Module 3

Question 1

What is the 5 component characteristics?

Answer 1

Composable, deployable, documented, independent and standarized

Question 2

A component being composable means?

Answer 2

All external interactions must be through public interfaces. It must also provide information about itself, such as methods and attributes

Question 3

A component being deployable means?

Answer 3

Has to be self contained, and able to operate as a stand-alone entity. (Generally means it is binary and does not need for it to be compiled)
Being deployed by the service provider

Question 4

How do you make a singleton (design pattern) class?

Answer 4

A private constructor in the class. Other classes can’t access the constructor, and should only get that one instance of the class.

Question 5

What does a proxy do?

Answer 5

It acts as intermediary between the web application and the remote service.
it will handle requests, limit and availability checks before forwarding them to the real object.

Question 6

What does DOM stand for?

Answer 6

Document Object Model

Question 7

What does MQTT stand for?

Answer 7

Message queuing telemetry transport

Question 8

MQTT is designed for what kind of devices?

Answer 8

Machine-to-machine, IOT

Question 9

In MQTT, what is something published on?

Answer 9

A topic. Similiar as a news site. Subscribing to sports, sends current goal scorings

Question 10

MQTT protocal is made for low-bandwith high-latency systems?

Answer 10

True. Farms, Oil rigs and other far away systems that only needs information, when something changes

Question 11

In MQTT, what are the three levels of Quality of Service for delivery?

Answer 11

0 (At most once), 1(at least once), and 2 (exactly once)

Question 12

In MQTT, 0 level of QoS works how?

Answer 12

“At most one delivery” It will TRY to send a message once (new value on sensor e.g)

Question 13

In MQTT, 1st level of QoS works how?

Answer 13

“At least once” Broker will send a pull back message once received, as confirmation that it received new information and to not send it again.

Question 14

In MQTT, 2nd level of QoS works how?

Answer 14

“Exactly once”. Similar to a handshake, both the broker and the client confirm that each of them received it AND the other parts pull back message and ends the transaction.

Question 15

In MQTT, what are the three types of messages?

Answer 15

Publish, Subscribe and Unsubscribe