Study on Cloud Service Mode of Digital Libraries Based on Sharing Alliance

: As a new service model, cloud services have become the growth point of the service innovation of digital libraries. By analyzing and summarizing the cloud service mode of the digital libraries at home and abroad, this paper presents three-layer cloud service model of digital libraries which includes data layer, automated management layer and service layer from bottom to top. Based on this model, this paper puts forward the union mechanism established by some libraries which joint provide intelligence research service, knowledge push service, reference service and so on.


Introduction
With the development of cloud computing technology, the cloud service application research becomes a hot issue. The operating mode and technical architecture of cloud service are closely related to Google and Amazon. Google put forward a complete set of distributed parallel cluster infrastructure according to the characteristics of the large scale network data. And Google provides a series of SaaS for individual users and enterprises including the Google search engine, Google maps, photos and videos sharing, social networks, Gmail, Google calendar, Google Apps Market place and so on. In order to make full use of idle IT infrastructure, Amazon provided storage servers, bandwidth and CPU resource to the third party by Amazon Web Services in 2002. In 2006, the network service platform based on cloud computing were provided to enterprises so that they do not need to undertake the underlying work such as hardware maintenance and can focus on their own business.
Information industry is always an important field of information technology application. To apply cloud computing technology, a library can make full use of its resources and technical strength. The service efficiency can be enhanced obviously by innovating service mode.

Service Situation and Problems of Digital Libraries
Due to the monopoly service of domestic companies such as CNKI, WANFANG and Besides, the functions of cataloguing system and data processing system are unsatisfactory in some libraries because of limited capital and technical strength.
When processing literature data, data format conversion between different software results to inefficient data processing work.

Cloud Service Demand of Digital Libraries
Cloud service pattern will bring the library more flexible, rich and diversified service changes. For libraries, to innovating the service mode based on a cloud service alliance has become inevitable. Rich data resources are the basic guarantee of So the libraries at the same field can jointly build sharing alliance. Member libraries can carry out digital construction and service of Chinese-foreign resources to provide integrated retrieval and services for readers. The scale advantage of the library service will be helpful to ascend influence of the member libraries. Besides the interlibrary information sharing based on the same platform will be conducive to develop knowledge services and applications.

Cloud Service Mode of Digital Libraries based on Sharing Alliance
In the future libraries services will focus on SaaS based on data resources. Several libraries establish the co-construction and sharing system to expand the scope and service mode of information resources. Cloud computing technology is adopted to establish SaaS cloud platform to which member libraries can submit the metadata of their Chinese-foreign resources. Large joint library can provide single sign-on and one-stop service with huge amounts of resources for readers.

Cloud Service Model of Digital Library
The cloud service hierarchy should be built based on the standards system and supported by the operation maintenance and security system. The hierarchy includes data layer, automated management system layer and service layer from bottom to top.
The relationship and structure is shown in figure 1.

Figure 1 Cloud Service Model of Digital Library
The data layer is the underlying structure of the three layer service model of cloud services. This layer consists of data resources built by member libraries of shared alliance such as catalog database, abstract database, citation database, institutional repository and so on. The automated management system layer takes the system management based on data layer . The layer includes a set of middleware service such as user registration, service scheduling, unified authentication, search engine, load management, unified authorization, log statistics and service register.
The service layer is a set of services based on data layer and the automated management system layer. This layer is a software application model which provides cloud application service through the Internet transmission. The service can be divided into three categories: information service, information retrieval and data processing and management. The cloud services of data processing and management provide a cloud platform based on the unified metadata standard for member libraries.
The information cloud service based on co-build data helps member libraries to jointly carry out intelligence research, knowledge push, the original offer, check by services and so on. The information retrieval cloud service provides readers with the retrieval tools to quickly find the resources needed(Chen Chen et .al, 2012).

Cloud Service Mode of Digital Libraries based on Sharing Alliance
The cloud services based on sharing alliance consist of information service, information retrieval and data processing and management. Member libraries can use these cloud services in whole or in part according to need.

Information Service
(1)Intelligence Research Service. Intelligence research software based on co-built basic database can be provided to member libraries. By using the software, member libraries can understand their own competitiveness and analysis hot research field so as to provide the basis for future decision-making.
(2)Knowledge Push Service. Knowledge service software can be provided to member libraries. Thus the readers' access historical data can be analyzed in order to get the interest preference. By being selected, optimized and integrated, information resources can be further developed and pushed to readers. By intelligently filtering and recommending the information, service mode transformation can be promoted from passive service to active service, which the quality of information service can be significantly improved.
(3) Reference Consulting Service. Reference consulting software can be used online.
By using the software, librarians can query advisory forms and provide joint consultation among multiple libraries.

Information Retrieval
Unified retrieval function based on sharing alliance resources can be provided. By using the resources search engine, readers can retrieve all abstract information of books, journals, conference proceedings, reports, dissertations, standards and patent documents in cloud service platform to complete one-stop retrieval of printed and digital resources. The retrieval system can be used remotely or be embedded into the web systems of member libraries.

Data Processing and Management
(1)Joint Cataloging Services. Joint cataloging software can be provided for member libraries. By using the software, librarians can process metadata cataloging database of Chinese-foreign journals. Readers can log in the joint cataloging system of cloud services platform to search the resources of all member libraries.
(2)Joint Data Processing Services. Joint data processing software can be provided for member libraries. Librarians can adopt the unified standard to process data so as to provide data support for the retrieval service of Chinese-foreign information resources.

Conclusion
The wide application of cloud computing technology has brought a revolution to library information service mode. Cloud service has become a growth point of the digital library service innovation. As SaaS, cloud service based on library sharing alliance can significantly improve the efficiency of access to information and the utilization of information resources. In the future libraries should focus on the cloud service mode and play advantages guided by demand.