use case diagram

writing is an activity that requires not only creativity, but rather the desire, feeling and idea of ​​the text. writing can also be a hobby to describe one's emotions which can not be described with words.
earlier times, writes synonymous with paper and pencil / pen to write by hand manually. but along with the times and technological advances, can writing using electronic media. with the electronic device can connect the user with a social media that can be writing hobby into a media which we often call the "Blog". 

Blog is short for web log is a web application that resembles the form of writings (published as a post) on a public web page. These writings are often published in reverse order (most recent content first and then followed the older content), although not necessarily so. Web sites like these can usually be accessed by all Internet users according to the topics and goals of the user's blog. The following is an image workflow use cases that can show the relationship between users with media "blog" related to each other. 

In software and systems engineering, a use case is a list of steps, typically defining interactions between a role (known in UML as an "actor") and a system, to achieve a goal. The actor can be a human or an external system.

In systems engineering, use cases are used at a higher level than within software engineering, often representing missions or stakeholder goals. The detailed requirements may then be captured in SysML or as contractual statements.

A use case defines the interactions between external actors and the system under consideration to accomplish a goal. Actors must be able to make decisions, but need not be human: "An actor might be a person, a company or organization, a computer program, or a computer system — hardware, software, or both.” Actors are always stakeholders, but many stakeholders are not actors, since they "never interact directly with the system, even though they have the right to care how the system behaves.” For example, "the owners of the system, the company's board of directors, and regulatory bodies such as the Internal Revenue Service and the Department of Insurance" could all be stakeholders but are unlikely to be actors.

the picture above is a picture that shows the use case among users with blogs. there are 3 actors associated with the use case. The third actor is the user, admin and visitors. not only an actor, in the groove there are some use cases that occur as manage profile, manage posts, manatize blog, and log in immediately before starting to write a post.

1. users

as a user, we can manage profile, manage posts, and manage your own blog.

• Manage profiles is the beginning when we joined the blog. because in the profile, we can put our personal data or to share the joy, hobbies, etc.. in managing profile, we can change the existing data on the profile, or delete data in the profile.

• Manage the posting is a stage that have been targeted in a blog. we can share findings, along with pictures of the photo description of the meaning, sharing of knowledge that can be a life saver or just write the reference of the emotional expression that is being felt in the post. in managing the post, there are some use cases that can be described as, uploading stuff we want to share, modify existing posts, or delete posts that have been uploaded.

• Manatize Blog is a step in changing the blog design that we have a blog that has become an attractive design in accordance with our expectations. we can change the position of text, change the color, font size and font type that we will use in the blog. not only change the font and layout, manatize blog can also change the look of our blog with a background image of your choice according to our will.

2. Admin

The next actor associated with this flow is admin. admin are the main actors behind the scenes role in the success of a blog. admin log-in controls use case when we want to open the blog site. admin who told whether the username and password used is appropriate or not. if both are false, then the admin will send the information to the user and make sure the username and password are entered correctly. in addition, the admin is in control of all the blogs listed. 

3. Visitor

The actor who plays a role in the next use case is a visitor. visitors was actor money targeted a post in the upload. visitors who read all the contents of the blogs that have terposting and provide a rebuttal or criticism and suggestions on these postings.

Limitations of use cases include:

• Use cases are not well suited to capturing non-interaction based requirements of a system (such as algorithm or mathematical requirements) or non-functional requirements (such as platform, performance, timing, or safety-critical aspects). These are better specified declaratively elsewhere.

• Use case templates do not automatically ensure clarity. Clarity depends on the skill of the writer(s).

• For some products and systems, use cases are complex to write and to understand, for both end users and developers who are not well trained.

• As there are no fully standard definitions of use cases, each project must form its own interpretation.

• Some use case relationships, such as extends, are ambiguous in interpretation and can be difficult for stakeholders to understand.