Class: OpenWFE::Extras::CsvTable

A ‘CsvTable’ is called a ‘decision table’ in OpenWFEja (the initial Java implementation of OpenWFE).

A csv table is a description of a set of rules as a CSV (comma separated values) file. Such a file can be edited / generated by a spreadsheet (Excel, Google spreadsheets, Gnumeric, …)

The following CSV file

    in:topic,in:region,out:team_member
    sports,europe,Alice
    sports,,Bob
    finance,america,Charly
    finance,europe,Donald
    finance,,Ernest
    politics,asia,Fujio
    politics,america,Gilbert
    politics,,Henry
    ,,Zach

embodies a rule for distributing items (piece of news) labelled with a topic and a region to various members of a team. For example, all news about finance from Europe are to be routed to Donald.

Evaluation occurs row by row. The "in out" row states which field is considered at input and which are to be modified if the "ins" do match.

The default behaviour is to change the value of the "outs" if all the "ins" match and then terminate. An empty "in" cell means "matches any".

Enough words, some code :

    table = CsvTable.new("""
        in:topic,in:region,out:team_member
        sports,europe,Alice
        sports,,Bob
        finance,america,Charly
        finance,europe,Donald
        finance,,Ernest
        politics,asia,Fujio
        politics,america,Gilbert
        politics,,Henry
        ,,Zach
    """)

    h = {}
    h["topic"] = "politics"

    table.transform(h)

    puts h["team_member"]
        # will yield "Henry" who takes care of all the politics stuff,
        # except for Asia and America

’>’, ’>=’, ’<’ and ’<=’ can be put in front of individual cell values :

    table = CsvTable.new("""
        ,
        in:fx, out:fy
        ,
        >100,a
        >=10,b
        ,c
    """)

    h = { 'fx' => '10' }
    table.transform(h)

    require 'pp'; pp h
        # will yield { 'fx' => '10', 'fy' => 'b' }

Such comparisons are done after the elements are transformed to float numbers. By default, non-numeric arguments will get compared as Strings.

Ruby ranges are also accepted in cells.

    in:f0,out:result
    ,
    0..32,low
    33..66,medium
    67..100,high

will set the field ‘result’ to ‘low’ for f0 => 24

Disclaimer : the decision / CSV table system is no replacement for full rule engines with forward and backward chaining, RETE implementation and the like…

Options :

You can put options on their own in a cell BEFORE the line containing "in:xxx" and "out:yyy" (ins and outs).

Currently, two options are supported, "ignorecase" and "through".

"ignorecase", if found by the CsvTable will make any match (in the "in" columns) case unsensitive.
"through", will make sure that EVERY row is evaluated and potentially applied. The default behaviour (without "through"), is to stop the evaluation after applying the results of the first matching row.
"accumulate", behaves as with "through" set but instead of overriding values each time a match is found, will gather them in an array.
```
  accumulate
  in:f0,out:result
  ,
  ,normal
  >10,large
  >100,xl
```
will yield { result => [ ‘normal’, ‘large’ ]} for f0 => 56

CSV Tables are available to workflows as CsvParticipant.

Classes and Modules

Class OpenWFE::Extras::CsvTable::Header

Attributes

 accumulate
 first_match
 header
 ignore_case
 rows

Public Class methods

new(csv_data)

The constructor for CsvTable, you can pass a String, an Array (of arrays), a File object. The CSV parser coming with Ruby will take care of it and a CsvTable instance will be built.

Methods

Classes and Modules

Attributes

Public Class methods

Public Instance methods

Protected Instance methods