Web Services

Question 1

API

Answer 1

Application Programming Interface

Question 2

• Set of clearly defined methods of communication between various components.
• Is also used to refer to a published document that defines how these methods of communication can be used.

Answer 2

API

Question 3

• Refers to the actual implementation of an interface that other app/programs can call on.
• It is also used informally to refer to the document that describes the usage of this interface.

Answer 3

API

Question 4

True or False

Airline websites offer an API/Web Service for other apps (like CheapFlights) to access their data.

Answer 4

True

Question 5

Web Services vs API

Answer 5

Web Services involve network communication.
APIs can use any means of communication.

Question 6

True or False

Web Services are APIs designed to support interoperable machine-to-machine interaction over a network.

Answer 6

True

Question 7

True or False

WS expose services to clients over a network, using a uniform interface.

Answer 7

True

Question 8

True or False

Many systems inherently interoperate well, thus APIs/web services are uncommonly used.

Answer 8

False

Many systems do not inherently interoperate well, thus the need for APIs/web services.

Question 9

2 types of Web Service Implementations

Answer 9

1. Simple Object Access Protocol (SOAP)
2. Representational State Transfer (REST)

Question 10

• ________ Web Services usage revolves around the exchange of XML messages.
• Is transport agnostic.
• Messages can be exchanged using SMTP, FTP, HTTP, or any network protocol.

Answer 10

SOAP

Question 11

True or False

In designing web services, the format of the request/response messages is defined by the developer, and usually published somewhere.

Answer 11

True

Question 12

In SOAP web services, these formats are formally defined in ________________ files.

Answer 12

Web Service Definition (WSD)

These WSD files function similarly to the DTD in HTML files.

Question 13

• ____ are written in Web Service Definition Language (WSDL), which has an XML-like structure.
• ____ define the structure of the SOAP Request and Response messages.
• It is the API, or interface definition for SOAP.

Answer 13

WSDs

Question 14

__________ use the Universal Description, Discovery, and Integration (UDDI) framework for sharing and finding WSDs.

Answer 14

Discovery services

Question 15

REST stands for

Answer 15

Representational State Transfer

Question 16

• Introduced and defined by Roy Fielding in 2000 for his PhD dissertation.
• Is a software architectural style.

Answer 16

REST

Question 17

Design Principles

Answer 17

Transport, Data Formats, Stateless

Question 18

REST uses the HTTP/HTTPS protocol for message __________

Answer 18

transport

Question 19

• Request/response payloads for RESTful web services can use any __________
• Text, XML, JSON, CSV, etc.

Answer 19

data format

Question 20

RESTful web services are __________. Each exchange between service and client is self-contained.

Answer 20

stateless

Question 21

True or False

The design of RESTful web services are guided by 7 constraints, which limit the ways the server can process and respond to requests.

Answer 21

False

Question 22

• RESTful WS use _____, and thus use _____ urls.
• These urls are usually designed in a self-descriptive, directory-like pattern.

Same Answer

Answer 22

HTTP

Question 23

By sticking to these constraints, the system will more easily be able achieve desired performance, scalability, and other architectural goals. What are the constraints?

Answer 23

1. Client-Server
2. Stateless
3. Cache
4. Uniform Contract
5. Layered System
6. Code-on-Demand* (optional)

Question 24

True or False

These constraints produce an architecture similar to that of the Web.
Architectures that don’t conform to these are not considered RESTful architectures.

Answer 24

True

Question 25

_\_\_\_\_\_\_\_\_\_ is separated into consumer and service logic.

Answer 25

Solution Logic

Question 26

# True or False * Consumers invoke services using a published ‘technical contract’. * Services passively wait for consumers to invoke them. * This allows for independent evolution of client and server-side logic.

Answer 26

True

Question 27

* Each request sent and processed is self contained. * It doesn’t depend on context from an earlier message. * This frees up server storage space and processing power that would otherwise be used to store and read earlier messages.

Answer 27

Stateless

Question 28

# True or False Response messages are implicitly labeled as cacheable or non-cacheable for potential reuse.

Answer 28

False ## Footnote Response messages are **explicitly** (not implicitly) labeled as cacheable or non-cacheable for potential reuse.

Question 29

Cache-Control

Answer 29

* Ways to tell if request messages are equivalent or not. * Ways to label if a response is cacheable or not, by whom, and for how long.

Question 30

Improves runtime efficiency by eliminating the need to send duplicate responses.

Answer 30

Cache

Question 31

Service consumers and service providers share a common, general technical contract.

Answer 31

Uniform Contract

Question 32

# True or False Clients of a RESTful WS need to know: * The URL and HTTP method for a particular operation * The required inputs * The returned outputs

Answer 32

True

Question 33

* A common general contract standardizes the interaction between different entities, making interoperability possible. * It is in the interest of all parties that this uniform contract change as little as possible.

Answer 33

Uniform Contract

Question 34

* Solutions can be comprised of multiple architectural layers. * Each layer can’t ‘see’ past the next layer. Each service is only concerned about interacting with the next layer. * Each layer’s logic can evolve independently of the others, as long as the general contract (the API) between them remains the same.

Answer 34

Layered System

Question 35

* Service consumers can support the execution of deferred service logic. * Disadvantage: Consumers need an execution environment for the deferred process. * May prevent server bottlenecks. But requires additional features on the consumer’s part.

Answer 35

Code-on-Demand

Question 36

REST Architectural Goals

Answer 36

1. Performance 2. Scalability 3. Simplicity 4. Modifiability 5. Visibility 6. Portability 7. Reliability ## Footnote Note that these aren’t unique to web services. These are common goals for many software development projects.

Question 37

Factors to consider: * Throughput & latency of request and responses * Resource utilization in the server

Answer 37

Performance

Question 38

* What data actually needs to be sent? * How much overhead can be eliminated (either in processing, or in the messages exchanged)? * Can the order of data being sent be rearranged to make it seem fast? * User perception is important. Sometimes the order of messages/data sent can be tweaked to make the response seem faster without actually changing the actual time to process.

Answer 38

Performance

Question 39

* Addresses an architecture’s need to support a varying number of concurrent connections. * Must be able to easily scale-up to serve sudden a influx of clients. * Conversely, it should be easy to scale down (to cut down costs) if client numbers are reduced.

Answer 39

Scalability

Question 40

* Reduce the complexity of the app by separating functionalities into modules. Each unit must be distinct. * Benefits: Easier debugging/refactoring.

Answer 40

Simplicity

Question 41

* Required for an app that will change over time. * New functionality might be needed, or obsolete ones removed. It should be easy to make these changes.

Answer 41

Modifiability

Question 42

* Self monitoring and regulating parts of the architecture, with the goal of optimizing performance. * To some extent, it benefits different modules to know the inner workings of the others (though it may seem contradictory to the Layered System requirement, or the modularity approach). * This can have benefits in the form of optimization of outputs or processing.

Answer 42

Visibility

Question 43

Refers to the ease of moving applications from deployed location to another. From one software server to another in the same machine? Or the same network? Or a different network altogether? e.g live migration

Answer 43

Portability

Question 44

The degree of the service’s susceptibility to failure. Downtimes must be kept to a minimum even in cases of partial or complete failure. This can be addressed by using redundant servers.

Answer 44

Reliability