Rule example formatting

[VladimirAlexiev]

https://w3c.github.io/N3/spec/#example-23

Is this really a good way to format a rule?

{ :weather a :Raining
} => {
  :weather a :Cloudy
} . 

Maybe change to this:

{
  :weather a :Raining
} => {
  :weather a :Cloudy
} . 

Or this

{ :weather a :Raining }
 => 
{ :weather a :Cloudy } . 

Sorry for the nitpicking, but many people (me included) learn by copy-paste :-)

[TallTed]

fwiw, I prefer the latter.

[william-vw]

I'd opt to avoid discussions on personal formatting preferences unless the chosen formatting is misleading (see my comment on PR https://github.com/w3c/N3/pull/147) or, of course, the discussion is about best practices (which we haven't done).

[VladimirAlexiev]

Formatting Rules

N3 is a free-form language (whitespace doesn't matter). However, by following some formatting rules in your N3 files, you can make them easier to read by humans, and ensure consistency.

(By "elements" below we mean RDF terms or triple patterns).

• Don't have any spaces at end of line, because these are not visible
• Surround punctuation (brackets, parentheses, commas, semicolons, dots) with spaces, to more clearly separate them from elements

  # OK
  :LoisLane :believes { :Superman :can :fly } .
  # NOK
  :LoisLane :believes {:Superman :can :fly}.

• If there are a few elements within brackets/parentheses, then open and close the brackets on the same line

  # OK
  { :weather a :Raining }
  =>
  { :weather a :Cloudy  } .
  # NOK
  { :weather a :Raining
  } => {
  :weather a :Cloudy
  } . 

• If there are many elements within brackets/parentheses, then put the open and close brackets, and each element on separate lines. Use the same indentation for the elements

  # OK
  {
  :race :finalists ?finalists .
  ?finalists list:iterate ( ?i ?finalist ) .
  ( ?i ". " ?finalist "<br />" ) string:concatenation ?entry
  } => {
  :race :entries ?entry 
  }
  # NOK
  { :race :finalists ?finalists .
  ?finalists list:iterate ( ?i ?finalist ) .
  ( ?i ". " ?finalist "<br />" ) string:concatenation ?entry }
  => { :race :entries ?entry }

• If the elements of a complex list are placed on separate lines, then indent them the same

  # OK
  {
  ?hero a :SuperHero .
  (
  ?enemy
  { ?enemy :enemyOf ?hero ; :defeated true }
  ?enemies
  ) log:collectAllIn _:t .
  }
  # NOK
  {
  ?hero a :SuperHero .
  (?enemy
  {
  ?enemy :enemyOf ?hero ;
    :defeated true .
  }
  ?enemies) log:collectAllIn _:t .
  }

• Align punctuation to better show the "parallelism" of elements where appropriate; in particular the => (log:implies) relation

  # OK
  { ?slinger a :WebSlinger } => { ?slinger :locomotion :flying } .
  { ?heli    a :Helicopter } => { ?heli    :locomotion :flying } .
  # NOK
  { ?slinger a :WebSlinger } => { ?slinger :locomotion :flying } .
  { ?heli a :Helicopter } => { ?heli :locomotion :flying  } .

• You can put the closing bracket of the premise and the opening bracket of the conclusion on the same line: } => {, or keep them on separate lines:

  # OK
  {
  <http://example.com> log:content ?content .
  (?content "<title>(.*?)</title>") string:scrape ?title .
  } => {
  <http://example.com> :title ?title
  } .
  # OK
  {
  <http://example.com> log:content ?content .
  (?content "<title>(.*?)</title>") string:scrape ?title .
  } 
  => 
  {<http://example.com> :title ?title} .

• You can put a dot after the last triple pattern of a quoted graph (before the closing bracket), but it is preferred not to (since it is redundant)

  # ALLOWED
  { ?slinger a :WebSlinger } => { ?slinger :locomotion :flying . } 
  # PREFERRED
  { ?slinger a :WebSlinger } => { ?slinger :locomotion :flying } 

• You can put an "empty semicolon" at the end of a property-object list, and put the dot on a separate line. In this way you can sort or add to the property-object list, without worrying you'll break the syntax

  # OK
  :mary-jane
  :knowsIdentityOf :spiderman ; 
  :keepsSecrets    true ;
  .

[VladimirAlexiev]

@william-vw , @TallTed please comment on the principles above.

• Once agreed, I'll rework and resubmit https://github.com/w3c/N3/pull/147.
• Can we also include them in the spec?

[TallTed]

@VladimirAlexiev — Looks good to me! It would be best to make plain that the whitespace formatting described above is meant for human-focused educational examples, optimally with a single click to see a "machine optimized" version without the extra whitespace as might be found in actual deployment.