The following figure describes the seven-layer architecture of the Semantic Web: Self-description

Document Data Data Rules Trust Proof Number

Words

Signature

Logical ontology RDF+RDF Schema XML+NS+XML Schema namespace Unicode URI First level: Unicode and URI.

Unicode is a character set. All characters in this character set are represented by two bytes and can represent 65536 characters, which basically includes characters from all languages ??in the world. The advantage of using Unicode as a data format is that it supports a mix of all major languages ??in the world and can be retrieved simultaneously. URI (Uniform ResourceIdentifier), a uniform resource locator, is used to uniquely identify a concept or resource on the network. In the Semantic Web architecture, this layer is the foundation of the entire Semantic Web, where Unicode is responsible for processing the encoding of resources, and URI is responsible for the identification of resources.

The second layer: XML+NS+xmlschema.

XML is a streamlined standard universal markup language that combines the rich functionality of standard universal markup language with the ease of use of HTML. It allows users to add arbitrary structures to documents without describing these structures. meaning. NS (NameSpace) is the namespace, which is determined by the URI index. The purpose is to prevent different applications from using the same characters to describe different things. XML Schema is a replacement for document type definition (foreign language abbreviation: DTD). It itself uses XML syntax, but is more flexible than DTD, provides more data types, can better serve valid XML documents and provide data verification. mechanism. It is precisely because of the flexible structure of XML, the data determinability brought by URI-indexed NS, and the multiple data types and verification mechanisms provided by XMLSchema that it has become an important part of the Semantic Web architecture. This layer is responsible for grammatically representing the content and structure of data, and separating the representation form, data structure and content of network information by using standard languages.

The third layer: RDF+rdfschema.

The Resource Description Framework (foreign language abbreviation: RDF) is a language for describing information resources on the WWW. Its goal is to establish a framework for the existence of multiple metadata standards. This framework can make full use of the advantages of various metadata for Web-based data exchange and reuse. RDF solves the problem of how to describe resource objects unambiguously using XML standard syntax, so that the metadata information of the described resources becomes machine-understandable information. If XML is regarded as a standardized metadata syntax specification, then RDF can be regarded as a standardized metadata semantic description specification. Rdfschema uses a machine-understandable system to define vocabulary for describing resources. Its purpose is to provide a mechanism or framework for vocabulary embedding, under which multiple vocabularies can be integrated to describe Web resources.

The fourth level: "Ontology vocabulary".

This layer is an abstract description of concepts and their relationships defined on the basis of RDF(S). It is used to describe knowledge in the application field, describe various types of resources and relationships between resources, and implement the vocabulary extension. At this level, users can define not only concepts but also rich relationships between concepts.

Levels five to seven: Logic, Proof, Trust.

Logic is responsible for providing axioms and reasoning rules. Once Logic is established, resources, relationships between resources, and reasoning results can be verified through logical reasoning to prove their effectiveness. Through Proof exchange and digital signature, a certain trust relationship is established to prove the reliability of the Semantic Web output and whether it meets the user's requirements.