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Memelang v5

Memelang is a concise query language for structured data, knowledge graphs, retrieval-augmented generation, and semantic data. See the Python GitHub repository.

Memes

A meme comprises key-value pairs separated by spaces and is analogous to a relational database row.

m=123 R1=A1 R2=A2 R3=A3;

M-identifier: an arbitrary integer in the form m=123, analogous to a primary key
R-relation: an alphanumeric key analogous to a database column
A-value: an integer, decimal, or string analogous to a database cell value
Non-alphanumeric A-values are CSV-style double-quoted ="John ""Jack"" Kennedy"
Memes end with a semicolon ;
Comments are prefixed with double forward slashes //

// Example memes for the Star Wars cast
m=123 actor="Mark Hamill" role="Luke Skywalker" movie="Star Wars" rating=4.5;
m=456 actor="Harrison Ford" role="Han Solo" movie="Star Wars" rating=4.6;
m=789 actor="Carrie Fisher" role=Leia movie="Star Wars" rating=4.2;

Queries

Queries are partial memes with empty parts as wildcards:

Empty A-values retrieve all values for the specified R-relation
Empty R-relations retrieve all relations for the specified A-value
Empty R-relations and A-values (=) retrieve all pairs in the meme

// Query for all movies with Mark Hamill as an actor
actor="Mark Hamill" movie=;

// Query for all relations involving Mark Hamill
="Mark Hamill";

// Query for all relations and values from all memes relating to Mark Hamill:
="Mark Hamill" =;

A-value operators:

String: = !=
Numeric: = != > >= < <=

firstName=Joe;
lastName!="David-Smith";
height>=1.6;
width<2;
weight!=150;

Comma-separated values produce an OR list:

// Query for (actor OR producer) = (Mark OR "Mark Hamill")
actor,producer=Mark,"Mark Hamill"

R-relation operators:

! negates the relation name

// Query for Mark Hamill's non-acting relations
!actor="Mark Hamill";

// Query for an actor who is not Mark Hamill
actor!="Mark Hamill";

// Query all relations excluding actor and producer for Mark Hamill
!actor,producer="Mark Hamill"

A-Joins

Open brackets R1[R2 join memes with equal R1 and R2 A-values. Open brackets need not be closed, a semicolon closes all brackets.

// Generic example
R1=A1 R2[R3 R4>A4 A5=;

// Query for all of Mark Hamill's costars
actor="Mark Hamill" movie[movie actor=;

// Query for all movies in which both Mark Hamill and Carrie Fisher act together
actor="Mark Hamill" movie[movie actor="Carrie Fisher";

// Query for anyone who is both an actor and a producer
actor[producer;

// Query for a second cousin: child's parent's cousin's child
child= parent[cousin parent[child;

// Join any A-Value from the present meme to that A-Value in another meme
R1=A1 [ R2=A2;

Joined queries return one meme with multiple m= M-identifiers. Each R=A belongs to the preceding m= meme.

m=123 actor="Mark Hamill" movie="Star Wars" m=456 movie="Star Wars" actor="Harrison Ford";

Variables

R-relations and A-values may be certain variable symbols. Variables cannot be inside quotes.

@ Last matching A‑value
% Last matching R‑relation
# Current M-identifier

// Join two different memes where R1 and R2 have the same A-value (equivalent to R1[R2)
R1= m!=# R2=@;

// Two different R-relations have the same A-value
R1= R2=@;

// The first A-value is the second R-relation
R1= @=A2;

// The first R-relation equals the second A-value
=A1 R2=%;

// The pattern is run twice (redundant)
R1=A1 %=@;

// The second A-value may be Jeff or the previous A-value
R1= R2=Jeff,@;

M-Joins

Explicit joins are controlled using m and #.

m=# present meme (implicit default)
m!=# join to a different meme
m= join to any meme (including the present)
m=^# (or ]) resets m and # to the previous meme, acts as unjoin

// Join two different memes where R1 and R2 have the same A-value (equivalent to R1[R2)
R1= m!=# R2=@;

// Join any memes (including the present one) where R1 and R2 have the same A-value
R1= m= R2=@;

// Join two different memes, unjoin, join a third meme (equivalent statements)
R1[R2] R3[R4;
R1= m!=# R2=@ m=^# R3= m!=# R4=@;

// Unjoins may be sequential (equivalent statements)
R1[R2 R3[R4]] R5=;
R1= m!=# R2=@ R3= m!=# R4=@ m=^# m=^# R5=;

// Join two different memes on R1=R2, unjoin, then join the first meme to another where R4=R5
R1= m!=# R2=@ R3= m=^# R4= m!=# R5=@;

// Query for a meta-meme, R2's A-value is R1's M-identifier
R1=A1 m= R2=#

SQL Comparisons

Memelang queries are significantly shorter and clearer than equivalent SQL queries.

actor= role="Luke Skywalker","Han Solo" rating>4;
SELECT actor FROM movies WHERE role IN ('Luke Skywalker', 'Han Solo') AND rating > 4;

producer,actor="Mark Hamill","Harrison Ford" movie[movie actor=
SELECT m1.actor, m1.movie, m2.actor FROM movies m1 JOIN movies m2 ON m1.movie = m2.movie WHERE m1.actor IN ('Mark Hamill', 'Harrison Ford') or m1.producer IN ('Mark Hamill', 'Harrison Ford');