Week 4 Flashcards
1
Q
What are the 4 layers of an e-business technical infrastructure?
A
The infrastructure for e-Business comprises technologies that can be seen as different layers that built upon each other: (Computer networks)
- The bottom layer includes networking topologies, the Internet, and protocols such as TCP/IP. (computer can talk to each other)
- The layer above is the basic infrastructure layer that contains such as client/server and tiered architectures.
- The layer above this contains the technologies that are required to develop web-based applications.
- Finally, the top layer contains collaborative technologies such as workflow systems and Electronic Data Interchange (EDI).
2
Q
What is distributed computing and client-server computing?
A
- Distributed computing is the classical paradigm in support of e-Business processes & applications.
- A form of distributed processing is client server computing: it handles the need for both centralized data control and widespread data accessibility.
- Client/server is an architecture that involves client processes (service consumers) requesting service from server processes (service providers).
- Client/server computing does not emphasize hardware distinctions; it rather focuses on the applications themselves. (split into different processes, client/server processes etc.)
- The client/server model provides a typical way to interconnect programs that are distributed across different locations. Logical split of the client process and the consumer.
There are different ways in which processing tasks can be divided between the client and the server. They range from:
- Thin clients, with heavy servers (thin client can only do PO or orders)
- Servers that only contain common data with all the processing executed at the level of the client. (client will perform one of the data processing)
Solutions chosen to depend on specific application requirements, e.g., local vs. central control, # of users, processing needs etc.
3
Q
What are the basic features of the client/server model?
A
- Clients and servers are functional modules with well-defined interfaces. The functions of a client and a server can be implemented by a set of software modules, hardware components, or any combination thereof.
- Each client/server relationship is established between two functional modules, where one module, the client, initiates service requests and the other module, the server, responds to these requests.
- Information exchange between clients and servers, i.e., requests and responses, are typically through messages.
- Message exchange is typically interactive.
- Clients and servers may run on separate dedicated machines connected through a network.
4
Q
What is a “fat client”
A
The client in such a two-tier system is known as “fat client” while the server is commonly referred to as the database server. Conversations occur at the level of the server’s database language (SQL Query).
5
Q
what are the drawbacks of the two-tier client/server architecture?
A
- The two-tier architecture has several drawbacks, which are especially problematic for large and distributed applications:
- Scalability problems (sharing the application, how many requests that a server tier can serve)
- Poor business logic sharing
- Client reliance on the database structure (follow the basis)
- Limited interoperability (not integrated with other systems)
- High-maintenance costs (Any change you make, have big impact)
6
Q
2 tier vs 3 tier architecture
A
2 tier heeft die middelste niet
7
Q
Why use a three-tier architecture?
A
The three-tier architecture overcomes the limitations of the two-tier architecture. A middle tier is introduced between the user system interface client environment and the database management server environment.
8
Q
Explain the 3 tiers of the three tier architecture
A
- The application is partitioned into 3 logical tiers:
- presentation tier: responsible for the graphical user interface (GUI) layer usually in the form of a web-browser
- processing tier (or middle tier): contains the business logic & is responsible for the processing associated applications supported.
- data tier: holds the permanent data associated with the applications supported e.g., modern and legacy application databases, and transaction management applications. It interprets requests from a client and routes them to a suitable data resource. (data access)
9
Q
What does the processing tier do?
A
- The processing tier enables developers to isolate the main part of an application that can change over time: data & relationships inherent in the data.
- This tier has the effect of logically and physically decoupling business logic from the presentation and database functions. Here we can find business objects that correspond to entities in the business domain, e.g., sales orders, invoices, products…
- There are a variety of ways of implementing this middle tier, such as transaction processing monitors, message servers, or application servers.
10
Q
Explain web-based applications
A
- Web sites provide the content that is accessed by Web users. A Web site is a catalogue of info. for each content provider over the Web:
- Web server,
- content files (Web pages), and/or
- gateways (programs that access non-Web content, e.g., databases).
- A Web server is an application (technically a server process) that receives calls from Web clients and retrieves Web pages and/or receives information from gateways.
- Web browsers are the clients that typically use graphical user interfaces to wander through the Web sites.
11
Q
What are the 4 layers of web applications?
A
- The client-tier is implemented as a web browser running on the user’s client machine. It displays data & lets users & client applications enter/update data.
- The presentation-tier generates Web pages in which it includes dynamic content. It supports different types of clients, e.g., HTML & Java capable clients. A Web-server also finds the client application or user-entered data in Web pages coming back from the client & forwards it to the business logic-tier.
- Application logic is written in the processing or business logic-tier. This includes performing calculations and validations, managing workflow & all data access for the presentation-tier. An application-server supports the functions of business logic-tier.
- The data-tier is responsible for managing the data. It provides the business logic-tier with required data when needed & store data when requested.
12
Q
Explain a workflow
A
- A workflow system automates a business process, in whole or in part, during which documents, information, or tasks are passed from one participant to another for action, according to a set of rules.
- A workflow normally comprises a number of logical steps (activities).
- A workflow can depict various aspects of a business process including automated and manual activities, decision points and business rules, parallel and sequential work routes, and how to manage exceptions to the normal business process.
- Workflow technology enables developers to describe full intra- or inter-organisational business processes with dependencies, sequencing selection and iteration. It enables the workflow developers to describe the complex rules for processing in a business process & allows people to be deployed more productively within an organisation.
13
Q
Whats EDI?
A
Electronic Data Interchange (EDI) is defined as the transfer of structured data by agreed message standards between computer applications.
14
Q
Two key elements of basic EDI
A
- There are two key elements in basic EDI.
- Electronic documents replace their paper counterparts.
- The exchange of documents takes place in a standardized format.
15
Q
What are the problems of EDI?
A
- Fixed transaction sets
- Resilience to change
- Reliance on proprietary communications networks
- Encapsulation of business rules in transaction sets
