=Paper=
{{Paper
|id=None
|storemode=property
|title=The Ariadne Registry of LORs
|pdfUrl=https://ceur-ws.org/Vol-681/paper02.pdf
|volume=Vol-681
}}
==The Ariadne Registry of LORs==
https://ceur-ws.org/Vol-681/paper02.pdf
The Ariadne Registry of LORs
Jose Luis Santos, Joris Klerkx, and Erik Duval
joseluis.santos, joris.klerkx, erik.duval
@cs.kuleuven.be
Dept. Computerwetenschappen
K.U.Leuven
Celestijnenlaan 200A
B-3000 Leuven
Belgium
Abstract. The ARIADNE registry is one of the core components in an
architecture that promotes interoperability of networks of repositories
that facilitates the access to the learning content and encouraging the
share and reuse of digital content. This paper explains the development
of the ARIADNE registry of learning object repositories (LORs) and the
role played by standards and specifications.
1 Introduction
One of the problems of Technology Enhanced Learning (TEL) is that creating
Learning Objects (LOs) is expensive and time-consuming [1]. Sharing is one
of the possibilities to address this problem. When content creators search for
materials to reuse, they typically do not care about where the resource is located,
but want to find the best quality materials that satisfy their needs [2].
LOs are typically stored in Learning Objects Repositories (LORs). In ARI-
ADNE, considerable effort has been spent on the development of standards and
specifications for LORs [3], including IEEE LOM [4], SQI [5], SPI [6], OAI-PMH
[7] and PLQL [8]. These allow effective share and reuse of LOs between different
LORs and networks of LORs.
One of the problems for managing all these repositories within a network
is the scalability. Currently, every repository is added manuallyin the harvester
or in the federated search layer service. However, this time consuming process
requires that one person configures the targets and its parameters such as the
requirements (e.g. query languages for querying or metadata formats for har-
vesting).
In addition, some extra information about the content inside of the repos-
itories can be useful for managing this architecture. For instance, if we know
that one repository contains LOs focused on mathematics, and we are interested
in them, we can select this target to be harvested. To enable the sharing and
exchange of this information with other networks of repositories, the information
needs to be structured and managed.
13
This paper focuses on how the ARIADNE implements the ARIADNE Reg-
istry that has been integrated in the GLOBE architecture [9] and how ARIADNE
addresses the problems described above by:
1. using a reference implementation developed for the ASPECT project [10]
based on the concept of content collection. This content collection contains
relevant information about the content of the collections and technical in-
formation for accessing them;
2. creating a registry for managing this information;
3. using standards and specifications for increasing the interoperability within
networks of the repositories;
4. creating a network of registries in order to exchange the information between
them and to be able to access the LOs of other networks. In this way, all the
modifications done in a network can be widespread through all the networks
of the registries.
The paper is organized as follows: section 2 which shows a possible use case
of the approach. Section 3 introduces an explanation of the Registry Data Model
co-developed in ASPECT project. Section 4 explains the Registry Architecture.
Some statistics and data are presented in section 5.
2 Use Case. ARIADNE Foundation integrates the
ARIADNE registry in its infrastructure
This section focuses on a use case for the ARIADNE registry and discusses:
(i) the integration of the ARIADNE Registry in existing architectures and (ii)
increasing the collaboration between different institutions for exposing their LOs.
Also, we introduce some technical details about the implementation. The final
goal is to explain the use of the registry in a non formal way.
ARIADNE Foundation has several repositories where the LOs are described
by Learning Object Metadata. They expose the metadata using SQI and OAI-
PMH. However, they have noticed that the number of repositories is increasing
and it’s difficult to manage all the information from other content providers.
These content providers describe their LOs using different specifications like
LOM and Dublin Core(DC), on the other hand some content providers expose
the LOs using OAI-PMH and/or SQI. Looking for a good solution, they decide
to integrate the ARIADNE Registry to manage this information because:
1. The ARIADNE Registry allows the definition of LORs using IMS LODE.
That is open in terms of using specifications.
2. The ARIADNE Registry exposes the information using SQI, RSS and OAI-
PMH. SQI allows to query the registry. RSS alerts subscribers when a new
target is added. OAI-PMH allows to harvest all information from the ARI-
ADNE Registry. These three specifications allow to integrate their ARI-
ADNE Federated Search Layer which queries different repositories to obtain
different LOs from different repositories, the ARIADNE harvester which
14
harvests metadata from different repositories and to build a federation of
registries which allows to collaborate with different institutions.
The benefits that they obtain from the integration of the ARIADNE Registry
are:
1. They have centralized all the information from all the repositories where
they harvest from. It saves time in terms of administration tasks.
2. They can implement other services on top of the registry to check the avail-
ability of the different services. This service allows that other services can
check this information before trying to access the targets. This information
optimizes the performance behavior of these services.
3. The integration of the registry allows that new targets added are widespread
by different network of LORs which are federated with ARIADNE network.
3 ARIADNE Registry Data model
The ASPECT project [10] has co-developed an application profile of IMS LODE[11].
It is based on IMS Dublin Core Collections Application Profile specification and
complemented with ISO 2146 and IEEE LOM [12]. This specification uses the
concept of content collections. A content collection is defined as a group of dig-
ital content which is exposed to the world through some protocols based on
standards or specifications.
ARIADNE has chosen this specification, because it is not restrictive in terms
of use of specifications, and it increases the possibilities of interoperatibility
between architectures. In addition, the model does not restrict how the content
collections are created. This is an important issue, because the content providers
can choose how they create them and can offer metadata information about the
collections that they are interested in.
This model is represented by a schema that contains three main elements
Content Collection, Metadata Collection and Protocol.
1. Content Collection contains information about access rights, authoring, title
description, keywords, etc. This is information about the content itself.
2. Metadata Collection contains information about how the metadata is ex-
posed. Here, the content provider has to define which specification are used
to expose metadata. This part of the specification has an element for defining
the specification called Protocol Implementation Description which is used
for defining extra information like the query language supported by an SQI
interface or sets supported by an OAI-PMH interface.
3. Protocol contains specific information about the specification used like the
URL of the schema, namespace or the binding location.
Several examples can be found at the ARIADNE Registry site [13].
15
4 ARIADNE Registry Architecture
The implementation of the registry enables ARIADNE to build a federation of
registries, to provide access to collection information using SQI and to publish
new content collections using SPI.
Connections to all the networks
querying one registry
Federated Search Harvester
Registry 1
SQI
OAI-PMH
CC
RSS MC SQI
SPI MC OAI-PMH
CC SPI
MC SQI
Registry 2 SQI
CC
OAI-PMH MC
SRU/W
CC Synchronization
MC SQI RSS
SPI
MC OAI-PMH
Registry 3
CC SPI SQI
MC
SQI
OAI-PMH
CC
MC SQI
RSS
CC
MC OAI-PMH
MC SRU/W SPI
CC SPI
MC SQI
CC
MCSRU/W
Fig. 1. ARIADNE architecture approach
A registry can contain metadata collections (MC in the figure 1) or content
collections (CC). The latter contain metadata collections (MC).
The final goal of the registry is to create a network of networks of reposi-
tories, similar to current DNS functionality on the internet. All the registries
16
are synchronized so if a harvester or a federated search service queries a registry,
they can access all the content collections or metadata collections in the different
networks. This approach is important: it allows automated discovery, decreases
time spent managing repository information, and allows automated widespread
updates.
This architecture shows how the registry can be synchronized with other reg-
istries. The registry exposes its contents using OAI-PMH so that other registries
can harvest its content. In addition, the registry exposes its updates also using
the RSS 2.0 specification, so that registries can be synchronized also with RSS
feed readers. This RSS system can be used as a notification system, as it contains
all the targets published.
The registry uses SQI for querying because it is neutral in terms of query
language or results formats. Consequently, all SQI clients can query the registry.
The registry supports different query languages like PLQL, VSQL and Lucene
Query Language.
Finally, the registry implements an SPI interface for publishing content col-
lections. For instance, when other content collections are harvested, they are
inserted using SPI to publish content by reference, because the metadata in this
case defines a content collection already published elsewhere.
One of the main advantages of this implementation is that ARIADNE Reg-
istry is based on the ARIADNE Repository. This software is a flexible imple-
mentation that allows different models of metadata. For instance, it supports
LOM, ILOX, Dublin Core and this paper explains how it supports IMS LODE
Registry specification. The idea behind this software is that we can index all
kind of xml document. However, the final goal is that we can built combined
queries, for instance, using PLQL, based on the content of different tags.
Trying to validate this architecture, we have integrated the ARIADNE har-
vester with the registry. The following sequencing diagram 2 shows how a sys-
tem administrator can configure the harvester using the current implementation
where the system administration can query the registry and add the targets that
he/she is interested in.
5 Related Work
One of the main goals of ARIADNE is to encourage sharing and reusing LOs.
For this purpose, we have implemented a registry using the concept of content
collection, integrating some technical information in the data model and allow-
ing the federation of registries. Table 1 shows the similarities between existing
approaches and the ARIADNE approach.
Domain Name System (DNS)[14] has conceptual similarities with the ap-
proach explained in this paper. While DNS translates a name identifier to a
number identifier, the registry translate abstract information contained by the
content collection to a technical information contained in the metadata collec-
tion. In addition, the federation of DNS allows the propagation between them of
the new sites. It is a similar approach that ARIADNE Registry implements with
17
ARIADNE
User interface
ARIADNE Registry
Harvester
To Send keywords
To complete the query with (1)
Results
Forms for adding/update/delete
new targets
Request
Forms updated
(1) metadataCollection.target.targetdescription.protocolIdentifier.entry = "oai-pmh-v2"
Fig. 2. Interaction diagram - Configuring the harvester
Table 1. Similarites with an existing approaches (Non-exisiting, Weak and Strong)
Dif f erent approaches Content collection Extra technical inf ormation F ederation
DN S Non-exisiting Non-exisiting Strong
M W SDI Weak Strong Weak
IESR/OCKHAM Strong Weak Weak
CORDRA Strong Weak Weak
18
the federation of the registries (the new content collections should be propagated
among them)
METEOR’s Web Service Discovery Infrastructure (MWSDI) uses UDDI spec-
ification for defining the interfaces (web services) and it defines an ontology for
providing support to the infrastructure using OWL. MWSDI is based on the
need to decentralize an architecture for several reasons such as geographical
location, nature of registered services, business functionality, technical specifi-
cations and so on [15][16]. For this reason, it contains an ontology with details
of the domain, Registries, Ontologies and Registries federation and network of
relationship among them. The main difference is that MWSDI doesn’t contain
a content collection approach and the ARIADNE registry doesn’t implement an
hierarchical architecture of registries.
JISC Information Environment Service Registry (IESR)[17] and OCKHAM
NSF / NSDL Registry [18] are developed under Global initiatives Registries [18].
They introduce the concept of content collection approach, while IESR uses Re-
search Support Libraries Programme Collection Description schema (RLSPCD)
and Dublin Core, which allows the definition of some technical details of the
services which provide access to the collections[17], OCKHAM NSF/NSDL uses
Dublin Core. They consider the definition of how the repositories expose the
metadata considering protocols like Z39.50, Web Service SOAP, SRW and OAI-
PMH. However, they don’t provide extra information in their implementations
such as sets supported by OAI-PMH or query languages. The registries expose
their metadata through a SRU client [19, 16].
CORDRA / ADL registry (ADL-R) merges the concepts or MWSDI and
IESR/OCKHAM, introduces a hierarchical structure of registries and the con-
cept of content collection based on repositories which accept LOM as a metadata
of LOs [20] .
At the end, we can conclude that Ariadne Registry incorporate the best
characteristics from other approaches:
1. Conceptually, we implement similar approach to DNS widespread function-
ality.
2. IMS LODE Registry allows the definition of the services like UDDI specifi-
cation concept do.
3. IMS LODE Registry allows the content collection approach like the above
approaches mentioned do.
4. ARIADNE Registry allows the federation of the registries.
6 Statistics
In this section, we include some information about the metadata collections in-
serted and how they expose the metadata. It includes the number of records
harvested using the OAI-PMH protocol. However, SQI or SRU/W don’t provide
a way to get all the possible results, thus the SQI and SRU/W targets do not
contain information in date and records harvested field (table 2).
19
Table 2. Records harvested and protocols
id date records SQI SRU OAI SP I
dum rvp cz 09 Apr 2010 2323 No No Yes No
atlas f ri uni − lj s 12 Apr 2010 4400 No No Yes No
openlearn open ac uk 12 Apr 2010 535 No No Yes No
sodis de 12 Apr 2010 2277 No No Yes No
sdt sulinet hu 12 Apr 2010 18864 No No Yes No
ait opetaja ee 12 Apr 2010 4050 No No Yes No
193 43 17 27 12 Apr 2010 19309 No No Yes No
193 93 132 187 12 Apr 2010 3541 No No Yes No
www yteach com 12 Apr 2010 10 No No Yes No
aspect 12 Apr 2010 124933 Yes No Yes Yes
aspect cup cam ac uk 12 Apr 2010 8839 No No Yes No
melt contento se 12 Apr 2010 3014 No No Yes No
spindeln iml umu se 12 Apr 2010 6699 No No Yes No
lom emokykla lt u 1 12 Apr 2010 1101 No No Yes No
195 82 131 106 12 Apr 2010 196 No No Yes No
aplitic xtec cat 12 Apr 2010 9876 No No Yes No
www klascement net 12 Apr 2010 17739 No No Yes No
www portaldasescolas pt 12 Apr 2010 1554 No No Yes No
f enix isf tic mepsyd es 12 Apr 2010 26666 No No Yes No
M ace 0 13 Apr 2010 180461 No No Yes No
Globe 13 Apr 2010 385739 Yes No Yes No
caad asro kuleuven be 3 May 2010 450 No No Yes No
caad asro kuleuven be 0 3 May 2010 65 No No Yes No
caad asro kuleuven be 1 3 May 2010 171 No No Yes No
caad asro kuleuven be 2 3 May 2010 890 No No Yes No
caad asro kuleuven be 3 3 May 2010 2773 No No Yes No
caad asro kuleuven be 4 3 May 2010 50 No No Yes No
caad asro kuleuven be 5 3 May 2010 2106 No No Yes No
cumincad scix net 3 May 2010 9636 No No Yes No
ariadne members 3 May 2010 3290 Yes No Yes No
ariadne partners 3 May 2010 71600 Yes No Yes No
icoper 3 May 2010 16454 Yes No Yes No
eun 3 May 2010 187722 Yes No Yes No
ourj code 3 May 2010 297 Yes No Yes No
iskme 3 May 2010 30907 No No Yes No
oai rails it com 3 May 2010 211 No No Yes No
oai rails it com 0 3 May 2010 2223 No No Yes No
oai rails it com 1 3 May 2010 29 No No Yes No
kocw Not applicable Not applicable Yes No No No
merlot Not applicable Not applicable Yes No No No
educanext Not applicable Not applicable Yes No No No
lornet Not applicable Not applicable Yes No No No
espol Not applicable Not applicable Yes No No No
agrega Not applicable Not applicable Yes No No No
nime Not applicable Not applicable Yes No No No
f edora Not applicable Not applicable No Yes No No
T otal 1151000 14 1 38 1
20
Table 2 shows that the registry contains fourteen repositories which sup-
port SQI, one repository which supports SRU/W, twenty-five which support
OAI-PMH and one which supports SPI. As the ARIADNE harvester relies on
the registry, we know how many objects are exposed through OAI-PMH. The
information is shown in the table.
The result is that we expose 1151000 metadata instances through the ARI-
ADNE registry so far, although, we have to remark that some of them are du-
plicated, because some targets harvest other targets. But it means that we can
expose a large amount of metadata instances specifying the protocol to access
to them. All the harvesters which implement OAI-PMH can connect easily to
the registry, using an SQI client for finding the targets and harvesting all the
metadata from all the repositories described in the registry.
7 Conclusions and future work
We have developed a LOR registry, which enables us to set up a federation
of registries. Different federations of repositories can easily obtain information
from other federations through the registries. In this context, we will deploy the
ARIADNE Registry in the ASPECT project, and we will evaluate the pros and
cons of the federation.
In the scope of this work, we have considered some of the main specifications
about querying, harvesting and publishing like SQI, OAI-PMH and SPI. We have
spent some efforts to define extra information for the SRU/W. However, we have
to validate this specification. Also, we would like to consider more specifications
such as OKI OSID.
Now, we have integrated the ARIADNE harvester with the registry, in addi-
tion, we have to work on the Federate Search Layer to allow querying based on
the content of the registries.
Acknowledgment The ARIADNE Registry has been funded partially by the
ASPECT project: Adopting Standards and Specifications for Educational Con-
tent (Grant agreement number ECP-2007- EDU-417008) and by the CEN/ISSS
workshop on Learning Technologies (WS-LT). Thanks also to our colleagues
Ivana Bosnic and Katrien Verbert for helping us in this work.
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