Digital Object: A Virtual Online Storage Solution 598C Course Project Huajing Li

Digital Contents: not just documents… Some conventional objects Some conventional objects Complex, compound, dynamic objects Complex, compound, dynamic objects

Traditional Online Access Method The web server & application must be aware of the types and components of the managed digital contents. The web server & application must be aware of the types and components of the managed digital contents. HTML documents… HTML documents… JPG/GIF photos… JPG/GIF photos… Video clips… Video clips… Stream media… Stream media… System developer and interface designer must provide appropriate handler for these file types. System developer and interface designer must provide appropriate handler for these file types.

Traditional Data Storage Access For tuples stored in a relational database, the system developer must have knowledge of the table schema and encode it explicitly in a query: For tuples stored in a relational database, the system developer must have knowledge of the table schema and encode it explicitly in a query: Select name from authors where affiliation=“Penn State”; Select name from authors where affiliation=“Penn State”; For on-disk file access, a file path needs to be specified. For on-disk file access, a file path needs to be specified.

Problems Lack of flexibility Lack of flexibility Lack of extensibility Lack of extensibility Lack of support for complex data structures Lack of support for complex data structures Lack of security control at the data level Lack of security control at the data level Unnecessary duplicate work needs to be performed by different applications / parties Unnecessary duplicate work needs to be performed by different applications / parties

Key Research Questions How can clients interact with heterogeneous collections of complex objects in a simple and interoperable manner? How can clients interact with heterogeneous collections of complex objects in a simple and interoperable manner? How can complex objects be designed to be both generic and genre-specific at the same time? How can complex objects be designed to be both generic and genre-specific at the same time? How can we associate services and tools with objects to provide different presentations or transformations of the object content? How can we associate services and tools with objects to provide different presentations or transformations of the object content? How can we associate specialized, fine-grained access control policies with specific objects, or with groups of objects? How can we associate specialized, fine-grained access control policies with specific objects, or with groups of objects? How can we facilitate the long-term management and preservation of objects? How can we facilitate the long-term management and preservation of objects?

Look into the Nature, We Have the Hints… Data is no longer an isolate existence in most current applications. Data is no longer an isolate existence in most current applications. Metadata Metadata Structural information Structural information Legal methods that can be applied to the data Legal methods that can be applied to the data Access control policies Access control policies Links to other digital contents Links to other digital contents These features can be grouped into an integral unit, which in return simplify the applications. These features can be grouped into an integral unit, which in return simplify the applications. Sort of similar with a Java class Sort of similar with a Java class

Solution We propose a middleware which virtually represents each digital content in a generic model. This middleware separates front-end applications from the back-end storages, gives abstraction to both sides. We propose a middleware which virtually represents each digital content in a generic model. This middleware separates front-end applications from the back-end storages, gives abstraction to both sides.

Persistent ID (PID) Default Disseminator SystemMetadata Datastream (item) Digital object identifier Service Perspective: methods for disseminating “views” of content Internal: key metadata necessary to manage the object Item Perspective: Set of content or metadata items Digital Object Model Architectural View Datastream (item) Your Extension

A Well-Known Digital Object Management System: Fedora

Fedora Service Framework

My Project Work Bring new features into the previous framework. Bring new features into the previous framework. Fedora does not provide powerful indexing and query capabilities. Fedora does not provide powerful indexing and query capabilities. Full text indexing based on Lucene. Full text indexing based on Lucene. Dynamic field indexing. Dynamic field indexing. Dynamically build in-memory indexing to improve query performance. Dynamically build in-memory indexing to improve query performance.