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205 Stars 69 Forks 131 Commits 58 Opened issues


RelaX - a relational algebra calculator

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A relational algebra calculator

How to build

  • Install yarn
  • Install node
  • Clone the repo
  • Checkout the
  • Execute
    yarn install
    to install all dependencies
  • Execute
    yarn serve
    to locally run the webapp on port 8088
  • (Optional) open folder with and install the workspace recommended extensions (includes tasks)

How to Release

  • Clone the repo
  • Checkout the
  • Execute
    yarn install
    to install all dependencies
  • Use
    yarn build
    to create release build in the
  • Copy the content of your
    folder somewhere outside of the repository
  • Checkout the branch
  • Remove everything there and pase content of the former
  • Push to github (the person doing this must be an administrator of the project)


  • Contributions are highly appreciated
  • Please create a pull request for the development branch

Add a new Language

  • Open
    as csv with e.g. libreoffice (use ',' as delimiter and '"' as string marker)
  • Every column represents a language, every row a value
  • Create a new column (use the country code as first row/header cell)
  • Insert a string for every language key there is (pay attention to {{variables}} as they must stay untouched)
  • When finished, execute the script
    which generates the json files based on the csv
  • In
    add an import for this file as well as initializing it in the i18n init function (see other languages for examples)
  • Add a new dropdown entry to
  • Test your language
  • Create a pull request to the development branch


Data Sources

There are two ways to provide a group of tables:

  • static groups: the groups and tables are loaded from a text file stored on the server
  • github gist: the groups and tables are loaded from a github gits via its unique id

In the group's description markdown code can be used but javascript code will be removed for security reasons.

Static Groups

Static groups are loaded from the file

. In this file multiple groups can be declared in the following text format.

A group starts with the group header:

    group:sample group
    description:this is the description

Every keyword can be followed by either a colon and a single line of content terminated with a line break or the content is surrounded with '[[' and ']]' if the content spans multiple lines.

    group:sample group
    description[[this is the description
        that spans multiple lines]]

Headers can also be provided for different languages e.g.

[email protected]:...

After the group header the tables are defined using the variable assignment syntax. The name of the variable is used for the tables name and the assigned RA-expression defines its content. Every valid RA-expression can be used if the only relations used are defined in that group. The qualifier of each column is its tables name and is automatically added at runtime.

    group:sample group
    description:this is the description

A = {a, b
    1, 2
    3, 4
B = {a, c, d
    1, 'test', 1970-01-01
    3, 'test2', null
    42, 'test3', null
C = A x B

Github Gist

The program can load groups from a gist. This allows any user to use their own tables and share them with others.

The format to define a group in the gist ist the same format as for the static group definition.

The data can be loaded by adding the git's id to the query string. If you call the application with the query string

, it tries to load additional groups from the gits with the id ac267b9cc810ac5f20e2.

So a user could publish a url like
to share the group with other users.


  • Spanish translation was contributed by
  • Korean translation was contributed by

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