Rest representational state transfer

web services - What does Representational State mean in REST

http://www.parts-depot.com/parts/00345 3. Categorize your resources according to whether clients can just receive a representation of the resource, or whether clients can modify (add to) the resource. For the former, make those resources accessible using an HTTP GET. For the later, make those resources accessible using HTTP POST, PUT, and/or DELETE. The Representational State Transfer (REST) style is an abstraction of the architectural elements within a distributed hypermedia system. REST ignores the details of component implementation and protocol syntax in order to focus on the roles of components, the constraints upon their interaction..

Video: Understanding REST (Representational State Transfer

What is REST - Learn to create timeless REST API

Fielding Dissertation: CHAPTER 5: Representational State Transfer

The design rationale behind the Web architecture can be described by an architectural style consisting of the set of constraints applied to elements within the architecture. By examining the impact of each constraint as it is added to the evolving style, we can identify the properties induced by the Web's constraints. Additional constraints can then be applied to form a new architectural style that better reflects the desired properties of a modern Web architecture. This section provides a general overview of REST by walking through the process of deriving it as an architectural style. Later sections will describe in more detail the specific constraints that compose the REST style. Depending on the message control data, a given representation may indicate the current state of the requested resource, the desired state for the requested resource, or the value of some other resource, such as a representation of the input data within a client's query form, or a representation of some error condition for a response. For example, remote authoring of a resource requires that the author send a representation to the server, thus establishing a value for that resource that can be retrieved by later requests. If the value set of a resource at a given time consists of multiple representations, content negotiation may be used to select the best representation for inclusion in a given message.http://roy.gbiv.com/untangled/2008/rest-apis-must-be-hypertext-driven http://www.ics.uci.edu/~fielding/pubs/dissertation/rest_arch_style.htm

Why is it called Representational State Transfer

  1. Douglas K Barry is also the author of a book that explains Web Services, service-oriented architecture, and Cloud Computing in an easy-to-understand, non-technical manner.
  2. The state of the resource at any particular timestamp is known as resource representation. A representation consists of data, metadata describing the data and hypermedia links which can help the clients in transition to the next desired state.
  3. GET is used to retrieve a representation (or, "stuff") from a resource. GET is widely used today for downloading web pages. However, it might be used to GET any kind whatever representation a resource may provide, including XML data.
  4. A: We need to have an endpoint to start process X B: Ok let's do POST /processes/X/start A: Should we use POST or PUT? B: If we follow REST, we will use PUT I could go on and on. I am highly confident that you might have at least encountered one of those scenarios. Those discussions showcase fundamental flaws in the understanding of REST.
  5. REST provides a hybrid of all three options by focusing on a shared understanding of data types with metadata, but limiting the scope of what is revealed to a standardized interface. REST components communicate by transferring a representation of a resource in a format matching one of an evolving set of standard data types, selected dynamically based on the capabilities or desires of the recipient and the nature of the resource. Whether the representation is in the same format as the raw source, or is derived from the source, remains hidden behind the interface. The benefits of the mobile object style are approximated by sending a representation that consists of instructions in the standard data format of an encapsulated rendering engine (e.g., Java [45]). REST therefore gains the separation of concerns of the client-server style without the server scalability problem, allows information hiding through a generic interface to enable encapsulation and evolution of services, and provides for a diverse set of functionality through downloadable feature-engines.

5.1.1 Starting with the Null Style

REST - representational state transfer, is not related to any HTTP verb nor is it tied to how URLs look like. In fact, REST is not related to HTTP. REST is a set of guidelines which if followed will yield the benefits promise for a RESTful system. REST is not a protocol, not a standard, REST is a set of principles:In the article you said “In simplest words, in the REST architectural style, data and functionality are considered resources…”, can you give an example of a functionality as a resource? A process view of an architecture is primarily effective at eliciting the interaction relationships among components by revealing the path of data as it flows through the system. Unfortunately, the interaction of a real system usually involves an extensive number of components, resulting in an overall view that is obscured by the details. Figure 5-10 provides a sample of the process view from a REST-based architecture at a particular instance during the processing of three parallel requests. REST consists of a set of architectural constraints chosen for the properties they induce on candidate architectures. Although each of these constraints can be considered in isolation, describing them in terms of their derivation from common architectural styles makes it easier to understand the rationale behind their selection. Figure 5-9 depicts the derivation of REST's constraints graphically in terms of the network-based architectural styles examined in Chapter 3.

The data format of a representation is known as a media type [48]. A representation can be included in a message and processed by the recipient according to the control data of the message and the nature of the media type. Some media types are intended for automated processing, some are intended to be rendered for viewing by a user, and a few are capable of both. Composite media types can be used to enclose multiple representations in a single message. A resolver translates partial or complete resource identifiers into the network address information needed to establish an inter-component connection. For example, most URI include a DNS hostname as the mechanism for identifying the naming authority for the resource. In order to initiate a request, a Web browser will extract the hostname from the URI and make use of a DNS resolver to obtain the Internet Protocol address for that authority. Another example is that some identification schemes (e.g., URN [124]) require an intermediary to translate a permanent identifier to a more transient address in order to access the identified resource. Use of one or more intermediate resolvers can improve the longevity of resource references through indirection, though doing so adds to the request latency.

REST - Representational State Transfer

Representational State Transfer (REST

5.1.5 Uniform Interface

A data view of an architecture reveals the application state as information flows through the components. Since REST is specifically targeted at distributed information systems, it views an application as a cohesive structure of information and control alternatives through which a user can perform a desired task. For example, looking-up a word in an on-line dictionary is one application, as is touring through a virtual museum, or reviewing a set of class notes to study for an exam. Each application defines goals for the underlying system, against which the system's performance can be measured. DELETE, as you can imagine, deletes information that one stores. If there is a resource that one would like to remove from the server, DELETE is the method one should use.

If we will provide full device information in search query results, the client may start using these URIs to get and utilize individual device information – Which is wrong. The principled use of the REST style in the Web, with its clear notion of components, connectors, and representations, relates closely to the C2 architectural style [128]. The C2 style supports the development of distributed, dynamic applications by focusing on structured use of connectors to obtain substrate independence. C2 applications rely on asynchronous notification of state changes and request messages. As with other event-based schemes, C2 is nominally push-based, though a C2 architecture could operate in REST's pull style by only emitting a notification upon receipt of a request. However, the C2 style lacks the intermediary-friendly constraints of REST, such as the generic resource interface, guaranteed stateless interactions, and intrinsic support for caching. Since REST-based architectures communicate primarily through the transfer of representations of resources, latency can be impacted by both the design of the communication protocols and the design of the representation data formats. The ability to incrementally render the response data as it is received is determined by the design of the media type and the availability of layout information (visual dimensions of in-line objects) within each representation. Some cache connectors are shared, meaning that its cached responses may be used in answer to a client other than the one for which the response was originally obtained. Shared caching can be effective at reducing the impact of "flash crowds" on the load of a popular server, particularly when the caching is arranged hierarchically to cover large groups of users, such as those within a company's intranet, the customers of an Internet service provider, or Universities sharing a national network backbone. However, shared caching can also lead to errors if the cached response does not match what would have been obtained by a new request. REST attempts to balance the desire for transparency in cache behavior with the desire for efficient use of the network, rather than assuming that absolute transparency is always required.Roy Fielding has never mentioned any recommendation around which method to be used in which condition. All he emphasizes is that it should be uniform interface. If you decide HTTP POST will be used for updating a resource – rather than most people recommend HTTP PUT – it’s alright and application interface will be RESTful.

“Another thing which will help you while building RESTful APIs is that query based API results should be represented by a list of links with summary information, not by arrays of original resource representations because the query is not a substitute for identification of resources.” In the world of REST, there are two key terms that you need to learn: resources and representations. These are actually both very simple concepts, but admittedly confusing the first time one encounters the words. But, we are fairly certain that these words were created because it sounds much better than referring to a "thing" you want to talk to and the "stuff" you want to send. We believe you might agree. The final form of connector type is a tunnel, which simply relays communication across a connection boundary, such as a firewall or lower-level network gateway. The only reason it is modeled as part of REST and not abstracted away as part of the network infrastructure is that some REST components may dynamically switch from active component behavior to that of a tunnel. The primary example is an HTTP proxy that switches to a tunnel in response to a CONNECT method request [71], thus allowing its client to directly communicate with a remote server using a different protocol, such as TLS, that doesn't allow proxies. The tunnel disappears when both ends terminate their communication.

REST Tutorial - What is Representational State Transfer - YouTub

REST uses a resource identifier to identify the particular resource involved in an interaction between components. REST connectors provide a generic interface for accessing and manipulating the value set of a resource, regardless of how the membership function is defined or the type of software that is handling the request. The naming authority that assigned the resource identifier, making it possible to reference the resource, is responsible for maintaining the semantic validity of the mapping over time (i.e., ensuring that the membership function does not change). REST is an acronym standing for Representational State Transfer. Interconnected resource representations - the representations of the resources are interconnected using URLs, thereby enabling a client to progress from one state to another Control data defines the purpose of a message between components, such as the action being requested or the meaning of a response. It is also used to parameterize requests and override the default behavior of some connecting elements. For example, cache behavior can be modified by control data included in the request or response message. Each option has its advantages and disadvantages. Option 1, the traditional client-server style [31], allows all information about the true nature of the data to remain hidden within the sender, preventing assumptions from being made about the data structure and making client implementation easier. However, it also severely restricts the functionality of the recipient and places most of the processing load on the sender, leading to scalability problems. Option 2, the mobile object style [50], provides information hiding while enabling specialized processing of the data via its unique rendering engine, but limits the functionality of the recipient to what is anticipated within that engine and may vastly increase the amount of data transferred. Option 3 allows the sender to remain simple and scalable while minimizing the bytes transferred, but loses the advantages of information hiding and requires that both sender and recipient understand the same data types.This is essentially the architecture of the Internet and helps to explain the popularity and ease-of-use for REST.

Understand Representational State Transfer (REST) in Ruby

The primary connector types are client and server. The essential difference between the two is that a client initiates communication by making a request, whereas a server listens for connections and responds to requests in order to supply access to its services. A component may include both client and server connectors. Still, REST has its place in the world and is significantly simpler to understand and implement than SOAP or some other technologies. With REST, one normally just uses HTTP and includes XML in the message body when appropriate. It is a fairly simple concept, but provides a lot of functionality. PUT is not safe, because if you store something on the server, then you are creating a new resource or you are modifying a resource. (Of course, one might modify a resource to contain the same representation, but that is a corner case and not the general rule we apply to PUT.) This constraint induces the properties of visibility, reliability, and scalability. Visibility is improved because a monitoring system does not have to look beyond a single request datum in order to determine the full nature of the request. Reliability is improved because it eases the task of recovering from partial failures [133]. Scalability is improved because not having to store state between requests allows the server component to quickly free resources, and further simplifies implementation because the server doesn't have to manage resource usage across requests.


While all HTTP methods might be used by a RESTful web service, the ones that are really important are GET, PUT, POST, DELETE, and HEAD. A: Do you know REST? B: Yes A: Can you write the URLs for a REST API for a user profile? B: Ok, there; GET /profiles GET /profiles/123 POST /profiles PUT /profiles/123 PATCH /profiles/123 DELETE /profiles/123 A: Perfect This probably looks familiar if you are a Software Engineer. The following conversation as well:Great intro, thanks. On the second paragraph though, it is “its own 6 guiding constraints”, not “it’s”. Representational State Transfer (REST) is a design approach, not a new technology. In the world of REST, there are two key terms that you need to learn: resources and representations. These are actually both very simple concepts, but admittedly confusing the first time one encounters the words

Representational State Transfer (REST) - Definition from Techopedi

  1. ed dynamically by the target of each request. Connectors need only be aware of each other's existence during the scope of their communication, though they may cache the existence and capabilities of other components for performance reasons.
  2. There are two common perspectives on the process of architectural design, whether it be for buildings or for software. The first is that a designer starts with nothing--a blank slate, whiteboard, or drawing board--and builds-up an architecture from familiar components until it satisfies the needs of the intended system. The second is that a designer starts with the system needs as a whole, without constraints, and then incrementally identifies and applies constraints to elements of the system in order to differentiate the design space and allow the forces that influence system behavior to flow naturally, in harmony with the system. Where the first emphasizes creativity and unbounded vision, the second emphasizes restraint and understanding of the system context. REST has been developed using the latter process. Figures 5-1 through 5-8 depict this graphically in terms of how the applied constraints would differentiate the process view of an architecture as the incremental set of constraints is applied.
  3. 1. Overview 2. How does REST link with HTTP protocol 3. What have we learnt 1. Overview Countless time, I have seen the following:
  4. DELETE is also idempotent. If you delete a resource once, it is gone. One cannot delete it again and, if one tried, it would have obviously not make state changes to the resource, since there is no resource to change.
  5. Uniform interface Resources can be accessed through URIs. There should be a common approach to access them and to act on them which is familiar with all other APIs. Each resource should have only one logical URI and when fetched, should return links which points to related resources. The client should be able to discover the whole API content by navigating from the root (HATEOAS).
  6. REST uses various connector types, summarized in Table 5-2, to encapsulate the activities of accessing resources and transferring resource representations. The connectors present an abstract interface for component communication, enhancing simplicity by providing a clean separation of concerns and hiding the underlying implementation of resources and communication mechanisms. The generality of the interface also enables substitutability: if the users' only access to the system is via an abstract interface, the implementation can be replaced without impacting the users. Since a connector manages network communication for a component, information can be shared across multiple interactions in order to improve efficiency and responsiveness.
  7. The data format of a representation is known as a media type. The media type identifies a specification that defines how a representation is to be processed. A truly RESTful API looks like hypertext. Every addressable unit of information carries an address, either explicitly (e.g., link and id attributes) or implicitly (e.g., derived from the media type definition and representation structure).
Web services soap and rest by mandakini for TechGigHow to Deploy ONTAP Select Clusters Using REST Web Services

REST concentrates all of the control state into the representations received in response to interactions. The goal is to improve server scalability by eliminating any need for the server to maintain an awareness of the client state beyond the current request. An application's state is therefore defined by its pending requests, the topology of connected components (some of which may be filtering buffered data), the active requests on those connectors, the data flow of representations in response to those requests, and the processing of those representations as they are received by the user agent. An interesting observation is that the most efficient network request is one that doesn't use the network. In other words, the ability to reuse a cached response results in a considerable improvement in application performance. Although use of a cache adds some latency to each individual request due to lookup overhead, the average request latency is significantly reduced when even a small percentage of requests result in usable cache hits.Ideally, everything that is needed to change the resource state shall be part of API response for that resource – including methods and in what state they will leave the representation.

More precisely, a resource R is a temporally varying membership function MR(t), which for time t maps to a set of entities, or values, which are equivalent. The values in the set may be resource representations and/or resource identifiers. A resource can map to the empty set, which allows references to be made to a concept before any realization of that concept exists -- a notion that was foreign to most hypertext systems prior to the Web [61]. Some resources are static in the sense that, when examined at any time after their creation, they always correspond to the same value set. Others have a high degree of variance in their value over time. The only thing that is required to be static for a resource is the semantics of the mapping, since the semantics is what distinguishes one resource from another. REST components perform actions on a resource by using a representation to capture the current or intended state of that resource and transferring that representation between components. A representation is a sequence of bytes, plus representation metadata to describe those bytes. Other commonly used but less precise names for a representation include: document, file, and HTTP message entity, instance, or variant. That said, REST is not without faults. REST relies on HTTP and, quite often, carries an XML payload. Therefore, when two devices are communicating, versioning becomes an issue. The XML versioning guidelines provide a means of addressing this issue. It is important to note here that versioning on a web server could be performed using URIs that contain versioning information. For example, Yahoo has a search API that looks like " http://search.yahooapis.com/WebSearchService/V1/webSearch". The "V1" indicate the version, which works perfectly well, since Yahoo! will likely only add more versions and all versions will be available simultaneously. However, when using various independent devices like mobile phones, LCD panels, or network servers not under the control of the equipment manufacturer, there may be a number of versions of any given interface employed in those devices. So, the XML versioning rules are quite important. Client-server architecture The client and server are decoupled. They follow a different lifecycle and can evolve independentely of each other. TL;DR. Representational state transfer or simply REST is a term for exchanging data in well-defined formats in order to increase interoperability. Through application of certain constraints decoupling from clients to servers should be achived which make the former one more robust and the latter one more..

What is REST? Manipulation of Resources Through Representation

  1. REST does not restrict communication to a particular protocol, but it does constrain the interface between components, and hence the scope of interaction and implementation assumptions that might otherwise be made between components. For example, the Web's primary transfer protocol is HTTP, but the architecture also includes seamless access to resources that originate on pre-existing network servers, including FTP [107], Gopher [7], and WAIS [36]. Interaction with those services is restricted to the semantics of a REST connector. This constraint sacrifices some of the advantages of other architectures, such as the stateful interaction of a relevance feedback protocol like WAIS, in order to retain the advantages of a single, generic interface for connector semantics. In return, the generic interface makes it possible to access a multitude of services through a single proxy. If an application needs the additional capabilities of another architecture, it can implement and invoke those capabilities as a separate system running in parallel, similar to how the Web architecture interfaces with "telnet" and "mailto" resources.
  2. http://www.boeing.com/aircraft/747 A representation of the resource is returned (e.g., Boeing747.html). The representation places the client application in a state. The result of the client traversing a hyperlink in Boeing747.html is another resource is accessed. The new representation places the client application into yet another state. Thus, the client application changes (transfers) state with each resource representation --> Representational State Transfer!
  3. The central feature that distinguishes the REST architectural style from other network-based styles is its emphasis on a uniform interface between components (Figure 5-6). By applying the software engineering principle of generality to the component interface, the overall system architecture is simplified and the visibility of interactions is improved. Implementations are decoupled from the services they provide, which encourages independent evolvability. The trade-off, though, is that a uniform interface degrades efficiency, since information is transferred in a standardized form rather than one which is specific to an application's needs. The REST interface is designed to be efficient for large-grain hypermedia data transfer, optimizing for the common case of the Web, but resulting in an interface that is not optimal for other forms of architectural interaction.
  4. The application state is controlled and stored by the user agent and can be composed of representations from multiple servers. In addition to freeing the server from the scalability problems of storing state, this allows the user to directly manipulate the state (e.g., a Web browser's history), anticipate changes to that state (e.g., link maps and prefetching of representations), and jump from one application to another (e.g., bookmarks and URI-entry dialogs).
  5. http://www.parts-depot.com/parts/00345 is a logical URL, not a physical URL. Thus, there doesn't need to be, for example, a static HTML page for each part. In fact, if there were a million parts then a million static HTML pages would not be a very attractive design.
  6. Resources are decoupled from their representation so that their content can be accessed in a variety of formats, such as HTML, XML, plain text, PDF, JPEG, JSON, and others. Metadata about the resource is available and used, for example, to control caching, detect transmission errors, negotiate the appropriate representation format, and perform authentication or access control. And most importantly, every interaction with a resource is stateless.
  7. The HTTP protocol is a well established protocol and extremely well documented. Implementing it allows;

Brief Representational State Transfer (REST) Courser

Video: Guiding Principles of REST

Regarding the 6th guiding principle – coding on demand, does this include single page application in which code is downloaded from a server to the UI when invoked? The word "idempotent" means that, regardless of how many times a given method is invoked, the end result is the same. GET and HEAD are idempotent. GET and HEAD are both safe and idempotent, actually. A: We need to design an endpoint which returns the profile B: Ok let's do ~ GET /profiles(id:123,key:123) A: Nah, that's not good. B: Why? A: This URL does not follow REST Or another example: Representational state transfer (REST) is a distributed system framework that uses Web protocols and technologies. The REST architecture involves client and server interactions built around the transfer of resources. The Web is the largest REST implementation The interaction method of sending representations of resources to consuming components has some parallels with event-based integration (EBI) styles. The key difference is that EBI styles are push-based. The component containing the state (equivalent to an origin server in REST) issues an event whenever the state changes, whether or not any component is actually interested in or listening for such an event. In the REST style, consuming components usually pull representations. Although this is less efficient when viewed as a single client wishing to monitor a single resource, the scale of the Web makes an unregulated push model infeasible.

REST and HTTP are not same !!

If you ask me if my “APIs are RESTful”? To be honest, it doesn’t matter. The answer I will give you depend on which side you are in. REST - Representational State Transfer. Since the past 5 years, there has been an increasing demand to know how to build RESTful Web Services. Never had a job interview for Software Engineering failed to include at least one question about REST or RESTful Web Services and never a.. PUT is used to store a representation at a resource. That sounds strange, but said another way, this is a way to perhaps upload a file and have it stored at a particular URI at the web server or to perhaps create a user account on a web forum. Imagine, if you will, creating a new blog entry that has some files attached. PUT would be the appropriate method to use to upload those files, especially if the client (or "user agent") knows exactly where those files should be placed. If one issues a PUT two times, then the second representation overwrites the first representation. This is entirely harmless if a file is uploaded two times, since the end result is the same file. However, if two different users issue a PUT to the same URI, the representation stored at a given URI will be the last one received. It’s nice explaining clearly how REST API works. Can you please send the soft copy of REST API and how to automate.

The primary disadvantage of layered systems is that they add overhead and latency to the processing of data, reducing user-perceived performance [32]. For a network-based system that supports cache constraints, this can be offset by the benefits of shared caching at intermediaries. Placing shared caches at the boundaries of an organizational domain can result in significant performance benefits [136]. Such layers also allow security policies to be enforced on data crossing the organizational boundary, as is required by firewalls [79].The reason why REST is associated with HTTP protocol is that the HTTP protocol itself, if implemented in a certain way, answers part of the requirements of a RESTful service. Over the years it has become a default protocol to be used to build RESTful services and terminology has been mixed now speaking about RESTful APIs while speaking about HTTP web services respecting partially REST architecture. So, what about POST? Some argue that POST is not safe. But, we argue that "it depends". If a POST operation is used to create a resource (e.g., a blog entry), then it is not safe. However, if POST is used to send an e-mail, then why would it not be considered safe? In the latter case, the state of the resource did not change. As such, it is safe.

MQTT vs REST | Difference between MQTT and REST Protocols

We next add a constraint to the client-server interaction: communication must be stateless in nature, as in the client-stateless-server (CSS) style of Section 3.4.3 (Figure 5-3), such that each request from client to server must contain all of the information necessary to understand the request, and cannot take advantage of any stored context on the server. Session state is therefore kept entirely on the client. This probably requires a more concrete example. Suppose you wish to post a blog entry. You might press the "post a blog entry" link, which might result in creating a resource called "http://example.org/blog/post/123" and your web browser is now showing a web form that allows you to type the contents of the blog. When you press the "submit" button, the HTTP POST is issued to the URL "http://example.org/blog/post/123" and, once that is received, and further posting attempts are rejected. If you had inadvertently clicked on the "post a blog entry" two times, two different blog posting resources might have been created (e.g., 122 and 123), but the first one (122) should be deleted automatically at some point, restoring the server state with no ill side-effects. But, since there are no standard procedures, then we cannot tell you exactly how to implement the logic. Hopefully, you get some idea.

5.2 REST Architectural Elements

Now that we have an understanding of the REST architectural elements in isolation, we can use architectural views [105] to describe how the elements work together to form an architecture. Three types of view--process, connector, and data--are useful for illuminating the design principles of REST. Another issue for REST is that is a resource on a server is generally a simple, independent "thing". But, what if a client needs to manipulate three different resources in succession in order to achieve a desired result? For example, perhaps a client needs to post a blog entry, upload a referenced file, and then request that the RSS feed be updated to include the new blog entry. What does the client do if the first operation succeeds, but the last one fails? REST does not have the concept of "transactions" and, indeed, if those operations are performed over a plurality of devices, it is a complicated problem. Still, some type of transaction support is necessary in some cases and achievable, but just not readily achievable. An application reaches a steady-state whenever it has no outstanding requests; i.e., it has no pending requests and all of the responses to its current set of requests have been completely received or received to the point where they can be treated as a representation data stream. For a browser application, this state corresponds to a "web page," including the primary representation and ancillary representations, such as in-line images, embedded applets, and style sheets. The significance of application steady-states is seen in their impact on both user-perceived performance and the burstiness of network request traffic.

Intermediary components act as both a client and a server in order to forward, with possible translation, requests and responses. A proxy component is an intermediary selected by a client to provide interface encapsulation of other services, data translation, performance enhancement, or security protection. A gateway (a.k.a., reverse proxy) component is an intermediary imposed by the network or origin server to provide an interface encapsulation of other services, for data translation, performance enhancement, or security enforcement. Note that the difference between a proxy and a gateway is that a client determines when it will use a proxy. Representational state transfer (REST) is a software architectural style that defines a set of constraints to be used for creating Web services

5.3 REST Architectural Views

The next chapter presents an evaluation of the REST architecture through the experience and lessons learned from applying REST to the design, specification, and deployment of the modern Web architecture. This work included authoring the current Internet standards-track specifications of the Hypertext Transfer Protocol (HTTP/1.1) and Uniform Resource Identifiers (URI), and implementing the architecture through the libwww-perl client protocol library and Apache HTTP server.Cacheability Resources provided by your interface will provide their cacheability settings which will allow any server or client to know how to cache them.

Nutanix and Veeam Spread REST API Joy - Wahl Network

Video: Why is it called Representational State Transfer?

http://api.example.com/cart-management/users/{id}/cart/checkout http://api.example.com/song-management/users/{id}/playlist/play For example, the "authors' preferred version" of an academic paper is a mapping whose value changes over time, whereas a mapping to "the paper published in the proceedings of conference X" is static. These are two distinct resources, even if they both map to the same value at some point in time. The distinction is necessary so that both resources can be identified and referenced independently. A similar example from software engineering is the separate identification of a version-controlled source code file when referring to the "latest revision", "revision number 1.2.7", or "revision included with the Orange release."Put in this way, IMHO, I think the sentence is misleading. Reading the phrase what I understand is that for each resource I MUST create a custom media type, for example application/vnd.book+json, application/vnd.author+json and application/vnd.user+json if my application handles book, author and user resources. Albeit this is not forbidden by the REST principles I think that a more appropriate sentence would be:

REST is acronym for REpresentational State Transfer. It is architectural style for distributed hypermedia systems and was first presented by Roy Fielding in 2000 in his famous dissertation. The model application is therefore an engine that moves from one state to the next by examining and choosing from among the alternative state transitions in the current set of representations. Not surprisingly, this exactly matches the user interface of a hypermedia browser. However, the style does not assume that all applications are browsers. In fact, the application details are hidden from the server by the generic connector interface, and thus a user agent could equally be an automated robot performing information retrieval for an indexing service, a personal agent looking for data that matches certain criteria, or a maintenance spider busy patrolling the information for broken references or modified content [39].

Since the components are connected dynamically, their arrangement and function for a particular application action has characteristics similar to a pipe-and-filter style. Although REST components communicate via bidirectional streams, the processing of each direction is independent and therefore susceptible to stream transducers (filters). The generic connector interface allows components to be placed on the stream based on the properties of each request or response. In order to further improve behavior for Internet-scale requirements, we add layered system constraints (Figure 5-7). As described in Section 3.4.2, the layered system style allows an architecture to be composed of hierarchical layers by constraining component behavior such that each component cannot "see" beyond the immediate layer with which they are interacting. By restricting knowledge of the system to a single layer, we place a bound on the overall system complexity and promote substrate independence. Layers can be used to encapsulate legacy services and to protect new services from legacy clients, simplifying components by moving infrequently used functionality to a shared intermediary. Intermediaries can also be used to improve system scalability by enabling load balancing of services across multiple networks and processors.> So in practice, you CAN end up creating lots of custom media-types – POTENTIALLY one media-type associated with one resource.It is important to note that REST is a style of software architecture as opposed to a set of standards. As a result, such applications or architectures are sometimes referred to as RESTful or REST-style applications or architectures. REST has proved to be a popular choice for implementing Web Services. For example, the books suggested at the bottom of many of these article pages are dynamically generated, in part, using a REST architecture. It is one of the options for Amazon Web Services Traditional hypertext systems [61], which typically operate in a closed or local environment, use unique node or document identifiers that change every time the information changes, relying on link servers to maintain references separately from the content [135]. Since centralized link servers are an anathema to the immense scale and multi-organizational domain requirements of the Web, REST relies instead on the author choosing a resource identifier that best fits the nature of the concept being identified. Naturally, the quality of an identifier is often proportional to the amount of money spent to retain its validity, which leads to broken links as ephemeral (or poorly supported) information moves or disappears over time.

REST - An Architectural Style, Not a Standard

The Uber API is a RESTful API. This means that the API is designed to allow you to get, create, update, delete objects with the HTTP verbs GET, POST, PUT, PATCH, DELETE.Hypertext (or hypermedia) means the simultaneous presentation of information and controls such that the information becomes the affordance through which the user (or automaton) obtains choices and selects actions. Remember that hypertext does not need to be HTML (or XML or JSON) on a browser. Machines can follow links when they understand the data format and relationship types. The advantage of adding cache constraints is that they have the potential to partially or completely eliminate some interactions, improving efficiency, scalability, and user-perceived performance by reducing the average latency of a series of interactions. The trade-off, however, is that a cache can decrease reliability if stale data within the cache differs significantly from the data that would have been obtained had the request been sent directly to the server. Douglas K Barry. This is a guide for the savvy manager who wants to capitalize on the wave of change that is occurring with Web Services, service-oriented architecture, and—more recently—Cloud Computing

All REST interactions are stateless. That is, each request contains all of the information necessary for a connector to understand the request, independent of any requests that may have preceded it. This restriction accomplishes four functions: 1) it removes any need for the connectors to retain application state between requests, thus reducing consumption of physical resources and improving scalability; 2) it allows interactions to be processed in parallel without requiring that the processing mechanism understand the interaction semantics; 3) it allows an intermediary to view and understand a request in isolation, which may be necessary when services are dynamically rearranged; and, 4) it forces all of the information that might factor into the reusability of a cached response to be present in each request. The user-perceived performance of a browser application is determined by the latency between steady-states: the period of time between the selection of a hypermedia link on one web page and the point when usable information has been rendered for the next web page. The optimization of browser performance is therefore centered around reducing this communication latency. Component interactions occur in the form of dynamically sized messages. Small or medium-grain messages are used for control semantics, but the bulk of application work is accomplished via large-grain messages containing a complete resource representation. The most frequent form of request semantics is that of retrieving a representation of a resource (e.g., the "GET" method in HTTP), which can often be cached for later reuse.

Have you ever visited a web site to post an article or blog entry, or make a payment and accidentally press "submit" twice? Often, the server will accept that and perform the request two times, because POST is not idempotent. To be useful, though, one might design a means of using POST in such a way as to make it idempotent. There are a few non-standard mechanisms out there for that, the most common approach being to use POST to first create a new resource used to accept a subsequent POST method. Then, once the POST method is received for the given resource, the resource refuses to accept any additional POST requests. This is a guide for the savvy manager who wants to capitalize on the wave of change that is occurring with Web Services, service-oriented architecture, and—more recently—Cloud Computing. The changes wrought by these technologies will require both a basic grasp of the technologies and an effective way to deal with how these changes will affect the people who build and use the systems in our organizations. This book covers both issues. Managers at all levels of all organizations must be aware of both the changes that we are now seeing and ways to deal with issues created by those changes.

In order to improve network efficiency, we add cache constraints to form the client-cache-stateless-server style of Section 3.4.4 (Figure 5-4). Cache constraints require that the data within a response to a request be implicitly or explicitly labeled as cacheable or non-cacheable. If a response is cacheable, then a client cache is given the right to reuse that response data for later, equivalent requests.Today is a big day, my 100th post! I wanted to take this opportunity to tackle REST and all its misconception. The message that I wanted to transmit is that there isn’t any right or wrong. There isn’t any side to choose. All that matters is how we master our own APIs. How we provide to our users a unified way accross all our endpoints to understand and discover our APIs functionalities and best is if they can themselves guess what sort of functionalities we provide. REST provides a handful set of guidelines which, if followed, yield nicely built APIs. But so far, I have never built a truely 100% RESTful web service and I suspect most of us have not. Anyway all I am saying is that it doesn’t matter. Maybe one day I will realize that it does actually matter, until then, what matters to me is how comfortable are the users of my APIs. Hope you enjoyed this post as much as I enjoyed writting it! See you next time!Maybe the solution is to simply call our services Web APIs instead of RESTful APIs. If I had to take a side, I would take the I don’t care side.Statelessness Each request to the server is stateless. All information needed to perform the action at the server is provided by the client. In other words, all inputs are provided by the client for the server to perform its task.Correct – “its” is the possessive form, and “it’s” is a contraction for “it is.”

The Classic REST System

This chapter introduced the Representational State Transfer (REST) architectural style for distributed hypermedia systems. REST provides a set of architectural constraints that, when applied as a whole, emphasizes scalability of component interactions, generality of interfaces, independent deployment of components, and intermediary components to reduce interaction latency, enforce security, and encapsulate legacy systems. I described the software engineering principles guiding REST and the interaction constraints chosen to retain those principles, while contrasting them to the constraints of other architectural styles. The important thing to understand, though, is that REST actually encourages the use of more HTTP methods than what most web browser support (at least at the time of this writing in 2008). Most web browsers only support two HTTP methods, namely GET and POST. Yet, HTTP also defines the methods PUT, DELETE, OPTIONS, HEAD, TRACE, and CONNECT.

Parts Depot Web Services

Like any other architectural style, REST also does have it’s own 6 guiding constraints which must be satisfied if an interface needs to be referred as RESTful. These principles are listed below.In simplest words, in the REST architectural style, data and functionality are considered resources and are accessed using Uniform Resource Identifiers (URIs). The resources are acted upon by using a set of simple, well-defined operations. The clients and servers exchange representations of resources by using a standardized interface and protocol – typically HTTP.

Consider the example of Google Maps API. You provide the source and destination and the API will give you the list of waypoints(route) to your destination. This chapter introduces and elaborates the Representational State Transfer (REST) architectural style for distributed hypermedia systems, describing the software engineering principles guiding REST and the interaction constraints chosen to retain those principles, while contrasting them to the constraints of other architectural styles. REST is a hybrid style derived from several of the network-based architectural styles described in Chapter 3 and combined with additional constraints that define a uniform connector interface. The software architecture framework of Chapter 1 is used to define the architectural elements of REST and examine sample process, connector, and data views of prototypical architectures.The key abstraction of information in REST is a resource. Any information that can be named can be a resource: a document or image, a temporal service, a collection of other resources, a non-virtual object (e.g. a person), and so on. REST uses a resource identifier to identify the particular resource involved in an interaction between components.

The word "safe" means that if a given HTTP method is invoked, the resource state on the server remains unchanged. In theory, GET is always safe. No matter how many times you download this web page, the contents of it will not change due to your repeated downloads, since you cannot change the web page in that way. That sounds obvious, but if you build a RESTful web service that uses GET in such a way as to modify any state contained within a resource, then you have violated the rules. The key abstraction of information in REST is a resource. Any information that can be named can be a resource: a document or image, a temporal service (e.g. "today's weather in Los Angeles"), a collection of other resources, a non-virtual object (e.g. a person), and so on. In other words, any concept that might be the target of an author's hypertext reference must fit within the definition of a resource. A resource is a conceptual mapping to a set of entities, not the entity that corresponds to the mapping at any particular point in time.I struggle to comprehend this without an example. Let us say, our API is supposed to retrieve data, such as employee data from database server in JSON format to be consumed by client app. What is “a list of links with summary information” that we can expect as the result of the API. Currently I am using PHP + Laravel. Maybe someone can explain or give an example of the above statement, preferably using Laravel routing statement.

A user agent uses a client connector to initiate a request and becomes the ultimate recipient of the response. The most common example is a Web browser, which provides access to information services and renders service responses according to the application needs. OK, that last sentence will raise a few eyebrows in the REST community. But, alas, what system exists where there are not some "things" that do something, other than store information? If one wishes to transmit an e-mail message, for example, POST is the method to use. In that case, some action is performed, but a new resource is not created as a consequence. The REST style draws from many preexisting distributed process paradigms [6, 50], communication protocols, and software fields. REST component interactions are structured in a layered client-server style, but the added constraints of the generic resource interface create the opportunity for substitutability and inspection by intermediaries. Requests and responses have the appearance of a remote invocation style, but REST messages are targeted at a conceptual resource rather than an implementation identifier. The next control state of an application resides in the representation of the first requested resource, so obtaining that first representation is a priority. REST interaction is therefore improved by protocols that "respond first and think later." In other words, a protocol that requires multiple interactions per user action, in order to do things like negotiate feature capabilities prior to sending a content response, will be perceptively slower than a protocol that sends whatever is most likely to be optimal first and then provides a list of alternatives for the client to retrieve if the first response is unsatisfactory.Though, because REST also intends to make the web (internet) more streamline and standard, he advocates using REST principles more strictly. And that’s from where people try to start comparing REST with web (HTTP). Roy fielding, in his dissertation, nowhere mentioned any implementation directive – including any protocol preference and HTTP. Till the time, you are honoring the 6 guiding principles of REST, you can call your interface RESTful.

Representational State Transfer (REST) is a design approach, not a new technology. Even so, people speak of implementing REST and REST interfaces as if it is a new technology, so we will not try to persuade the world that REST is more theory than practice. In practice, REST is implemented with HTTP and XML or JSON. For example, a Web browser that can incrementally render a large HTML document while it is being received provides significantly better user-perceived performance than one that waits until the entire document is completely received prior to rendering, even though the network performance is the same. Note that the rendering ability of a representation can also be impacted by the choice of content. If the dimensions of dynamically-sized tables and embedded objects must be determined before they can be rendered, their occurrence within the viewing area of a hypermedia page will increase its latency. An origin server uses a server connector to govern the namespace for a requested resource. It is the definitive source for representations of its resources and must be the ultimate recipient of any request that intends to modify the value of its resources. Each origin server provides a generic interface to its services as a resource hierarchy. The resource implementation details are hidden behind the interface.Since the past 5 years, there has been an increasing demand to know how to build RESTful Web Services. Never had a job interview for Software Engineering failed to include at least one question about REST or RESTful Web Services and never a week passed with at least hearing one comment like “if we do x, it will not be RESTful”. Everyone seems to be on top of it, know everything about REST. But is it true? Do they really know REST? How certain can one be that her system is RESTful? Today I would like to share my point of view about REST by going through three points:PHP Laravel works on restful api features… There each request send and received through only with these 6 features….

There are two other terms associated with REST that you should know, simply because they appear in all of the literate related to REST. Those are the words "safe" and "idempotent". These words do not come from Fielding's original PhD thesis on REST, but do appear in RFC 2616 and have been popularized through the book RESTful Web Services from O'Reilly. PUT is also idempotent. If you issue PUT 100 times, the resource state on the server is exactly the same as if you use the PUT method one time. REST is acronym for REpresentational State Transfer. Stateless - Each request from client to server must contain all of the information necessary to understand the request, and cannot take advantage of any stored context on the server A distributed hypermedia architect has only three fundamental options: 1) render the data where it is located and send a fixed-format image to the recipient; 2) encapsulate the data with a rendering engine and send both to the recipient; or, 3) send the raw data to the recipient along with metadata that describes the data type, so that the recipient can choose their own rendering engine.

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