reqif 0.0.23

Python library for ReqIF format. ReqIF parsing and unparsing.

ReqIF

ReqIF is a Python library for working with ReqIF format.

The project is under construction.

Supported features

• Parsing/unparsing ReqIF
• Formatting (pretty-printing) ReqIF

To be implemented:

• Validating ReqIF
• Converting from/to Excel and other formats

Getting started

pip install reqif

Using ReqIF as a library

Parsing ReqIF

reqif_bundle = ReqIFParser.parse(input_file_path)
for specification in reqif_bundle.core_content.req_if_content.specifications
    print(specification.long_name)

    for current_hierarchy in reqif_bundle.iterate_specification_hierarchy(specification):
        print(current_hierarchy)

Unparsing ReqIF

reqif_bundle = ReqIFParser.parse(input_file_path)
reqif_xml_output = ReqIFUnparser.unparse(reqif_bundle)
with open(output_file_path, "w", encoding="UTF-8") as output_file:
    output_file.write(reqif_xml_output)

The contents of reqif_xml_output should be the same as the contents of the input_file.

Using ReqIF as a command-line tool

Passthrough command

Before using the ReqIF library, it is useful to check if it fully understands a particular ReqIF file format that a user has in hand. The passthrough command first parses the ReqIF XML into in-memory Python objects and then unparses these Python objects back to an output ReqIF file.

If everything goes fine, the output of the passthrough command should be identical to the contents of the input file.

tests/integration/examples contains samples of ReqIF files found on the internet. The integration tests ensure that for these samples, the passthrough command always produces outputs that are identical to inputs.

Formatting ReqIF

The format command is similar to clang-format for C/C++ files or cmake-format for CMake files. The input file is parsed and then pretty-printed back to an output file.

This command is useful when dealing with ReqIF files that are hand-written or ReqIF files produced by the ReqIF tools that do not generate a well-formed XML with consistent indentation.

The tests/integration/commands/format contains typical examples of incorrectly formatted ReqIF files. The integration tests ensure that the format command fixes these issues.

Implementation details

The core of the library is a ReqIF first-stage parser that only transforms the contents of a ReqIF XML file into a ReqIF in-memory representation. The in-memory representation is a tree of Python objects that map directly to the objects of the ReqIF XML file structure (e.g, Spec Objects, Spec Types, Data Types, Specifications, etc.).

Parsing: Converting from ReqIF to other formats

The first-stage parser (implemented by the class ReqIFParser) can be used by user's second-stage parser/converter scripts that convert the ReqIF in-memory structure into a desired format such as Excel, HTML or other formats. The two-stage process allows the first stage parsing to focus solely on creating an in-memory ReqIF object tree, while the second stage parsing can further parse the ReqIF object tree according to the logical structure of user's documents as encoded in the ReqIF XML file that was produced by user's requirements management tool.

Unparsing: Converting from other formats to ReqIF

The reverse process is also possible. A user's script converts another format's contents into a ReqIF in-memory representation. The ReqIF un-parser (implemented by the class ReqIFUnparser) can be used to render the in-memory objects to the ReqIF XML file.

Tolerance

The first-stage parser is made tolerant against possible issues in ReqIF. It should be possible to parse a ReqIF file even if it is missing important information. A separate validation command shall be used to confirm the validity of the ReqIF contents.

A bottom-up overview of the ReqIF format

• ReqIF is a standard. See reference document RD01.
• ReqIF has a fixed structure (see "What is common for all ReqIF documents" below)
• ReqIF standard does not define a document structure for every documents so a ReqIF tool implementor is free to choose between several implementation approaches. There is a ReqIF Implementation Guide that attempts to harmonize ReqIF tool developments. See also "What is left open by the ReqIF standard" below.
• ReqIF files produced by various tool often have incomplete schemas.

What is common for all ReqIF documents

• All documents have ReqIF tags:
  • Document metadata is stored inside tags of REQ-IF-HEADER tag.
  • Requirements are stored as <SPEC-OBJECT>s
  • Requirements types are stored as <SPEC-TYPE>s
  • Supported data types are stored as <DATATYPE>
  • Relationships such as 'Parent-Child' as stored as <SPEC-RELATIONS>

What is left open by the ReqIF standard

• How to distinguish requirements from headers/sections?
  • One way: create separate SPEC-TYPES: one or more for requirements and one for sections.
  • Another way: have one spec type but have it provide a TYPE field that can be used to distinguish between REQUIREMENT or SECTION.

Reference documents

[RD01] ReqIF standard

The latest version is 1.2: Requirements Interchange Format

[RD02] ReqIF Implementation Guide

ReqIF Implementation Guide v1.8