Diagramming Software for designing UML Sequence Diagrams

"A help desk is a resource intended to provide the customer or end user with information and support related to a company's or institution's products and services. The purpose of a help desk is usually to troubleshoot problems or provide guidance about products such as computers, electronic equipment, food, apparel, or software. Corporations usually provide help desk support to their customers through various channels such as toll-free numbers, websites, instant messaging, or email. There are also in-house help desks designed to provide assistance to employees." [Help desk. Wikipedia]
The UML sequence diagram example "Help desk" 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.

"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.