Comparing Formats（Comparing with other data formats）学习笔记

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地址：http://www.w3.org/2000/10/swap/doc/formats

下面通过不同的语言和格式描述同一件事情：一个叫Pat的人，也被称为Pat Smith或Patrick Smith，他有一个叫Rover的宠物狗。

英语（非常非正式）

There is person, Pat, known as "Pat Smith" and "Patrick Smith". Pat has a pet dog named "Rover".

英语超文本（非正式）

这里术语的歧义通过为词加上超链接来区分，这些链接是否有效，依赖于涉及到的服务器。

Pat is a human with the names "Pat Smith" and "Patrick Smith". Pat has a pet, a dog, with the name "Rover".

N3

@prefix : <http://www.w3.org/2000/10/swap/test/demo1/about-pat#> .
  
  

@prefix bio: <http://www.w3.org/2000/10/swap/test/demo1/biology#> .
  
  

@prefix per: <http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#> .
  
  

:pat     a bio:Human;
  
  

     per:name "Pat Smith",
  
  

              "Patrick Smith";
  
  

     per:pet  [
  
  

         a bio:Dog;
  
  

         per:name "Rover" ] .
  
  

Directed Labeled Graph有向标记图

图见原文……

N-Triples

使用@prefix：

@prefix : <http://www.w3.org/2000/10/swap/test/demo1/about-pat#> .
  
  

@prefix bio: <http://www.w3.org/2000/10/swap/test/demo1/biology#> .
  
  

@prefix per: <http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#> .
  
  

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>.
  
  

:pat rdf:type bio:Human.
  
  

:pat per:name "Pat Smith".
  
  

:pat per:name "Patrick Smith".
  
  

:pat per:pat _:genid1.
  
  

_:genid1 rdf:type bio:Dog.
  
  

_:genid1 per:name "Rover".
  
  

标准形式：

<http://www.w3.org/2000/10/swap/test/demo1/about-pat#pat> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/2000/10/swap/test/demo1/biology#Human> .
  
  

<http://www.w3.org/2000/10/swap/test/demo1/about-pat#pat> <http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#name> "Pat Smith" .
  
  

<http://www.w3.org/2000/10/swap/test/demo1/about-pat#pat> <http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#name> "Patrick Smith" .
  
  

<http://www.w3.org/2000/10/swap/test/demo1/about-pat#pat> <http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#pet> _:genid1 .
  
  

_:genid1 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/2000/10/swap/test/demo1/biology#Dog> .
  
  

_:genid1 <http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#name> "Rover" .
  
  

RDF/XML

<rdf:RDF xmlns="http://www.w3.org/2000/10/swap/test/demo1/about-pat#"
  
  

    xmlns:bio="http://www.w3.org/2000/10/swap/test/demo1/biology#"
  
  

    xmlns:per="http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#"
  
  

    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
  
  

    <bio:Human rdf:about="#pat">
  
  

        <per:name>Pat Smith</per:name>
  
  

        <per:name>Patrick Smith</per:name>
  
  

        <per:pet>
  
  

            <bio:Dog>
  
  

                <per:name>Rover</per:name>
  
  

            </bio:Dog>
  
  

        </per:pet>
  
  

    </bio:Human>
  
  

</rdf:RDF>
  
  

XML（但不是RDF/XML）

Striped或alternating-normal form方案使用为应用设计的标记语言，转换至三元形式或者从三元形式转换过来需要使用特定的软件。

<Human>
  
  

  <uri>http://www.w3.org/2000/10/swap/test/demo1/about-pat#pat</uri>
  
  

  <name>Pat Smith</name>
  
  

  <pet>
  
  

    <Dog>
  
  

     <name>Rover</name>
  
  

    </Dog>
  
  

  </pet>
  
  

</Human>
  
  

另一选择是使用XML Triples。这不需要特定领域的标记。有些候选DTDs/Schemes已经被提议作参考，不过这只是一个草案（strawman）。对于一些应用，这种语法可能比RDF/XML或striped syntax更容易。

<!DOCTYPE Graph [
  
  

 <!ENTITY rdf    "http://www.w3.org/1999/02/22-rdf-syntax-ns#">
  
  

 <!ENTITY bio    "http://www.w3.org/2000/10/swap/test/demo1/biology#">
  
  

 <!ENTITY ns1    "http://www.w3.org/2000/10/swap/test/demo1/about-pat#">
  
  

 <!ENTITY per    "http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#">
  
  

]>
  
  

<Graph>
  
  

  <Triple>
  
  

    <subject><uri>&ns1;pat</uri></subject>
  
  

    <predicate><uri>&rdf;type</uri></predicate>
  
  

    <object><uri>&bio;Human</uri></object>
  
  

  </Triple>
  
  

  <Triple>
  
  

    <subject><uri>&ns1;pat</uri></subject>
  
  

    <predicate><uri>&per;name</uri></predicate>
  
  

    <object><literal>Pat Smith</literal></object>
  
  

  </Triple>
  
  

  <Triple>
  
  

    <subject><uri>&ns1;pat</uri></subject>
  
  

    <predicate><uri>&per;pet</uri></predicate>
  
  

    <object><nodeID>genid1</nodeID></object>
  
  

  </Triple>
  
  

  <Triple>
  
  

    <subject><nodeID>genid1</nodeID></subject>
  
  

    <predicate><uri>&rdf;type</uri></predicate>
  
  

    <object><uri>&bio;Dog</uri></object>
  
  

  </Triple>
  
  

  <Triple>
  
  

    <subject><nodeID>genid1</nodeID></subject>
  
  

    <predicate><uri>&per;name</uri></predicate>
  
  

    <object><literal>Rover</literal></object>
  
  

  </Triple>
  
  

</Graph>
  
  

Prolog

不使用命名空间，很简洁：

human(pat).
  
  

dog(rover).            % we have to assign a name
  
  

name(pat, "Pat Smith").
  
  

name(pat, "Patrick Smith").
  
  

name(rover, "Rover").
  
  

pet(pat, rover).
  
  

使用命名空间的方案之一：

ns(ns1_, "http://www.w3.org/2000/10/swap/test/demo1/about-pat").
  
  

ns(bio_, "http://www.w3.org/2000/10/swap/test/demo1/biology#").
  
  

ns(per_, "http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#").
  
  

bio_Human(ns1_pat).
  
  

bio_Dog(rover).      # unprefix could be be NodeIDs...
  
  

per_name(ns1_pat, "Pat Smith").
  
  

per_name(ns1_pat, "Patrick Smith").
  
  

per_name(rover, "Rover").
  
  

per_pet(ns1_pat, rover).
  
  

Javascript与Python

RDF模型可以相当好的映射到一些通用编程结构，尤其是那些解释型的面向对象语言，比如JavaScript和Python。当然，这种映射并不完美。

忽略URI和基数问题的简单方案—只允许Pat有一个名字和一个宠物：

pat = Human()
  
  

rover = Dog()
  
  

pat.name = "Pat Smith"
  
  

rover.name = "Rover"
  
  

pat.pet = rover
  
  

考虑基数的方案：

pat = Human()
  
  

rover = Dog()
  
  

pat.name.append("Pat Smith")
  
  

rover.name.append("Rover")
  
  

pat.pet.append(rover
  
  

再完善一点，需要这样—这会丢掉内置模型的简单性：

pat = Resource()
  
  

rover = Resource()
  
  

pat.addProperty(  ns.rdf.type, ns.bio.Human)
  
  

rover.addProperty(ns.rdf.type, ns.bio.Dog)
  
  

pat.addProperty(  ns.per.name, "Pat Smith")
  
  

rover.addProperty(ns.per.name, "Rover")
  
  

pat.addProperty(  ns.perpet, rover)
  
  

SQL

Table Relatiing URIs to Internal IDs

如果uri是NULL，那么这个资源就是匿名的，如aNode, RDF/XML中的NodeID。

CREATE TABLE uri (
  
  

  id INT AUTO_INCREMENT PRIMARY KEY,    # PRIMARY = UNIQUE and NOT NULL
  
  

  uri BLOB,   # BLOB is also called LONGVARBINARY 
  
  

  UNIQUE KEY uri (uri(64))  # length is just a tuning knob
  
  

);
  
  

INSERT INTO uri (uri) VALUES ('http://www.w3.org/1999/02/22-rdf-syntax-ns#type');
  
  

INSERT INTO uri (uri) VALUES ('http://www.w3.org/2000/10/swap/test/demo1/biology#Human');
  
  

INSERT INTO uri (uri) VALUES ('http://www.w3.org/2000/10/swap/test/demo1/biology#Dog');
  
  

INSERT INTO uri (uri) VALUES ('http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#name');
  
  

INSERT INTO uri (uri) VALUES ('http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#pet');
  
  

INSERT INTO uri (uri) VALUES ('http://www.w3.org/2000/10/swap/test/demo1/about-pat#pat');
  
  

INSERT INTO uri (uri) VALUES (NULL);   # this is rover, who has no URI
  
  

选择1：一张表，每个断言一列

这是一个简单、凭直觉的方案，但是：

²  每次使用一个新断言，就要添加一个新列

²  Predicates must be known to be individual-valued or data-valued; and if data-valued, then what type?

²  无法拥有多值属性

CREATE TABLE resource ( 
  
  

  id INT PRIMARY KEY,
  
  

  type INT,           # http://www.w3.org/1999/02/22-rdf-syntax-ns#type
  
  

  name varchar(255),  # http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#name
  
  

  pet INT             # http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#pet
  
  

);
  
  

INSERT INTO resource (id, type, name, pet) VALUES (6, 2, 'Pat Smith', 7);
  
  

INSERT INTO resource (id, type, name) VALUES (7, 3, 'Rover');
  
  

Id
      
      

type
      
      

name
      
      

Pet
      
      

6
      
      

2
      
      

Pat Smith
      
      

7
      
      

7
      
      

3
      
      

Rover
      
      

NULL
      
      

选择2：每个类一张表，每个断言一列

这里，由于不支持继承，所以human.name和dog.name之间有概念冗余。
   
   

CREATE TABLE human (  # http://www.w3.org/2000/10/swap/test/demo1/biology#Human
  
  

  id INT PRIMARY KEY,
  
  

  name varchar(255),  # http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#name
  
  

  pet INT             # http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#pet
  
  

);
  
  

CREATE TABLE dog (  # http://www.w3.org/2000/10/swap/test/demo1/biology#Dog
  
  

  id INT PRIMARY KEY,
  
  

  name varchar(255)   # http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#name
  
  

);
  
  

INSERT INTO human VALUES (6, 'Pat Smith', 7);
  
  

INSERT INTO dog   VALUES (7, 'Rover');
  
  

mysql> select * from human, dog where human.pet=dog.id;
  
  

选择3：每个断言一张表

这里指出完全一样的值。

CREATE TABLE name (  # http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#name
  
  

  subject INT NOT NULL,
  
  

  object varchar(255),
  
  

  INDEX(subject),
  
  

  UNIQUE INDEX(subject, object)
  
  

);
  
  

CREATE TABLE pet (   # http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#pet
  
  

  subject INT NOT NULL,
  
  

  object INT,
  
  

  INDEX(subject),
  
  

  UNIQUE INDEX(subject, object)
  
  

);
  
  

CREATE TABLE type (   # http://www.w3.org/1999/02/22-rdf-syntax-ns#type
  
  

  subject INT NOT NULL,
  
  

  object INT,
  
  

  INDEX(subject),
  
  

  UNIQUE INDEX(subject, object)
  
  

);
  
  

INSERT INTO name VALUES (6, 'Pat Smith');
  
  

INSERT INTO name VALUES (6, 'Patrick Smith');
  
  

INSERT INTO name VALUES (7, 'Rover');
  
  

INSERT INTO pet VALUES (6, 7);
  
  

INSERT INTO type VALUES (6, 2);
  
  

INSERT INTO type VALUES (7, 3);
  
  

mysql> select * from name;                   
  
  

subject
      
      

object
      
      

6
      
      

Pat Smith
      
      

6
      
      

Patrick Smith
      
      

7
      
      

Rover
      
      

mysql> select * from pet;
  
  

Subject
      
      

Object
      
      

6
      
      

7
      
      

mysql> select * from type;
  
  

选择4：一个三元式的表，一个资源的表

如果用文字和URIs重新将URIs表做成一个资源表resources，会有更多选择。

CREATE TABLE resources (
  
  

  id INT AUTO_INCREMENT PRIMARY KEY,    # PRIMARY = UNIQUE and NOT NULL
  
  

  # either provide a uri
  
  

  uri BLOB, 
  
  

  # or a literal_value, which might have a datatype and language
  
  

  literal_value BLOB,
  
  

  datatype INT,
  
  

  language VARCHAR(5),
  
  

  UNIQUE KEY (uri(64))  # length is just a tuning knob
  
  

);
  
  

INSERT INTO resources (uri) VALUES ('http://www.w3.org/1999/02/22-rdf-syntax-ns#type');
  
  

INSERT INTO resources (uri) VALUES ('http://www.w3.org/2000/10/swap/test/demo1/biology#Human');
  
  

INSERT INTO resources (uri) VALUES ('http://www.w3.org/2000/10/swap/test/demo1/biology#Dog');
  
  

INSERT INTO resources (uri) VALUES ('http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#name');
  
  

INSERT INTO resources (uri) VALUES ('http://www.w3.org/2000/10/swap/test/demo1/friends-vocab#pet');
  
  

INSERT INTO resources (uri) VALUES ('http://www.w3.org/2000/10/swap/test/demo1/about-pat#pat');
  
  

INSERT INTO resources (uri) VALUES (NULL);   # this is rover, who has no URI
  
  

INSERT INTO resources (literal_value) VALUES ('Pat Smith');
  
  

INSERT INTO resources (literal_value) VALUES ('Patrick Smith');
  
  

INSERT INTO resources (literal_value) VALUES ('Rover');
  
  

mysql> select * from resources;
  
  

三元式：

CREATE TABLE triples (
  
  

  subject INT NOT NULL,
  
  

  predicate INT NOT NULL,
  
  

  object INT NOT NULL,
  
  

  UNIQUE INDEX(subject, predicate, object),
  
  

  INDEX(predicate, object),
  
  

  INDEX(object, predicate)
  
  

);
  
  

INSERT INTO triples VALUES (6, 4, 8);
  
  

INSERT INTO triples VALUES (6, 4, 9);
  
  

INSERT INTO triples VALUES (7, 4, 10);
  
  

INSERT INTO triples VALUES (6, 1, 2);
  
  

INSERT INTO triples VALUES (7, 1, 3);
  
  

INSERT INTO triples VALUES (6, 5, 7);
  
  

mysql> select * from triples;
  
  

mysql> select s.id, s.uri, p.uri as "predicate", 
  
  

       o.id, o.uri, o.literal_value as "lit"
  
  

       from triples, resources as s, resources as p, resources as o
  
  

       where s.id=triples.subject AND
  
  

             p.id=triples.predicate AND
  
  

             o.id=triples.object;
  
  

subject                   predicate        object           ObjectValue
  
  

But Remember

当心将RDF看做序列化对象的一种格式（Beware of thinking of RDF as a format for serializing object），语义网是不同的。

²  Any document can (potentially) say anything about anything. There is no set of "slots" or "attributes" for a class. The properties defined in a schema are not the only properties which one can use to describe something which is in that class.

²  An object can be in many classes. When you create a semantic web document about something, others can deduce more things about it, in vocabularies you have never heard of.

²  Entity-Relationship and UML diagrams are useful for describing RDF -- so long as you remember the above.

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