XBRL

XBRL (eXtensible Business Reporting Language; XBRL 2.1, Recommendation 31 December 2003, errata 2013) carries financial statements as facts. Each fact is an element from a taxonomy (an XSD of concepts such as revenue), and points to a context (who and which period) and a unit (currency). This sample instance uses an invented BookNest taxonomy:

booknest-xbrl.xml: three facts, two contexts, one unitXML

<!-- Sample data: an XBRL-style instance for an imaginary BookNest filing -->
<xbrli:xbrl xmlns:xbrli="http://www.xbrl.org/2003/instance"
    xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink"
    xmlns:iso4217="http://www.xbrl.org/2003/iso4217"
    xmlns:bn="https://booknest.example.com/xbrl">
  <link:schemaRef xlink:type="simple" xlink:href="booknest-taxonomy.xsd"/>
  <xbrli:context id="FY2025">
    <xbrli:entity><xbrli:identifier scheme="urn:bn">BN</xbrli:identifier></xbrli:entity>
    <xbrli:period><xbrli:startDate>2025-01-01</xbrli:startDate>
      <xbrli:endDate>2025-12-31</xbrli:endDate></xbrli:period></xbrli:context>
  <xbrli:context id="AsOf2025">
    <xbrli:entity><xbrli:identifier scheme="urn:bn">BN</xbrli:identifier></xbrli:entity>
    <xbrli:period><xbrli:instant>2025-12-31</xbrli:instant></xbrli:period></xbrli:context>
  <xbrli:unit id="USD"><xbrli:measure>iso4217:USD</xbrli:measure></xbrli:unit>
  <bn:Revenue contextRef="FY2025" unitRef="USD" decimals="0">1284500</bn:Revenue>
  <bn:NetIncome contextRef="FY2025" unitRef="USD" decimals="-3">96000</bn:NetIncome>
  <bn:Inventory contextRef="AsOf2025" unitRef="USD" decimals="0">212300</bn:Inventory>
</xbrli:xbrl>

xbrl_facts.py: resolving each fact's context into a rowPython

from lxml import etree
X = {"x": "http://www.xbrl.org/2003/instance"}
doc = etree.parse("booknest-xbrl.xml")
periods = {c.get("id"): " to ".join(c.xpath(".//x:period/*/text()", namespaces=X))
           for c in doc.xpath("//x:context", namespaces=X)}
for fact in doc.xpath("/x:xbrl/*[@contextRef]", namespaces=X):   # every fact names a context
    print(f"{etree.QName(fact).localname:10} {int(fact.text):>9,} {fact.get('unitRef')}"
          f"  {periods[fact.get('contextRef')]:24} decimals={fact.get('decimals')}")

Output

Revenue    1,284,500 USD  2025-01-01 to 2025-12-31 decimals=0
NetIncome     96,000 USD  2025-01-01 to 2025-12-31 decimals=-3
Inventory    212,300 USD  2025-12-31               decimals=0

decimals="-3" means accurate to thousands. Real filings use Inline XBRL, facts tagged inside an XHTML report, which the US SEC requires for 10-K and 10-Q filings under a 2018 rule (XBRL in Regulatory Filings). The open-source Arelle (github.com/Arelle/Arelle (https://github.com/Arelle/Arelle 247 )) validates filings against their taxonomies (not run here: the taxonomies are large).

Extensible Business Reporting Language (XBRL) is an XML-based standard for reporting business information, such as financial statements, using standardized taxonomies (for example, IFRS).

The following is an XBRL instance document reporting financial figures against an IFRS taxonomy.

ch12-xbrl-instance-example.xmlXML

<?xml version="1.0" encoding="UTF-8"?>
<xbrli:xbrl
    xmlns:ifrs-gp="http://xbrl.iasb.org/int/fr/ifrs/gp/2005-05-15"
    xmlns:iso4217="http://www.xbrl.org/2003/iso4217"
    xmlns:xbrli="http://www.xbrl.org/2003/instance"
    xmlns:xbrll="http://www.xbrl.org/2003/linkbase"
    xmlns:xlink="http://www.w3.org/1999/xlink">

   <xbrll:schemaRef
       xbrll:href="http://www.org.com/xbrl/taxonomy"
       xlink:type="simple"/>

   <ifrs-gp:OtherOperatingIncomeTotalFinancialInstitutions
       contextRef="J2004" decimals="0" unitRef="EUR">
      38679000000
   </ifrs-gp:OtherOperatingIncomeTotalFinancialInstitutions>
   <ifrs-gp:OtherAdministrativeExpenses
       contextRef="J2004" decimals="0" unitRef="EUR">
      35996000000
   </ifrs-gp:OtherAdministrativeExpenses>
   <ifrs-gp:OtherOperatingExpenses
       contextRef="J2004" decimals="0" unitRef="EUR">
      870000000
   </ifrs-gp:OtherOperatingExpenses>
   ...
   <ifrs-gp:OtherOperatingIncomeTotalByNature
       contextRef="J2004" decimals="0" unitRef="EUR">
      10430000000
   </ifrs-gp:OtherOperatingIncomeTotalByNature>

   <xbrli:context id="BJ2004">
      <xbrli:entity>
         <xbrli:identifier scheme="www.iqinfo.com/xbrl">ACME</xbrli:identifier>
      </xbrli:entity>
      <xbrli:period>
         <xbrli:instant>2004-01-01</xbrli:instant>
      </xbrli:period>
   </xbrli:context>
   <xbrli:context id="EJ2004">
      <xbrli:entity>
         <xbrli:identifier scheme="www.iqinfo.com/xbrl">ACME</xbrli:identifier>
      </xbrli:entity>
      <xbrli:period>
         <xbrli:instant>2004-12-31</xbrli:instant>
      </xbrli:period>
   </xbrli:context>
   <xbrli:context id="J2004">
      <xbrli:entity>
         <xbrli:identifier scheme="www.iqinfo.com/xbrl">ACME</xbrli:identifier>
      </xbrli:entity>
      <xbrli:period>
         <xbrli:startDate>2004-01-01</xbrli:startDate>
         <xbrli:endDate>2004-12-31</xbrli:endDate>
      </xbrli:period>
   </xbrli:context>

   <xbrli:unit id="EUR">
      <xbrli:measure>iso4217:EUR</xbrli:measure>
   </xbrli:unit>
</xbrli:xbrl>

(Courtesy of http://en.wikipedia.org/wiki/XBRL 30 )

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