurred in the munication backbone are not handled. ? Since the control center is also built on top of the munication backbone, ., it uses the backbone for munication. ? In this case, if the backbone fails, the faulttolerant control center will fail too. ? The munication backbone can be a puting platform, such as .NET, or ESB. Microsoft developed a reliable messaging service called Indigo that provides faulttolerant munications between services. ? ESB is essentially a serviceoriented middleware that allows services to municate with each other. ? (D,R,XX,SY) Architecture ? In (D, R, XX, SY), if X and Y are variables, it introduces a family in which different system engineering supports are added to the operation infrastructure. ? IBM SOA Foundation architecture includes modeling/specification, verification and validation, assembling, deployment, and management. ? Automated tools can help tune the deployment environment and deploy the application into the tuned environment. SOA Architecture Classification ? Evaluation criteria for the different architectures: ? Complexity: The architecture plexity will increase as we move the architecture from the top to the bottom and from the left to the right in the architecture roadmap. Thus (S, N, FN, SN) is the simplest architecture and the (D, R, FB/FC, SY) is the most plex one. ? Dependability: If the faulttolerant mechanisms are implemented properly, the dependability should enhance as we move the architecture from top to bottom and from left to right of the map, because more and more faulttolerance capabilities areintroduced into the architectures. ? Efficiency: As the plexity increases, the efficiency can decrease if additional resources and putation power outperform the benefit. Evaluation is necessary to evaluate the efficiency. ? Adaptability: Architecture styles with the reposition capability have higher adaptability than those without the capability. Thus the adaptability should increase when the architecture moves from the top to the bottom and from the left towards the right of the map. Higher adaptabilityalso indicates the better selfmonitoring, selfhealing, and selfgoverning capabilities. SOA Architecture Classification ? Difficulty to implement: The simplest architecture style is the easiest one to use because it doesn’t require many plex techniques. ? Cost of Development: The architecture that is the easiest to implement has the lowest development cost. ? Cost of Maintenance: As one advances from the top towards the