Test Data Markup Language (TDML)

Test Data Markup Language (TDML) it is a way of specifying a DFDL schema, input test data, and expected result or expected error/diagnostic messages, all self-contained in an XML file. IBM created TDML to capture tests for their own DFDL implementation. Daffodil latched onto this and has since extended it a bit, though there is an effort to reconcile TDML dialects so that all implementations can run the same tests.

A TDML file is often useful just to ask a question about how something in DFDL works, for example, to get a clarification. It allows for a level of precision that is often lacking, but also often required when discussing complex data format issues. As such, providing a TDML file along with a bug report is the absolutely best way to demonstrate a problem.

By convention, a TDML file uses the file extension .tdml, or .tdml.xml when used with the TDML “tutorial” feature.

The schema for a TDML file is available on GitHub.

Below is an annotated TDML file for a very simple example:

<?xml version="1.0" encoding="ASCII"?>
  suiteName="Bug Report TDML Template"
  description="Illustration of TDML for bug reporting."
  xsi:schemaLocation="http://www.ibm.com/xmlns/dfdl/testData tdml.xsd"
    This example TDML file is for a self-contained bug report.
    It shows the definition of an inline schema and parse test and unparse test that use that schema.

    A DFDL schema is defined inside the tdml:defineSchema element. The contents
    are similar to a normal DFDL schema, allowing for imports, defining a
    global format via dfdl:defineFormat and dfdl:format, and defining schema

  <tdml:defineSchema name="bug01Schema" elementFormDefault="unqualified">
      schemaLocation="IBMdefined/GeneralPurposeFormat.xsd" />
    <dfdl:defineFormat name="myFormat">
      <dfdl:format ref="gpf:GeneralPurposeFormat"
        separator="" />
    <dfdl:format ref="ex:myFormat" />
    <xs:element name="myTestRoot" type="xs:dateTime"
      dfdl:calendarPattern="MM.dd.yyyy 'at' HH:mm:ssZZZZZ"
      dfdl:terminator="%NL;" />
    Define a parse test case, using the above schema and root element. Input
    data is defined along with the expected infoset.

  <tdml:parserTestCase name="dateTimeTest" root="myTestRoot" model="bug01Schema"
    description="A hypothetical bug illustration about parsing a date time.">
     <tdml:documentPart type="text"
       replaceDFDLEntities="true"><![CDATA[04.02.2013 at 14:00:56 GMT-05:00%LF;]]></tdml:documentPart>

    Define an unparse test case, using the above schema and root element. An
    input infoset is defined along with the expected unparsed data.
  <tdml:unparserTestCase name="unparseDateTimeTest" root="myTestRoot" model="bug01Schema"
    description="Another bug illustration, this time unparsing direction.">
      <tdml:documentPart type="text"
        replaceDFDLEntities="true"><![CDATA[04.02.2013 at 14:00:56-05:00%CR;%LF;]]></tdml:documentPart>

Suppose you save the above out as a file myDateTimeBug.tdml. You can then run it using the test subcommand of the Daffodil Command Line Interface:

$ daffodil test myDateTimeBug.tdml

Specifying Test Data

Test data can be specified in text, hexadecimal, individual bits, or in an external file by setting the type attribute in the tdml:documentPart element. Multiple tdml:documentPart elements are combined to create the test data. The different documentPart types are illustrated below.

    A document part with type="text" is text. It is often a good idea to use
    CDATA to avoid whitespace changes made by some autoindenting IDE's.

    So in the example below, the line ending after '250;' and after '967;' are
    intentional parts of the data so as to illustrate that the whitespace is

    If you care exactly which kind of line ending is used, then you can use
    DFDL character entities to insert a %CR; %LF; or both. In this example,
    because the whitespace is expressed as whitespace, it depends on the
    platform where you edit this file whether the line ending is a LF (Unix
    convention), or a CRLF (MS Windows convention). By convention, it is
    usually recommended to use Unix style line-endings in TDML files and use
    character entities if explicit line endings are being tested.

    If you want to use DFDL character entities, you must turn on the
    replaceDFDLEntities="true" feature of the documentPart element.

  <tdml:documentPart type="text"><![CDATA[quantity:250;

    In 'text' both XML character entities, and DFDL's own character entities
    are interpreted.

    So here is a NUL terminated string that contains a date with some Japanese
    Kanji characters. The Japanese characters are expressed using XML numeric
    character entities. The NUL termination is expressed using a DFDL character

    In this example one has no choice but to use a DFDL character entity. The
    NUL character (which has character code zero), is not allowed in XML
    documents, not even using an XML character entity. So you have to write
    '%NUL;' or '%#x00;' to express it using DFDL character entities.

  <tdml:documentPart type="text"
    replaceDFDLEntities="true"><![CDATA[1987&#x5E74;10&#x6708;&#x65e5; BCE%NUL;]]></tdml:documentPart>

    Type 'byte' means use hexadecimal to specify the data. Freeform whitespace
    is allowed and  any character that is not a-zA-Z0-9 is ignored. So you can
    use "." or "-" to separate groups of hex digits if you like.

  <tdml:documentPart type="byte">
    9Abf e4c3

    Type 'bits' allows you to specify individual 0 and 1. Any character other
    than 0 or 1 is ignored.

    The number of bits does not have to be a multiple of 8. That is, whole
    bytes are not required.

  <tdml:documentPart type="bits">
    1.110 0.011 1   First 5 bit fields.

    Type 'file' means the content is a file name where to get the data

  <tdml:documentPart type="file">/some/directory/testData.in.dat</tdml:documentPart>


Note that in order for a test to be considered successful, it must consume all the data defined in the tdml:document element. Otherwise the test will fail with a message about “left over data”.

Specifying the Infoset

The infoset can be provided either as an inline XML infoset or as a path to an external file by setting the type attribute on the tdml:dfdlInfoset element. If not provided, the type defaults to inline XML. For example:

  <tdml:dfdlInfoset type="infoset">

  <tdml:dfdlInfoset type="file">/some/directory/testData.in.xml</tdml:dfdlInfoset>

Note that the tdml:dfdlInfoset may need to contain characters that are not legal in XML documents. Daffodil remaps these characters into legal XML characters in the Unicode Private Use Areas (PUA). See XML Illegal Characters for details.

Negative Tests: Expecting Errors/Warnings

A poor or missing diagnostic message is a bug just as much as a broken feature. TDML allows for creating negative tests to expect errors and warnings. To do expect errors, replace the tdml:infoset element with a tdml:errors element:

  <tdml:error>Schema Definition Error</tdml:error>

Each tdml:error child element contains a sub-string which must be found somewhere in the set of diagnostic messages that come out of the test. The comparison is case-insensitive.

The tdml:warnings and tdml:warning elements behave just like the error counterparts to define warnings that should be created during the test. Note that warnings are considered non-fatal and so can appear alongside tdml:errors and tdml:infoset elements.

  <tdml:warning>Schema Definition Warning</tdml:warning>
  <tdml:warning>'http://www.ogf.org/dfdl/dfdl-1.0/' should be 'http://www.ogf.org/dfdl/'</tdml:warning>

Using CDATA Regions

XML CDATA regions indicate XML data that should not be interpreted as XML. Although in general is it used to easily include XML special characters in XML data, its use has other benefits in TDML files as well. Below are examples of what scenarios when CDATA regions should and should not be used.

 As a clear way represent XML special characters

The characters <, >, &, ', and " must be represented in XML with &lt;, &gt;, &amp;, &apos;, and &quot;, respectively. These special characters are not escaped when used in CDATA tags, which can make the data more clear. For example, the following are equivalent:


 To preserve textual formatting within TDML - for clarity reasons

Often times IDE’s and XML editors will indent, wrap, and remove redundant whitespace in XML data. However, sometimes it is desired that such formatting is maintained for readability purposes. Many tools refuse to perform modifications on CDATA regions, so they can be used as a way to maintain formatting. For example:

<tdml:documentPart type="byte"><![CDATA[
00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
20 21    23 24 25    27 28 29 2a 2b 2c 2d 2e 2f
30 31 32 33 34 35 36 37 38 39 3a 3b    3d    3f
40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f
50 51 52 53 54 55 56 57 58 59 5a 5b 5c 5d 5e 5f

The data holes in the above matrix of hex would be hard to understand without the formatting. But logically, the whitespace is irrelevant when the documentPart type is “byte”. In effect, we have CDATA here so that tooling like IDEs, XML editor, etc. will not mess with the formatting of the content.

 To avoid insertion of whitespace that would make things incorrect

Let us assume that the input document should contain exactly two letters: a年. This might be represented as the following in a TDML file:

  <documentPart type="text">a年</documentPart>

The problem is that it is possible that an XML tool might reformat the XML as this:

  <documentPart type="text">

But this is a text documentPart containing some letters with surrounding whitespace. Our test, in this case, expects data of length exactly 2 characters, so could cause a failure. CDATA can be used to prevent many XML tools from reformatting and inserting whitespace that could affect the test input data:

  <documentPart type="text"><![CDATA[a年]]></documentPart>

 To preserve specific line endings

Using CDATA does NOT necessarily preserve line endings. So if you had a test where you have this:

<documentPart type="text"><![CDATA[Text followed by a CR LF

If you edit that on a windows machine, where CRLF is the usual text line ending, then the file will actually have a CRLF line ending in that text. If the test has say, dfdl:terminator="%CR;%LF;", then this should fail because, no matter what, XML always standardizes line endings to just one character: LF. XML replaces CRLF with LF, and isolated CR with LF. The net result: by the time a program is reading the XML data, it should only see LF line endings.

It is possible to get a literal CR character into XML content, but ONLY by using the numeric character entity notation, i.e., &#xD;. So one might try to write the above test as:

<documentPart type="text"><![CDATA[Text followed by a CR LF]]></documentPart>
<documentPart type="text">&#xD;&#xA;</documentPart>

Even this, however, is not a sure thing, because re-indenting the XML might cause you to get:

<documentPart type="text"><![CDATA[Text followed by a CR LF]]></documentPart>
<documentPart type="text">

Which would be broken because of the whitespace insertions around the &#xD;&#xA;.

There are two good solutions to this problem. First one can use type=”byte” document parts:

<documentPart type="text"><![CDATA[Text followed by a CR LF]]></documentPart>
<documentPart type="byte">0D 0A</documentPart>

This will always create exactly the bytes 0D and 0A, and documentParts are concatenated together with nothing between. However, this will break if the documentPart has an encoding where CR and LF are not exactly represented by the bytes 0D and 0A. For example currently we support encoding="us-ascii-7-bit-packed". In that encoding, CR and LF each take up only 7 bits, resulting in 14 bits rather than 2 full bytes.

The best way to handle this problem is to use the documentPart replaceDFDLEntities attribute:

<documentPart type="text" replaceDFDLEntities="true"><![CDATA[Text followed by a CR LF%CR;%LF;]]></documentPart>

The line gets kind of long, but those %CR; and %LF; are DFDL entities syntax for those Unicode characters. These are translated into whatever encoding the documentPart specifies, so this will be robust even if the encoding is say, UTF-16 or the 7-bit encoding.

If you have a multi-line piece of data and need CRLFs in it, then this does get a bit clumsy as you have to do it like this where each text line gets its own documentPart:

<documentPart type="text" replaceDFDLEntities="true"><![CDATA[Of all the gin joints%CR;%LF;]]></documentPart>
<documentPart type="text" replaceDFDLEntities="true"><![CDATA[In all the towns in the world%CR;%LF;]]></documentPart>
<documentPart type="text" replaceDFDLEntities="true"><![CDATA[She walked into mine%CR;%LF;]]></documentPart>

So the general rule is that CDATA regions cannot be used to ensure that specific kinds of line endings will be preserved in a file.

Some tests, however, are insensitive to the presence of whitespace. This is true of many tests for delimited text formats. In those cases you may want CDATA to preserve formatting of text (so it won’t be re-indented), and to preserve some line endings. If this same test example was instead using dfdl:terminator="%NL;", the NL entity matches CRLF, CR, or LF, and even some other obscure Unicode line ending characters. In that case, the original documentPart XML:

<documentPart type="text"><![CDATA[Of all the gin joints
In all the towns of the world
She walked into mine

is fine, and will work and be robust.