SE lec6

In the Advantages of layered model Redundant facilities (e.g. Authentication) can be provided in each layer to increase the......... of the system

dependability يعني يكون free of errors

System functionality organized into layers, with each layer only dependent on the previous layer

Layered model

What are the components in client/server architecture

1-a set of servers that offer services 2-set of clients that call on the services 3- network that allows client to access the services

Subsystems often exchange and work with the same data. This can be done in two ways What are they?

1-each system maintains its own database and passes that explicitly to other subsystems 2-share data is held in a central repository, and may be accessed by all subsystems

Why Explicitly plan architecture?

1-enable stakeholder communication 2-enable system analysis 3-enable large-scale reuse 4-bad architectural design means bad security

What are the architectural models

1-layered 2-shared repository 3-client/server 4-pipe & filter

What are some of the architecture and system characteristics?

1-performance 2-security 3-safety 4-availability 5-maintainability

What is example of client/server architecture?

A film and video/DVD library organized as a client server system

Give me example of layered model

A layerd model of a system for sharing copyright documents, held in different libraries

High-level presentation of the system Can be provided after A-enable stakeholder communication B-enable large-scale reuse C-bad architectural design means bad security

A-enable stakeholder communication

What are the advantages of layered model?

Allows replacement of entire layers so long as the interface is maintained

Are the technical interface between the customer and the contractor building the building, (and the software)

Architectural plans

In architecture and system characteristics Include redundant components and mechanisms for fault tolerance

Availability

Controlling access is the first line of defense. Can be provided after understanding that A-enable large- scale reuse B-bad architectural design means security C-enable stakeholder communication

B-bad architectural design means security

Planning subsystems as independent entities allows their reuse in other systems A-enable stakeholder communication B-enable large- scale reuse C-enable system analysis

B-enable large- scale reuse

Can look for problems before coding, can be provided after A-but architectural design means security B-enable large-scale reuse C-enable system analysis

C-enable system analysis

What does control models include

Centralized control and event-driven models

Functionality organized into services distributed across a range of components

Client-server architecture

The functionality of the system is organized into services

Client-server architecture

May be used when the load on a system is variable

Client/server architecture

Used when data in a shared database has to be accessed from a range of locations

Client/server architecture

In the layered model The lowest level layers represents...?

Core services That are likely to be used throughout the system

Useful for judging performance, security, availability

Dynamic view

Visualize entities communicating during runtime execution

Dynamic view

What are the disadvantages of client/server architecture?

Each service is a single point of failure so susceptible to denial of service attacks or server failure. باختصار ممكن يتعرض للهجوم

A layer provide services to the layer below it

False A layer provide services to the layer above it

In Pipe and filter architecture Can be only implemented as sequential

False As sequential or concurrent system

Server cannot be replicated

False Can be replicated that's why we use it when a shared database Has to be accessed from a range of locations

A bad architectural design for a building can be rescued by good construction (Same for software)

False Cannot be rescued by good construction

In repository model Components interact directly

False Do not interact directly , only through the repository

In Pipe and filter architecture It is hard to understand and support transformation reuse

False Easy to understand and support transformation reuse

Is efficient in organizing all communication through repository

False Inefficiencies من عدم الكفاءة

Distributing the repository across several computers is so easy

False May be difficult

Complex systems must always follow a single model

False Might not follow a single model-mix and match

Pipe and filter architecture is really suitable for interactive systems

False Not really suitable

In client/ server architecture We can predict the performance of the network as well as the system

False Performance may be unpredictable, because it depends on network as well as the system

Layered model does not support incremental development

False Supports incremental development

Allows elements to change independently

Layered model

Organizes the system into layers with related functionality associated with each layer

Layered model

Used when building new facilities on top of existing system; 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 مهم

Layered model

In architecture and system characteristics Use fine-grain, replaceable components

Maintainability

In architecture and system characteristics Localize critical operations, and minimize communications. Use large rather than fine-grain components

Performance

How hardware and software communicate, and how software is distributed across processes

Physical view

Commonly used in data processing applications(both batch-and transaction-based) where inputs are processed in separate stages to generate related output

Pipe and filter architecture

Functional transformations process their input to produce outputs

Pipe and filter architecture

The processing of the data in a systems is organized so that each processing component(filter) is a discrete and carries out one type of data transformation. The date flows(as in a pipe) from one component to another for processing

Pipe and filter architecture

Variants of this approach are very common

Pipe and filter architecture

When transformations are sequential, this is a batch sequential model, which is extensively used in data processing systems

Pipe and filter architecture

Like what a set of servers

Print server, file server, code compilation server.etc

All data in the system is managed in a central repository that is accessible to all systems components

Repository model

Components can be independent—-they do not need to know of the existence of other components. Changes made by one component can be propagated to all components. All data can be managed consistently for example back up is done at the same time as it is all in one place

Repository model

You can use it in data-driven systems were the inclusion of data in the repository triggers an action or tool

Repository model

You should use this pattern when you have a system in which large volumes of information are generated that has to be stored for a long time

Repository model

In architecture and system characteristics Localize, safety-critical features in a small number of sub-systems

Safety

In architecture and system characteristics Use a layered architecture with critical assets in the inner layers

Security

What are the advantages of client/server architecture?

Servers can be distributed across a network. General functionality(e.g. Printing service) can be available to all clients and does not need to be implemented by all services.

Is responsible for deriving a system structure, a control model, and a modular decomposition

Software architect

Is the fundamental organization of a system, embodied in its components, their relationships to one another and environment, and the principles governing its design and evolution

Software architecture

Logical view-given the services we want to offer. How does it make sense to delegate responsibility? Relate requirements to entities in the system.

Static view

Is structured around the latter

The repository model

Architectural models can help organize a system But large systems rarely confirm to one model

True

Example of layered model the eLearn system?

True

In Pipe and filter architecture Workflow style matches the structure of many business processes

True

In client/server architecture Each service delivered from a separate server , and clients are users of these services, and access servers to make use of them

True

In client/server architecture May be management problems if servers are owned by different organizations

True

Pipe and filter architecture Evaluation by adding transformation is straightforward

True

The clients can call the services through locally-installed front end

True

The model used affects the performance robustness availability maintainability,etc of the system

True

The repository is a single point of failure so problems in the repository affect the whole system

True

There are specialist types of building architects, and architecture styles

True

Give me example of pipe and filter architecture

Used for processing invoices معالجة الفواتير