【導(dǎo)讀】隨著互聯(lián)網(wǎng)的發(fā)展，網(wǎng)絡(luò)信息資源呈幾何態(tài)勢(shì)增加。信息資源日益豐富，用戶。因此，我們一直處在網(wǎng)上“找”信息的時(shí)代。近年來(lái)出現(xiàn)的可擴(kuò)展標(biāo)。映數(shù)據(jù)內(nèi)容的標(biāo)簽，實(shí)現(xiàn)數(shù)據(jù)內(nèi)容和數(shù)據(jù)表現(xiàn)方式的分離。目前，越來(lái)越多的網(wǎng)站。開(kāi)發(fā)使用XML，這使得將有用信息“推”向用戶成為可能。RSS實(shí)現(xiàn)了這一功能，可使用戶自動(dòng)獲取所需的相關(guān)信息。比較普遍的說(shuō)法有兩種，一種是“RichSiteSummary”或“RDFSite. RSS是某一站點(diǎn)用來(lái)和其它站點(diǎn)之間。方便地實(shí)現(xiàn)對(duì)某類信息的全程跟蹤、即時(shí)更新以及網(wǎng)上搜索。在不遠(yuǎn)的將來(lái)，RSS. 子商務(wù)、互動(dòng)交流等領(lǐng)域產(chǎn)生難以估量的影響。版本的RSS規(guī)范之后，并沒(méi)有將研發(fā)工作繼續(xù)下去。2020年，著名的博客戴夫·溫那的公司UserLand接手RSS技術(shù)標(biāo)。了重新定義，發(fā)布，并將RSS定義為“RDFSiteSummary”。UserLand于2020年9月發(fā)布了最新版。由于雙方的分歧和各。2020年，美國(guó)迎來(lái)了RSS的術(shù)的飛速發(fā)展期?；赗SS的深度應(yīng)用，其產(chǎn)品已經(jīng)在證券等多個(gè)行業(yè)得到采用。系統(tǒng)響應(yīng)速度并降低了系統(tǒng)資源占用。

　　

【正文】 , URIrefs from a particular vocabulary can be used in RDF statements even though a given application may not be able to associate any special meanings with them. For example, generic RDF software would recognize that the above expression is an RDF statement, that ed:dsfbups is the predicate, and so on. It will simply not associate with the triple any special meaning that the vocabulary developer might have associated with a URIref like ed:dsfbups. Moreover, based on their understanding of a given vocabulary, people can write RDF applications to behave in accordance with the special meanings assigned to URIrefs from that vocabulary, even though that meaning will not be accessible to RDF applications not written in that way. 4. An XML Syntax for RDF: RDF/XML RDF39。s conceptual model is a graph. RDF provides an XML syntax for writing down and exchanging RDF graphs, called RDF/XML. Unlike triples, which are intended as a shorthand notation, RDF/XML is the normative syntax for writing RDF. RDF/XML is defined in the RDF/XML Syntax Specification [RDFSYNTAX]. This section describes this RDF/XML syntax. The basic ideas used by RDF/XML to encode an RDF graph as XML elements, attributes, element content, and attribute values. The URIrefs of predicates (as well as some nodes) are written as XML QNames, consisting of a short prefix denoting a namespace URI, together with a local name denoting a namespacequalified element or attribute, as described in Appendix B. The (namespace URIref, local name) pair is chosen so that concatenating them forms the URIref of the original node or predicate. The URIrefs of subject nodes are written as XML attribute values (URIrefs of object nodes may sometimes be written as attribute values as well). Literal nodes (which are always object nodes) bee element text content or attribute values. (Many of these options are described later in the Primer。 all of these options are described in [RDFSYNTAX].) The RDF/XML syntax provides a number of abbreviations to make mon uses easier to write. For example, it is typical for the same resource to be described with several properties and values at the same time. RDF/XML provides several ways to represent graphs containing blank nodes. These are all described in [RDFSYNTAX]. The approach illustrated here, which is the most direct approach, is to assign a blank node identifier to each blank node. A blank node identifier serves to identify a blank node within a particular RDF/XML document but, unlike a URIref, is unknown outside the document in which it is assigned. A blank node is referred to in RDF/XML using an rdf:nodeID attribute, with a blank node identifier as its value, in places where the URIref of a resource would otherwise appear. Specifically, a statement with a blank node as its subject can be written in RDF/XML using an rdf:Description element with an rdf:nodeID attribute instead of an rdf:about attribute. Similarly, a statement with a blank node as its object can be written using a property element with an rdf:nodeID attribute instead of an rdf:resource attribute. The use of XML entities as an abbreviation mechanism is optional in RDF/XML, and hence the use of an XML DOCTYPE declaration is also optional in RDF/XML. (For readers familiar with XML, RDF/XML is only required to be wellformed XML. RDF/XML is not designed to be validated against a DTD by a validating XML processor. This is discussed more fully in Appendix B, which provides additional information about XML.) Although additional abbreviated forms for writing RDF/XML are available, the facilities illustrated so far provide a simple but general way to express graphs in RDF/XML. Using these facilities, an RDF graph is written in RDF/XML as follows: All blank nodes are assigned blank node identifiers. Each node is listed in turn Compared to some of the more abbreviated approaches described in [RDFSYNTAX], this simple approach provides the most direct representation of the actual graph structure, and is particularly remended for applications in which the output RDF/XML is to be used in further RDF processing. 5. Other RDF Capabilities RDF provides a number of additional capabilities, such as builtin types and properties for representing groups of resources and RDF statements, and capabilities for representing XML fragments as property values. These additional capabilities are described in the following sections. There is often a need to describe groups of things: for example, to say that a book was created by several authors, or to list the students in a course, or the software modules in a package. RDF provides several predefined (builtin) types and properties that can be used to describe such groups. RDF applications sometimes need to describe other RDF statements using RDF, for instance, to record information about when statements were made, who made them, or other similar information (this is sometimes referred to as provenance information). Sometimes the value of a property needs to be a fragment of XML, or text that might contain XML markup. For example, a publisher might maintain RDF metadata that includes the titles of books and articles. While such titles are often just simple strings of characters, this is not always the case. For instance, the titles of books on mathematics may contain mathematical formulas that could be represented using MathML [MATHML]. 6. Defining RDF Vocabularies: RDF Schema RDF provides a way to express simple statements about resources, using named properties and values. However, RDF user munities also need the ability to define the vocabularies (terms) they intend to use in those statements, specifically, to indicate that they are describing specific kinds or classes of resources, and will use specific properties in describing those resources.