With the continuous expansion and multimedia technology in the application, there are many restrictions and lacks of relational databases, so database technology has entered the "post-relational database era". The document database is now delivered. This paper summarizes three aspects of data format, database structure, and web publishing data, which distinguishes different file systems with the Document database with the past stored data. Keywords: Database Internet Document Database Web Database Server
I. The advantages of the relationship database and the current problems
Since the end of the 1960s, database technology has experienced hierarchical databases, network databases and relational databases and enters the Database Management System (DBMS) phase, and research on database technology has also been progressing. In the 1980s, the relational database became the mainstream of development, and almost all new DBMS products were relationships. The relational database is an important milestone in the history of computer data management. This database has the advantages of data structure, minimum redundancy, higher procedures and data independence, easy to expand, and easy to prepare applications. The big information system is based on the design of the structured database.
However, with the rapid development of network technology and software technology, in particular the development of Internet and intranet technology, the application of non-structured data is increasingly expanded. Relationship database has developed from 1970, although the function is becoming more and more perfect, but the processing of data type is limited to numbers, characters, etc., the processing of multimedia information is only stored in a simple binary code file. However, as the user's application demand, the development of hardware technology and the multi-color multimedia communication method provided by intranet / Internet, the user's requirements for multimedia processing are rising from simple storage to identify, retrieve and in-depth processing, is the user's call out The "General" database server processes complex data types such as 60% of the total amount of information, images, time series signals, and video. According to relevant data, in 1996, sales of global database markets were close to $ 4 billion, and it is expected that by 2000, the sales of database markets will reach 8 billion US dollars. Huge growth potential comes from the processing requirements of complex data types, so that the "Super Media" database that handles complex data types will become the focus of investment research and development of companies.
Second. New "document data? Quot; Concept
Since 1989, Lotus proposes a new concept of database technology through its group product Notes - Document Database, Document Database Area is used in traditional other databases, which is used to manage documents. In a conventional database, the information is split into a discrete data segment, and in the document database, the document is the basic unit of processing information. One document can be very long, very complicated, can be similar, similar to the word processing document.
Document databases are different from the five or 1960s, and the document database remains in a database. First, files in the file system basically correspond to an application. Each file must also be established when the data required for different applications is part of the data, and the data cannot be shared, and the document database can share the same data. Therefore, the file system is more redundant than the document database data, more waste storage, and is more difficult to manage maintenance. Second, the file in the file system is for a particular application service, so it is difficult to add some new applications to existing data, and the system is not easy to expand. Data and procedures lack independence. The document database has data physical independence and logical independence, data and procedures separation.
Document databases are different from relational databases, and the relational database is highly structured, and Notes's document database allows you to create many different types of unstructured or arbitrary formats, and the main difference between the relational database is not available to parameters. Support for integrity and distribution, but with relational databases is not mutually exclusive, and they can exchange data between each other, thus complement each other, expand.
Third. Different Database and Document Database
The difference between the two databases is compared from three aspects:
1. Format Text / Multimedia (Rich Text / MultiMedia)
In the information age, all information can be generally divided into two categories: a class of information can be represented by data or unified structures. For example, cost, cost, personnel, salary, and employee performance, etc., can be described or expressed by numbers or text. This type of information has the same level or network structure, which we calls structured data; and the other information cannot be represented by digital or unified structures, such as images, sound, etc., we call non-structured data. . These non-structured data can be in a block containing a large number of additional information (such as typography information), or a sound, image, and even images. For the relationship between structured data and unstructured data, the non-structured data includes structured data, but it is more than structured data; structured data belongs to unstructured data, which is a special case of non-structured data. In general, in people's awareness, the most important feature of relational database is the structured structure of data. However, with the rapid development of network technology and software technology, in particular the development of Internet and intranet technology, the application of non-structured data is increasingly expanded. Relational databases are highly structured. This data structure makes the relational database lowest redundancy, and the program and data independence are high, easy to expand, and easy to prepare the application. However, with the continuous expansion of the application, in order to meet the requirements of the application to continuously "harsh", people have begun to discover a lot of restrictions and deficiencies in relational databases. Because the basic element of the document database is the document itself, and the document in the database can contain both structured and unstructured information, the document database can store and manage non-structured data such as documentation. In particular, Notes's object library is an ideal business information memory that can be used to efficiently store, propagate, assign, and manage such information. This type of information usually has a rich data type, such as a table (which can be obtained from a relational database or electronic meter software), formatted text, www page, graphic, ole object, or scanning image, and fax parts. , Multimedia information such as audio or video signals. 2. Structure
The relational database is the application of mathematical methods to handle database data. The data model is also based on mathematical concepts. In the relational model, the logical structure under the user's point of view is a two-dimensional table. Lotus Notes is a document database management system, the basic element of the document database is a document. The records here are similar in the documentation and relational databases. The structure of the Notes document is defined by forms (form), and the form consists of a set of various fields.
· Field, Domain and Field (Field)
In the relational database, domain is a collection of attribute values, such as a positive integer greater than 0 less than 150, a string set of less than 25, and the like. In the document database, the field of domain (field) appears in the form object, the domain is a single element stored on the form, and the domain determines a separate document that can contain any data. Although the Chinese translations are the same, their actual significance and role are different. Instead, the concept of domain in the document database is similar to the field (field) in the relational database.
· Items (Item) and Attribute
In the relational database, the concept of attribute, that is, each column in the two-dimensional table is called an attribute, which gives each column that is the attribute name. In the document database, there is no "attribute", the document has an entry (ITEM), and the entry is the number of data stored in the document. Each entry represents a piece of data in the document, in the user interface, is a domain in the form to display an entry in the document. Although the two are named, the author believes that it is more likely to understand the meaning of the entry in the document database from the perspective of "attribute". · View (View)
In the relational database and document database, there are views of the view. In the relational database, the view refers to a table exported from one or several basic tables (or views). The views and basic tables are different, the view is a virtual table, that is, the data corresponding to the view is not actually stored in the database, and only the definition of the view is stored in the database (in the presence of data dictionary). In the document database, the user browses the document via the Notes view. The view is a very convenient directory, and the user can see the status of the profile information and documentation of the document, and then access a specific Notes document. Document Database can display all or part of the content in the view, through the view, the user can see a key domain of a set of documents, and can classify and sort the information displayed in a criterion. Essentially, both logically very similar, that is, the data corresponding to the view is not actually stored in the database, and only the definition of the view is stored in the database.
3. The web database has experienced a significant change in the network architecture in recent years. The client / server structure is more and more popular. Intranet has spread rapidly in just a year in just a year, facing new patterns, how to easily realize Client / Server Connection and "Web / Intranet" connection becomes the focus of database managers. The development of computer technology and network technology has enabled the network-centric computation to pay attention, the WWW system and database become the basis of network information services. If you can connect the document database to the WWW server, you can retrieve the document from your browser. This integrated information network system: Database WWW server, is a new field for the next generation of Internet development. Currently, a typical database application on the Web should include three parts: web browser, HTTP server, and web database server. For general relational databases, there are usually two ways to implement web databases: one is a web server providing an intermediate connection web server and a database server; the other is to download the application to the client directly access the database. The most common intermediate technology has two types of general gateway interface (CGI) and application programming interface (API). The CGI program defect is that the CGI interface does not support the continuous interoperability between users and databases, and then the efficiency of CGI is low, and multiple CGI programs are required. Each time you connect to the server, both the server wants to create a copy of a transaction or run the CGI program. This will increase the burden of the server for a complex application or multiple user access. The API has overat of CGI's disadvantages, but its compatibility is poor and difficult to develop, but also make the majority of developers. The client access database mainly includes Java Script and Database Connector (IDC). Developing a Web database with Java Script and IDC is simple but also has limited functionality, it cannot fully control the shortcomings of its procedure. Therefore, they cannot be eligible for the development of more complex web databases. Is there a development method for developing relatively easy, powerful and efficient web databases? Yes, the answer is -lotus notes. Lotus Notes implements multimedia document management through document databases to support client / server work. Each data can contain several different forms of Notes documents. Store on one or more Notes servers, allowing many users to access the database called a shared database. By utilizing security measures such as server access and data inventory control, database administrators can specify who can access databases and use databases within what scope, and each database is synchronized online by replication functions online. In this way, users can access, track storage and organize information on the network through document database users. Fourth. Conclusion
In recent years, my country's database market has developed rapidly, and will have a more huge growth potential, which is characterized by the following characteristics: First, in the past five years, the user's selection concept has changed significantly, more users Putting the importance of the database is very important. The main reason is that the user will put application software and application requirements first. Whether the application satisfies the user's demand is a symbol of the entire project, and the application software is directly dependent on the database. development tools. In fact, a large amount of potential investments are developed in the development of application software; another reason is that hardware has increasing characteristics with the development of chip technology, the hardware indicators will become secondary considerations. For industry applications, it is used to develop several hardware products as a preferred, and now it is the preferred database manufacturer and consider hardware manufacturers. It is this change in user needs to provide new opportunities for database manufacturers. Lotus Notes provides a powerful document database development platform for each database system integrator, and Notes combines three powerful technologies such as enterprise email, distributed document database and fast application development, fully integrated Internet technology, providing users complete, A network-centered application technology platform. It can be predicted that in the near future, Lotus Notes' document database will become another hotpoint technology after the hierarchical database, a mesh database, and a relational database.
