Dev:Use cases

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railML®
XML Railway exchange format
http://railml.org
Latest release: 2.3 (March 9th, 2016)
Subschemas
Use cases
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Use cases

In this page you learn what is a use case, how to contribute to writing good railML®-Use Cases and where to find them in this wiki.

While the emphasis of the railML®-wiki lies in documenting single elements in a bottom-up approach, we also try to help users to capture the concepts of railML® via examples and use cases in a top down approach.

What is a use case?

A use case can be defined as a single task, performed by the end user of a system, that has some useful outcome*. It is described as a list of steps (actions or events) to achieve this outcome.

A use case in terms of railML® is an application of data exchange between at least two IT systems in the railway domain, where railML® can be used as a format and language for the data to be exchanged. The aim of the use case description is to formulate requirements on the technical implementation of the data exchange.

What distinguishes a use case from an example is, that examples will typically consist of pieces of railML®-code, whereas use cases will typically be formulated in natural language or Unified Modelling Language (UML). Examples are solutions to use cases.

Use case's table of contents

As a single use case refers to certain subschema, they are listed along this line:

How to interpret the status

  Status Description participation
   
railML® community
reporting party
railML® scheme coordinator
railML® governance board
railML® scheme development group
pre development
planned the use case is planned, but there is no draft available by now; usually there will be no article about this use case in the wiki; Sometimes some basic ideas will be published ×
draft a user has submitted a draft. Usually there will exist an article about the use case where you find the draft
consolidated the draft has been reviewed and accepted by the scheme coordinator × × ×
development phase
requirements the development phase begins with an assessment, if and how the railML® schema has to be refined as to depict the use case × ×
model the requirements of this use case have been implemented into the currant railML® schema ×
finished the use case has been completely implemented, documented and released ×
postponed if an unfinished use case is not being barried further for several months, it will be listed as postponed
×=participates — ☒=is responsible

What makes a good use case?

A good use case should be complete, comprehensible and practically relevant. Ideally, it should be perceivable by the public (A problem that can be understood by and occur to everybody is more illustrative than one that only occurs to a small subgroup of users). Finally, the use case should be objective in the sense that it is not biased to the requirements or solutions of a certain organization or company.

Structure

Each use case is assigned to a subschema. The article name should follow the paradigm <subschema>:UC:<use case>, e.g. IS:UC:Timetabling.

In railML®, use cases are usually presented with the following structure (which, too, can be seen in the example of IS:UC:Timetabling):

  • Head/Title
  • Description: A sketch of the task, the necessary steps and the requirements in general.
It is important to note, to which railML® versions a use case or certain aspects of it apply, as use cases will develop further with the development of railML®.
  • Data flows and interfaces
  • Interference with other railML® schemas
  • Characterizing Data
    • How often do the data change (update)?
    • How big are the data fragments to be exchanged (complexity)
    • Which views are represented by the data (focus)?
    • Which specific timetable data do you expect to receive/send (elements)?
Template

If you start a new use case description you can copy this copy template to support a correct structure. To get an impression how to employ the templates of this list see Dev:Use case example.

{{UseCase|<subschema>|<version>|title=}}
{{UC title}}
{{UC description}}
{{UC flows}}
{{UC interference}}
{{UC data}}
{{UC update}}
{{UC complexity}}
{{UC focus}}
{{UC elements}}

How to contribute a use case

  1. Please, get into contact with the coordinator of the respective subschema before you start writing a use case. Feel free to start an article in your userspace at your own risk of doing obsolete work.
  2. Develop the use case according to the mentioned criteria (especially #structure and #What makes a good use case?).
  3. Let the subschema coordinator review the article.
  4. The subschema coordinator will take care of publishing the article. He will version the use case and match it with the railML®-versions to which it applies — both the use case and railML® will evolve in the course of time. Finally, the article will be entered into the use case collection of the respective subschema, as in #Lists.

References