TagSet -G and -M Elements

Updated: September 7, 1999

TagSet-G Elements Defined Within the Text of Z39.50-1995

The original 19 elements retain their numbering, however several are deprecated (recommended that they not be used, in favor of new elements), bodyOfDisplay is renamed displayObject, 'date' is renamed 'dateTime' ('time' is deprecated) and datatypes for several of the elements are revised.

  1. title
    datatype:
    • InternationalString, or
    • structured into following sub-elements:
      • 'wellKnown', tagSet-M element 19, dataType InternationalString
      • 'type' tagSet-M element 23
      • 'scheme' tagSet-M element 24

  2. author
    datatype: Same datatype definition as title.

  3. publicationPlace
    datatype: InternationalString

  4. publicationDate
    datatype: InternationalString.
    It is recommended that publicationDate not be used; it may be covered by 'date', qualified by 'type'.

  5. documentId
    datatype: InternationalString.
    It is recommended that documentId not be used; it may be covered by 'identifier', qualified by 'type'.

  6. abstract
    datatype: internationalString
    It is recommended that 'abstract' not be used; it may be covered by 'description', qualified by 'type'.

  7. name
    datatype: Same datatype definition as title.

  8. dateTime (previously 'date')
    datatype:
    1. EXTERNAL ( Z3950DateTime), or
    2. GeneralizedTime, or
    3. InternationalString, or
    4. structured into following sub-elements:
      • 'wellKnown', tagSet-M element 19, dataType 1, 2, or 3 above.
      • 'type' tagSet-M element 23
      • 'scheme' tagSet-M element 24

  9. displayObject
    datatype: OCTET STRING

  10. organization
    datatype: InternationalString

  11. postalAddress
    datatype: InternationalString

  12. networkAddress
    datatype: InternationalString

  13. eMailAddress
    datatype: InternationalString

  14. phoneNumber
    datatype: InternationalString

  15. faxNumber
    datatype: InternationalString

  16. country
    datatype:

  17. description
    datatype:

  18. time
    It is recommended that 'time' not be used; it may be covered by 'dateTime'.

  19. DocumentContent
    dataType OCTET STRING

    Approved extensions to TagSet-G

  20. language
    datatype:
    • InternationalString, or
    • structured into following sub-elements:
      • 'wellKnown', tagSet-M element 19, dataType InternationalString
      • 'scheme' tagSet-M element 24

  21. subject
    datatype: Same dataType definition as title.

  22. resourceType
    datatype:
    • InternationalString, or
    • structured into following sub-elements:
      • 'wellKnown', tagSet-M element 19, dataType InternationalString
      • 'scheme' tagSet-M element 24

  23. city
    datatype: InternationalString

  24. stateOrProvince
    datatype: InternationalString

  25. zipOrPostalCode
    datatype: InternationalString

  26. cost
    datatype:
    • InternationalString, or
    • IntUnit, or
    • structured into following sub-elements:
      • 'wellKnown', tagSet-M element 19, dataType InternationalString or IntUnit,
      • 'costInfo' tagSet-M element 25; datatype: InternationalString
      • 'costFlag' tagSet-M element 26; datatype: Boolean

  27. format
    datatype:
    • InternationalString, or
    • structured into following sub-elements:
      • 'wellKnown', tagSet-M element 19, dataType InternationalString
      • 'scheme' tagSet-M element 24

  28. identifier
    datatype: Same dataType definition as title.

  29. rights
    datatype: Same dataType definition as title.

  30. relation
    datatype: Same dataType definition as title.

  31. publisher
    datatype: Same dataType definition as title.

  32. contributor
    datatype: Same dataType definition as title.

  33. source
    datatype: Same dataType definition as title.

  34. coverage
    datatype: Same dataType definition as title.

  35. private
    datatype: dataType definition defined by schema.

    Following tag set G elements approved at August 1999 ZIG meeting

  36. databaseName
    datatype: InternationalString
    format: Z39.50s URL. See     RFC 2056. The database name (optional in RFC 2056) must be supplied.
    meaning/usage: Identifies a Z39.50 database.

  37. recordId
    datatype: InternationalString
    format: Z39.50r URL. as described in RFC 2056.
    meaning/usage: Identifies a Z39.50 database record.

Proposed extensions to TagSet-G

None currently.

TagSet-M Elements Defined Within the Text of Z39.50-1995

The original 21 elements retain their numbering, however in several cases the data types have been generalized.

  1. schemaIdentifier
    datatype: OBJECT IDENTIFIER

  2. elementsOrdered
    datatype: BOOLEAN

  3. elementOrdering
    datatype: INTEGER

  4. defaultTagType
    datatype: INTEGER

  5. defaultVariantSetId
    datatype: OBJECT IDENTIFIER

  6. defaultVariantSpec
    datatype: VariantSpec

  7. processingInstructions
    datatype: InternationalString

  8. recordUsage
    datatype: INTEGER

  9. restriction
    datatype: InternationalString

  10. rank
    datatype: INTEGER

  11. userMessage
    datatype: InternationalString

  12. url
    datatype: InternationalString

  13. record
    datatype: structured

  14. localControlNumber
    datatype: same as tagSet-G element 'identifier'

  15. creationDate
    datatype: same as tagSet-G element dateTime

  16. dateOfLastModification
    datatype: same as tagSet-G element dateTime

  17. dateOfLastReview
    datatype: same as tagSet-G element dateTime

  18. score
    datatype: INTEGER

  19. wellKnown
    datatype: Defined by schema; default InternationalString

  20. recordWrapper
    datatype: structured

  21. defaultTagSetId
    datatype: OBJECT IDENTIFIER

    Approved extensions to TagSet-M

  22. languageOfRecord
    datatype: Same as tagSet-G element 'language'

  23. type
    datatype: INTEGER or InternationalString

  24. Scheme
    datatype: INTEGER or InternationalString

  25. costInfo
    datatype: InternationalString

  26. costFlag
    datatype: BOOLEAN ('true' means there is a cost)

    Following tag set M elements approved at August 1999 ZIG meeting

  27. Record Created By
    datatype: InternationalString

  28. Record Modified By
    datatype: InternationalString

Proposed Extensions to TagSet-M

None Currently.

Principles, Usage, and Scope of TagSet-G

TagSet-G includes elements with common usage within a significant number of user communities. In the absence of a schema that specifies stricter semantics, TagSet-G elements have broad, loose semantics. They implicitly inherit more specific semantics when used within a specific user community. When used across communities, a schema should be used to tighten those semantics.

For example, the Museum community can use the Title element interoperably with loose semantics; within that community they all know what they mean by a Title. Similarly, the Genealogy community uses Title as well, but with different implied semantics. The problem arises when the Museum of Genealogy wants to provide records. Then they will need a schema that defines the semantics of Title.

Scope and Criteria

A generic element may be proposed for addition to tagSet-G, by a group of implementors developing a Z39.50 profile or a schema, if that group believes that the element will provide utility beyond their specific application. The Z39.50 Maintenance Agency establishes procedures pertaining to Z39.50 objects and definitions.These procedures will directly address the process of adoption or rejection of a proposed element.

Generic Semantics of TagSet-G Elements

Each tagSet-G element will be assigned generic semantics that may be inferred by a client when the element occurs outside the context of any specific schema.

Context specific semantics of TagSet-G Elements

Generic semantics attributed to a tagSet-G element are (in general) weaker than the semantics of that element as defined within a schema. The intent is that general elements may be inherited by schema for more specific usage.

Thus a tagSet-G element may be attributed stronger semantics when it occurs within the context of a specific schema. For example, the element Author has generic semantics such that if it occurs outside the context of a schema it is interpreted as "Author or Creator". A specific schema (for example, pertaining to museum objects) may confine its meaning to "Creator".

For the remainder of this discussion an element occurrence is referred to as "context specific" or "generic" depending respectively on whether it occurs within or not within the context of a specific schema.

Schema context of TagSet-G Element

A tagSet-G element may occur within a retrieval record as generic or context specific. A client may infer that a generic occurrence pertains to the record at large, and the client should attribute generic semantics. If the occurrence is context specific and if the client does not support the context (i.e. the schema), the client should not infer any information from the occurrence. A tagSet-G element may have both context specific and generic occurrences within the same record; in that case if the client does not support the context, the client may infer that the generic occurrences apply, while ignoring any context specific occurrences.

For example, suppose a client executes a search across databases creating a result set that represents records from potentially several domains. When the client retrieves a record from the result set, unless the retrieval record includes a schema identifier, the client might not know what schema governs the interpretation of the elements of the record. Suppose in this case the first several elements are from tagSet-G, say: Author, Title, and subject. Following these initial tagSet-G elements, assume there is a structured element with subelements, the first of which is a schemaIdentifier (tagSet-M element 1). Suppose that the client does not support the identified schema, and suppose further that there are several tagSet-G elements following the schema identifier. The client is able to discern that the Author, Title, and Subject pertain to the record, but the client is not able to process the record further, in particular, the client may not infer information from the second set of tagSet-G elements. In this case, the client may be able to inform the user that there is a potential record of interest, and that in order to interpret the record, support for the specific schema is necessary.

As another example, consider a database where an individual record corresponds to a physical object (for example, a work of art) and the record includes one or more digital renditions of the object. An abstract record structure may specify that tagSet-G elements may occur at the beginning of the record, outside the context of a specific schema, followed by a schema identifier, followed by a repeating, structured element, with a repetition for each rendition. There may be tagSet-G elements within each such "rendition" element, and these would pertain to the specific rendition. (The 'Title' or 'Author' for the first rendition may be different from those of the 'second' rendition. For example, the first rendition may be "black and white still image, 35mm" where the listed 'Author' is the photographer; while the second rendition may be a sketch of the physical object, where the listed 'Author' is the artist of the sketch. The Title and Author in both cases would be different from those of the object itself.)

TagSet-G element used as utility elements, within a Tag Path

TagSet-G elements may be used within a tag path, as for example in the GILS abstract record structure: there is an element 'availability' (GILS element 70), subordinate to which is an element distributor (GILS element 90), and thus is constructed the element availability/distributor. Subordinate to this element are several tagSet-G elements: name, organization, address, and telephone. Thus are constructed the following elements: In this scheme These four tagSet-G elements play the role of utility elements, allowing GILS to avoid the need to define special tags for these commonly used elements.

A client receiving a record that includes these GILS elements (assuming the GILS schema to be in effect) should not infer any information from the presence of these tagSet-G elements, unless the client supports the GILS schema.

Utility container elements

Elements such as displayObject (formerly bodyOfDisplay) and documentContent are available as container elements. Additional utility elements may be added, if deemed generally useful.
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