Use-case

This library aims to solve problems in documenting large javascript software. It will enable software authors to document UML Use-cases while implementing their definitions before detailing them later with use-case relationships and activity workflows with Apptivity.

Installation

Use-case is packaged by npm. Source can be found in github repository.

npm install use-case --save

Usage

To better understand how to use this library, we are going to run through a quick start guide.

Quick Start Guide

1. Translate User Stories into Use-case manifest using use-case definition objects.

The following are the User Stories gathered from the My Auth Website app.

1. As a visitor, I can visit the public area of the system.
2. As a visitor or guest, I can login and change my role into admin.
3. As an admin, I can logout and change my role back into visitor.
4. As an admin, I can update my profile in the users control panel.

Below is the sample translation of User Stories into Use-cases using use-case definition object.

var USECASE = require("use-case");
USECASE.system("My Auth Website").
        as("guest").
            emulating("visitor").
        as("visitor").
            accessing("public area").
                can("visit web pages").
                can("login").
                    soThat("I can change my role into admin.",
                            "Or, change role depending on what is assigned after server authentication.").
        as("admin").
            accessing("private area").
                can("logout").
                    soThat("I can be a visitor/guest again.").
            accessing("users control")
                can("update my profile").
                    soThat("I can customize my something-whatever.");

2. Further detail the Use-cases and Activities.

Use-cases can be defined further into subjects namespace and specific use-case. When usecases and it's relationships are all defined, their equivalent activities should also be defined to complete the whole Use-case definitions.

var myApp = USECASE.system("My auth website");

// don't worry, system, subject, usecase, and actors are case-insensitive
myApp.subject("Public area").
        usecase("navigate").
        usecase("login").
            extend("get auth info"),
            include("authenticate");

// here you're going to define activity of the defined usecases
myApp.activity("public area", "navigate").
        input("choosePage").
        action("navigate");

myApp.activity("public area", "login").
        action("validate");

myApp.activity("public area", "get auth info").
        action("showLoginPage").
        input("authData");

myApp.activity("public area", "authenticate").
        action("authenticate").
            handler(function (input) {
                console.log("authenticating to backend? ", input);
                return client.authToBackend(input);
            }).
        action("setAuthToken");

The example above is for demo purposes only. That is why, Activity definitions and implementations were defined in one script file. The best practice in coding Apptivity is to split definitions (like the action("setAuthToken"); line above.) from implementations using Apptivity.task(name:String, runner:Function) method in a separate implementation script file.

3. Run a completely defined Use-case.

Complete Use-cases are use-cases having complete definitions of Actor, Subject, optional Usecase relationships, and Activity within the System. Use-cases cannot run using the code below if it is not completely defined.

USECASE("My auth website://guest@public area/visit web pages").
    on("state-change",
        function (process, state) {
            console.log("current state ", state.toJS());
        }).
    on("prompt",
        function (process, action, initialInput) {
            console.log("what to do with prompts? ", action, initialInput);
            process.answer({ value: "my answer to this prompt." });
        }).
    run({ page: "/about_us.html" }).
        then(function (result) {
            console.log("showing about us? ", result);
            return result;
        },
        function (error) {
            console.log('yes! an error!', error);
            return Promise.reject(error);
        });

API

Main USECASE Function and method properties.

The following are the methods defined in USECASE object found in the examples above.

USECASE(url:String):Process

Creates an instance of a Use-case Process using system, actor, subject and usecase info extracted from the url parameter.

url string syntax is [system-name]://[actor]@[subject]/[usecase].

USECASE.system(name:String, [contextCallback:Function]):SystemDefinition

Defines a system named after its name parameter. If system do not exist, the method will create one. Optional contextCallback parameter is used to access concurrent system definitions, preprocess, and configurations inside the callback function.

Example of organizing modules in CommonJS

lib/my-website/definitions.js

const USECASE = require("use-case");

USECASE.system("my-website",
            require("./definition.js"));

// ... and other definitions

lib/my-website/route/guest.js

module.exports = function(system) {

system.as("guest").
            emulating("visitor");
};

USECASE.subscribe(filter:String, event:String|RegExp, handler:Function):Function

Subscribes a Process event filtered by filter parameter.

filter parameter syntax is: "system=[system-name], actor=[actor-name], subject=[subject-name], usecase|use-case=[use-case-name]". All comma-separated "name=value" pairs are optional. If filter string is malformed, event subscription matches all running process.

Available events are the following:

process-create (process:Process)

• "process-create" event is dispatched after Process is instantiated.

process-destroy (process:Process)

• "process-destroy" event is dispatched before Process is destroyed undergoing destruction phase.

process-start (process:Process, url:String, input:Mixed)

• "process-start" event is dispatched before use-case process starts running.

process-end (process:Process, url:String, output:Mixed)

• "process-end" event is dispatched after use-case process has finished running.

state-change (process:Process, state:Immutable)

• "state-change" event is dispatched when use-case process changes state data. State data are Immutable objects based from published events of a running apptivity workflow session.

  The immutable state data object has the following properties:

var stateData = Immutable.fromJS({
    url: "[system-name]://[actor]@[subject]/[usecase]",
    activity: "[system-name]://[subject]/[usecase]",
    action: "[apptivity-action-name]",
    state: "[apptivity-fsm-state]",
    input: { ... [apptivity action input] },
    data: { ... [apptivity action output] }
});

prompt (process:Process, action:String, initialInput:Mixed)

• "prompt" event is dispatched when currently running workflow session is waiting for an input. It can be answered by calling process.answer(myInput) or manually calling workflowSession.answer(myInput) if workflow session is accessible.

answer (process:Process, action:String, newInput:Mixed)

• "answer" event is dispatched when workflow session input has been answered.

USECASE.activity(activityName:String):Activity

Defines an Activity used as option parameters of condition action or sub-processe parameters of fork action.

This method is an alias of apptivity.activity(name:String) .

System Definition Object

systemDefinition.as(actorName:String, [contextCallback:Function]):ActorDefinition

Creates an Actor if specified actorName actor do not exist and returns an actorDefinition object for chain-calling actor definitions.

If contextCallback optional parameter is provided, it will be called with ActorDefinition object of actorName for further actor definition. This will come in handy when actor definitions are required from other module files.

contextCallback will be called with actorDefinition object as in:

contextCallback(actorDefinition:ActorDefinition)

Example of using contextCallback to split "guest" actor definitions from "system".

file: /my-auth-website/index.js

require("use-case").
    system("My Auth Website").
        as("guest", require("./actor/guest.js"));

file: /my-auth-website/actor/guest.js

function defineActor(asGuest) {
    asGuest.
        accessing("public area").
            can("visit web pages").
                soThat("I will have an overview of the system.").

            can("login").
                soThat("I can change role and further control the system");
};

module.exports = defineActor;

systemDefinition.subject(subjectName:String, [contextCallback:Function]):SubjectDefinition

Creates Subject namespace if specified subjectName subject do not exist and returns subjectDefinition object for chain-calling subject definitions.

contextCallback will be called with subjectDefinition object as in:

contextCallback(subjectDefinition:SubjectDefinition)

systemDefinition.activity(subject:String, usecase:String, [contextCallback:Function]):ActivityDefinition

Creates Subject and Use-case specified by subject and usecase parameters if they do not exist and returns Apptivity workflow definition object to further detail the Use-case activity.

contextCallback will be called with workflowActivity, subject and usecase as in:

contextCallback(workflowActivity:Activity, subject:String, usecase:String)

Actor Definition Object

actorDefinition.emulating(actor:String, [actor:String, ...]):ActorDefinition

Generalize Actor by inheriting Use-cases specified by actor parameters.

actorDefinition.accessing(subjectName:String, [contextCallback:Function]):ActorDefinition

Creates Subject namespace if specified subjectName subject do not exist and changes the default Subject context specified by subjectName parameter for the next Use-case chain-definitions. It returns actorDefinition object for chain-calling actor definitions.

contextCallback will be called with actorDefinition object as in:

contextCallback(actorDefinition:ActorDefinition)

actorDefinition.can(usecase:String, [contextCallback:Function]):ActorDefinition

Creates Use-case within the default Subject context if specified usecase do not exist and returns actorDefinition object for chain-calling actor or use-case definitions.

Warning! calling this method without defining default Subject context with actorDefinition.accessing(subjectName) will result in a fatal error

contextCallback will be called with actorDefinition object as in:

contextCallback(actorDefinition:ActorDefinition)

actorDefinition.soThat([description:String, ...]]):ActorDefinition

Describes the currently defined Use-case with description parameters for documentation purposes.

Warning! calling this method without defining default Subject and Use-case context with actorDefinition.accessing(subjectName) and actorDefinition.can(usecase) will result in a fatal error

Subject Definition Object

subjectDefinition.usecase(usecase:String, [contextCallback:Function]):SubjectDefinition

subjectDefinition.extend([subject:String,] usecase:String, [condition:Function]]):SubjectDefinition

subjectDefinition.include([subject:String,] usecase:String):SubjectDefinition

subjectDefinition.generalize([subject:String,] usecase:String):SubjectDefinition

Process Object

process.info(propertyName:String):Mixed

process.currentState():Object|null

process.run(data:Mixed):Promise

process.runOnce(data:Mixed):Promise

process.reset():Process

process.current():Process

process.previous():Process

process.next():Process

process.subscribe(event:String|RegExp, handler:Function):Function

process.answer(input:Mixed):Process

process.destroy():Process

(To be continued... very sleepy!)

License

MIT