REPOSITORIES REPOSITORIES In a repository style there are

REPOSITORIES

REPOSITORIES • In a repository style there are two quite kinds of components: • A central data structure represents the current state, and the collection of independent components operate on the central data store. • Interactions between the repository and it’s external component can vary significantly between system. If the type of transaction in an input stream of transaction. S trigger selection of process to execute, the repository be an traditional database. If the current state of the central data structure is the main trigger of selecting process to execute, The repository can be a blackboard.

REPOSITORY

BLACKBOARD • The blackboard model is usually presented with three major parts: 1. The knowledgesources: separate, independent parcels of application dependent knowledge. Interaction among knowledgesources takes place solely through the blackboard. 2. The blackboard data structure : problem sloving data, organized into an application dependent hierarchy. Knowledge sources make changes to the blackboard that lead incrementally solution to the problem. 3. Driven entirely by state of blackboard. Knowledge sources respond opportunistically when changes in the blackboard Make them applicable.

INTERPRETERS • In an interpreter organization a virtual machine Is produced in software. • An interpreter includes psudeo-program being interpreted and the interpretation engine itself. • The interpretation engine includes both the definition of the interpreter and the currnt state of its execution.

INTERPRETERS • Interpreter has four components: 1)an interpretation engine to do the work. 2)a memory that contains pseudo –code to be interpreted. 3)a representation of a control state of the interpretation engine. 4)a representation of a current state of the program being stimulated.

INTERPRETERS

INTERPRETERS • Interpreters are commonly used to build virtual machine that are close the gap between the computing engine expected by the semantics of the program and the computing engine available in hardware. • We occasionally speak of a programming language as providing, say a “virtual Pascal machine “.

PROCESS CONTROL • Process control architecture is a type of data flow architecture where data is either batched sequential nor pipelined stream. • The flow of data comes from a set of variables, which control the execution of process. • It decomposes the entire system into subsystems or modules and connect them.

FEEDBACK CONTROL

PROCESS CONTROLS

OTHER FAMILIAR ARCHITECTURE • There are numerous other architectural styles and patterns. • Some are widespread and others are specific to particular domain. • Distributed process: distributed systems have developed a number of common organizations for multiple process system. Some can be characterised primarily by their topological features, such as ring and star organizations. Interprocess protocols used for communication. Ex: heartbeat algorithms.

PROCESS CONTROLS • Main program/sub routine organisations : the primary organization of many systems mirrors the programming language in which the system is written. For language without support for modularization this often results in a system organised round a main program and a set of subroutines. • Domain specific s/w architecture : recently there has been considered interested in developing “reference” architecture for specific domain. These architectures provide an organization structure tailored to a family of applications, such as avionics, command control, Or ve. Hicle management system.

PROCESS CONTROL State transition systems: a common for many reactive systems is the state transition systems. These system is defined in terms a set of states and a set of named transitions that move a system for one state to another. • Process control systems : systems intended to provide the dynamic control of the physical environment are often organized as process control systems. These systems are roughly characterised as a feedback loop in which input loop from sensors are used by the process control systems to determine a set of outputs that will produce a new state of the environment.

HETEROGENEOUS ARCHITECTURE • Thus far we have been speaking primarily of “pure” architectural styles. While it is important to understand The individual nature of these styles, most systems typically involves some combination of several styles. • There are Different ways in which architectural styles can be combined. • One way is through hierarchy. • A component of some system organised in one architectural style may have an internal structure that is developed A completely in different style. • Ex: a Unix pipeline the individual components may be represented internally using virtually any style including, of course, another pipe and filter, system.

HETEROGENEOUS ARCHITECTURE • A second way styles to be combined is to permit a single component To use a mixture of architecture connectors. • Ex: 1)A components might access a repository through part of its interface, but interact with pipes and other components in a system, and accepts control information through another part of interface. 2)active database: this is a repository which activates external component through implicit invocation. In this organization external components register interest in portions of the database.

HETEROGENEOUS ARCHITECTURE • A third way for styles to be combined is to elaborate one level of architecture description in a completely different architecture styles.