facts-db/cl-facts/README.md

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• Hash : 69636d17
  Author : Thomas de Grivel
  Date : 2023-07-11T12:24:49
  

  README.md

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(facts:add ("Blade Runner" :is-a :movie
                           :director "Ridley Scott"
                           :actor "Harison Ford"
                           :actor "Rutger Hauer")
           ("Snow White" :is-a :movie
                         :director "William Cottrell"
                         :director "David Hand"))

(facts:add (?movie :is-a :movie
                   :title "Blade Runner"
                   :director "Ridley Scott"
                   :actor "Harrison Ford"
                   :actor "Rutger Hauer"))

(facts:add (?movie :is-a :movie
                   :title "Snow White and the Seven Dwarfs"
                   :director "William Cottrell"
                   :director "David Hand"))

(facts:rm (?movie :actor "Harison Ford"))

(with ((?s ?p ?o)
  (format t "~&~S ~S ~S~&" ?s ?p ?o))

=>
"Blade Runner" :ACTOR "Harison Ford"
"Blade Runner" :ACTOR "Rutger Hauer"
"Blade Runner" :DIRECTOR "Ridley Scott"
"Blade Runner" :IS-A :MOVIE
"Snow White" :DIRECTOR "David Hand"
"Snow White" :DIRECTOR "William Cottrell"
"Snow White" :IS-A :MOVIE

(facts:with ((?movie :is-a :movie
                     :title ?title
                     :director ?director))
  (format t "~A directed ~A~%" ?director ?title))

(with ((?s ?p ?o)
       (:not ?s :actor "Harison Ford"))
  (format t "~&~S ~S ~S~&" ?s ?p ?o))

=>
"Snow White" :DIRECTOR "David Hand"
"Snow White" :DIRECTOR "William Cottrell"
"Snow White" :IS-A :MOVIE

Source

• README.md

• facts-db/cl-facts
  =================
  
  > 1.1 The world is the totality of facts, not of things.
  >
  > --  Ludwig Wittgenstein, Tractatus Logico Philosophicus
  
  cl-facts is a small in-memory graph database for Common Lisp.
  It features :
  * a triple store based on unlabelled skip lists
  * a very simple query language (facts:with)
  * transactions using rollback functions
  * logging and replay of transactions to/from disk
  * dumping and loading the database to/from disk
  
  ---
  
  Requirements
  ------------
  
  You will need :
  * https://git.kmx.io/facts-db/cl-compare
  * https://git.kmx.io/facts-db/cl-rollback
  
  ---
  
  Usage
  -----
  
  ### FACTS:ADD &rest SPECS
  Adds facts (triples) to the database. Triples can be grouped by subject.
  
  ```common-lisp
  (facts:add ("Blade Runner" :is-a :movie
                             :director "Ridley Scott"
                             :actor "Harison Ford"
                             :actor "Rutger Hauer")
             ("Snow White" :is-a :movie
                           :director "William Cottrell"
                           :director "David Hand"))
  
  ```
  
  or either
  
  ```common-lisp
  (facts:add (?movie :is-a :movie
                     :title "Blade Runner"
                     :director "Ridley Scott"
                     :actor "Harrison Ford"
                     :actor "Rutger Hauer"))
  
  (facts:add (?movie :is-a :movie
                     :title "Snow White and the Seven Dwarfs"
                     :director "William Cottrell"
                     :director "David Hand"))
  
  ```
  
  The second version with `?movie` will generate an anonymous symbol prefixed with `movie-`.
  It is considered a more clean and efficient way to abstract identifiers.
  
  ---
  
  ### FACTS:RM &rest SPECS
  
  ```common-lisp
  (facts:rm (?movie :actor "Harison Ford"))
  
  ```
  
  ---
  
  ### FACTS:WITH SPECS &body BODY
  
  To follow Wittgenstein's view of the world, all queries get turned into
  testing the presence or absence of triples (facts).
  
  Variables are prefixed with a question mark symbol "?" and are
  wildcards, matching everything. Nested queries get their variables
  expanded, giving pattern matching abilities. For instance :
  
  ```common-lisp
  (with ((?s ?p ?o)
    (format t "~&~S ~S ~S~&" ?s ?p ?o))
  
  =>
  "Blade Runner" :ACTOR "Harison Ford"
  "Blade Runner" :ACTOR "Rutger Hauer"
  "Blade Runner" :DIRECTOR "Ridley Scott"
  "Blade Runner" :IS-A :MOVIE
  "Snow White" :DIRECTOR "David Hand"
  "Snow White" :DIRECTOR "William Cottrell"
  "Snow White" :IS-A :MOVIE
  
  ```
  
  Multiple queries on the same subject can be grouped together easily :
  
  ```common-lisp
  (facts:with ((?movie :is-a :movie
                       :title ?title
                       :director ?director))
    (format t "~A directed ~A~%" ?director ?title))
  
  ```
  
  Negative facts specifications will remove matching facts from the
  results.
  
  
  ```common-lisp
  (with ((?s ?p ?o)
         (:not ?s :actor "Harison Ford"))
    (format t "~&~S ~S ~S~&" ?s ?p ?o))
  
  =>
  "Snow White" :DIRECTOR "David Hand"
  "Snow White" :DIRECTOR "William Cottrell"
  "Snow White" :IS-A :MOVIE
  
  ```
  
  ---
  
  ### FACTS:\*DB\*
  The current facts database.
  
  ---
  
  ### FACTS:CLEAR-DB
  Clears the database from every facts.
  
  ---
  
  ### FACTS:SAVE-DB &key INTO (READABLY T)
  Dump the database facts into filespec INTO.
  
  ---
  
  ### FACTS:LOAD-DB SRC
  Load the facts from SRC into \*db\*.
  
  ---
  
  ### FACTS:WITH-TRANSACTION &body BODY
  Enclose BODY database operations into a transaction.
  
  A transaction ensures that all database operations will succeed or be
  reverted using their respective rollback functions.
  
  Transactions can be nested safely.
  
  ---
  
  TODO
  ----
  
   - binding of negation : :not resulting from another binding
   - barriers / hooks : functions that will be called when a spec is added
     or removed.
  

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