Alf — Relational Algebra at your Fingertips

Alf provides you with the relational algebra in Shell and in Ruby. It is a successful meeting between:

• A sound flavor of relational algebra borrowed from The Third Manifesto and Tutorial D;
• The pragmatism and beauty of the Ruby programming language;
• Open-Source Software development (MIT Licence)

Example

#
# What is the total weight of supplied products,     
# by city, then by product id?                    
#                                                 
(group                                            +--------+---------------------+
  (summarize (join :parts, :supplies),            | :city  | :supplying          |
    [:city, :pid],                                +--------+---------------------+
    :total => sum{ weight * qty }),               | London | +------+---------+  |
  [:pid, :total], :supplying)                     |        | | :pid | :total  |  |
                                                  |        | +------+---------+  |
                                                  |        | | P1   | 7200.00 |  |
                                                  |        | | P4   | 7000.00 |  |
                                                  |        | | P6   | 1900.00 |  |
                                                  | ...    | | ...  | ...     |  |

How to install?

Alf requires an installation of the Ruby programming language. We strongly recommend using ruby 1.9.2. If you are under windows or if you are familiar with Java, have a look at JRuby, it's simple to install and easy to use.

Then, the gem command is bundled with your Ruby installation and allows automatically installing alf and its dependencies:

[sudo] gem install alf [fastercsv] [sequel] [sqlite3 pg ...]

Where

• fastercsv is only required under ruby 1.8.7, if you plan to use .csv files
• sequel is required if you plan to connect to SQL databases
• sqlite3, pg and the like are required for connecting to a specific SQL DBMS

Then ?

• Guided Tour gives you an overview of Alf features.
• Using Alf in Shell is the reference guide for using Alf in Shell. It contains lots of examples.
• Using Alf in Ruby is the reference guide for using Alf in Ruby. It contains lots of examples as well.

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