UML sequence diagram - GET request

"Request methods.
An HTTP 1.1 request made using telnet. The request, response headers and response body are highlighted.
HTTP defines methods (sometimes referred to as verbs) to indicate the desired action to be performed on the identified resource. What this resource represents, whether pre-existing data or data that is generated dynamically, depends on the implementation of the server. Often, the resource corresponds to a file or the output of an executable residing on the server. The HTTP/ 1.0 specification:section 8 defined the GET, POST and HEAD methods and the HTTP/ 1.1 specification:section 9 added 5 new methods: OPTIONS, PUT, DELETE, TRACE and CONNECT. By being specified in these documents their semantics are well known and can be depended upon. Any client can use any method and the server can be configured to support any combination of methods. If a method is unknown to an intermediate it will be treated as an unsafe and non-idempotent method. There is no limit to the number of methods that can be defined and this allows for future methods to be specified without breaking existing infrastructure. For example, WebDAV defined 7 new methods and RFC5789 specified the PATCH method.
GET.
Requests a representation of the specified resource. Requests using GET should only retrieve data and should have no other effect. (This is also true of some other HTTP methods.)" [Hypertext Transfer Protocol. Wikipedia]
The UML sequence diagram example "GET request" was created using the ConceptDraw PRO diagramming and vector drawing software extended with the Rapid UML solution from the Software Development area of ConceptDraw Solution Park.

"State machine diagram is a behavior diagram which shows discrete behavior of a part of designed system through finite state transitions. State machine diagrams can also be used to express the usage protocol of part of a system. Two kinds of state machines defined in UML 2.4 are:
(1) behavioral state machine, and
(2) protocol state machine.
The following nodes and edges are typically drawn in state machine diagram: behavioral state, behavioral transition, protocol state, protocol transition, different pseudostates. ...
Behavioral state machine is specialization of behavior and is used to specify discrete behavior of a part of designed system through finite state transitions. The state machine formalism used in this case is an object-based variant of Harel statecharts.
Behavior is modeled as a traversal of a graph of state nodes connected with transitions. Transitions are triggered by the dispatching of series of events. During the traversal, the state machine could also execute some activities. ...
Protocol state machine is a specialization of behavioral state machine and is used to express usage protocol or lifecycle of a classifier. It specifies which operations of the classifier can be called in which state and under which condition, thus specifying the allowed call sequences on the classifier’s operations. Protocol state machines express the legal transitions that a classifier can trigger." [uml-diagrams.org/ state-machine-diagrams.html]
The template "UML state machine diagram" for the ConceptDraw PRO diagramming and vector drawing software is included in the Rapid UML solution from the Software Development area of ConceptDraw Solution Park.
www.conceptdraw.com/ solution-park/ software-uml