Visual User-Defined Data Implementation Based On Metadata

According to the condition of ever changing user requirements,the shortcomings of traditional RDBMS (relational database management system )which can't support user-defined data have been coming into our sight.At the same time,user-defined data Implementation becomes to be an essential part in modern administrative system.Metadata is boldly introduced in this paper , according to the system mode of information-controlled platform of program for development of science and technology in jilin province.The goals of user-defined data implementation,flow control,user authority control and the clients relations management are achieved by defining and adding different types of Metadata.Metadata is usually defined as data about data whose object to be described is mainly the basic information of data .It is different from routine data that it has a ability of controlling and managing information resource,apart from description.Metadata--a kind of data to indentify,describe and define system resource,is applicable to the description of any data and information,at the same time it can promote the organization of system resource and information obtaining.According to its function,we divide Metadata into Descriptive Metadata,Structural Metadata and Managing Metadata.1,Descriptive Metadata: a kind of Metadata that is used to describe the content of document Resources .It is generally considered that all Metadata is descriptive,but some is called descriptive Metadata who directly describes the inherent fundamental propertis of resource object ,such as name,theme,type,etc.2,Structural Metadata:used to define the physical structrue of a complex resource object in order to promote navigation,information retrieval and display,such as Metadata that is used to describe how every component part is integrated.3,Managing Metadata:a kind of Metadata that is used to manage the resource object,including the display,note,use and long term management of resource object,such as management of ownership;the time and way of creation;file type;other technological information;authority management on the aspect of using or getting information. The capital work of this paper is based on the information-controlled platform of program for development of science and technology in jilin province.By designing the structure of database ,data dictionary model is set up and visual user-defined data implementation based on Metadata is presented .The system is used for typical workflow system that orients database to access data. In this system,user's operational data is mainly stored in the database which user's different business processes and different steps within the process share,various user-defined operations are carried out within the specific context environment,apart from changing the state of business process,adding,deleting and modifying the operational data become the main operations . System framework is set up by extracting commonness from systems of this kind,expressing the meanings by using MetaData ,describing the operational data on the abstraction level,both make the system deal with all of the operational data in a unified way.In the aspect of design of database, RDBMS is still used,however, an idea of Metadata is introduced as well in this system which is different from traditional RDBMS.Display of pages ,user authority control and the system of workflow are all controlled by the MetaData stored in the data dictionary. User-defined data implementation the function of which includes table establishment, data adding and query in major part,and description of information are controlled by different types of MetaData.In the module of table establishment, user-defined implementation of type, structure and user authority of the tables is realized by drawing up structural MetaData. In order to make it easier for user to create tables, according to the type of table,it could be divided into three different types-auxiliary table, informative table and application table. Auxiliary table is a kind of table that is used to help the implementation of the functions of the system,it is invisible for the user on the client side. Informative table is used to store descriptive MetaData and draw up appropriate attributes needed to describe the object. Application table is also used to store descriptive MetaData and describe the various information on declaring projects . Application table is divided into two types which is diferent from informative table:the first one is main table,the system will add some flow control fields automatically within the system itself,which is invisible for all users.The second one is subtable that simplifies the complex structure of tables.We could treat subtable as one part separated from the main table, so it seems necessary to build a relationship between main table and subtable logically.Data adding falls into two parts,structural MetaData adding and descriptive MetaData adding. Table created by structural MetaData adding is used to store descriptive MetaData, in other words ,descriptive MetaData is used to describe structural MetaData. In the view of users, structural MetaData orients administrators but descriptive MetaData orients general users.Data query is one of the primary functions that is needed to realize.Different user roles have different rights in the system,so certain user-role may face with too much data in the process of interactivity ,different tables may have different query fields.Display of query fields could be realized by controlling the query fields in the data dictionary. The conditions of query could be divided into inclusive, equal, unequal, data sorting methods which contain descending sort and ascending sort are controlled by sorting fields stored in the data dictionaryIn the process of realization of system, the problems involved are as follows: storage of MetaData, building a relationship between main table and subtable and the controlling of roles and rights.In the aspect of storage of MetaData, descriptive MetaData is stored unifically while other kinds of MetaData is stored separately. MetaData used to describe data fields mainly includes information about data description, information about display description , information about authority controlling,etc.In the aspect of correspondence between main table and subtable, tables are divided into several levels, the table of lower levels is called subtable of the table of higher levels if they have already built a relationship.In order to reduce the difficulty,all subtables are defined within level two.The main table and subtable have two corresponding relationship: one to one,one to many.In the aspect of role and right controlling, the authority falls into three levels:hidden,writable,readable which is demonstrated on pages,hidden means invisible,readable means that user can read but can't write , writable means that user can read and write.The division of authority could be integrated into data fields due to different users.In this paper,the functions of Visual User-Defined Implementation Based on MetaData are mainly realized, which makes the flexibility of system greatly improved. Users could define their data due to their own needs ,promoting the whole system.Of cource ,some problems are also found in the process of implementation , focusing on the management of data and MetaData, who has no detail classifications ,as a result it takes a long time in data query when there is too much data stored in the database, in the aspect of user-defined data implementation ,we can't add data fields in large scale which means more work for our users.The next step is aimed at improving the storage structure of MetaData, the correspondence relationship between MetaData and data, at the same time, the way of user-defined implementation should be promoted in order to make the user-define process more and more fast, convenient.