DCC

A Ruby library for parsing, validating, converting, signing, and building PTB Digital Calibration Certificates (DCC) and D-SI quantity documents.

Built on top of the lutaml-model framework, dcc provides a fully typed Ruby object representation of both the DCC and D-SI XML schemas, with per-major-version class hierarchies mirroring the approach used by the mml gem for MathML.

What is a Digital Calibration Certificate?

A Digital Calibration Certificate (DCC) is an XML-based, machine-readable calibration certificate developed by Germany’s national metrology institute, the Physikalisch-Technische Bundesanstalt (PTB). It is designed to replace traditional paper-based calibration certificates with a format that both humans and machines can process automatically.

A DCC document contains three primary sections:

• Administrative data — identifies the calibration laboratory, the customer, the calibrated item(s), responsible persons, performance dates, and any statements about traceability or conformity.

• Measurement results — the actual calibration data: measured values, uncertainties, units, environmental conditions, and the methods/equipment used. Each measurement quantity is expressed using the D-SI format.

• Document — optional attached files (PDF reports, spreadsheets, images) embedded as base64 binary data.

The certificate can be digitally signed using W3C XMLDSig to guarantee authenticity and integrity.

What is D-SI?

D-SI (Digital System of Units) is a companion XML format for expressing SI-based measurement quantities with full uncertainty information. A D-SI quantity carries the value, unit (in siunitx notation), and an uncertainty model (standard, expanded with coverage factor k, or coverage interval).

For example, a resistance measurement of 100.0225 Ω ± 0.003 Ω (k=2):

<si:real>
<si:value>100.0225</si:value>
<si:unit>\ohm</si:unit>
<si:expandedMU>
<si:valueExpandedMU>0.003</si:valueExpandedMU>
<si:coverageFactor>2</si:coverageFactor>
<si:coverageProbability>0.95</si:coverageProbability>
</si:expandedMU>
</si:real>

D-SI also supports complex quantities, constants, lists (both verbose and compact XML-list forms), hybrid multi-unit representations, covariance matrices, and coverage regions for multivariate uncertainties.

Highlights

• Fully typed object model for DCC v2.x and v3.x (no more XPath over lxml)

• Fully typed object model for D-SI v1.x and v2.x

• Lossless round-trip XML fidelity (parsing then serializing is byte-equivalent after canonicalization via moxml)

• Pure-Ruby Schematron engine implementing the 14 PTB Schematron patterns (no Java/Saxon-HE dependency)

• XSD validation against all 12 bundled DCC schema versions

• JSON / YAML / CSV / HTML converters

• MathML formula support via the mml gem (typed model, not raw strings)

• XMLDSig signature signing and verification via moxml native Signature

• Programmatic DCC builder DSL for issuing new certificates

• Structural diff of two certificates

• Version migration helpers

• Thor-based CLI with validate, convert, extract, signature, transform, inspect, diff, and issue commands

Quick start

Install the gem:

$ gem install dcc

Parse a certificate:

require"dcc"dcc=Dcc.parse(File.read("certificate.xml"))dcc.administrative_data.core_data.unique_identifierdcc.measurement_results.measurement_result.first.results.result.first.data.first.quantity.first.name

Validate:

result=Dcc::Validate::Xsd.call(File.read("certificate.xml"),version: "3.3.0")result.ok?# => true

Building a new DCC

Use the builder DSL to issue a certificate programmatically:

require"dcc"dcc=Dcc.build(version: 3)doadministrative_datadocore_datadounique_identifier"urn:uuid:00000000-0000-0000-0000-000000000001"country_code"DE"used_lang"en"mandatory_lang"en"begin_performance_dateDate.todayend_performance_dateDate.todayenditemsdoitem(model: "Pt100",manufacturer: "ACME Sensors")doname{contentlang: "en",value: "Resistance Thermometer"}endendcalibration_laboratorydocalibration_laboratory_code"PTB-123"contactdoname{contentlang: "en",value: "Calibration Lab"}e_mail"lab@example.org"locationdocity"Berlin"country_code"DE"endendendresp_personsdoresp_persondopersondoname{contentlang: "en",value: "Dr. Jane Doe"}e_mail"jane@example.org"endmain_signertrueendendcustomerdoname{contentlang: "en",value: "Acme Corp"}endendmeasurement_resultsdomeasurement_resultdoname{contentlang: "en",value: "Resistance at 0 °C"}resultsdoresultdoname{contentlang: "en",value: "R(0 °C)"}datadoquantitydoname{contentlang: "en",value: "Measured resistance"}# D-SI quantity element (si:real) is wired via the typed modelendendendendendendendputsdcc.to_xml

Signing a DCC

Sign with an X.509 certificate and RSA private key:

require"dcc"cert_pem=File.read("cert.pem")key_pem=File.read("cert.key")signed_xml=Dcc::Signature::Signer.call(File.read("certificate.xml"),cert_pem: cert_pem,key_pem: key_pem,)File.write("certificate_signed.xml",signed_xml)

Verify a signed certificate:

result=Dcc::Signature::Verifier.call(File.read("certificate_signed.xml"),ca_cert_pem: cert_pem,)result.valid?# => true

CLI

$ dcc inspect certificate.xml
$ dcc validate all certificate.xml
$ dcc convert json certificate.xml -o certificate.json
$ dcc extract files certificate.xml
$ dcc signature sign cert.pem key.pem certificate.xml -o signed.xml
$ dcc signature verify cert.pem signed.xml
$ dcc diff a.xml b.xml

Status

This gem is under active development. See TODO.complete/ for the current work breakdown.

License

MIT — see LICENSE.