Military Communications and Information Technology: A Trusted ...
Military Communications and Information Technology: A Trusted ... Military Communications and Information Technology: A Trusted ...
22 Military Communications and Information Technology... throughput have a direct impact on the operational processes and consequently on mission effects. Cost of removing performance problems detected during exploitation can be high, therefore, it is very important to evaluate SOA systems quality attributes during the design stage. In this paper the tools which can be used for performance evaluation of SOA system during the design stage are described. They allow to choose an architecture design which fulfills important non-functional requirements. System architecture is documented using standard notation, recognized in engineers environment, such as Unified Modeling Language (UML). Views from NATO Architecture Framework (NAF) are used to structure the specification of the system architecture. System models documented in NAF views are transformed into a performance model based on Layered Queuing Networks (LQN). The document is structured as follows. Section II presents work related to the system performance evaluation on the early development stages. Section III describes fundamental concepts such as SOA, software model, NAF and performance model. Section IV describes mapping between software and performance models. Section V presents an example the SOA model and a corresponding performance model. Finally, section VI concludes the paper. II. Related work Paper [1] describes the method for evaluation of quality attributes of a monolithic system that has its architecture documented using UML notation. Based on UML diagrams, annotated with extensions aggregated in UML profile „UML profile for Schedulability, Performance and Time” (SPT) [6], an LQN performance model is generated. Resultant model can be solved using a LQN solver (for example by the Layered Queuing Network Solver [18]). Similar approach is introduced in paper [2]. LQN model is generated from UML diagrams with annotations from the MARTE [7] profile. In work [5] the method for generating LQN model from the SOA specific models is presented. UML diagrams used to document architecture design contain description of workflows, components responsible for services realization, scenarios and distribution of software on resources. MARTE profile is used for models annotation. Paper [3] introduces the tool for architecture performance and scalability evaluation using discrete event simulation. Similarly to other approaches existing UML artifacts are used. Different models can be run simultaneously, which allow analysis of different alternative architectures. Simulation results of a single model in different configurations (for example with various workload) also can be compared. Authors of [8-11] concentrate on the services orchestration performance (composed from internal and provided external services) which is responsible for operational processes realization. Presented approaches allow to compare different
Chapter 1: Concepts and Solutions for Communications and Information Systems 23 sets of composite services and obtain optimal configuration from the performance point of view. III. Background System performance is determined by the way a system uses resources. Different implementations of the same functionality can have different computational complexity. In the performance domain three basic concepts can be distinguished: workload, resources and scenarios. Scenario describes the system’s behavior including demands for resources. Each scenario is executed with a frequency defined by a workload. Resources can represent software (passive resources – for example: buffer, critical section, database connection pool) or an underlying platform (active resources – for example: processor, disk, network). To conduct the system performance evaluation two questions should be answered: how the system will be documented and which performance model should be used. In the following subsections SOA concept is described including basic elements which should be documented allowing performance evaluation. Moreover, notations and framework used to document SOA architecture is outlined. Finally, the performance model is described. A. Service Oriented Architectures Service Oriented Architecture is a concept of an architecture that supports interoperability, scalability and flexibility of heterogeneous systems. SOA defines a ‘service’ concept which represents well defined fragment of an operational functionality. Services introduce new abstraction layer between operational logic and legacy systems used in organization increasing cohesion between them. SOA transforms architecture style of an application into a set of connected services used when they are considered necessary. Abstract view of SOA can be described using layered architecture. Fig. 1 depict high level view of layers [22]. Looking at layers presented in the diagram (Fig. 1), the most important is the identification of processes and business services used by consumers. An operational process describes how an organization achieves its goals. The processes layer allows to understand an operational domain which is the object of interest when the SOA architecture is defined. Furthermore, it allow to identify the process activities that should be supported by services. Services are described through well-defined interfaces. Interface definition is independent from an underlying platform on which the service implementation is running. This approach allows services, build on a heterogeneous systems, to interact in a uniform and universal manner. Two types of services can be defined:
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22 <strong>Military</strong> <strong>Communications</strong> <strong>and</strong> <strong>Information</strong> <strong>Technology</strong>...<br />
throughput have a direct impact on the operational processes <strong>and</strong> consequently on<br />
mission effects. Cost of removing performance problems detected during exploitation<br />
can be high, therefore, it is very important to evaluate SOA systems quality<br />
attributes during the design stage.<br />
In this paper the tools which can be used for performance evaluation of SOA<br />
system during the design stage are described. They allow to choose an architecture<br />
design which fulfills important non-functional requirements. System architecture<br />
is documented using st<strong>and</strong>ard notation, recognized in engineers environment, such<br />
as Unified Modeling Language (UML). Views from NATO Architecture Framework<br />
(NAF) are used to structure the specification of the system architecture. System<br />
models documented in NAF views are transformed into a performance model<br />
based on Layered Queuing Networks (LQN).<br />
The document is structured as follows. Section II presents work related to<br />
the system performance evaluation on the early development stages. Section III<br />
describes fundamental concepts such as SOA, software model, NAF <strong>and</strong> performance<br />
model. Section IV describes mapping between software <strong>and</strong> performance models.<br />
Section V presents an example the SOA model <strong>and</strong> a corresponding performance<br />
model. Finally, section VI concludes the paper.<br />
II. Related work<br />
Paper [1] describes the method for evaluation of quality attributes of a monolithic<br />
system that has its architecture documented using UML notation. Based<br />
on UML diagrams, annotated with extensions aggregated in UML profile „UML<br />
profile for Schedulability, Performance <strong>and</strong> Time” (SPT) [6], an LQN performance<br />
model is generated. Resultant model can be solved using a LQN solver (for example<br />
by the Layered Queuing Network Solver [18]). Similar approach is introduced<br />
in paper [2]. LQN model is generated from UML diagrams with annotations from<br />
the MARTE [7] profile.<br />
In work [5] the method for generating LQN model from the SOA specific<br />
models is presented. UML diagrams used to document architecture design contain<br />
description of workflows, components responsible for services realization,<br />
scenarios <strong>and</strong> distribution of software on resources. MARTE profile is used for<br />
models annotation.<br />
Paper [3] introduces the tool for architecture performance <strong>and</strong> scalability evaluation<br />
using discrete event simulation. Similarly to other approaches existing UML<br />
artifacts are used. Different models can be run simultaneously, which allow analysis<br />
of different alternative architectures. Simulation results of a single model in different<br />
configurations (for example with various workload) also can be compared.<br />
Authors of [8-11] concentrate on the services orchestration performance<br />
(composed from internal <strong>and</strong> provided external services) which is responsible for<br />
operational processes realization. Presented approaches allow to compare different
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