#pragma section-numbers 2 '''NOTE: This draft is not currently being edited - please see http://dublincore.org/documents/2008/03/31/dc-dsp/.''' = DCMI Description Set Profile = '''Important''': This document is currently in draft. Comments should please be sent to DC-ARCHITECTURE@JISCMAIL.AC.UK ([http://www.jiscmail.ac.uk/archives/dc-architecture.html Subscription and archives]) . '''Editor: ''' Mikael Nilsson * [attachment:dcap-model.ppt DCAP model as Powerpoint] * [attachment:dcap-model_printout.pdf DCAP model as PDF printout] || [[TableOfContents]] || == TODO == * Add hotlinks to DCAM concepts == Issues so far == * Simultaneous subproperty and property list constraints? * nonliteral constraint in the case type=unspecified. * class constraint, relating descriptions and "standalone" descriptions * description template matching based only on resource type, not path. == Introduction == The DCMI Description Set Profile specification describes an information model and XML expression of a "Description Set Profile" (DSP). The term ''description set'' and the associated concepts used in this specification are defined as in the DCMI Abstract model [[http://dublincore.org/documents/abstract-model DCAM]]. A DSP is a way of describing structural constraints on a description set. It constrains the resources that may be described by descriptions in the description set, the properties that may be used, and the ways a value surrogate may be given. A DSP can be used for many different purposes, such as: * as a formal representation of the constraints of a Dublin Core Application Profile * as configuration for databases * as configuration for metadata editing tools * etc. A DSP does ''not'' address the following: * Human-readable documentation. * Definition of vocabularies. * Version control. A DSP contains the formal syntactic constraints only, and will need to be combined with human-readable information, usage guidelines, version management, etc. in order to be used as an application profile. However, the design of the DSP information model is intended to facilitate the merging of DSP information and external information of the above kinds, for example by tools generating human-readable documentation for a Dublin Core Application Profile. A Dublin Core Application Profile is a document, or set of documents, that puts a Description Set Profile into a broader context of Functional Requirements, Domain Models (such as Functional Requirements for Bibliographic Records), guidelines on syntax and usage, and possibly data formats. The following figure depicts the basic elements of a Dublin Core Application Profile (this model will be elaborated in future documents). attachment:dcap-model.jpg == Basic structure == A DSP describes the structure of a Description Set by using the notions of "templates" and "constraints". A template describes the possible metadata structures in a conforming record. There are two levels of templates in a Description Set Profile: * '''Description templates''', that contains the statement templates that apply to a single kind of description as well as constraints on the described resource. * '''Statement templates''', that contains all the constraints on the property, value strings, vocabulary encoding schemes, etc. that apply to a single kind of statement. While templates are used to express structures, constraints are used to limit those structures. The following figure depicts the basic elements of the structure. attachment:dsp-uml.png == Basic semantics == The fundamental usage model for a DSP is to examine whether a metadata record ''matches'' the DSP. Matching of a description set is defined as follows: Binding of descriptions to description templates:: Each description is bound to a Description Template by evaluating the ''Resource Constraint'' of each Description Template against the described resource. Each description must be bound to exactly one Description Template. Binding of statements to statement templates:: For each description, each statement is bound to a Statement Templates in the corresponding Description Template by evaluating the ''Property Constraint''. Each statement must be bound to exactly one Statement Template. Evaluating constraints:: Now that all metadata in the description set has been bound to a template, all constraints can be verified. == Usage examples == === Example 1: Constraining the resource === The following DSP matches descriptions with a single resource. The resource must be an instance of {{{foaf:Person}}}. {{{ http://xmlns.com/foaf/0.1/Person }}} As it stands, this DSP does not allow for the description of that resource to contain any statements, so it is not very useful. === Example 2: Constraining a property === The following DSP adds a mandatory foaf:name property with a literal value to the previous example. {{{ http://xmlns.com/foaf/0.1/Person http://xmlns.com/foaf/0.1/name }}} === Example 3: Constraining the value === The following DSP constrains the value to be a literal without a language. {{{ http://xmlns.com/foaf/0.1/Person http://xmlns.com/foaf/0.1/name disallowed }}} === Example 4: Two resources === The following DSP allows for two kinds of resources: a single "document", and multiple "authors". The Person resources may only occur as values of the {{{dcterms:creator}}} property, not stand-alone. The value may only be described in a separate description with a mandatory {{{foaf:name}}} property. {{{ http://purl.org/dc/terms/Text http://purl.org/dc/terms/creator disallowed disallowed http://xmlns.com/foaf/0.1/Person http://xmlns.com/foaf/0.1/name disallowed }}} == Description Templates == A description Template has the following attributes. XML Element Name:: !DescriptionTemplate === Identifier === Summary:: A string that can be used in a Value Constraint to reference a description template that applies to the value resource. Allowed values:: A valid XML ID string. Default:: N/A XML Attribute Name:: ID === Standalone === Summary:: Whether descriptions matching this template are allowed to occur standalone, i.e. without being the value of a property. Allowed values:: "yes" / "no" / "both" Default:: "both" Conditions:: If standalone is "yes", a matching description may not be a description of value occurring elsewhere in the DSP. [[BR]]If standalone is "no", a matching description *must* be a description of value occurring elsewhere in the DSP. [[BR]] If standalone is "both", both are allowed. [[BR]] If this description template is referred to in a Value Constraint, standalone cannot be "yes". XML Attribute Name:: standalone === Minimum occurrence constraint === Summary:: The minimum number of times this kind of description must appear in the Description Set. Allowed values:: non-negative integer Default:: 0 Conditions:: must be equal or less than the Maximum occurrence XML Attribute Name:: minOccurs === Maximum occurrence constraint === Summary:: The maximum number of times this kind of description is allowed to appear in the Description Set. Allowed values:: non-negative integer or "infinity" Default:':: "infinity" Conditions:: must be equal or greater than the Minimum occurrence XML Attribute Name:: maxOccurs === Resource Class Membership Constraint === Summary:: Classes that the resource may be an instance of Allowed values:: a list of class URIs Default:: no constraint Conditions:: if given, the resource must be an instance of one of the given classes. XML Element Name:: !ResourceClass == Statement templates == A statement template has the following possible constraints. XML Element Name:: !StatementTemplate === Minimum occurrence constraint === Summary:: The minimum number of times this kind of statement must appear in the enclosing Description. Allowed values:: non-negative integer Default:: 0 Conditions:: must be equal or less than the Maximum occurrence XML Attribute Name:: minOccurs === Maximum occurrence constraint === Summary:: The maximum number of times this kind of statement is allowed to appear in the enclosing Description. Allowed values:: non-negative integer or "infinity" Default:':: "infinity" Conditions:: must be equal or greater than the Minimum occurrence XML Attribute Name:: maxOccurs === Type constraint === Summary:: The type of value surrogate (literal/non-literal) that is allowed in this Statement. Allowed values:: "literal" / "nonliteral" Default:: both allowed Conditions:: If no value is given, no further constraining on the value surrogate can be made. XML Attribute Name:: type ''Note:'' that the type constraint should follow any range given for the used properties. === Property constraints === There are two ways of constraining the property in a statement: * By giving an explicit list of allowed properties * By requiring the property to be a sub-property of a given property. Exactly one of the above methods must be used in a single statement template. ==== Property list constraint ==== Summary:: A set of properties that are allowed in this statement template. Allowed values:: a list of property URIs Default:: N/A Conditions:: cannot occur together with a sub-property constraint XML Element Name:: Property ==== Sub-property constraint ==== Summary:: Only sub-properties of the given property are allowed in this statement template. Note that the given property is included in this list (all properties are sub-properties of themselves). Allowed values:: a property URI Default:: N/A Conditions:: cannot occur together with a property list constraint XML Element Name:: !SubPropertyOf === Literal value constraints === Constrains a literal value surrogate in a statement. Only allowed in the case that the type constraint has the value "literal". XML Element Name:: !LiteralConstraint ==== Literal list constraint ==== Summary:: Literals that are allowed as values. Allowed values:: a list of literals, i.e. (string, language tag) or (string, syntax encoding scheme URI) pairs. Default:: no constraint Conditions:: if given, no other literal constraint may be given XML Element Name:: !LiteralOption ==== Literal language constraint ==== Summary:: Whether languages are allowed for the literal Allowed values:: "mandatory" / "optional" / "disallowed" Default:: "optional" Conditions:: if "mandatory", Syntax encoding schemes are automatically disallowed. XML Element Name:: !LanguageOccurrence ==== Literal language list constraint ==== Summary:: Languages allowed for the literal Allowed values:: a list consisting of language tags Default:: no constraint XML Element Name:: Language ==== Syntax Encoding Scheme constraint ==== Summary:: Whether Syntax Encoding Scheme are allowed for the literal Allowed values:: "mandatory" / "optional" / "disallowed" Default:: "optional" Conditions:: if "mandatory", language tags are automatically disallowed. XML Element Name:: !SyntaxEncodingSchemeOccurrence ==== Syntax Encoding Scheme list constraint ==== Summary:: Syntax encoding schemes allowed for the literal Allowed values:: a list consisting of syntax encoding scheme URIs Default:: no constraint XML Element Name:: !SyntaxEncodingScheme === Non-literal value constraints === Constrains the value surrogate in a statement. Only allowed in the case that the type constraint has the value "nonliteral". XML Element Name:: !NonLiteralConstraint ==== Description template reference ==== Summary:: A reference to a description template that may be used to describe the value Allowed values:: an identifier defined in a Description Template Default:: Related description not allowed Conditions:: if given, any related description of the value within the record must match the referenced Description Template. If the referenced Description Template contains mandatory Statement templates, such a description of the value must exist. XML Attribute Name:: descriptionTemplateRef ==== Class membership constraint ==== Summary:: Classes that the value may be an instance of Allowed values:: a list of class URIs Default:: no constraint Conditions:: if given, the value must be an instance of one of the given classes. XML Element Name:: !ValueClass '''Note:''' this is not a syntactic constraint, and as such might not be evaluated by all processors. If a type statement is desired, an explicit Statement template in a Description Template for the value resource should be created. ==== Value URI constraint ==== ===== Value URI occurrence constraint ===== Summary:: Whether a value URI must be given Allowed values:: "disallowed" / "optional" / "mandatory" Default:: "optional" Conditions:: XML Element Name:: !ValueURIOccurrence ===== Value URI list constraint ===== Summary:: URIs that are allowed as value URIs. Allowed values:: a list of URIs Default:: no constraint Conditions:: If a value URI is given, it must be taken from this list. Cannot be specified if value occurrence is "disallowed" XML Element Name:: !ValueURI ==== Vocabulary encoding scheme constraint ==== ===== Vocabulary encoding scheme occurrence constraint ===== Summary:: Whether a vocabulary encoding scheme must be given Allowed values:: "disallowed" / "optional" / "mandatory" Default:: "optional" Conditions:: XML Element Name:: !VocabularyEncodingSchemeOccurrence ===== Vocabulary encoding scheme list constraint ===== Summary:: URIs that are allowed as Vocabulary Encoding schemes. Allowed values:: a list of URIs Default:: no constraint Conditions:: If a vocabulary encoding scheme is given, it must be taken from this list. Cannot be specified if vocabulary encoding scheme occurrence is "disallowed" XML Element Name:: !VocabularyEncodingScheme ==== Value String Constraints ==== If at least one value string constraint is given, any value string must match at least one of the constraints. If no value string constraint is given, any value string is allowed. For each value string constraint, the following may be specified. XML Element Name:: !ValueStringConstraint ===== Minimum occurrence constraint ===== Summary:: The minimum number of times this kind of value string must appear in the enclosing Statement. Allowed values:: non-negative integer Default:: 0 Conditions:: must be equal or less than the Maximum occurrence XML Attribute Name:: minOccurs ===== Maximum occurrence constraint ===== Summary:: The maximum number of times this kind of value string is allowed to appear in the enclosing Statement. Allowed values:: non-negative integer or "infinity" Default:':: "infinity" Conditions:: must be equal or greater than the Minimum occurrence XML Attribute Name:: maxOccurs ===== Other constraints ===== All Literal constraints can be used for value strings as well. == XML structure == * [attachment:dcmi-dsp.xsd First version of XML schema] {{{ }}} == RDF variant == {{{ true 0 0 0 0 0 0 }}} == Examples == Simple DC: {{{ http://purl.org/dc/terms/title http://purl.org/dc/terms/title }}} == Simple FOAF == {{{ http://xmlns.com/foaf/0.1/Person http://xmlns.com/foaf/0.1/name http://xmlns.com/foaf/0.1/knows http://xmlns.com/foaf/0.1/Person }}}