元数据（Metadata):描述数据的数据
都柏林核心元素集（Dublin Core Element Set 简称DC）
http://lov.okfn.org/dataset/lov/vocabs/dce
核心元数据元素集：
Title
Creator
Subject
Description
Publisher
Contributor
Date
Type
Format
Identifier
Source
Language
Relation
Coverage
Rights Management
interoperability :the ability of multiple systems, using different hardware and software platforms, data structure, and interfaces, to exchange and share data.
metadata: structured information that describes, explains, locates, and otherwise makes it easier to retrieve and use an information resource
profile:a subset of a schema defined and used by a particular interest group to customize the scheme for its purposes.
scheme: a metadata element set and rules for using it.
semantics: the names and meanings of metadata elements
syntax: rules for how metadata elements and their content are encoded.
数据目录词汇表：DCAT
Catalog-Dataset-Distribution
Catalog
Dataset
dataset
theme
theme Taxonomy
accessURL
downloadURL
:catalog
a dct:Catalog;
dct:title “Imaginary Catalog”;
rdfs:label “Imaginary Catalog”;
foaf:homepage <’’’>;
dct:publisher :transparency-office;
dcat:dataset :dataset-001,:dataset-002,:dataset-003;
:dataset-001
a dcat:Dataset;
dct:title “Imagnary dataset”;
dcat:keyword “…”;
dct:issued “…”;
dct:modified “…”;
dcat:contactPoint <’’’>;
dct:temporal <’’’>;
dct:publisher “…”;
dcat:distribution :dataset-001-csv;
:dataset-001-csv
a dcat:Distribution;
dcat:downloadURL <’’’>;
dct:title “CSV”;
dcat:mediaType “text/csv”;
dcat:landingPage
JSON form :
XML格式：
RDF校验器：https://www.w3.org/RDF/Validator/