Official Site of Plain Sequence Chart is https://github.com/henryscala/plain_sequence_chart
PSC, or Plain Sequence Chart, is a tool to generate MSC , or Message Sequence Chart, in plain text format via commands.
I developed a skeleton of PSC years ago before I even knew github. Recently, I added new features to it and put it opensourced in github.
MSC is widely used in software development. There're plenty of tools to draw MSC. Followed a list of them.
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umlet is a light weight UML chart drawing tool. MSC is able to be drawn via it manually. There's also way to generate ALL-INE-ONE MSC via sequence of commands. I didn't find this way before I wrote PSC. If I knew this way in advance, I may not choose to implement PSC.
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js-sequence-diagrams turns commands into UML sequence diagrams. It is actually what I want to implement in PSC. The good thing is it runs in browser, which is very easy to launch. However, for the time being, it does not support to output diagrams to plain text format.
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asciiflow is able to draw plain text diagrams and it also runs in browser, but we have to draw the diagrams manually. We cannot generate charts via commands.
umlet, js-sequence-diagrams and asciiflow are all very good softwares. If you find that they fulfill your requirement, go to them without hesitation. I'd not implement PSC years ago if I knew these tools. PSC has the limitation that you can only run it in python(3.x) interpreter. I guess it is not a problem if you are a programmer. If you tolerate this limitation, it also has some features that other tools does not support, yet. I list some of them.
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It generates MSC in plain text format which is easy to be presented and carried.
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It supports parallel messages. It means messages are able to be sent between different instances(processes) in parallel, not necessarily in sequence.
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It supports abbreviated message names or instance names so as to shorten the width of generated chart.
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Process
In MSC, messages go between entities, or instances. I name the entities or instances as processes.
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Message
I think it is self-explanatory. Sometimes it is also referted to as primitive.
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State
It represents a process's status at a specific time. It can also be named as note or annotation.
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Alias
Give another name for messages or processes.
Currently following commands are supported. Command names and arguments are separated by spaces. A new line character stands for the end of commands. If a line starts with "#", it is a comment line.
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SND fromProcess toProcess message
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RCV toProcess fromProcess message
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STATE process stateName
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PROC a-list-of-process-names
This command is not mandatory. If you want to control the sequence of processes appeared in the generated chart, you may need it.
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ALIAS shortName longName
Parallel commands must locate in single line and separated by a "|" character.
Get PSC:
git clone https://github.com/henryscala/plain_sequence_chart.git
or
In your favorite shell only if it can run python(3.x), run "seqChart.py". Use input redirection operator "<" to specify input command file. Use output redirection operator ">" to specify to which file to generate the chart, otherwise the chart goes to standard output.
# python seqChart.py < inputFilePath > outputFilePath
Followed 2 examples.
###Basic Commands
In this example, there's only one command on each line. Get your hand wet and get a general idea of PSC. PROC, SND, RCV and STATE commands are concerned.
Input Commands:
#specify the sequence of processes
PROC ALICE BOB CATHERINE DANIEL
#messages between ALICE and BOB
SND ALICE BOB INVITE
RCV ALICE BOB 200
#messages between CATHERINE and DANIEL
SND CATHERINE DANIEL INVITE
RCV CATHERINE DANIEL 200
#messages between ALICE and DANIEL
SND ALICE DANIEL ACK
#set state of ALICE
STATE ALICE MID_SESSION
STATE DANIEL MID_SESSION
SND ALICE DANIEL BYE
RCV ALICE DANIEL 200
Output Chart:
|-----| |---| |---------| |------|
|ALICE| |BOB| |CATHERINE| |DANIEL|
|-----| |---| |---------| |------|
| | | |
-----INVITE----> | |
| | | |
<-----200------- | |
| | | |
| | -----INVITE---->
| | | |
| | <-----200-------
| | | |
---------------------ACK--------------------->
| | | |
(~~~~~~~~~~~) | | |
(MID_SESSION) | | |
(~~~~~~~~~~~) | | |
| | | |
| | | (~~~~~~~~~~~)
| | | (MID_SESSION)
| | | (~~~~~~~~~~~)
| | | |
---------------------BYE--------------------->
| | | |
<--------------------200----------------------
###Parallel Commands
In this example, there're parallel commands used separated by "|". Compare the differences with the first example(The two INVITEs are in the same line). PROC, SND, RCV, ALIAS and STATE commands are concerned.
Input Commands:
#specify alias first
ALIAS CAT CATHERINE
#specify the sequence of processes
PROC ALICE BOB CATHERINE DANIEL
#messages between ALICE and BOB | #messages between CATHERINE and DANIEL
SND ALICE BOB INVITE | SND CATHERINE DANIEL INVITE
RCV ALICE BOB 200 | RCV CATHERINE DANIEL 200
#messages between ALICE and DANIEL
SND ALICE DANIEL ACK
#set state of ALICE
STATE ALICE MID_SESSION
STATE DANIEL MID_SESSION
SND ALICE DANIEL BYE
RCV ALICE DANIEL 200
Output Chart:
CAT = CATHERINE
|-----| |---| |---| |------|
|ALICE| |BOB| |CAT| |DANIEL|
|-----| |---| |---| |------|
| | | |
-----INVITE----> -----INVITE---->
| | | |
<-----200------- <-----200-------
| | | |
---------------------ACK--------------------->
| | | |
(~~~~~~~~~~~) | | |
(MID_SESSION) | | |
(~~~~~~~~~~~) | | |
| | | |
| | | (~~~~~~~~~~~)
| | | (MID_SESSION)
| | | (~~~~~~~~~~~)
| | | |
---------------------BYE--------------------->
| | | |
<--------------------200----------------------
PSC is a opensourced software without any guarantee, and it may destroy the planet. It is up to you to determine whether use it or not. If you like and trust it, feel free to use it.