ISOISO 25577 (MarcXchange) is an international standard that defines a generalized XML format for exchanging bibliographic records structured according to ISO 2709, the underlying standard for all MARC formats. Unlike MARCXML, which is specific to MARC 21, MarcXchange is designed to accommodate any MARC variant -- including MARC 21, UNIMARC, and national MARC formats -- within a single XML schema, making it a key enabler of cross-tradition bibliographic data exchange.
Background
The MARC family of formats has long been divided among national and regional variants, each serving its own library community. While MARCXML provided an XML serialization for MARC 21 records, libraries using UNIMARC or other ISO 2709-based formats lacked an equivalent standardized XML representation. MarcXchange was developed to bridge this gap, providing a format-neutral XML schema that could represent any ISO 2709-compliant record. The standard was first published as ISO 25577 in 2008 and revised in 2013 and 2020. The Danish national library (Det Kongelige Bibliotek) was instrumental in the standard's development.
Purpose & Scope
MarcXchange defines an XML schema for:
| Use Case | Description |
|---|---|
| Cross-format exchange | Transmitting MARC records between systems using different MARC variants |
| Web services | Embedding MARC data in XML-based library services (SRU/SRW, OAI-PMH) |
| Archival storage | Preserving MARC records in a self-describing, non-binary format |
| Format migration | Facilitating the conversion of records between MARC traditions |
The schema includes a format attribute on the root element that identifies which MARC variant the record conforms to (e.g., "MARC21", "UNIMARC", "DANMARC2"), making the XML both self-describing and variant-agnostic.
Key Elements / Properties
The MarcXchange XML schema defines a small set of elements that mirror the ISO 2709 record structure:
| Element | Description |
|---|---|
| collection | Root element containing multiple records |
| record | A single MARC record, with a format attribute |
| leader | The 24-character record leader |
| controlfield | Fixed-length fields (tags 001-009) |
| datafield | Variable-length fields with tag, ind1, and ind2 attributes |
| subfield | Individual subfields within a datafield, identified by a code attribute |
This structure maps directly to the ISO 2709 record model and is intentionally minimal.
Serializations & Technical Formats
MarcXchange is itself an XML format. The XSD schema is hosted by the Library of Congress. The namespace URI and schema location identify the standard version. MarcXchange records can be embedded in SRU/SRW responses, OAI-PMH records, and other XML transport mechanisms.
Governance & Maintenance
ISO 25577 is maintained by ISO Technical Committee 46 (Information and documentation), Subcommittee 4 (Technical interoperability). The Library of Congress hosts the schema files. The standard has been revised twice since its initial 2008 publication, with the most recent edition being ISO 25577:2020.
Notable Implementations
MarcXchange is used by national libraries and library networks that operate with non-MARC 21 formats and need XML-based exchange capabilities. The Danish library system, which uses DANMARC2, was an early adopter. European library networks that use UNIMARC benefit from MarcXchange for interoperability with MARC 21 systems. Library software that supports SRU/SRW may use MarcXchange as a record schema option.
Related Standards
- MARC 21 -- The most widely used MARC format; MarcXchange can encode MARC 21 records but is not limited to them.
- MARCXML -- The Library of Congress XML schema specifically for MARC 21 records. MarcXchange generalizes this concept to all ISO 2709-based formats.
- UNIMARC -- The Universal MARC Format used primarily in Europe, which can be encoded in MarcXchange XML.