Service Layer

The middle tier or service layer comprises all services and components of the UNICORE Service-Oriented Architecture (SOA) based on WS-RF 1.2, SOAP, and WS-I standards.

Gateway

The Gateway component acts as the entry point to a UNICORE site and performs the authentication of all incoming requests. From the UNICORE perspective it is the "door to the outside world" in a site firewall and may serve several resources/target systems behind it.

UNICORE/X

The UNICORE/X server is the heart of a UNICORE 6 site. Via WSRF compliant web services it provides access to storage resources, file transfer services and job submission and management services. Several services are available:

UNICORE's proprietary set of web service interfaces is called UAS (= UNICORE Atomic Services). It offers a complete, integrated set of basic services to higher level services, clients and users.
A standardised set of interfaces based on open, common standards (OGSA-*) is available in UNICORE 6 in addition to the UAS. Currently implemented standards are OGSA-BES and HPC-P, used for the creation, monitoring and control of jobs.

The UNICORE job definition is compliant with the JSDL (+ JSDL HPC extensions) standard. For file transfers (site-to-site and client-to-site), a variety of protocols are available (HTTPs, OGSA Byte-IO, UFTP, GridFTP and UDT).

For user authorisation, UNICORE/X can use a variety of attribute sources, like the XUUDB, UVOS or just flat files. The actual authorisation engine uses on XACML 2.0 policies. Full X.509 certificates are used as base line. Proxy certificates are optionally supported in UNICORE 6 e.g. to be able to use GridFTP.

UNICORE's internal execution management engine and link to the system layer is called XNJS.

IDB

The IDB (Incarnation Data Base) is used during job incarnation, i.e. the mapping of the abstract job description (in JSDL) to the concrete job description for a specific resource (a shell script). Information about available applications and resource characteristics has to be defined in this database.

XUUDB

The XUUDB user database provides a mapping from X.509 certificates to the actual users' logins and roles. The XUUDB component is a Web service in itself, so it can be used from multiple UNICORE installations, e.g. within the same computing centre.

UVOS

As an alternative to the XUUDB, a Virtual Organisation (VO) service can be used for user authorisation. The UNICORE VO Service (UVOS) uses the SAML standard and offers a wide variety of features.

Registry

Like many service-oriented environments, a global service registry is available, where the different services can register once they are started. A single service registry is necessary to build-up and operate a distributed UNICORE infrastructure. This service registry is contacted by the clients in order to "connect to the Grid". Therefore it is the central service of a UNICORE 6 Grid. Like UNICORE/X, the service registry runs in UNICORE's WS-RF hosting environment.

CIS

The Common Information Service (CIS) is the information service of UNICORE 6. It gathers both static and dynamic information from all connected XNJS, which are then displayed either in raw XML or human-readible text form. As longitude and latitude information is also stored, a google maps view allows a geographical representation of the Grid infrastructure.

CIS is based on the GLUE 2.0 standard from the Open Grid Forum. A central CIS is a useful complement to the central registry in an operational UNICORE infrastructure.

Workflow Engine

The workflow support in UNICORE 6 is implemented as a two-layered architecture consisting of a workflow engine and the service orchestrator layer. The workflow engine deals with high-level workflow execution, offering a wide range of control constructs and other features.

The workflow features of UNICORE 6 can be used from the graphical UNICORE Rich Client (URC) and from the command line with UCC. The URC offers a powerful graphical workflow editor and sophisticated workflow monitoring features.

Service Orchestrator

The service orchestrator layer is responsible to executing the individual tasks in a workflow, handling job execution and monitoring on the Grid. Different brokering strategies are implemented to find the best suited resources for each workflow step. Other brokering strategies can easily be plugged-in. To increase performance and scalability of the service orchestrator layer, multiple instances can be installed.