\documentclass{mlcennote}
\usepackage{longtable}
\title{MetaLex CEN Workshop Proposal}
\author{Alexander Boer}
\institute{\defaultaffiliation}
\author{Fabio Vitali}
\institute{Department of Computer Science\\University of Bologna\\Italy}
\runningauthor{Alexander Boer}
\correspondingauthor{Alexander Boer}
\email{aboer@leibnizcenter.org}
\Leibnizreportdate{november 2007}
\abstract{
The partial agreement of december 2006 was adopted by the workshop in the understanding that it will be augmented with additional agreements on ontological formalization, citation and reference, time and versioning, and components and component inclusion. This document proposes additional agreements (taking into account proposals from \cite{estrella3.2:07}), and clarifies terminology. Instead of submitting a consolidated agreement, the technical committee has described the additions and clarifications separately.
\textbf{Status:} This document is a \textbf{draft}. It does not necessarily reflect the opinions of the CEN workshop, the technical committee of the CEN workshop,
or even all of its authors.
}
\begin{document}
\maketitle
\section{Introduction}
The partial agreement of december 2006 was adopted by the workshop in the understanding that it will be augmented with additional agreements on ontological formalization, citation and reference, time and versioning, and components and component inclusion.
The MetaLex CEN workshop requested more rigorous formalization of the four ontological levels (work, expression, manifestation, item) at which a bibliographic entity exists, and what properties belong to which level. The technical committee will make a definitive list of properties of expressions that distinguishes version, variant, consolidation, original, translation, and localization.
As is implied by the FRBR definitions of bibliographic entities, the parts of a bibliographic entity are also bibliographic entities. Any part, except the top level element, of a standard MetaLex XML manifestation can be implemented as an inclusion pointer to an external object. On the manifestation level one for instance makes choices about object names and media formats (a tiff, jpeg, pdf image etc.). In some cases a text that is (or could be) embodied by a MetaLex manifestation (e.g. a chinese appendix of a treaty) is embodied alternatively by a media object. This document clarifies the position taken with respect to (de)composition of bibliographic objects.
This document proposes additional agreements (taking into account proposals from \cite{estrella3.2:07}), and clarifies terminology. Instead of submitting a consolidated agreement, the technical committee has described the additions and clarifications separately. Intended appendices to this document are:
\begin{enumerate}
\item A naming convention document;
\item A versioning document;
\item a semantic interpretation of citation document (informative only);
\item An XML schema;
\item A DTD++ schema; and
\item An OWL schema.
\end{enumerate}
Check for availability of the appendices. The latest version of this document can be downloaded on:
\small\begin{verbatim}
http://svn.metalex.eu/svn/MetaLexWS/documentation/2007proposal/
\end{verbatim}
\normalsize Please regularly check for updates. Public comments on this document and its appendices sent to Alexander Boer will be posted on:
\small\begin{verbatim}
http://wiki.metalex.eu/index.php/2007_Addendum_Discussion_Page
\end{verbatim}
\normalsize
\section{Bibliographic Entities}
The use of bibliographic terminology in the CEN MetaLex standard is inspired by the \emph{IFLA Functional Requirements for Bibliographic Records} (cf. \cite{Saur1998}):
\begin{itemize}
\item A \textbf{bibliographic object} is a bounded representation of a body of information,
designed with the intent to communicate, preserved in a form independent of a sender or receiver. A bibliographic work, expression, manifestation, and item are bibliographic objects.
\item A \textbf{bibliographic citation} is a representation of a bibliographic identifier of a bibliographic object, with the intent of referring to that bibliographic object. \emph{Article 1}, \emph{the first article} and \emph{the previous article} are examples of citation, and \emph{the Minister}, the \emph{President of the Republic}, \emph{the accused}, and \emph{We, Beatrix} are examples of references to other, interesting but non-bibliographic, things.
\item A \textbf{unique bibliographic identifier} identifies a bibliographic object \\uniquely. The \emph{uniform resource identifier} can for instance be used as a unique bibliographic identifier.
\item A \textbf{bibliographic work} is a bibliographic object, realized by one or more expressions, and created by one or more persons in a single creative process ending in a publication event. A work has an author or authors, and is the result of a publication event. We recognize the work through individual expressions of the work, but the work itself exists only in the commonality of \emph{content} between and among the various expressions of the work: it is an intentional object\footnote{I.e. it exists only as the object of one's thoughts and communication acts, and not as a physical object.}.
\item An \textbf{bibliographic expression} is a realization of one bibliographic work in the form of signs, words, sentences, paragraphs, etc. by the author of that work. Physical form aspects, as typeface or page-layout, are generally speaking excluded from the expression level. Any change in \emph{content} constitutes a gives rise to a new expression. If an expression is revised or modified, the resulting expression is considered to be a new expression, no matter how minor the modification may be. Expression is an intention object.
\item A \textbf{bibliographic manifestation} embodies one expression of one bibliographic work. The boundaries between one manifestation and another are drawn on the basis of both content and physical form. When the production process involves changes in physical form the resulting product is considered a new manifestation. Thus, a specific XML representation, a PDF file (as generated by printing into PDF a specific Word file with a specific PDF distiller), a printed booklet, all represent different manifestations of the same expression of a work. Manifestation is an intention object. A MetaLex XML element is a bibliographic manifestation.
\item A \textbf{bibliographic item} exemplifies one manifestation of one expression of one work: a specific copy of a book on a specific shelf in a library, a file stored on a computer in a specific location, etc. Items stored on a computer can be easily copied to another location, resulting in another item, but the same manifestation. This makes adding metadata about the item to the item in principle impossible. On the Internet generally speaking only the \emph{uniform resource locator} (URL) is an item-specific datum. An item is a physical object.
\end{itemize}
\subsection{Elements, Documents, and Composition}
The compound documents in the CEN MetaLex standard is inspired by the \emph{Compound Document by Reference Framework} (CDRF)\footnote{http://www.w3.org/TR/CDR/}:
\begin{itemize}
\item A \textbf{MetaLex element}, is a MetaLex conformant manifestation of an expression component of a bibliographic source of law, or of metadata about that expression component, in the form of an XML element, conforming to a version of the MetaLex/CEN specification.
\item A \textbf{MetaLex root element} is an outermost MetaLex XML element, i.e. an element that is not part of the content of another MetaLex element.
\item A \textbf{MetaLex XML document} is, for the purposes of this standard, a synonym of a MetaLex root element. This mapping is included to match the terminology of the FRBR to the terminology of the CDRF.
\item A \textbf{MetaLex XML child document} is a MetaLex XML document that is included by reference (with the \textbf{src} property) in another MetaLex XML document.
\item A \textbf{MetaLex XML parent document}, or \textbf{compound document}, is a MetaLex XML document that includes other bibliographic objects by reference (with the \textbf{src} property).
\end{itemize}
\subsection{Legal Bibliographic Entities}
Some additional terminology is introduced to capture some bibliographic phenomena relevant to law, as well as operational criteria for recognizing these in a MetaLex XML document:
\begin{itemize}
\item A \textbf{bibliographic source of law} is a bibliographic object that can be, is, was, or presumably will be referred to, by way of bibliographic citation, to back an argument claiming the existence of a legal rule in a certain legal system, or, alternatively, a bibliographic object published or realized by a competent legislator to communicate a legal rule to a certain group of addressees. Both the legislator and the user of the bibliographic source of law understand it as a medium used for communicating the existence of legal rules, including auxiliary declarations required for the proper understanding of legal rules, between legislator and user.
\item An \textbf{initial version} of a bibliographic work is the expression that realizes the work at the time of publication, its official release in the public domain. It is the \textbf{metalex-owl:result} of a \textbf{metalex-owl:Publication}.
\item A \textbf{version} of a bibliographic work is either the initial version of the work, or an expression realized by modification of a version. It is the \textbf{metalex-owl:result} of a \textbf{metalex-owl:modification} of the (\textbf{metalex-owl:matter}) previous version.
\item A \textbf{version in force} of a bibliographic work is a version that is, was, or will be \emph{in force}\footnote{See the appendix on versioning for details.} during a specific time interval. The in force time intervals of versions in force of the same work do not overlap.
\item A \textbf{consolidation} of a bibliographic work is a version realized by the execution of legal rules found in another bibliographic source of law to the previous version. It is the \textbf{metalex-owl:result} of a \textbf{metalex-owl:Modification} of the (\textbf{metalex-owl:matter}), which is the previous version, by the (\textbf{metalex-owl:instrument}), which is the other bibliographic source of law stipulating the modification, usually when it enters into force.
\item A \textbf{variant} of a version in force of a bibliographic work is an expression that shares its \emph{in force} time interval. Although the concept variant is often nominalized, it is a symmetric relationship (\textbf{metalex-owl:variant}) between two expressions.
\item A \textbf{language variant} of an expression of a bibliographic work is an expression that shares its in force time interval, and differs in nothing but language. For instance, the English, Dutch, Italian, and German versions of a European directive are different language variants. It is also a symmetric relationship (derived on \textbf{metalex-owl:variant}). In a MetaLex manifestation of the expression this is expressed in different values of the \textbf{xml:lang} attribute.
\item A \textbf{translation} of an expression of a bibliographic work is an expression that shares its in force time interval, differs in nothing but language, and has been realized by way of translation of one expression into another expression. Translation is an asymmetric relation between bibliographic expressions, expressed by a \textbf{metalex-owl:Translation} event, which has a \textbf{metalex-owl:translator}, taking the initial expression as a \textbf{metalex-owl:matter}, and the translated document as \textbf{metalex-owl:result}. The translation should not be confused with language variant: while language variants can be realized concurrently by the legislator, and are equally authoritive if they are, the translation of an expression is generally speaking less authoritive than the expression it is a translation of, even if \emph{officially} translated.
\end{itemize}
\subsection{Bibliographic Identity}
Each bibliographic item exemplifies exactly one manifestion that embodies exactly one expression that realizes exactly one work. Because all these mappings are \emph{functional}, i.e. unambiguously maps to one entity, item identity can be, and often is, used as an indirect identifier of the other objects, similar to how, for instance, email addresses usually have a functional mapping to persons and can be used as an indirect identifier of persons. One can for instance refer to a work by referring to its initial expression in a context where a reference to a work is expected.
The inverse of these relations is however often not a function. One can think of the work as an abstraction of 1+ expressions, the expression as an abstraction of 1+ manifestations, the manifestation as an abstraction of 1+ items. The manifestation, expression, and work are intentional objects whose existence is conditioned to the existence of at least one item, manifestation, expression, respectively. There is no such thing as an expression that is not embodied, a work that is not realized, etc.
Besides the hierarchical constitutive relationships between the four levels, there are also horizontal relations between the objects within a level. The expressions of a work in the legal field are usually either the initially published expression, or expressions derived by content modification activity or translation activity. Manifestations of an expression are either the initially created one(s), or manifestations derived by physical modification activity. Items of a manifestation are either the initially created one(s), or copies of them.
The \texttt{metalex-owl} schema includes a number of event type definitions (cf. \cite{BoerEtAl2004}, and generally \cite{LagozeEtAl2000} on linking metadata to events) to make these horizontal relations explicit for the expression level. At the item level they cannot be embedded in a MetaLex item for reasons pointed out earlier.
For the manifestation level this is still an open issue: manifestation level version management is indeed desirable, but it is questionable whether this should be part of MetaLex/CEN. Appropriate manifestation level version management methods and tools exist (CVS, SVN, etc.).
Most legislative events happen at the work and expression levels. Content-related events like markup, metadating, and digital signature happen at the manifestation level.
The MetaLex/CEN standard aims to provide metadata for describing both the hierarchical and relational way of positioning and identifying bibliographic objects, at least at the work and expression level, at the relevant levels of granularity.
%\section{Decomposition of Bibliographic Objects}\marginpar{\Huge?}
%\emph{Here something about parts and wholes (root element, parent element, child element, leaf element on the manifestation level), and downward inheritance and overriding of metadata/attribute values. Something about the distinction between composition/compound documents (manifestation/item level structure decisions(?)) and logical structure of the work/expression}
%\emph{Ideally per level which attribute value or metadata statement refers to it.}
\section{Conformance and Transformation}
\textbf{To be written.} Conformance in the strict sense means 1) validation of XML documents against a schema that includes the MetaLex XML schema, 2) the theoretical possibility of obtaining an XML document that uses solely MetaLex generic elements and validates against the MetaLex XML schema by way of simple substitution, and 3) conformance to the MetaLex CWA written guidelines.
Any XML encoding is \emph{transformation conformant} if instances can be transformed automatically into conformant MetaLex XML documents. The workshop recommends implementing the transformation in the form of an XSL transformation (XSLT\footnote{See \texttt{http://www.w3.org/TR/xslt}}). The workshop also recommends copying any attributes from the original XML encoding into the MetaLex XML document.
\section{Naming and Addressing}
The previous workshop agreement did not specify a naming convention for the MetaLex CEN schemas: this document rectifies this omission. The namespace of MetaLex/CEN as adopted on december 15, 2007 is:
\small{\begin{verbatim}
http://www.metalex.eu/metalex/2007-12-15
\end{verbatim}}
XML elements, XML attributes, XML schema named complex types, etc, as well as OWL classes and OWL properties are declared in this namespace. Since ambiguity could arise in MetaLex/CEN specification documents as to whether a name in this namespace refers to an XML Schema or OWL entity, we use the \emph{NCName} \texttt{metalex} for XML, and \texttt{metalex-owl} for OWL\footnote{XML elements and types, and OWL classes and properties are already distinguished by typographic conventions in MetaLex/CEN. Note that OWL names only occur in MetaLex XML documents as the \emph{value} of XML attributes.}, i.e. it assumes the existence of two namespace declarations providing two different names for the \emph{same namespace}:
\small{\begin{verbatim}
xmlns:metalex="http://www.metalex.eu/metalex/2007-12-15"
xmlns:metalex-owl="http://www.metalex.eu/metalex/2007-12-15"
\end{verbatim}}
The OWL schema is published in conformance to the \emph{Best Practice Recipes for Publishing RDF Vocabularies}\footnote{http://www.w3.org/TR/swbp-vocab-pub/} guidelines as a hash namespace (recipe 3).
MetaLex/CEN elements and attributes \textbf{must} be namespace qualified, even though they may be associated to a default namespace without prefix.
Each bibliographic \emph{item} encoded in the MetaLex CEN standard has a URI. It must be possible to establish the \emph{xml base} of an item, in conformance with the XML Base specification\footnote{http://www.w3.org/TR/REC-xml/} and IETF RFC 3986 (or 2396). The concatenation of the established \emph{xml base} and the \textbf{metalex:id} of an element should result in a valid URI reference for the element, conformant to the addressing recommendations of W3C, which counts as a bibliographic identifier of the element as a bibliographic \emph{item}.
Note that if one uses an explicit \textbf{xml:base} attribute it remains the same after copying the document, which means that it also behaves like a manifestation level identifier, which is not intended. It is in principle not possible to encode item level information in the manifestation. There are however legitimate use cases of the \textbf{xml:base}, where it is inserted as a temporary identifier to an XML subtree in an XML processing pipeline.
The manifestation, expression, and work \textbf{must} also have at least one URI, which counts as their manifestation, expression, work base, respectively.
The \textbf{metalex:id} value of an element is a manifestation fragment identifier. Concatenated to the manifestation level document identifier it globally identifies the element at the manifestation level, concatenated to the expression level document identifier it globally identifies the expression embodied by the content of the element, concatenated to the work level document identifier it presumably globally identifies a structural element common to various expressions of the work.
The \textbf{metalex:numbering} attribute, already present in the 2006 CWA proposal, is reintroduced, but with a URI as value: its purpose is creating a predictable correspondence of \textbf{metalex:id} values between different manifestations of the same expression.
There are two different methods for uncovering the relationship between manifestation, expression, and work, which have a direct impact on naming and addressing:
\begin{enumerate}
\item An \textbf{explicit encoding} of the relation between these URIs, and/or the class of the object designated by the URI, as metadata.
\item A \textbf{naming convention} for manifestations, expressions, and works that establishes a systematic relationship between transparent URIs, as proposed in the naming convention appendix, which allows one to derive the URI of one from the other.
\end{enumerate}
The XML document declares what it is a manifestation of by way of metadata. Assuming \texttt{about=""} (i.e. empty string URI reference\footnote{Note that URI, which is absolute, and URI reference (cf. IETF 3986), which is absolute or relative, and can therefore be empty, are different. URI are globally unique, but URI references are not: only after resolution to a URI they are globally unique.}) refers to the document itself, the following declares a standard manifestation, expression, and work base (using the naming convention):
\small\begin{verbatim}
\end{verbatim}
The RDF reading of \textbf{m1} is as follows: \textbf{m1} is a statement that states that the (referent of) \texttt{metalex:exemplifies} of (the referent of) \texttt{(empty string)} is (the referent of) \texttt{/tv/act/2004-02-13/2/tv}. An alternative, simpler form that is also permitted is the following:
\small\begin{verbatim}
\end{verbatim}
The properties \textbf{metalex-owl:exemplifies}, \textbf{metalex-owl:embodies}, \textbf{metalex-owl:realizes} are already part of the 2006 CWA. The semantics of \textbf{metalex-owl:thisEmbodies} and \textbf{metalex-owl:thisRealizes} are as follows, assuming \texttt{{p, q, r, s}} is a set of URI references:
\begin{enumerate}
\item If \texttt{p metalex-owl:exemplifies q} and \texttt{q metalex-owl:embodies r} \\then \texttt{p metalex-owl:thisEmbodies r}
\item If \texttt{p metalex-owl:exemplifies q} and \texttt{q metalex-owl:embodies r} and \\\texttt{r metalex-owl:realizes s} then \texttt{p metalex-owl:thisRealizes z}.
\end{enumerate}
It is also possible to directly state the type of a bibliographic object with the MetaLex OWL vocabulary, although this is rarely useful, since the domain and range restrictions of various metadata properties already convey this information:
\small\begin{verbatim}
\end{verbatim}
Read for \texttt{meta} in the examples above any appropriate element that permits metadata attributes. The URIs are relative, conforming to the naming convention: the base is set by the processing environment. This means that the \emph{mURI} of the naming convention describes a URI \emph{reference} that potentially resolves to large set of URIs for each bibliographic object: one for each processing environment that sets its own base.
The alternative to explicit processing of the relation between the bibliographic objects the item represents, is depending on a systematic relationship between transparent URIs. This proposal includes the \textbf{mURI} naming convention for the construction of these transparent URIs as an annex.
The URIs \texttt{http://gov.tv/tv/act/2004-02-13/2/tv} and \texttt{http://gov.tv/tv/act/2004-02-13} are examples of its use. \texttt{/2/tv} adds the information, appended to the work URI, that the reference is to the second version, and the Tuvaluan language variant.
Assuming both alternatives are adopted, there is a need to explicitly encode in an attribute, \textbf{metalex:naming} whether the manifestation respects the naming convention or using some other user community naming schema. Similar to \textbf{xml:base} and \textbf{xml:lang}, the value of \textbf{metalex:naming} applies to the content of the element that carries the attribute, except when overridden by other \textbf{metalex:naming} attributes. The value of \textbf{metalex:naming} is a URI. The standard defines two naming schemes: \textbf{metalex-owl:NoNamingScheme}, which allows any URI, and \textbf{metalex-owl:MetaLexNamingScheme}, which is the proposed naming scheme.
\section{Attributes and Content Models Addendum}
The technical committee proposes the following additions and clraifications pertaining to the attributes and content models specification in the december 6 2006 workshop agreement:
\begin{enumerate}
\item Clarification: every MetaLex element \textbf{must} have an \textbf{metalex:id} attribute.
\item The \textbf{xml:lang}\footnote{Used in conformance with \texttt{http://www.w3.org/TR/REC-xml/} and IETF RFC 3066.} \textbf{must} be recoverable from the context of the element.
\item Attributes from any other (\textbf{\#other}) namespace \textbf{may} be used on any MetaLex element.
\item The \textbf{metalex:src} (URI value) attribute is used to include a component by \emph{reference}.
\item The \textbf{metalex:naming} (URI value) attribute is used to signal conformance to a naming convention. Its values are URI references to allow for extensions without the possibility of name clashes. It \textbf{must} be recoverable from the context of the element.
\item The \textbf{metalex:numbering} attribute is split into two attributes and will define the mechanism by which the \textbf{metalex:id} of the element is generated. It \textbf{must} be recoverable from the context of the element.
\item The optional metadata attribute \textbf{metalex:showAs} \textbf{must} contain a human readable label of the \emph{whole} metadata statement, i.e. of its subject, property and object.
\item Patterns of the form \texttt{a*} (zero or more \texttt{a}'s) and \texttt{a+} (one or more \texttt{a}'s) in the XML schema are replaced by the pattern \texttt{a*|a,a*|a,a,a*|a,a,a,a*|a,a,a,a,a*}, respectively \texttt{a+|a,a+|a,a,a+|a,a,a,a+|a,a,a,a,a+} to align the semantics of the DTD++ schema and the XML Schema, at least for up to 5, or any other appropriately large number, to the discretion of the technical committee, different restrictions of \texttt{a} in derived conformant content models. In XML schema, if \texttt{b} and \texttt{c} are restrictions of \texttt{a}, the pattern \texttt{b,c} is not accepted as a restriction of \texttt{a+} or \texttt{a*}: the intended reading of the technical committee is that it should be.
\item The \textbf{metalex:rootType} content model, and its associated types and elements, disappear from the schema: instead the \textbf{metalex:containerType} content model is used. The \textbf{metalex:containerType} content model permits the use of an \textbf{metalex:mcontainerType} element as initial element.
\end{enumerate}
\section{Metadata}
MetaLex uses the conventions of RDF/A processing for embedding RDF metadata statements inside MetaLex XML. Consult \texttt{http://www.w3.org/TR/rdf-primer/} for more information about RDF and \texttt{http://www.w3.org/TR/xhtml-rdfa-primer/} for RDF/A. In any case of ambiguity this specification takes precedence over RDF/A specifications.
The next section is a rewrite of the corresponding section in the december 2006 Workshop Agreement, taking into account the W3C RDF/A Working Draft of 18 October 2007 (\textbf{http://www.w3.org/TR/2007/WD-rdfa-syntax-20071018/}). The special subject resolution rules for \textbf{meta} have been removed, and this specification purposely restricts the use of RDF/A compared to the RDF/A specifications.
The purpose of MetaLex embedded metadata is nothing more than storage of RDF formatted metadata in MetaLex XML. An RDF description of a resource consists of a set of statements. The MetaLex standard includes an OWL schema that specifies commonly required properties and classes in RDF statements about legal and legislative resources. This schema may be used with RDF stored outside the document in question, and the embedded metadata processing mechanism may be used with other metadata schemas like Dublin Core or PRISM.
The main difference between storage inside and outside the standard XML manifestation is the identification of the metadata author: the metadata inside the document is associated to the editor of the manifestation, who may be presumed to be the author of the metadata. An RDF statement has the following components:
\begin{description}
\item[subject:] the thing the statement describes;
\item[predicate:] a specific property;
\item[object:] the thing the statement says is the value of the property, for the thing the statement describes.
\end{description}
The subject and the property value are always URIs. The object is either a URI or a (optionally datatyped) literal.
See the RDF specifications at \texttt{http://www.w3.org/2001/sw/RDFCore/} for details on RDF literals and datatyping of literals.
A Metalex document \textbf{must} declare what it is a manifestation of, as follows:
\small\begin{verbatim}
\end{verbatim}
Other metadata \emph{may} be embedded.
\subsection{Embedded Metadata Processing}
RDF/A statements \emph{may} be added to any MetaLex element if the content model allows it. Elements derived from the \textbf{metalex:urMetaType} type \emph{must} contain RDF/A attributes expressing an RDF statement. Relative URI references in RDF/A attributes are relative to the \emph{xml base} of the containing element.
An RDF/A element is any XML element that contains either the attribute \textbf{property}, \textbf{rel}, or \textbf{rev}. Exactly one RDF statement is generated per \textbf{rel} (relation), \textbf{property}, or \textbf{rev} (reverse) attribute by an RDF/A processor: the attribute indicates a new statement whose \emph{predicate} is the URI value of that attribute. In the case of \textbf{rel} and \textbf{property}, the subject of the statement is decided by \emph{subject resolution}.
In the case of \textbf{rel}, the object is decided by \emph{URI reference object resolution}. In the case of \textbf{property}, the object is decided by \emph{literal object resolution}. In the case of \textbf{rev}, the subject of the triple is decided by \emph{URI reference object resolution} and the object of the triple is decided by \emph{subject resolution}. If both \textbf{rel} and \textbf{rev} attributes are used within the same element, two RDF statements are generated.
Literal object resolution yields either the value of the \textbf{content} attribute or, if it is absent, the element content. The value of the content attribute is by default interpreted as a plain literal. The element content is by default interpreted as an XML literal.
The \textbf{datatype} attribute is used to specify a specific XML Schema datatype \\(cf. \texttt{http://www.w3.org/TR/xmlschema11-2/}).
URI reference object resolution yields either the URI value of the \textbf{resource} attribute or, if absent, the \textbf{href} or \textbf{src} attribute. The \textbf{resource} attribute is only used to specifically communicate that the URI is not intended to be ``clickable'', or if a \textbf{href} or \textbf{src} attribute is already present on the element for other reasons and does not refer to the intended object. Use the \textbf{href} attribute whenever reasonable.
Subject resolution usually yields the URI value of the \textbf{about} attribute, or, if the RDFa element that includes the predicate attribute does not have an \textbf{about} attribute, the \textbf{about} attribute of the first ancestor element that has an \textbf{about} attribute. In the absence of an \textbf{about} attribute within scope, it yields the \emph{xml base} of the element.
\subsection{OWL Schema Addendum}
Concerns the following additions to \texttt{http://www.metalex.eu/metalex/2007-12-15.owl}:
\begin{enumerate}
\item The \textbf{metalex-owl:matter} property is a thematic role relation between an Event and another entity: the thing to which it happened. Just like a \textbf{metalex-owl:instrument} it is immanent and a source.
\item The \textbf{metalex-owl:variant} property is a symmetric relation between to bibliographic expressions.
\item The \textbf{metalex-owl:language-variant} property is a symmetric relation between to bibliographic expressions, and a subproperty of \textbf{metalex-owl:variant}. If there is a \textbf{metalex-owl:variant} relationship between to bibliographic expressions, and both bibliographic expressions have a different \textbf{xml:lang} value.
\item The \textbf{metalex-owl:Translation} event takes the initial expression to be translated as a \textbf{metalex-owl:matter}, and the translated document as \textbf{metalex-owl:result}.
\item The \textbf{metalex-owl:Modification} event is a subclass of \textbf{metalex-owl:Creation}, takes as (\textbf{metalex-owl:instrument}) a modifying bibliographic source of law, as \textbf{metalex-owl:result} a next version, and as \textbf{metalex-owl:matter} the previous version.
\item \textbf{metalex-owl:Publication} is a \textbf{metalex-owl:Creation}.
\end{enumerate}
\section{Citation and Reference}
In principle references to URI are made with the \textbf{href} attribute. Because the href attribute is also an RDF/A attribute the referring element also encodes a metadatum.
Another addition to the OWL schema is required: The RDF/A \textbf{rel/href} pair is i.a. used for references and citation, which makes reference and citation elements a type of metadata elements. The distinguishing property of references is that the (\textbf{rel}) value is a subproperty of \textbf{metalex-owl:refersTo}, which appeals to RDF Schema semantics. Citation uses a property value that is a subproperty of \textbf{metalex:cites}, which is itself a subproperty of \textbf{metalex-owl:refersTo}.
This means that the fact that some MetaLex XML element refers to another entity can also be stored in RDF, external to the MetaLex XML document.
A reference is something that refers to or designates something else, or acts as a standin for a relation between two things: the \emph{referrer} and the \emph{referent}. Since a relation can also be identified, the generic form of a reference is \emph{(referrer, predicate, referent)}, where predicate is the name of the relation, and are represented as RDF or RDF/A.
In the sense intended here a reference is an XML element (directly or indirectly) containing text, and the text refers deemed to refer to something else. The XML element will typically be of the \textbf{inline} content model type. A \textbf{citation} is an expression that refers to something intralinguistic, i.e. to another XML element (directly or indirectly) containing text, or to the bibliograpgic objects directly or indirectly embodied by it. Other references refer to something extralinguistic, i.e. something other than text, recoverable from the context in which the document was produced.
\emph{Article 1, the first article} and \emph{the previous article} are examples of citation, and \emph{the Minister, the President of the Republic, the accused}, and \emph{We, Beatrix, etc.} are examples of relevant references to other things.
A similar distinction, that should be distinguished from the previous one, is the distinction between exophora and endophora in linguistics. Take the following sentences:
\begin{enumerate}
\item \emph{Theft} is the unlawful taking of a good wholly or partially belonging to another.
\item \emph{It} (\emph{The theft}) must have been done with the intent to appropriate.
\end{enumerate}
\emph{It} (or \emph{The theft}) obviously refers back to Theft in the previous sentence. It is an endophoric proform expression, as opposed to exophoric (That must have been done intentionally, pointing to an act of taking in progress). Exophoric proform expressions are obviously rare in legal resources.
There is however a difference between the reference \emph{It} referring to theft as defined in the previous sentence and \emph{the previous sentence} as referring to a sentence. Theft and it are coreferents of something other than text: it is not an intralinguistic reference. Expressions like it do stand in for another expression (Theft), but only to indirectly reference meaning recoverable from context. They are used to avoid repetitive expressions and in quantification (i.e. carrying a variable from one sentence into the next one).
The following are examples of inline reference and citation:
\begin{verbatim}
\end{verbatim}
\begin{verbatim}
\end{verbatim}
In principle any element that can take metadata properties (in particular \texttt{rel}, \texttt{href}) can behave as a reference or citation element. The standard defines no specific content model for reference and citation: the user is free to define inline element structures of his own.
It is important to distinguish between two different reading of citation:
\begin{enumerate}
\item The purely operational criterium, which holds that a reference or citation is an element that has the right property value; and
\item The semantic interpretation, which holds that reference/citation is the meaning of the content enclosed by the XML element: even if there is no metadata identifying the target of the reference/citation, it still remains a reference/citation because this is inherent in the meaning of the content.
\end{enumerate}
While the technical committee agrees that the second reading is the ultimately correct one, it subscribes to the \textbf{design principle that content models should be identified by structure and attributes, and not their meaning}: giving meaningful names to elements is left to the user. While defining inline elements for citation is undoubtedly useful, it should not be part of an abstract meta standard like the MetaLex/CEN schema.
See the Semantic Interpretation of Citation appendix for a discussion on marking up citations. This text is informative only.
A citation in legislation usually refers to a work. A reference to legislation in a court verdict necessarily refers to an expression. References in other documents can refer to any level.
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