Mario Antonioletti

Introduction to OGSA-DAI services

In todays large collaborative environments, potentially composed of multiple distinct organisations, uniform controlled access to data has become a key requirement if these organisations are to work together as Virtual Organisations. We refer to such an integrated set of data resources as a virtual data warehouse. The Open Grid Services Architecture – Data Access and Integration (OGSA-DAI) project was established to produce a common middleware solution, aligned with the Global Grid Forums (GGF) OGSA vision [OGSA] to allow uniform access to data resources using a service based architecture. In this paper the service infrastructure provided by OGSA-DAI is presented providing a snapshot of its current state, in an evolutionary process, which is attempting to build infrastructure to allow easy integration and access to distributed data using grids or web services. More information about OGSA-DAI is available from the project web site: www.ogsadai.org.

The WS-DAI family of specifications for web service data access and integration

This month, we are pleased to provide to our readers a column that addresses an important aspect of grid computing: data access.

Integrating distributed data sources with OGSA–DAI DQP and Views

OGSA-DAI (Open Grid Services Architecture Data Access and Integration) is a framework for building distributed data access and integration systems. Until recently, it lacked the built-in functionality that would allow easy creation of federations of distributed data sources. The latest release of the OGSA-DAI framework introduced the OGSA-DAI DQP (Distributed Query Processing) resource. The new resource encapsulates a distributed query processor, that is able to orchestrate distributed data sources when answering declarative user queries. The query processor has many extensibility points, making it easy to customize. We have also introduced a new OGSA-DAI Views resource that provides a flexible method for defining views over relational data. The interoperability of the two new resources, together with the flexibility of the OGSA-DAI framework, allows the building of highly customized data integration solutions.

Distributed Data Management with OGSA–DAI

OGSA–DAI provides a framework for sharing and managing distributed data. OGSA–DAI is highly customizable and can be used to manage, share and process distributed data (e.g. relational, XML, files and RDF triples). It does this by executing workflows that can encapsulate complex distributed data management scenarios in which data from one or more sources can be accessed, updated, combined and transformed. Moreover, the data processing capabilities provided by OGSA–DAI are further augmented by a powerful distributed query processor and relational views component that allow distributed data sources to be viewed and queried as if they were a single resource. OGSA–DAI allows researchers and business users to move away from logistical and technical concerns such as data locations, data models, data transfers and optimization strategies for data integration and instead focus on application-specific data analysis and processing.

Building Bridges between Islands of Data - An Investigation into Distributed Data Management in the Humanities

Ancient documents represent a primary source for research in the humanities. A substantial body of digital material has evolved containing information about these documents. Unfortunately these digital resources are often held within myriad locations, owned by a range of groups or individuals, are held within a diverse range of formats and are either unavailable or are available only in isolation. This paper describes a successful investigation into using the OGSA-DAI distributed data management software to build bridges between these islands of data and so to facilitate navigation across a larger data space than is otherwise achievable. An overview of a proof-of-concept that was developed is given along with the technical challenges encountered. Discussion from researchers in the humanities about such an architecture reveals the possibility of creating virtual data centres for the coordinated sharing of such resources. It also raises important questions as to how distributed data resources can be meaningfully federated and queried.

Accessing Data in Grids Using OGSA-DAI

The grid provides a vision in which resources, including storage and data, can be shared across organisational boundaries. The original emphasis of grid computing lay in the sharing of computational resources but technological and scientific advances have led to an ongoing data explosion in many fields. However, data is stored in many different storage systems and data formats, with different schema, access rights, metadata attributes, and ontologies all of which are obstacles to the access, integration and management of this information.

An outline of the global grid forum data access and integration service specifications

Grid computing concerns itself with building the infrastructure to facilitate the sharing of computational and data resources to enable collaboration within virtual organisations. The Global Grid Forum (GGF) provides a framework for users, developers and vendors to come together to develop standards to ensure interoperability between middleware from different service providers. Central to this effort is the Open Grid Services Architecture (OGSA), and its associated specifications. These define consistent interfaces, generally couched as web services, and the components required to construct grid infrastructures. Both the web service and grid communities stand to benefit from the provision of consistent and agreed web service interfaces for data resources and the systems that manage them. This paper describes, motivates and presents the context for the work that has been undertaken by the GGF Data Access and Integration Services Working Group (DAIS-WG). The group has defined a set of data access and integration interfaces that are consistent with the OGSA vision. A brief overview of the current family of DAIS specifications is given: WS-DAI specifies a collection of generic data resource properties and messages that are specialised by WS-DAIR and WS-DAIX for use with relational and XML data resources, respectively. The WS-DAI specifications can be applied in regular web services environments or as part of a grid fabric.

Open Standards for Service-Based Database Access and Integration

The Database Access and Integration Services (DAIS) Working Group, working within the Open Grid Forum (OGF), has developed a set of data access and integration standards for distributed environments. These standards provide a set of uniform web service-based interfaces for data access. A core specification, WS-DAI, exposes and, in part, manages data resources exposed by DAIS-based services. The WS-DAI document defines a core set of access patterns, messages and properties that form a collection of generic high-level data access interfaces. WS-DAI is then extended by other specifications that specialize access for specific types of data. For example, WS-DAIR extends the WS-DAI specification with interfaces targeting relational data. Similar extensions exist for RDF and XML data. This chapter presents an overview of the specifications, the motivation for defining them and their relationships with other OGF and non-OGF standards. Current implementations of the specifications are described in addition to some existing and potential applications to highlight how this work can benefit web service-based architectures used in Grid and Cloud computing.The Database Access and Integration Services (DAIS) Working Group, working within the Open Grid Forum (OGF), has developed a set of data access and integration standards for distributed environments. These standards provide a set of uniform web service-based interfaces for data access. A core specification, WS-DAI, exposes and, in part, manages data resources exposed by DAIS-based services. The WS-DAI document defines a core set of access patterns, messages and properties that form a collection of generic high-level data access interfaces. WS-DAI is then extended by other specifications that specialize access for specific types of data. For example, WS-DAIR extends the WS-DAI specification with interfaces targeting relational data. Similar extensions exist for RDF and XML data. This chapter presents an overview of the specifications, the motivation for defining them and their relationships with other OGF and non-OGF standards. Current implementations of the specifications are described in addition to some existing and potential applications to highlight how this work can benefit web service-based architectures used in Grid and Cloud computing.

Grid enabling your data resources with OGSA-DAI

OGSA-DAI (Open Grid Services Architecture - Data Access and Integration) provides an extensible software framework allowing data resources, such as files, relational and XML databases, to be exposed through Web services acting within collaborative Grid environments or, more modestly, in stand-alone mode. OGSA-DAI may be deployed to WSRF-based platforms, such as the Globus Toolkit 4, as well as non-WSRF based ones, such as the UK OMII Server or standard versions of Tomcat and axis. Regardless of the platform, the core functionality provided remains the same. OGSA-DAI allows data resources to be accessed and integrated into the main infrastructures presently being used to construct Grids. OGSA-DAI provides a number of optimisations that reduce unnecessary data movement by shifting work to the Web service and encapsulating multiple client-Web service interactions into a single one, and allows for functionality to be added or customised based on the application. OGSA-DAI is widely used and is available from www.ogsadai.org.uk. It is also bundled with the OMII-UK and Globus Toolkit distributions. This paper gives an overview of what OGSA-DAI is, how it works, presents some usage scenarios, and outlines future enhancements.

Able but not willing? Exploring divides in digital versus physical payment use in China

Purpose – China is the world’s largest user market for digital technologies and experiencing unprecedented rates of rural-urban migration set to create the world’s first “urban billion”. This is an important context for studying nuanced adoption behaviours that define a digital divide. Large-scale studies are required to determine what behaviours exist in such populations, but can offer limited ability to draw inferences about why. The purpose of this paper is to report a large-scale study inside China that probes a nuanced “digital divide” behaviour: consumer demographics indicating ability to pay by electronic means but behaviour suggesting lack of willingness to do so, and extends current demographics to help explain this. Design/methodology/approach – The authors report trans-national access to commercial “Big Data” inside China capturing the demographics and consumption of millions of consumers across a wide range of physical and digital market channels. Focusing on one urban location we combine traditional demographics with a new measure that reflecting migration: “Distance from Home”, and use data-mining techniques to develop a model that predicts use behaviour. Findings – Use behaviour is predictable. Most use is explained by value of the transaction. “Distance from Home” is more predictive of technology use than traditional demographics. Research limitations/implications – Results suggest traditional demographics are insufficient to explain “why” use/non-use occurs and hence an insufficient basis to formulate and target government policy. Originality/value – The authors understand this to be the first large-scale trans-national study of use/non-use of digital channels within China, and the first study of the impact of distance on ICT adoption.