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Diagram Format Args

Format Arguments#

By default, sequence diagrams generated by sysl only show the data type that is returned by an endpoint. You can instruct sysl to show the arguments to your endpoint in a sequence diagram.


sysl sd -o 'call-login-sequence.png' --epfmt '%(epname) %(args)' -s 'MobileApp <- Login' /assets/call.sysl -v call-login-sequence.png

See args.sysl for complete example.

Sequence Diagram

A bit more explanation is required regarding epname and args keywords that are used in the epfmt command line argument.

Display built-in attributes in appfmt and epfmt#

appfmt and epfmt (app and endpoint format respectively) can be passed to the sysl sequence and sysl integrations commands. They control how the application or endpoint name is rendered as text.

There default value is %(appname) and %(epname) respectively.

These internal attributes are:

appnameshort name of the application
epnameshort name of the endpoint
eplongnameLong quoted name of the endpoint
controlscontrols defined on your endpoint


App "Descriptive Long Application name":  Endpoint-1 "Descriptive Long name for Endpoint 1":    ...  Endpoint-2 "Descriptive Long name for Endpoint 2":    ...


epnameEndpoint-1 or Endpoint-2
eplongname"Descriptive Long name for Endpoint 1" or "Descriptive Long name for Endpoint 2"
controlsControls defined on your endpoint

You can also refer to the attributes that you added by using [] or the Collector syntax.


TODO: Add more details about controls and an example TODO: Add more details about the Collector syntax

Display custom attributes in fmt#

You can display custom attributes in epfmt or appfmt arguments in the following ways:

%(@attrib_name)use @ to refer to attrib_name
%(@attrib_name? yes_stmt | no_stmt)use the ternary operator ? to test for existence of value
%(@attrib_name=='some_value'? yes_stmt | no_stmt)compare attrib's value to some constant
%(@attrib_name=='a'? yes_stmt |; @attrib_name=='b'? | ...)nested checks

The stmt can be any of the following types:

  • plain-text: will be copied as-is to the output
  • <color red>text or %(attrib_name)</color>: use html like syntax to color the output.


appfmt="%(@status?<color red>%(appname)</color>|%(appname))" epfmt="%(@status?<color green>%(epname)</color>|%(epname))"

See attribs.sysl for complete example. Notice how appfmt and epfmt use %(@status).

Sequence Diagram