Changes made by one component can be propagated to all components. All data can be managed consistently e. Disadvantages The repository is a single point of failure so problems in the repository affect the whole system. May be inefficiencies in organizing all communication through the repository. Distributing the repository across several computers may be difficult.
Name Client-server Description In a client-server architecture, the functionality of the system is organized into services, with each service delivered from a separate server. Clients are users of these services and access servers to make use of them. When used Used when data in a shared database has to be accessed from a range of locations. Because servers can be replicated, may also be used when the load on a system is variable. Advantages The principal advantage of this model is that servers can be distributed across a network.
General functionality e. Disadvantages Each service is a single point of failure so susceptible to denial of service attacks or server failure. Performance may be unpredictable because it depends on the network as well as the system.
May be management problems if servers are owned by different organizations. Name Pipe and filter Description The processing of the data in a system is organized so that each processing component filter is discrete and carries out one type of data transformation.
The data flows as in a pipe from one component to another for processing. When used Commonly used in data processing applications both batch- and transaction-based where inputs are processed in separate stages to generate related outputs. Advantages Easy to understand and supports transformation reuse. Workflow style matches the structure of many business processes. Evolution by adding transformations is straightforward. Can be implemented as either a sequential or concurrent system.
Disadvantages The format for data transfer has to be agreed upon between communicating transformations. Each transformation must parse its input and unparse its output to the agreed form. This increases system overhead and may mean that it is impossible to reuse functional transformations that use incompatible data structures. Separates presentation and interaction from the system data.
The display presented to the user frequently changes over time in response to input or computation. This involves separating the data being manipulated from the manipulation logic and the details of display using three components: Model a problem-domain component with data and operations, independent of the user interface , View a data display component , and Controller a component that receives and acts on user input.
Advantages: views and controllers can be easily be added, removed, or changed; views can be added or changed during execution; user interface components can be changed, even at runtime. Organizes the system into layers with related functionality associated with each layer.
Used when building new facilities on top of existing systems; when the development is spread across several teams with each team responsibility for a layer of functionality; when there is a requirement for multi-level security. It comes before the detailed design, coding, integration, and testing and after the domain analysis, requirements analysis, and risk analysis. The primary goal of the architecture is to identify requirements that affect the structure of the application.
A well-laid architecture reduces the business risks associated with building a technical solution and builds a bridge between business and technical requirements. Software architecture is still an emerging discipline within software engineering. Lack of analysis methods to predict whether architecture will result in an implementation that meets the requirements. Lack of understanding of the role of software architect and poor communication among stakeholders.
A Software Architect provides a solution that the technical team can create and design for the entire application. Expert in software design, including diverse methods and approaches such as object-oriented design, event-driven design, etc.
Lead the development team and coordinate the development efforts for the integrity of the design. Facilitates the technical work among team members and reinforcing the trust relationship in the team.
Protect the team members from external forces that would distract them and bring less value to the project. A document or process which ensures functional decomposition is followed, and the form of interfaces is controlled.
Quality is a measure of excellence or the state of being free from deficiencies or defects. Quality attributes are the system properties that are separate from the functionality of the system. Implementing quality attributes makes it easier to differentiate a good system from a bad one.
Attributes are overall factors that affect runtime behavior, system design, and user experience. Reflect the structure of a system and organization, directly related to architecture, design, and source code.
Though the architectural design is the responsibility of developers, some other people like user representatives, systems engineers, hardware engineers, and operations personnel are also involved. All these stakeholders must also be consulted while reviewing the architectural design in order to minimize the risks and errors. Architectural Design Representation. Architectural design can be represented using the following models.
Architectural Design Output. This document consists of a number of graphical representations thatcomprises software models along with associated descriptive text. The softwaremodels include static model, interface model, relationship model, and dynamic processmodel. They show how the system is organized into a process at run-time.
Architectural design document gives the developers a solution to the problem stated in the Software Requirements Specification SRS.
Note that it considers only those requirements in detail that affect the program structure. In addition to ADD, other outputs of the architectural design are listed below. Architectural styles define a group of interlinked systems that share structural and semantic properties. In short, the objective of using architectural styles is to establish a structure for all the components present in a system. If an existing architecture is to be re-engineered, then imposition of an architectural style results in fundamental changes in the structure of the system.
This change also includes re-assignment of the functionality performed by the components. By applying certain constraints on the design space, we can make different style-specific analysis from an architectural style. In addition, if conventional structures are used for an architectural style, the other stakeholders can easily understand the organization of the system. A computer -based system software is part of this system exhibits one of the many available architectural styles.
Every architectural style describes a system category that includes the following. Some of the commonly used architectural styles are data-flow architecture, object oriented architecture, layered system architecture, data-centered architecture, and call and return architecture.
Note that the use of an appropriate architectural style promotes design reuse, leads to code reuse, and supports interoperability. Data-flow architecture is mainly used in the systems that accept some inputs and transform it into the desired outputs by applying a series of transformations.
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