[Owl] Owl-related concepts-Relationship between XML, RDF, and OWL

Source: Internet
Author: User

Ontology comes from philosophical Vocabulary: Ontology (also translated into ontology ). RDF is a good way to describe Ontology. we can define the knowledge of a domain based on our understanding of the real world. However, RDF and RDF cannot define synonyms, antonyms, and relationships between descriptive words (relationships between classes and classes), such as equivalence, complementary exclusion, limit number, and attribute symmetry. Owl makes up for the shortcomings of RDF and uses logic theory in AI (in logic theory, people's thinking is expressed in formulas and the correctness of these formulas is proved) to give semantics to the net, form SW. In the definition of SW, the advantages of many knowledge are absorbed, such as Oo, logic theory, and tree structure.

From HTML to XML

HTML is our most common document markup language and has been widely used on the web. HTML can be used to describe resources, but its features limit that only people can understand the generated documents. HTML has two major limitations: one is its structure is not obvious, and it is difficult to be parsed by applications; the other is the limitation of description, such as the inability to describe certain scientific symbols.

In order for applications to understand the document, a good structure is required, so the simplest but powerful tree structure is adopted. XML is generated when the data is described in a tree structure. XML is used in various applications
The Inter-order and meta data exchange provides a consistent system and parser. However, XML itself does not have any semantic definition (or weak semantic definition), that is, the semantic machine of the data it describes cannot be understood.

The primary condition for understanding data is to record the data structure and type more easily. The predefined basic data types cannot meet the data requirements of most real-life data scenarios. We need to describe the data type more clearly, that is
More stringent data restrictions. XML Schema provides custom data types on predefined types, which can be parsed by the parser.

XML Schema

Schema (the definition mechanism of XML) provides the basic data types that can be used in XML (such as date and string, and DTD only provides string ).
To define a new type. Different from the document type of DTD, XML schema does not require another parser or editor.
However, XML Schema only defines the structure of the document, and still does not allow the application to understand the data semantics. In order to make the application understand the data, there is RDF.


From XML to RDF

RDF (Resource Description
Framework) is not a language, but a writing standard. The basic structure of RDF is a statement (or declaration, statement), which expresses a (resource, resource attribute,
Attribute Value) (subject-Attribute-object. RDF represents a data model. In short, a statement is a thing (resource). What attributes does this thing have?
The attribute value. XML is used as a specific writing method to describe this abstract data model (no XML is required, or other forms can be used to express RDF ). It is also because of the Super complexity of the real world.
Pre-defined words are not enough. We use the RDF Schema to customize words.

The characteristics of resources described by RDF are: attributes-centered thinking methods. Instead of defining the attribute value, you can define the scope of the subject (Resource) that owns the attribute (defined domain) and the value of this attribute.
Range (value range ). In this way, we can define words more accurately, not precisely because we cannot and do not need to define words accurately. What we care more about is the relationship between the word owner, that is, we cannot make machines
To understand a word, we still need to let it understand the relationship between words, so as to provide us with intelligent services.

RDF Schema

RDFS translation is the definition mechanism of the Resource Description Framework. Its relationship with RDF is different from that between XML and xmls. Xmls is used to define the structure (structure) of XML, while RDFS is used to define the words used in the RDF data model.

RDF + RDFS cannot provide us with a description of the relationship between words, resulting in the emergence of owl.



It evolved from DAML (DARPA agent Markup Language) + OIL (Ontology Inference Layer.
As an extension of RDF, owl provides a more extensive function for us to define RDFS vocabulary. It is more widely used to define the relationship between words and between classes, the relationship between attributes.


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