Although this set can be expanded, additional methods cannot be assumed to share the same semantics for separately extended clients and servers. The Host request-header field section Implementors should be aware that the software represents the user in their interactions over the Internet, and should be careful to allow the user to be aware of any actions they might take which may have an unexpected significance to themselves or others.

In particular, the convention has been established that the GET and HEAD methods SHOULD NOT have the significance of taking an action other than retrieval. These methods ought to be considered "safe". This allows user agents to represent other methods, such as POST, PUT and DELETE, in a special way, so that the user is made aware of the fact that a possibly unsafe action is being requested.

Naturally, it is not possible to ensure that the server does not generate side-effects as a result of performing a GET request; in fact, some dynamic resources consider that a feature. The important distinction here is that the user did not request the side-effects, so therefore cannot be held accountable for them.

The methods GET, HEAD, PUT and DELETE share this property. Also, the methods OPTIONS and TRACE SHOULD NOT have side effects, and so are inherently idempotent.

However, it is possible that a sequence of several requests is non- idempotent, even if all of the methods executed in that sequence are idempotent.

A sequence is idempotent if a single execution of the entire sequence always yields a result that is not changed by a reexecution of all, or part, of that sequence. For example, a sequence is non-idempotent if its result depends on a value that is later modified in the same sequence. A sequence that never has side effects is idempotent, by definition provided that no concurrent operations are being executed on the same set of resources. If the OPTIONS request includes an entity-body as indicated by the presence of Content-Length or Transfer-Encodingthen the media type MUST be indicated by a Content-Type field.

Although this specification does not define any use for such a body, future extensions to HTTP might use the OPTIONS body to make more detailed queries on the server. A server that does not support such an extension MAY discard the request body.

If the Request-URI is not an asterisk, the OPTIONS request applies only to the options that are available when communicating with that resource. A response SHOULD include any header fields that indicate optional features implemented by the server and applicable to that resource e. The response body, if any, SHOULD also include information about the communication options. The format for such a. Content negotiation MAY be used to select the appropriate response format. If no response body is included, the response MUST include a Content-Length field with a field-value of "0".

The Max-Forwards request-header field MAY be used to target a specific proxy in the request chain. When a proxy receives an OPTIONS request on an absoluteURI for which request forwarding is permitted, the proxy MUST check for a Max-Forwards field.

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If the Max-Forwards field-value is zero "0"the proxy MUST NOT forward the message; instead, the proxy SHOULD respond with its own communication options. If the Max-Forwards field-value is an integer greater than zero, the proxy MUST decrement the field-value when it forwards the request.

If no Max-Forwards field is present in the request, then the forwarded request MUST NOT include a Max-Forwards field. The GET method means retrieve whatever information in the form of an entity is identified by the Request-URI. If the Request-URI refers to a data-producing process, it is the produced data which shall be returned as the entity in the response and not the source text of the process, unless that text happens to be the output of the process.

The semantics of the GET method change to a "conditional GET" if the request message includes an If-Modified-Since, If-Unmodified-Since, If-Match, If-None-Match, or If-Range header field. A conditional GET method requests that iri stock market research sites in india entity be transferred only under the circumstances described by the conditional header field s.

The conditional GET method is intended to reduce unnecessary network usage by allowing cached entities to be refreshed without requiring multiple requests or transferring data already held by the client. The semantics of the GET method change to a "partial GET" if the request message includes a Range header field.

A partial GET forex atr breakout that only part of the entity be transferred, as described in section The partial GET method is intended to reduce unnecessary network usage by allowing partially-retrieved entities to be completed without transferring data already held by the client.

The response to a GET request is cacheable if and only if it meets the requirements for HTTP caching described in section The HEAD method is identical to GET except that the server MUST NOT return a message-body in the response.

The metainformation contained in the HTTP headers in response to a HEAD request SHOULD be identical to the information sent in response to a GET request. This method can be used for obtaining metainformation about the entity implied by the request without transferring the entity-body itself. This method is often used for testing hypertext links for validity, accessibility, and recent modification. The response to a HEAD put options s&p MAY be cacheable in the sense that the information contained in the response MAY be used to update a previously cached entity from that resource.

If the new field values indicate that the cached entity differs from the current forex dla bystrzakow empik as would be indicated by a change in Content-Length, Content-MD5, ETag or Last-Modifiedthen the cache MUST treat the cache entry as stale.

The POST method is used to request that the origin server accept the entity enclosed in ecn forex robot.rar request as a new subordinate of the resource identified by the Request-URI in the Request-Line.

POST is designed to allow a uniform method to cover the following functions:.

The actual function performed by the POST method is determined by the server and is usually dependent on work from home bathurst nb Request-URI.

The posted entity is subordinate to that URI in the same way that a file is subordinate to a directory containing it, a news article is subordinate to a newsgroup to which it is posted, or a record is subordinate to a database.

The action performed by the POST method might not result in a resource that can be identified by a URI. In this case, either OK or No Content is the appropriate response status, depending on whether or not the response includes an entity that describes the result. If a resource has been created on the origin server, the response SHOULD be Created and contain an entity which describes the status of the request and refers to the new resource, and a Location header see section Responses to this method are not cacheable, unless the response includes appropriate Cache-Control or Expires header fields.

However, the See Other response can be used to direct the user agent to retrieve a cacheable resource. The PUT method requests that the enclosed entity be stored under the supplied Request-URI. If the Request-URI refers to an already existing resource, the enclosed entity SHOULD be considered as a modified version of the one residing on the origin server.

If the Request-URI does not point to an existing resource, and that URI is capable of being defined as a new resource by the requesting user agent, the origin server can create the resource with that URI. If a new resource is created, the origin server MUST inform the user agent via the Created response. If an existing resource is modified, either the OK or No Content response codes SHOULD be sent to indicate successful completion of the request.

If the resource could not be created or modified with the Request-URI, an appropriate error response SHOULD be given that reflects the nature of the problem. Content-Range headers that it does not understand or implement and MUST return a Not Implemented response in such cases. If the request passes through a cache and the Request-URI identifies one or more currently cached entities, those entries SHOULD be treated as stale.

Responses to this method are not cacheable. 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. If the server desires that the request be applied to a different URI. A single resource MAY be identified by many different URIs.

For example, an article might have a URI for identifying "the current version" which is separate from the URI identifying each particular version. In this case, a PUT request on a general URI might result in several other URIs being defined by the origin server. Unless otherwise specified for a particular entity-header, the entity-headers in the PUT request SHOULD be applied to the resource created or modified by the PUT.

The DELETE method requests that the origin server delete the resource identified by the Request-URI. This method MAY be overridden by human intervention or other means on the origin server. The client cannot be guaranteed that the operation has been carried out, even if the status code returned from the origin server indicates that the action has been completed successfully.

However, the server SHOULD NOT indicate success unless, at the time the response is given, it intends to delete the resource or move it to an inaccessible location.

Put Option

A successful response SHOULD be OK if the response includes an entity describing the status, Accepted if the action has not yet been enacted, or No Content if the action has been enacted but the response does not include an entity. The TRACE method is used to invoke a remote, application-layer loop- back of the request message.

The final recipient of the request SHOULD reflect the message received back to the client as the entity-body of a OK response. The final recipient is either the.

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A TRACE request MUST NOT include an entity. TRACE allows the client to see what is being received at the other end of the request chain and use that data for testing or diagnostic information.

The value of the Via header field section Use of the Max-Forwards header field allows the client to limit the length of the request chain, which is useful for testing a chain of proxies forwarding messages in an infinite loop. Responses to this method MUST NOT be cached. This specification reserves the method name CONNECT for use with a proxy that can dynamically switch to being a tunnel e.