Block 2. Part 1: Architectures

Question 1

What is architecture?

Answer 1

Architecture specifies the componenets that make up a system, their functionality and how they interact or communicate.

Question 2

What are the 2 different approaches to architecture that are investigated?

Answer 2

1. Client-server and other multi-tier approaches. These are used to ensure a modular design of an application or service.
2. More distributed ‘network’ type architectures such as ‘service-oreintated architecture’ (SOA)

Question 3

What is Two-Tier architecture?

Answer 3

commonly seen as a client-server architecture where the application is divided into two parts, ‘client’ and ‘server’.

the server part provides the central functionality.

Question 4

describe the figure that represents a simple client-server application.

Answer 4

file:///tmp/calibre_1.25.0_tmp_1Dhl2s/jTCZJn_ebook_iter/OPS/assets/tt284_b2_p1_f02.eps.jpg

Question 5

What is the difference between a thin client and a thick (or thicker) client?

Answer 5

a web browser with little functionality of its own is often termed a thin client, while the ‘mor eintelligent’ client is usually termed a thick client.

Question 6

What is multi-tier architecture?

Answer 6

The approach of splitting an application into tiers can be taken further. Both the client and the server parts can be further subdivided if this is appropriate for tha application. The lcient, for example, may be responsible both for some processing of data( such as totalling) and for the presentation of information. These two functions might be seperated into two tiers at the client end.

Question 7

What are two advantages of using a multi-tier architecture?

Answer 7

Splitting data up in this way would, for examlple, allow occasional backups of the more static data with more frequent backuos of the dynamic data.

Each tier can be changed more easily as it is less dependant on the precise details of the other componenets with which it interacts.

Question 8

what is the middle ware?

Answer 8

a tier that handles interactions with the dat atier, such as rretreiving reqeusted information or validating data that is put into the data stores. This tier, between the data tier and the web server application is sometimes termed the ‘middle tier’ or middleware. AN application that uses middleware to handle data requests between a user and a database is said to employ multi-tier architecture.

Question 9

What is SOA?

Answer 9

Service-orientated Architecture is based around the idea of breaking down an application into a set of much smaller tasks that can be performed by small independant pieces of software, each performing a discrete task commonly called a service. Examples of services might be surrency conversion or data storage.

Question 10

What are the three main components or roles of SOA?

Answer 10

1. a requester that can both search and discover web services and use or ‘bind’ to a web service by communicating with XML messages.
2. a directory or registry that holds the details of web services that are available.
3. the services themselves. Each service has its details published as an XML description in any number of directories. The description includes details of what the service does and how to use the service in terms of how to call it and what response to expect.
   file: ///tmp/calibre_1.25.0_tmp_1Dhl2s/jTCZJn_ebook_iter/OPS/assets/tt284_b2_p1_f04.eps.jpg

Question 11

What is WSA?

Answer 11

Web Service Architecture is a particular realisation of SOA that is used to provide services over the internet. It has 4 distinct layers which are termed as the ‘web services protocol stack’.

Question 12

What is the ‘web services protocol stack’?

Answer 12

it has 4 distinct layers. The upper layers build on the lower levels, so, for example, service descriptions are expressed using XML, and SOAP messages are usually exchanged using HTTP.

Question 13

What are the 4 levels of the ‘web service protocol stack’ and what are their roles?

Answer 13

1. Network transport layer. This supports the passing of messages between components in the archtecture. Common protocols used here atr HTTP, FTP and SMTP.
2. Message encoding layer. This provides a standard approach to encoding information in messages so that they can be understood. Web service messaging approaches such as XML -RPC and SOAP are based on XML
3. Service description layer. This provides a way to describe a web service so that it can be accessed and used. The Web Services Descruiption Language (WSDL) is used to describe services
4. service discovery layer. This provides the means to publish descriptions of and find web services in a central repository. The Univeral Description, Discovery and Integration (UDDI) registry standard supports this layer.

Question 14

What is the first layer of the ‘web services protocol stack’?

Answer 14

1. Network transport layer. This supports the passing of messages between components in the archtecture. Common protocols used here atr HTTP, FTP and SMTP.

Question 15

What is the second layer of the ‘web services protocol stack’?

Answer 15

2. Message encoding layer. This provides a standard approach to encoding information in messages so that they can be understood. Web service messaging approaches such as XML -RPC and SOAP are based on XML

Question 16

What is the third layer of the ‘web services protocol stack’?

Answer 16

3. Service description layer. This provides a way to describe a web service so that it can be accessed and used. The Web Services Descruiption Language (WSDL) is used to describe services

Question 17

What is the last layer of the ‘web services protocol stack’?

Answer 17

. service discovery layer. This provides the means to publish descriptions of and find web services in a central repository. The Univeral Description, Discovery and Integration (UDDI) registry standard supports this layer.