I am doing attach and detach operations in my below controller like detaching the relationship from a OU to a ModuleDevice.
What http verbs would those operations mean in a REST API?
ModuleDevicesToOUController
Api/ModuleDevicesToOU/1/OU/1 // Attach for ModuleDevice with Id 1 the OU with Id 1
PUT/Delete/Patch ??? Attach…
Api/ModuleDevicesToOU/1/OU/1// Detach for ModuleDevice with Id 1 the OU with Id 1
PUT/Delete/Patch ??? Detach…
How about using the LINK method? https://datatracker.ietf.org/doc/html/draft-snell-link-method-08
If that's a little experimental for you then just use POST.
If I understand your API correctly, the call is doing a change in the resource at the server, this means that you should use a POST:
Per RFC 2616 , the POST method should be used for any context in
which a request is non-idempotent: that is, it causes a change in
server state each time it is performed, such as submitting a comment
to a blog post or voting in an online poll. In practice, GET is often
reserved, not simply for idempotent actions, but for nullipotent ones,
ones with no side-effects (in contrast to "no side effects on second
or future requests" as with idempotent operations)
http://en.wikipedia.org/wiki/POST_%28HTTP%29
http://en.wikipedia.org/wiki/Http
This is, in my opinion, a very important point between the difference between GET and POST. POST is not only there to allow you to send information in the body, but also to modify the state of the server. I always have it in mind when designing REST interfaces.
I hope it helps.
Related
This is more a theorical question than a practical one.
We have a backend application that uploads csv files to a frontend application, then and only then the backend sends an empty POST request to tell the frontend to start to process those files to update its database.
For this question it doesn't matter if this is a good design (I think it isn't), what are those files, and what database is: I am only want to know better about the REST "sintax".
I'm referring to wikipedia and restfulapi.net, but I'm not convinced about any alternative, because:
GET: Request sender doesn't receive data;
POST (the currently used): Request sender doesn't want to insert data that are on the request body (just data from external files, if existent. Also they can be insert/update/delete);
PUT: Sounds good, but again, data are not on the request body;
PATCH: Sounds best, but data are not on the body (Also, I am wrong or is it deprecated/unused?);
DELETE: Doesn't always need to delete.
I know it is habit to use POST requests to let machines yell "go!" to each other, but I never thought it was right.
What do you think - in theory - would be the proper method?
The actual reference for the semantics of the HTTP methods is the RFC 7231 and not the ones you referenced in your question.
POST is a catch all method and requests that the target resource process the representation enclosed in the request according to the resource's own specific semantics.
4.3.3. POST
The POST method requests that the target resource process the
representation enclosed in the request according to the resource's
own specific semantics. For example, POST is used for the following
functions (among others):
Providing a block of data, such as the fields entered into an HTML
form, to a data-handling process;
Posting a message to a bulletin board, newsgroup, mailing list,
blog, or similar group of articles;
Creating a new resource that has yet to be identified by the
origin server; and
Appending data to a resource's existing representation(s).
[...]
Responses to POST requests are only cacheable when they include
explicit freshness information. However, POST caching is not widely implemented.
In these scenarios, the receiving application knows where the CSV files will be and monitors that location. When it finds one, it processes it and then deletes or archives it. The application will likely have its own criteria for considering itself ready to process, e.g. time of day, size of file etc.
If the data load on the front end takes a long time you could "partition" the updates based on "importance". How you define importance would be up to your business rules. You could then POST a list of CSV filenames/locations to the front end. The list would be ordered by importance. The front end could then update its database based on that importance. Scheduling less important data for a more appropriate time of day.
If the backend knows the difference between new users and updated users you could use PUT and POST. The front end could assign higher priority to PUT requests as they relate to new users, perhaps assigning lower priority and staggered syncing for CSV filenames in POST requests.
I need to delete multiple items by id in the batch however HTTP DELETE does not support a body payload.
Work around options:
1. #DELETE /path/abc?itemId=1&itemId=2&itemId=3 on the server side it will be parsed as List of ids and DELETE operation will be performed on each item.
2. #POST /path/abc including JSON payload containing all ids. { ids: [1, 2, 3] }
How bad this is and which option is preferable? Any alternatives?
Update: Please note that performance is a key here, it is not an option execute delete operation for each individual id.
Along the years, many people fell in doubt about it, as we can see in the related questions here aside. It seems that the accepted answers ranges from "for sure do it" to "its clearly mistreating the protocol". Since many questions was sent years ago, let's dig into the HTTP 1.1 specification from June 2014 (RFC 7231), for better understanding of what's clearly discouraged or not.
The first proposed workaround:
First, about resources and the URI itself on Section 2:
The target of an HTTP request is called a "resource". HTTP does not limit the nature of a resource; it merely defines an interface that might be used to interact with resources. Each resource is identified by a Uniform Resource Identifier (URI).
Based on it, some may argue that since HTTP does not limite the nature of a resource, a URI containing more than one id would be possible. I personally believe it's a matter of interpretation here.
About your first proposed workaround (DELETE '/path/abc?itemId=1&itemId=2&itemId=3') we can conclude that it's something discouraged if you think about a resource as a single document in your entity collection while being good to go if you think about a resource as the entity collection itself.
The second proposed workaround:
About your second proposed workaround (POST '/path/abc' with body: { ids: [1, 2, 3] }), using POST method for deletion could be misleading. The section Section 4.3.3 says about POST:
The POST method requests that the target resource process the representation enclosed in the request according to the resource's own specific semantics. For example, POST is used for the following functions (among others): Providing a block of data, such as the fields entered into an HTML form, to a data-handling process; Posting a message to a bulletin board, newsgroup, mailing list, blog, or similar group of articles; Creating a new resource that has yet to be identified by the origin server; and Appending data to a resource's existing representation(s).
While there's some space for interpretation about "among others" functions for POST, it clearly conflicts with the fact that we have the method DELETE for resources removal, as we can see in Section 4.1:
The DELETE method removes all current representations of the target resource.
So I personally strongly discourage the use of POST to delete resources.
An alternative workaround:
Inspired on your second workaround, we'd suggest one more:
DELETE '/path/abc' with body: { ids: [1, 2, 3] }
It's almost the same as proposed in the workaround two but instead using the correct HTTP method for deletion. Here, we arrive to the confusion about using an entity body in a DELETE request. There are many people out there stating that it isn't valid, but let's stick with the Section 4.3.5 of the specification:
A payload within a DELETE request message has no defined semantics; sending a payload body on a DELETE request might cause some existing implementations to reject the request.
So, we can conclude that the specification doesn't prevent DELETE from having a body payload. Unfortunately some existing implementations could reject the request... But how is this affecting us today?
It's hard to be 100% sure, but a modern request made with fetch just doesn't allow body for GET and HEAD. It's what the Fetch Standard states at Section 5.3 on Item 34:
If either body exists and is non-null or inputBody is non-null, and request’s method is GET or HEAD, then throw a TypeError.
And we can confirm it's implemented in the same way for the fetch pollyfill at line 342.
Final thoughts:
Since the alternative workaround with DELETE and a body payload is let viable by the HTTP specification and is supported by all modern browsers with fetch and since IE10 with the polyfill, I recommend this way to do batch deletes in a valid and full working way.
It's important to understand that the HTTP methods operate in the domain of "transferring documents across a network", and not in your own custom domain.
Your resource model is not your domain model is not your data model.
Alternative spelling: the REST API is a facade to make your domain look like a web site.
Behind the facade, the implementation can do what it likes, subject to the consideration that if the implementation does not comply with the semantics described by the messages, then it (and not the client) are responsible for any damages caused by the discrepancy.
DELETE /path/abc?itemId=1&itemId=2&itemId=3
So that HTTP request says specifically "Apply the delete semantics to the document described by /path/abc?itemId=1&itemId=2&itemId=3". The fact that this document is a composite of three different items in your durable store, that each need to be removed independently, is an implementation details. Part of the point of REST is that clients are insulated from precisely this sort of knowledge.
However, and I feel like this is where many people get lost, the metadata returned by the response to that delete request tells the client nothing about resources with different identifiers.
As far as the client is concerned, /path/abc is a distinct identifier from /path/abc?itemId=1&itemId=2&itemId=3. So if the client did a GET of /path/abc, and received a representation that includes itemIds 1, 2, 3; and then submits the delete you describe, it will still have within its own cache the representation that includes /path/abc after the delete succeeds.
This may, or may not, be what you want. If you are doing REST (via HTTP), it's the sort of thing you ought to be thinking about in your design.
POST /path/abc
some-useful-payload
This method tells the client that we are making some (possibly unsafe) change to /path/abc, and if it succeeds then the previous representation needs to be invalidated. The client should repeat its earlier GET /path/abc request to refresh its prior representation rather than using any earlier invalidated copy.
But as before, it doesn't affect the cached copies of other resources
/path/abc/1
/path/abc/2
/path/abc/3
All of these are still going to be sitting there in the cache, even though they have been "deleted".
To be completely fair, a lot of people don't care, because they aren't thinking about clients caching the data they get from the web server. And you can add metadata to the responses sent by the web server to communicate to the client (and intermediate components) that the representations don't support caching, or that the results can be cached but they must be revalidated with each use.
Again: Your resource model is not your domain model is not your data model. A REST API is a different way of thinking about what's going on, and the REST architectural style is tuned to solve a particular problem, and therefore may not be a good fit for the simpler problem you are trying to solve.
That doesn’t mean that I think everyone should design their own systems according to the REST architectural style. REST is intended for long-lived network-based applications that span multiple organizations. If you don’t see a need for the constraints, then don’t use them. That’s fine with me as long as you don’t call the result a REST API. I have no problem with systems that are true to their own architectural style. -- Fielding, 2008
I read (among others) the following blog about API design: https://www.thoughtworks.com/insights/blog/rest-api-design-resource-modeling. It helped me to better understand a lot of aspects, but I have one question remaining:
How do I deal with functionality that processes some data and gives a response directly. Think, verbs like translate, calculate or enrich. Which noun should they have and should they be called by GET, PUT or POST?
P.S. If it should be GET, how to deal with the maximum length of a GET request
This is really a discussion about naming more so than functionality. Its very much possible to have processed logic in your API, you just need to be careful about naming it.
Imaginary API time. Its got this resource: /v1/probe/{ID} and it responds to GET, POST, and DELETE.
Let's say we want to launch our probes out, and then want the probe to give us back the calculated flux variation of something its observing (totally made up thing). While it isn't a real thing, let's say that this has to be calculated on the fly. One of my intrepid teammates decides to plunk the calculation at GET /v1/1324/calculateflux.
If we're following real REST-ful practices... Oops. Suddenly we're not dealing with a noun, are we? If we have GET /v1/probe/1324/calculateflux we've broken RESTful practices because we're now asking for a verb - calculateflux.
So, how do we deal with this?
You'll want to reconsider the name calculateflux. That's no good - it doesn't name a resource on the probe. **In this case, /v1/probe/1324/fluxvalue is a better name, and /v1/probe/1324/flux works too.
Why?
RESTFUL APIs almost exclusively use nouns in their URIs - remember that each URI needs to describe a specific thing you can GET POST PUT or DELETE or whatever. That means that any time there is a processed value we should give the resource the name of the processed (or calculated) value. This way, we remain RESTful by adhering to the always-current data (We can re-calculate the Flux value any time) and we haven't changed the state of the probe (we didn't save any values using GET).
Well, I can tell you that I know about this.
GET // Returns, JUST return
DELETE // Delete
POST // Send information that will be processed on server
PUT // Update a information
This schema is for laravel framework. Will be most interesting that you read the link in ref
Ref:
https://rafaell-lycan.com/2015/construindo-restful-api-laravel-parte-1/
You should start with the following process:
Identify the resources (nouns) in your system.
They should all respond to GET.
Let's take your translation example. You could decide that every word in the source language is a resource. This would give:
http://example.com/translations/en-fr/hello
Which might return:
Content-Type: text/plain
Content-Language: fr
bonjour
If your processes are long-running, you should create a request queue that clients can POST to, and provide them with another (new) resource that they can query to see if the process has completed.
I'm building a collection of RESTful resources that work like the following: (I'll use "people" as an example):
GET /people/{key}
- returns a person object (JSON)
GET /people?first_name=Bob
- returns a list of person objects who's "first_name" is "Bob" (JSON)
PUT /people/{key}
- expects a person object in the payload (JSON), updates the person in the
datastore with the {key} found in the URL parameter to match the payload.
If it is a new object, the client specifies the key of the new object.
I feel pretty comfortable with the design so far (although any input/criticism is welcome).
I'd also like to be able to PUT a list of people, however I'm not confident in the RESTfulness of my design. This is what I have in mind:
PUT /people
- expects a list of objects in JSON form with keys included in the object
("key":"32948"). Updates all of the corresponding objects in the datastore.
This operation will be idempotent, so I'd like to use "PUT". However its breaking a rule because a GET request to this same resource will not return the equivalent of what the client just PUT, but would rather return all "people" objects (since there would be no filters on the query). I suspect there are also a few other rules that might be being broken here.
Someone mentioned the use of a "PATCH" request in an earlier question that I had: REST resource with a List property
"PATCH" sounds fantastic, but I don't want to use it because its not in wide use yet and is not compatible with a lot of programs and APIs yet.
I'd prefer not to use POST because POST implies that the request is not idempotent.
Does anyone have any comments / suggestions?
Follow-up:::
While I hesitated to use POST because it seems to be the least-common-denominator, catch-all for RESTful operations and more can be said about this operation (specifically that it is idempotent), PUT cannot be used because its requirements are too narrow. Specifically: the resource is not being completely re-written and the equivalent resource is not being sent back from a GET request to the same resource. Using a PUT with properties outside of it's specifications can cause problems when applications, api's, and/or programmers attempt to work with the resource and are met with unexpected behavior from the resource.
In addition to the accepted answer, Darrel Miller had an excellent suggestion if the operation absolutely had to be a PUT and that was to append a UUID onto the end of the resource path so an equivalent GET request will return the equivalent resource.
POST indicates a generic action other than GET, PUT, and DELETE (the generic hashtable actions). Because the generic hashtable actions are inappropriate, use POST. The semantics of POST are determined by the resource to which an entity is POSTed. This is unlike the semantics of the generic hashtable methods, which are well-known.
POST /people/add-many HTTP/1.1
Host: example.com
Content-Type: application/json
[
{ "name": "Bob" },
{ "name": "Robert" }
]
Using PUT is definitely the wrong verb in this case. POST is meant to do exactly what you are asking. From the HTTP specification:
The fundamental difference between the POST and PUT requests is reflected in the different meaning of the Request-URI. The URI in a POST request identifies the resource that will handle the enclosed entity. That resource might be a data-accepting process, a gateway to some other protocol, or a separate entity that accepts annotations. In contrast, the URI in a PUT request identifies the entity enclosed with the request -- the user agent knows what URI is intended and the server MUST NOT attempt to apply the request to some other resource...
As such, if you want to update multiple resources in a single call, you have to use POST.
Just be cause PUT is required to be idempotent and POST is not, does not mean that POST cannot be idempotent. Your choice of HTTP verb should not be based on that, but based on the relationship of the requested resource and the resource acted upon. If your application is directly handling the resource requested, use PUT. If it is acting on some other resource (or resources, as in your case), use POST.
I really don't see any easy way you could use PUT to create an arbitrary set of people. Unless, you are prepared to have the client generate a GUID and do something like,
PUT /PeopleList/{1E8157D6-3BDC-43b7-817D-C3DA285DD606}
On the server side you could take the people from the list and add them to the /People resource.
A slight variation to this approach would be to get the server to include a link such as
<link rel="AddList" href="/PeopleList/{1E8157D6-3BDC-43b7-817D-C3DA285DD606}"/>
in the People resource. The client would need to know that it needs to PUT a list of people to the AddList link. The server would need to make sure that each time it renders the /People resource it creates a new url for the AddList link.
Regarding Darren Miller's suggestion of using PUT to a GUID (I can't comment...), the point of using PUT would be to achieve idempotency for the operation. The litmus test if idempotency would be this conversation between the client and server:
PUT /PeopleList/{1E8157D6-3BDC-43b7-817D-C3DA285DD606}
204 NO CONTENT (indicates that it all went well)
client loses connection and doesn't see the 204
client automatically retries
PUT /PeopleList/{1E8157D6-3BDC-43b7-817D-C3DA285DD606}
How would the server differentiate the two? If the GUID is "used up" so to speak then the server would have to respond 404 or 410. This introduces a tiny bit of conversational state on the server to remember all the GUIDs that have been used.
Two clients would often see the same I guess, because of caching or simply keeping stale responses around.
I think a smart solution is to use POST to create an (initially empty, short lived) holding area for a resource to which you can PUT, i.e. clients need to POST to create the GUID resource instead of discovering it via a link:
POST /PeopleList/CreateHoldingArea
201 CREATED and Location: /PeopleList/{1E8157D6-3BDC-43b7-817D-C3DA285DD606}
PUT /PeopleList/{1E8157D6-3BDC-43b7-817D-C3DA285DD606}
This would mean that the lost idempotency would not result in much overhead; clients simply create new GUIDs (by POSTing) if they didn't see the initial 201 CREATED response. The "tiny bit of conversational state" would now only be the created but not yet used holding areas.
The ideal solution would of course not require any conversational state on the server, but it eludes me.
What is the practical benefit of using HTTP GET, PUT, DELETE, POST, HEAD? Why not focus on their behavioral benefits (safety and idempotency), forgetting their names, and use GET, PUT or POST depending on which behavior we want?
Why shouldn't we only use GET, PUT and POST (and drop HEAD, DELETE)?
The [REST][1] approach uses POST, GET, PUT and DELETE to implement the CRUD rules for a web resource. It's a simple and tidy way to expose objects to requests on the web. It's web services without the overheads.
Just to clarify the semantic differences. Each operation is rather different. The point is to have nice HTTP methods that have clear, distinct meanings.
POST creates new objects. The URI has no key; it accepts a message body that defines the object. SQL Insert. [Edit While there's no technical reason for POST to have no key, the REST folks suggest strongly that for POST to have distinct meaning as CREATE, it should not have a key.]
GET retrieves existing objects. The URI may have a key, depends on whether you are doing singleton GET or list GET. SQL Select
PUT updates an existing object. The URI has a key; It accepts a message body that updates an object. SQL Update.
DELETE deletes an existing object. The URI has a key. SQL Delete.
Can you update a record with POST instead of PUT? Not without introducing some ambiguity. Verbs should have unambiguous effects. Further, POST URI's have no key, where PUT must have a key.
When I POST, I expect a 201 CREATED. If I don't get that, something's wrong. Similarly, when I PUT, I expect a 200 OK. If I don't get that, something's wrong.
I suppose you could insist on some ambiguity where POST does either POST or PUT. The URI has to be different; also the associated message could be different. Generally, the REST folks take their cue from SQL where INSERT and UPDATE are different verbs.
You could make the case that UPDATE should insert if the record doesn't exist or update if the record does exist. However, it's simpler if UPDATE means UPDATE and failure to update means something's wrong. A secret fall-back to INSERT makes the operation ambiguous.
If you're not building a RESTful interface, then it's typical to only use GET and POST for retrieve and create/update. It's common to have URI differences or message content differences to distinguish between POST and PUT when a person is clicking submit on a form. It, however, isn't very clean because your code has to determine if you're in the POST=create case or POST=update case.
POST has no guarantees of safety or idempotency. That's one reason for PUT and DELETE—both PUT and DELETE are idempotent (i.e., 1+N identical requests have the same end result as just 1 request).
PUT is used for setting the state of a resource at a given URI. When you send a POST request to a resource at a particular URI, that resource should not be replaced by the content. At most, it should be appended to. This is why POST isn't idempotent—in the case of appending POSTS, every request will add to the resource (e.g., post a new message to a discussion forum each time).
DELETE is used for making sure that a resource at a given URI is removed from the server. POST shouldn't normally be used for deleting except for the case of submitting a request to delete. Again, the URI of the resource you would POST to in that case shouldn't be the URI for the resource you want to delete. Any resource for which you POST to is a resource that accepts the POSTed data to append to itself, add to a collection, or to process in some other way.
HEAD is used if all you care about is the headers of a GET request and you don't want to waste bandwidth on the actual content. This is nice to have.
Why do we need more than POST? It allows data to flow both ways, so why would GET be needed? The answer is basically the same as for your question. By standardizing the basic expectations of the various methods other processes can better know what to do.
For example, intervening caching proxies can have a better chance of doing the correct thing.
Think about HEAD for instance. If the proxy server knows what HEAD means then it can process the result from a previous GET request to provide the proper answer to a HEAD request. And it can know that POST, PUT and DELETE should not be cached.
No one posted the kind of answer I was looking for so I will try to summarize the points myself.
"RESTful Web Services" chapter 8 section "Overloading POST" reads: "If you want to do without PUT and DELETE altogether, it’s entirely RESTful to expose safe operations on resources through GET, and all other operations through overloaded POST. Doing this violates my Resource-Oriented Architecture, but it conforms to the less restrictive rules of REST."
In short, replacing PUT/DELETE in favor of POST makes the API harder to read and PUT/DELETE calls are no longer idempotent.
In a word:
idempotency
In a few more words:
GET = safe + idempotent
PUT = idempotent
DELETE = idempotent
POST = neither safe or idempotent
'Idempotent' just means you can do it over and over again and it will always do exactly the same thing.
You can reissue a PUT (update) or DELETE request as many times as you want and it will have the same effect every time, however the desired effect will modify a resource so it is not considered 'safe'.
A POST request should create a new resource with every request, meaning the effect will be different every time. Therefore POST is not considered safe or idempotent.
Methods like GET and HEAD are just read operations and are therefore considered 'safe' aswell as idempotent.
This is actually a pretty important concept because it provides a standard/consistent way to interpret HTTP transactions; this is particularly useful in a security context.
Not all hosters don't support PUT, DELETE.
I asked this question, in an ideal world we'd have all the verbs but....:
RESTful web services and HTTP verbs
HEAD is really useful for determining what a given server's clock is set to (accurate to within the 1 second or the network round-trip time, whichever is greater). It's also great for getting Futurama quotes from Slashdot:
~$ curl -I slashdot.org
HTTP/1.1 200 OK
Date: Wed, 29 Oct 2008 05:35:13 GMT
Server: Apache/1.3.41 (Unix) mod_perl/1.31-rc4
SLASH_LOG_DATA: shtml
X-Powered-By: Slash 2.005001227
X-Fry: That's a chick show. I prefer programs of the genre: World's Blankiest Blank.
Cache-Control: private
Pragma: private
Connection: close
Content-Type: text/html; charset=iso-8859-1
For cURL, -I is the option for performing a HEAD request. To get the current date and time of a given server, just do
curl -I $server | grep ^Date
To limit ambiguity which will allow for better/easier reuse of our simple REST apis.
You could use only GET and POST but then you are losing out on some of the precision and clarity that PUT and DELETE bring. POST is a wildcard operation that could mean anything.
PUT and DELETE's behaviour is very well defined.
If you think of a resource management API then GET, PUT and DELETE probably cover 80%-90% of the required functionality. If you limit yourself to GET and POST then 40%-60% of your api is accessed using the poorly specified POST.
Web applications using GET and POST allow users to create, view, modify and delete their data, but do so at a layer above the HTTP commands originally created for these purposes. One of the ideas behind REST is a return to the original intent of the design of the Web, whereby there are specific HTTP operations for each CRUD verb.
Also, the HEAD command can be used to improve the user experience for (potentially large) file downloads. You call HEAD to find out how large the response is going to be and then call GET to actually retrieve the content.
See the following link for an illustrative example. It also suggests one way to use the OPTIONS http method, which hasn't yet been discussed here.
There are http extensions like WebDAV that require additional functionally.
http://en.wikipedia.org/wiki/WebDAV
The web server war from the earlier days probably caused it.
In HTTP 1.0 written in 1996, there were only GET, HEAD, and POST. But as you can see in Appendix D, vendors started to add their own things. So, to keep HTTP compatible, they were forced to make HTTP 1.1 in 1999.
However, HTTP/1.0 does not sufficiently take into consideration
the effects of hierarchical proxies, caching, the need for
persistent connections, or virtual hosts. In addition, the proliferation
of incompletely-implemented applications calling themselves
"HTTP/1.0" has necessitated a protocol version change in order for
two communicating applications to determine each other's true capabilities.
This specification defines the protocol referred to as "HTTP/1.1". This protocol includes more stringent requirements than HTTP/1.0 in order
to ensure reliable implementation of its features.
GET, PUT, DELETE and POST are holdovers from an era when sophomores thought that a web page could be reduced to a few hoighty-toity principles.
Nowadays, most web pages are composite entities, which contain some or all of these primitive operations. For instance, a page could have forms for viewing or updating customer information, which perhaps spans a number of tables.
I usually use $_REQUEST[] in php, not really caring how the information arrived. I would choose to use GET or PUT methods based on efficiency, not the underlying (multiple) paradigms.