Ruby API for parsing and generating ASC X12 EDI transactions
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Stupidedi is a high-quality library for parsing, generating, validating, and manipulating ASC X12 EDI documents. Very roughly, it's jQuery for EDI.

For those unfamiliar with ASC X12 EDI, it is a data format used to encode common business documents like purchase orders, delivery notices, and health care claims. It is similar to XML in some ways, but precedes it by about 15 years; so if you think XML sucks, you will love to hate EDI.

What problem does it solve?

Transaction set specifications can be enormous, boring, and vague. Trading partners can demand strict adherence (often to their own unique interpretation of the specification) of the documents you generate. However, documents they generate themselves are often non-standard and require flexibility to parse them.

Stupidedi enables you to encode these transaction set specifications directly in Ruby. From these specifications, it will generate a parser to read incoming messages and a DSL to generate outgoing messages. This approach has a huge advantage over writing a parser from scratch, which can be error-prone and difficult to change.

Significant thought was put into the design of the library. Some of the features are described here.

Robust tokenization and parsing

Delimiters, line breaks, and out-of-band data between interchanges are handled correctly. While many trading partners follow common conventions, it only takes one unexpected deviation, like swapping the ":" and "~" delimiters, to render a hand-written parser broken.

Stupidedi handles many edge cases that can only be anticipated by reading carefully between the lines of the X12 documentation.

Instant feedback on error conditions

When generating EDI documents, validation is performed incrementally on each segment. This means the instant your client code violates the specification, an exception is thrown with a meaningful stack trace. Other libraries only perform validation after the entire document has been generated, while some don't perform validation at all.

Stupidedi performs extensive validation and ensures well-formedness. See the human readable documentation in doc/ for more details.

Encourages readable client code

Unlike other libraries, generating documents doesn't involve naming obscure identifiers from the specification (like C001, DE522 or LOOP2000), for elements of the grammar that don't actually appear in the output.

Like HAML or Builder::XmlMarkup, the DSL for generating documents closely matches terminology from the problem domain. You can see in the example below that code looks very similar to an EDI document. This makes it easy to understand, assuming a reasonable familiarity with EDI.

Efficient parsing and traversing

The parser is designed using immutable data structures, making it thread-safe for runtimes that can utilize multiple cores. While in certain cases, immutability places higher demand on garbage collection, this has been mitigated with careful optimization. Input is streamed incrementally, so large files aren't read into memory all at once.


segments 1.9.3 1.9.2 rbx-head jruby-1.6.6
1680 2107.90 2007.17 503.14 317.52
3360 2461.54 2420.75 731.71 477.07
6720 2677.29 2620.90 950.63 685.15
13440 2699.88 2663.50 1071.00 897.50
26880 2558.54 2510.51 1124.50 1112.67
53760 2254.94 2164.16 1039.81 1292.62

These benchmarks aren't scientific by any means. They were performed on a MacBook Pro, 2.2GHz Core i7 with 8GB RAM by reading the X222-HC837 fixture data files, in serial. The results show the parser runtime is O(n), linear in the size of the input, but the drop in throughput at 13K+ segments is likely due to memory allocation. The steady increase in throughput on JRuby and Rubinus is probably attributable optimizations performed by the JIT compiler.

Lastly, these results should approximate the performance of document generation with BuilderDSL, except BuilderDSL API should have less overhead, as it skips the tokenizer. On the other hand, BuilderDSL frequently queries the call stack to track provenance of elements in the parse tree. In common real-world use, custom application logic and database access are going to bottleneck performance, rather than Stupidedi.

Helps developers gain familiarity

Why not a commercial translator?

Commercial EDI translators solve a different set of problems. Many focus on translating between EDI and another data format, like XML, CSV, or a relational database. This isn't particularly productive, as you still have to unserialize the data to do anything with it.

What doesn't it solve?

It isn't a translator. It doesn't have bells and whistles, like the commercial EDI translators have, so it...

  • Doesn't convert to/from XML, CSV, etc
  • Doesn't transmit or receive files
  • Doesn't do encryption
  • Doesn't connect to your database
  • Doesn't queue messages for delivery or receipt
  • Doesn't generate acknowledgements
  • Doesn't have a graphical interface

These features are orthogonal to the problem Stupidedi aims to solve, but they can certainly be implemented with other code taking advantage of Stupidedi.

Alternative libraries

Stupidedi is an opinionated library, and maybe you don't agree with it. Here are a few alternative libraries:


In addition to these breif examples, see sample code in the notes directory and the human-readable Markdown documentation in doc.


Pretty print the syntax tree

$ ./bin/edi-pp spec/fixtures/X222-HC837/1-good.txt
        TableVal[Table 3 - Summary](
          SegmentVal[SE: Transaction Set Trailer](
            Nn.value[  E96: Number of Included Segments](45),
            AN.value[ E329: Transaction Set Control Number](0021)))), 
      SegmentVal[GE: Functional Group Trailer](
        Nn.value[  E97: Number of Transaction Sets Included](1),
        Nn.value[  E28: Group Control Number](1))), 
    SegmentVal[IEA: Interchange Control Trailer](
      Nn.value[  I16: Number of Included Functional Groups](1),
      Nn.value[  I12: Interchange Control Number](905))))
49 segments
49 segments
0.140 seconds

Perform validation on a file

$ ./bin/edi-ed spec/fixtures/X222-HC837/1-bad.txt
[AK905(file spec/fixtures/X222-HC837/1-bad.txt,
       line 16, column 4, is not an allowed value,
       ID.value[ E479: Functional Identifier Code](XX)),
 IK304(file spec/fixtures/X222-HC837/1-bad.txt,
       line 33, column 1,
       missing N4 segment, NM1),
 IK304(file spec/fixtures/X222-HC837/1-bad.txt,
       line 35, column 1,
       missing N4 segment, NM1)]
46 segments
0.177 seconds

Generating, Writing

require "stupidedi"

# You can customize this to delegate to your own grammar definitions, if needed.
config = Stupidedi::Config.default

b =

# These methods perform error checking: number of elements, element types, min/max
# length requirements, conditionally required elements, valid segments, number of
# segment occurrences, number of loop occurrences, etc.
b.ISA("00", "", "00", "",
      "ZZ", "SUBMITTER ID",
      "ZZ", "RECEIVER ID",
      "990531", "1230", nil, "00501", "123456789", "1", "T", nil)

# The API tracks the current position in the specification (e.g., the current loop,
# table, etc) to ensure well-formedness as each segment is generated.
b.GS("HC", "SENDER ID", "RECEIVER ID", "19990531", "1230", "1", "X", "005010X222")

# The `b.default` value can be used to generate the appropriate value if it can
# be unambigously inferred from the grammar.
b.ST("837", "1234", b.default)
  # You can use string representations of data or standard Ruby data types, like Time.
  b.BHT("0019", "00", "X"*30, "19990531",, "CH")
  b.NM1(b.default, "1", "PREMIER BILLING SERVICE", "", "", "", "", "46", "12EEER000TY")
  b.PER("IC", "JERRY THE CLOWN", "TE", "3056660000")

  b.NM1("40", "2", "REPRICER JONES", "", "", "", "", "46", "66783JJT")
    b.HL("1", "", "20", "1")

  b.NM1("85", "2", "PREMIER BILLING SERVICE", "", "", "", "", "XX", "123234560")
    b.N3("1234 SEAWAY ST")
    b.N4("MIAMI", "FL", "331111234")
    b.REF("EI", "123667894")
    b.PER("IC", b.blank, "TE", "3056661111")

  b.NM1("87", "2")
    b.N3("2345 OCEAN BLVD")
    b.N4("MIAMI", "FL", "33111")

b.HL("2", "1", "22", "0")
  b.SBR("S", "18", "", "", "12", "", "", "", "MB")

  b.NM1("IL", "1", "BACON", "KEVIN", "", "", "", "MI", "222334444")
    b.N3("236 N MAIN ST")
    b.N4("MIAMI", "FL", "33413")
    b.DMG("D8", "19431022", "F")

b.machine.zipper.tap do |z|
  # The :component, and :repitition parameters can also be specified as elements
  # of the ISA segment, at `b.ISA(...)` above. When generating a document from
  # scratch, :segment and :element must be specified -- if you've parsed the doc
  # from a file, these params will default to whatever was used in the file, or
  # you can override them here.
  separators =    => "~\n",
                                        :element    => "*",
                                        :component  => ":",
                                        :repetition => "^")

  # You can also serialize any subtree within the document (e.g., everything inside
  # some ST..SE transaction set, or a single loop.
  w =, separators)

Reading, Traversing

require "stupidedi"

config = Stupidedi::Config.default
parser =

input  = if RUBY_VERSION > "1.8"
 "spec/fixtures/X221-HP835/1-good.txt", :encoding => "ISO-8859-1")

# accepts IO (File), String, and DelegateInput
parser, result =

# Report fatal tokenizer failures
if result.fatal?
  result.explain{|reason| raise reason + " at #{result.position.inspect}" }

# Helper function
def el(m, *ns, &block)
  if Stupidedi::Either === m
    m.tap{|m| el(m, *ns, &block) }
    yield(*{|n| m.element(*n).map(&:node).map(&:value).fetch(nil) })

# Print some information
  .flatmap{|m| m.find(:GS) }
  .flatmap{|m| m.find(:ST) }
  .tap do |m|
    el(m.find(:N1, "PR"), 2){|e| puts "Payer: #{e}" }
    el(m.find(:N1, "PE"), 2){|e| puts "Payee: #{e}" }
  .flatmap{|m| m.find(:LX) }
  .flatmap{|m| m.find(:CLP) }
  .flatmap{|m| m.find(:NM1, "QC") }
  .tap{|m| el(m, 3, 4){|l,f| puts "Patient: #{l}, #{f}" }}