Misplaced Pages

#838161

45-518: OLAC advises on best practices in language archiving, and works to promote interoperation between language archives. The OLAC metadata set is based on the complete set of Dublin Core metadata terms DCMT, but the format allows for the use of extensions to express community-specific qualifiers. It is often contrasted to IMDI (ISLE Metadata Initiative). The OLAC metadata is based on five primary attributes, refine, code, scheme, lang, and langs , although

90-457: A Uniform Resource Identifier (URI). An object can also be a literal value. This simple, flexible data model has a lot of expressive power to represent complex situations, relationships, and other things of interest, while also being appropriately abstract. RDF was adopted as a W3C recommendation in 1999. The RDF 1.0 specification was published in 2004, and the RDF 1.1 specification in 2014. SPARQL

135-410: A labeled , directed multigraph . This makes an RDF data model better suited to certain kinds of knowledge representation than other relational or ontological models. As RDFS , OWL and SHACL demonstrate, one can build additional ontology languages upon RDF. The initial RDF design, intended to "build a vendor-neutral and operating system- independent system of metadata", derived from

180-569: A DCMI Usage Board within the context of a DCMI Namespace Policy. This policy describes how terms are assigned and also sets limits on the amount of editorial changes allowed to the labels, definitions, and usage comments. The Dublin Core Metadata Terms vocabulary has been formally standardized internationally as ISO 15836 by the International Organization for Standardization (ISO) and as IETF RFC 5013 by

225-586: A URI could represent absolutely anything. However, there is broad agreement that a bare URI (without a # symbol) which returns a 300-level coded response when used in an HTTP GET request should be treated as denoting the internet resource that it succeeds in accessing. Therefore, producers and consumers of RDF statements must agree on the semantics of resource identifiers. Such agreement is not inherent to RDF itself, although there are some controlled vocabularies in common use, such as Dublin Core Metadata, which

270-453: A single scope identifier to be associated with a statement that has not been assigned a URI, itself. Likewise named graphs in which a set of triples is named by a URI can represent context without the need to reify the triples. The predominant query language for RDF graphs is SPARQL . SPARQL is an SQL -like language, and a recommendation of the W3C as of January 15, 2008. The following

315-414: A specific element refinement term should be able to ignore the qualifier and treat the metadata value as if it were an unqualified (broader) element. While this may result in some loss of specificity, the remaining element value (without the qualifier) should continue to be generally correct and useful for discovery. Qualified Dublin Core added qualifiers to these elements: And added three elements not in

360-542: A statement can be associated with a context, named by a URI, in order to assert an "is true in" relationship. As another example, it is sometimes convenient to group statements by their source, which can be identified by a URI, such as the URI of a particular RDF/XML document. Then, when updates are made to the source, corresponding statements can be changed in the model, as well. Implementation of scopes does not necessarily require fully reified statements. Some implementations allow

405-402: A type of database called a triplestore . The subject of an RDF statement is either a uniform resource identifier (URI) or a blank node , both of which denote resources . Resources indicated by blank nodes are called anonymous resources. They are not directly identifiable from the RDF statement. The predicate is a URI which also indicates a resource, representing a relationship. The object

450-433: Is SHACL (Shapes Constraint Language). SHACL specification is divided in two parts: SHACL Core and SHACL-SPARQL. SHACL Core consists of a list of built-in constraints such as cardinality, range of values and many others. SHACL-SPARQL describes SPARQL-based constraints and an extension mechanism to declare new constraint components. Other non-standard ways to describe and validate RDF graphs include: The following example

495-411: Is a URI, blank node or a Unicode string literal . As of RDF 1.1 resources are identified by Internationalized Resource Identifiers (IRIs); IRI are a generalization of URI. In Semantic Web applications, and in relatively popular applications of RDF like RSS and FOAF (Friend of a Friend), resources tend to be represented by URIs that intentionally denote, and can be used to access, actual data on

SECTION 10

#1732766294839

540-722: Is a major component in the W3C's Semantic Web activity: an evolutionary stage of the World Wide Web in which automated software can store, exchange, and use machine-readable information distributed throughout the Web, in turn enabling users to deal with the information with greater efficiency and certainty . RDF's simple data model and ability to model disparate, abstract concepts has also led to its increasing use in knowledge management applications unrelated to Semantic Web activity. A collection of RDF statements intrinsically represents

585-438: Is a standard query language for RDF graphs. RDF Schema (RDFS), Web Ontology Language (OWL) and SHACL (Shapes Constraint Language) are ontology languages that are used to describe RDF data. The RDF data model is similar to classical conceptual modeling approaches (such as entity–relationship or class diagrams ). It is based on the idea of making statements about resources (in particular web resources) in expressions of

630-608: Is an example of a SPARQL query to show country capitals in Africa, using a fictional ontology: Other non-standard ways to query RDF graphs include: SHACL Advanced Features specification (W3C Working Group Note), the most recent version of which is maintained by the SHACL Community Group defines support for SHACL Rules, used for data transformations, inferences and mappings of RDF based on SHACL shapes. The predominant language for describing and validating RDF graphs

675-599: Is optional and may be repeated. There is no prescribed order in Dublin Core for presenting or using the elements. The Dublin Core Element Set was a response to concern about accurate finding of resources on the Web, with some early assumptions that this would be a library function. In particular it anticipated a future in which scholarly materials would be searchable on the World Wide Web. Whereas HTML

720-472: Is partially mapped to a URI space for use in RDF. The intent of publishing RDF-based ontologies on the Web is often to establish, or circumscribe, the intended meanings of the resource identifiers used to express data in RDF. For example, the URI: http://www.w3.org/TR/2004/REC-owl-guide-20040210/wine#Merlot is intended by its owners to refer to the class of all Merlot red wines by vintner (i.e., instances of

765-401: Is rather a URI reference , containing the '#' character and ending with a fragment identifier . The body of knowledge modeled by a collection of statements may be subjected to reification , in which each statement (that is each triple subject-predicate-object altogether) is assigned a URI and treated as a resource about which additional statements can be made, as in " Jane says that John

810-521: Is some resource or literal. More statements about the original statement may also exist, depending on the application's needs. Borrowing from concepts available in logic (and as illustrated in graphical notations such as conceptual graphs and topic maps ), some RDF model implementations acknowledge that it is sometimes useful to group statements according to different criteria, called situations , contexts , or scopes , as discussed in articles by RDF specification co-editor Graham Klyne . For example,

855-432: Is taken from the W3C website describing a resource with statements "there is a Person identified by http://www.w3.org/People/EM/contact#me, whose name is Eric Miller, whose email address is e.miller123(at)example (changed for security purposes), and whose title is Dr." The resource "http://www.w3.org/People/EM/contact#me" is the subject. The objects are: The subject is a URI. The predicates also have URIs. For example,

900-811: Is the Open Source Metadata Framework (OMF) specification. OMF is in turn used by Rarian (superseding ScrollKeeper ), which is used by the GNOME desktop and KDE help browsers and the ScrollServer documentation server. PBCore is also based on Dublin Core. The Zope CMF's Metadata products, used by the Plone , ERP5 , the Nuxeo CPS Content management systems , SimpleDL , and Fedora Commons also implement Dublin Core. The EPUB e-book format uses Dublin Core metadata in

945-431: Is the author of document X". Reification is sometimes important in order to deduce a level of confidence or degree of usefulness for each statement. In a reified RDF database, each original statement, being a resource, itself, most likely has at least three additional statements made about it: one to assert that its subject is some resource, one to assert that its predicate is some resource, and one to assert that its object

SECTION 20

#1732766294839

990-487: Is used as a foundation for RDF Schema , where it is extended. Several common serialization formats are in use, including: RDF/XML is sometimes misleadingly called simply RDF because it was introduced among the other W3C specifications defining RDF and it was historically the first W3C standard RDF serialization format. However, it is important to distinguish the RDF/XML format from the abstract RDF model itself. Although

1035-564: The DCMI Metadata Terms was created using a RDF data model. This expanded element set incorporates the original 15 elements and many of the qualifiers of the qualified Dublin Core as RDF properties. The full set of elements is found under the namespace http://purl.org/dc/terms/ . There is a separate namespace for the original 15 elements as previously defined: http://purl.org/dc/elements/1.1/ . The Dublin Core vocabulary published in 1999 consisted of 15 terms: The vocabulary

1080-689: The Internet Engineering Task Force (IETF), as well as in the U.S. as ANSI/NISO Z39.85 by the National Information Standards Organization (NISO). Syntax choices for metadata expressed with the Dublin Core elements depend on context. Dublin Core concepts and semantics are designed to be syntax independent and apply to a variety of contexts, as long as the metadata is in a form suitable for interpretation by both machines and people. One Document Type Definition based on Dublin Core

1125-507: The OPF file . Qualified Dublin Core is used in the DSpace archival management software. The Australian Government Locator Service (AGLS) metadata standard is an application profile of Dublin Core. Resource Description Framework The Resource Description Framework ( RDF ) is a method to describe and exchange graph data. It was originally designed as a data model for metadata by

1170-611: The University of Michigan . In 1999, the W3C published the first recommended RDF specification, the Model and Syntax Specification ("RDF M&S"). This described RDF's data model and an XML serialization. Two persistent misunderstandings about RDF developed at this time: firstly, due to the MCF influence and the RDF "Resource Description" initialism, the idea that RDF was specifically for use in representing metadata; secondly that RDF

1215-525: The World Wide Web Consortium (W3C). It provides a variety of syntax notations and data serialization formats, of which the most widely used is Turtle (Terse RDF Triple Language). RDF is a directed graph composed of triple statements. An RDF graph statement is represented by: (1) a node for the subject, (2) an arc from subject to object, representing a predicate, and (3) a node for the object. Each of these parts can be identified by

1260-481: The Dublin Core Element Set allowed authors of web pages a vocabulary and method for creating simple metadata for their works. It provided a simple, flat element set that could be used Qualified Dublin Core was developed in the late 1990s to provide an extension mechanism to the vocabulary of 15 elements. This was a response to communities whose metadata needs required additional detail. In 2012,

1305-467: The RDF/XML format is still in use, other RDF serializations are now preferred by many RDF users, both because they are more human-friendly, and because some RDF graphs are not representable in RDF/XML due to restrictions on the syntax of XML QNames . With a little effort, virtually any arbitrary XML may also be interpreted as RDF using GRDDL (pronounced 'griddle'), Gleaning Resource Descriptions from Dialects of Languages. RDF triples may be stored in

1350-645: The URI for each predicate: In addition, the subject has a type (with URI http://www.w3.org/1999/02/22-rdf-syntax-ns#type), which is person (with URI http://www.w3.org/2000/10/swap/pim/contact#Person). Therefore, the following "subject, predicate, object" RDF triples can be expressed: In standard N-Triples format, this RDF can be written as: Equivalently, it can be written in standard Turtle (syntax) format as: Or, it can be written in RDF/XML format as: Certain concepts in RDF are taken from logic and linguistics , where subject-predicate and subject-predicate-object structures have meanings similar to, yet distinct from,

1395-638: The W3C's Platform for Internet Content Selection (PICS), an early web content labelling system, but the project was also shaped by ideas from Dublin Core , and from the Meta Content Framework (MCF), which had been developed during 1995 to 1997 by Ramanathan V. Guha at Apple and Tim Bray at Netscape . A first public draft of RDF appeared in October 1997, issued by a W3C working group that included representatives from IBM , Microsoft , Netscape , Nokia , Reuters , SoftQuad , and

OLAC - Misplaced Pages Continue

1440-435: The World Wide Web. But RDF, in general, is not limited to the description of Internet-based resources. In fact, the URI that names a resource does not have to be dereferenceable at all. For example, a URI that begins with "http:" and is used as the subject of an RDF statement does not necessarily have to represent a resource that is accessible via HTTP , nor does it need to represent a tangible, network-accessible resource — such

1485-448: The above URI each represent the class of all wine produced by a single vintner), a definition which is expressed by the OWL ontology — itself an RDF document — in which it occurs. Without careful analysis of the definition, one might erroneously conclude that an instance of the above URI was something physical, instead of a type of wine. Note that this is not a 'bare' resource identifier, but

1530-489: The base 15: Qualified Dublin Core is often used with a "dot syntax", with a period separating the element and the qualifier(s). This is shown in this excerpted example provided by Chan and Hodges: Title: D-Lib Magazine Title.alternative: Digital Library Magazine Identifier.ISSN: 1082-9873 Publisher: Corporation for National Research Initiatives Publisher.place: Reston, VA. Subject.topical.LCSH: Digital libraries - Periodicals The DCMI Metadata Terms lists

1575-514: The color", and an object denoting "blue". Therefore, RDF uses subject instead of object (or entity ) in contrast to the typical approach of an entity–attribute–value model in object-oriented design : entity (sky), attribute (color), and value (blue). RDF is an abstract model with several serialization formats (being essentially specialized file formats ). In addition the particular encoding for resources or triples can vary from format to format. This mechanism for describing resources

1620-478: The current set of the Dublin Core vocabulary. This set includes the fifteen terms of the DCMES (in italic ), as well as many of the qualified terms. Each term has a unique URI in the namespace http://purl.org/dc/terms , and all are defined as RDF properties. It also includes these RDF classes which are used as domains and ranges of some properties: Changes that are made to the Dublin Core standard are reviewed by

1665-593: The element, its function, notes on its usage, and examples of its coding. In addition, OLAC provides a list of metadata extensions to augment descriptions. This computing article is a stub . You can help Misplaced Pages by expanding it . Dublin Core The Dublin Core vocabulary , also known as the Dublin Core Metadata Terms ( DCMT ), is a general purpose metadata vocabulary for describing resources of any type. It

1710-401: The form subject – predicate – object , known as triples . The subject denotes the resource; the predicate denotes traits or aspects of the resource, and expresses a relationship between the subject and the object . For example, one way to represent the notion "The sky has the color blue" in RDF is as the triple: a subject denoting "the sky", a predicate denoting "has

1755-406: The last attribute is only for completed metadata sets. Each attribute serves a different function and is applicable in a different section of the metadata. There are currently 23 different elements that OLAC lists on its metadata page. Elements may be used more than once, and not every element is required in a metadata submission. Each element's entry on the official OLAC page includes the name of

1800-718: Was an XML format rather than a data model, and only the RDF/XML serialisation being XML-based. RDF saw little take-up in this period, but there was significant work done in Bristol , around ILRT at Bristol University and HP Labs , and in Boston at MIT . RSS 1.0 and FOAF became exemplar applications for RDF in this period. The recommendation of 1999 was replaced in 2004 by a set of six specifications: "The RDF Primer", "RDF Concepts and Abstract", "RDF/XML Syntax Specification (revised)", "RDF Semantics", "RDF Vocabulary Description Language 1.0", and "The RDF Test Cases". This series

1845-555: Was being used to mark-up the structure of documents, metadata was needed to mark-up the contents of documents. Given the great number of documents on, and soon to be on, the World Wide Web, it was proposed that "self-identifying" documents would be necessary. To this end, the Dublin Core Metadata Workshop met beginning in 1995 to develop a vocabulary that could be used to insert consistent metadata into Web documents. Originally defined as 15 metadata elements,

OLAC - Misplaced Pages Continue

1890-469: Was commonly expressed in HTML 'meta' tagging in the "<head>" section of an HTML-encoded page. The vocabulary could be used in any metadata serialization including key/value pairs and XML. Subsequent to the specification of the original 15 elements, Qualified Dublin Core was developed to provide an extension mechanism to be used when the primary 15 terms were not sufficient. A set of common refinements

1935-564: Was first developed for describing web content in the early days of the World Wide Web. The Dublin Core Metadata Initiative ( DCMI ) is responsible for maintaining the Dublin Core vocabulary. Initially developed as fifteen terms in 1998 the set of elements has grown over time and in 2008 was redefined as an Resource Description Framework (RDF) vocabulary. Designed with minimal constraints, each Dublin Core element

1980-511: Was provided in the documentation. These schemes include controlled vocabularies and formal notations or parsing rules. Qualified Dublin Core was not limited to these specific refinements, allowing communities to create extended metadata terms to meet their needs. The guiding principle for the qualification of Dublin Core elements, colloquially known as the Dumb-Down Principle , states that an application that does not understand

2025-413: Was superseded in 2014 by the following six "RDF 1.1" documents: "RDF 1.1 Primer", "RDF 1.1 Concepts and Abstract Syntax", "RDF 1.1 XML Syntax", "RDF 1.1 Semantics", "RDF Schema 1.1", and "RDF 1.1 Test Cases". The vocabulary defined by the RDF specification is as follows: rdf:Statement , rdf:subject , rdf:predicate , rdf:object are used for reification (see below ). This vocabulary

#838161