MIGRATION BETWEEN CONTENT MANAGEMENT SYSTEMS

Exploiting the JSR-170 Content Repository Standard

Michael Nebeling

Monash University, Australia/Ulm University, Germany

Grace Rumantir, Lindsay Smith

Berwick School of Information Technology, Monash University, Australia

Keywords: Enterprise Content Management (ECM), Content Management Systems (CMS), CMS Migration & Integra-

tion, CMS Interoperability.

Abstract: Content management systems (CMS) have evolved in diverse ways due to the lack of sufficient standards.

Even amongst CMS supporting JSR-170, the recent Java standard to organise and access content reposito-

ries, incompatible content structures exist due to substantial differences in the implemented content models.

This can be of primary concern when migration between CMS is required.

This paper proposes a framework to enable automated migrations between CMS in the absence of con-

sistency and uniformity in content structures. This framework serves as a starting point of a body of re-

search to design a common content model which can be implemented in future CMS to facilitate migration

between CMS based on JSR-170 and improve integration into existing information systems environments.

This is illustrated via a simple website created using two of the most popular open-source CMS supporting

JSR-170: Magnolia, and Alfresco. A model-based approach towards a generalised content structure is postu-

lated to resolve the differences between the proprietary content structures as identified in the visualisation of

the simple website created. The proposed model has been implemented in Jackrabbit, the JSR-170 reference

implementation, and the proposed framework therefore contains simple methods to transform content struc-

tures between Magnolia and Alfresco using this Jackrabbit implementation as an intermediator.

1 INTRODUCTION

Content management systems (CMS) provide the set

of technologies to support the processes involved in

the management of content lifecycles with software.

In a web context, common processes include creat-

ing, updating, publishing, and archiving web pages

that may contain text, images, and other forms of

multimedia. For CMS to be implemented, however,

there is currently no approach that can be considered

standard across the systems. This can be of primary

concern when migration from one CMS product to

another is required.

Possible scenarios for CMS migrations range

from a takeover by a company or merges of depart-

ments within the same company where different

CMS have been tailored to individual needs to the

case where a company decides to switch to another

CMS implementation due to stagnating development

progress or inadequate support of the product cur-

rently in use. Migration of content requires at least

partial integration of CMS and is therefore consid-

ered a special form of databases and information

systems integration.

This paper reports on the most essential findings

of a research project (Nebeling, 2007) designed to

investigate migration of content between two of the

most popular open-source CMS supporting JSR-170,

namely Magnolia (http://www.magnolia.info) and

Alfresco (http://www.alfresco.com).

Section 2 of this paper establishes the context of

the reported research. Section 3 describes the chosen

research design. Sections 4 and 5 present the results

as part of the artefact development and evaluation

processes of this research. Section 6 presents the

reflection involved in the research project. Section 7

draws conclusions based on the experiences gained

from this research project.

240

Nebeling M., Rumantir G. and Smith L. (2008).

MIGRATION BETWEEN CONTENT MANAGEMENT SYSTEMS - Exploiting the JSR-170 Content Repository Standard.

In Proceedings of the Tenth International Conference on Enterprise Information Systems - DISI, pages 240-245

DOI: 10.5220/0001699802400245

 SciTePress

2 RESEARCH CONTEXT

It is often argued in the literature that for content

management to be implemented effectively, the fo-

cus has to be on the design of the content model (eg.

Päivärinta et al., 2005; Grossniklaus et al., 2002).

Content models describe the relationships between

the most important aspects of content such as con-

tainer, type, structure, format, and metadata. Rela-

tively little research has been conducted into the

design of content models (cf. Tyrväinen et al.,

2006).

Grossniklaus et al. (2002) propose separate mod-

els of content, structure, and format for content

management implementations. While they focus

mainly on these components, Päivärinta et al. (2005)

require content lifecycles, metadata, and corporate

taxonomy to be integrated in the content model. As

yet, a unified model that can be implemented to sup-

port all of these components has not been presented.

In fact, in their analysis of 58 content management

projects and implementations, Päivärinta et al.

(2005) report “no mentions of explicit, let alone uni-

fied, content modelling approaches” (p. 3).

However, with the Content Repository API for

Java

Technology Specification (Nuescheler et al.,

2006) considerable work has been done to create a

Java standard under the Java Specification Request

170 (JSR-170) that provides the necessary constructs

for the implementation of content models. JSR-170

started as a proposal to be accepted as an industry

standard for the Java language and related platforms.

Members from more than 20 different companies,

well-known in the content management field, par-

ticipated in its development. While this research

focused on the recently approved JSR-170, a new

version specified as JSR-283 was under public re-

view in September 2007.

JSR-170 provides a hierarchical, tree-based view

of the content repository. Here, content is organised

in a structure similar to that of a folder and file struc-

ture known from the file system, where folders

would represent nodes and files would represent the

properties of the nodes. For the purpose of classifi-

cation, each node in the repository must be of a pri-

mary node type, and optionally, can add so called

mixin node types.

With the system view, JSR-170 also defines a

complete mapping of the content repository to XML.

System view XML exports and imports can in prin-

cipal be exploited to facilitate migration of content

between CMS based on JSR-170. However, this

requires an integrated content model that would re-

solve the differences between the content models of

the source and destination CMS implementations.

3 RESEARCH DESIGN

For this research, a design science approach (Hevner

et al., 2004) was chosen because the focus of the

research was on the design of an innovative artefact

that would facilitate migration between the selected

CMS implementations. Similar to Arnott (2006) the

research process involved the five distinct phases as

outlined in the following subsections.

3.1 Problem Recognition

The first phase of the research project aimed at the

identification of differences between the selected

CMS in terms of the implemented content models.

An experiment was designed in which the same

simple website (Figure 1) was created using each

product.

Figure 1: Structure of the simple website.

For the purpose of this investigation, the struc-

ture of the website was kept simple and the content

plain. Although more complex structures would

more realistically represent today’s websites, they

would largely produce repetitive content structures.

It was decided to concentrate on Magnolia and

Alfresco as they are two of the most popular open-

source products that support the JSR-170 standard to

organise and access the content repositories. Magno-

lia was the first open-source CMS to be based on

JSR-170, and therefore has found widespread accep-

tance. It uses Jackrabbit as the underlying JSR-170

content repository implementation. Alfresco, on the

other hand, implements its own fully compliant JSR-

170 repository and supports a range of industry-wide

Java standards, which is why it has become a popu-

lar choice for many content management projects.

Once the simple website had been created using

Magnolia and Alfresco (Section 4.1), the produced

content structures were mapped to XML using the

MIGRATION BETWEEN CONTENT MANAGEMENT SYSTEMS - Exploiting the JSR-170 Content Repository

Standard

241

system view export from each system. Also, for each

system, the implemented types used for the classifi-

cation of the proprietary content structures were

exported to XML. As the researcher found it diffi-

cult to explore and analyse the collected data in its

pure XML format, Extensible Stylesheet Transfor-

mations (XSLT) were applied to prepare the data for

visualisation using the GraphViz tools. This visuali-

sation then allowed the researcher to explore and

analyse the data more clearly.

3.2 Suggestion

The investigation conducted in the first step found

substantial differences in the content models imple-

mented by Magnolia and Alfresco. To resolve these

differences, the researcher proposed an integrated

content model based on the individual content mod-

els implemented by the selected systems.

Parsons et al. (2000) argue for the integration

process that it is necessary to regard “instances and

their properties independent of any classification”

(p. 239). In a JSR-170 compliant repository, all con-

tent “is ultimately accessed through properties”

(Nuescheler et al., 2006, p. 40), and nodes storing

content units only exist as members of node types.

Parsons et al. (2000) propose a two-layered ap-

proach to the integration process, which separates

the instances or nodes from the classes or node types

they belong to. Following this approach, the first

layer only represented the instance model providing

information about nodes stored in the repository and

their properties without any classification. The sec-

ond layer then represented the class model providing

information about node types only defined in terms

of their properties.

The two-layered approach had the advantage that

the integration of the content models could be per-

formed at the instance level without first agreeing on

a set of node types. As far as the class model is con-

cerned, Parsons et al. (2000) suggest that, once the

instance model has been combined, “the class model

can include all classes from all sources” (p. 248).

However, each CMS implementation then must have

at least partial knowledge about the node types de-

fined by the other system. In order for the class

model to represent only a global set of classes for

both Magnolia and Alfresco, a single generic node

type was defined for each set of similar content

structures. In making such an abstraction further

known as Generalisation, the researcher was able to

resolve most of the differences between the individ-

ual content models implemented by Magnolia and

Alfresco. This integrated model was then imple-

mented in Jackrabbit and simple repository trans-

formations were defined to exchange the simple

website between the systems (Figure 2).

Figure 2: Proposed framework for automated migrations

of content between Magnolia, Alfresco, and Jackrabbit

using simple transformation methods.

3.3 Artefact Development

The artefact at the core of this research was the Gen-

eralised Content Model (Section 4.2). This term was

chosen to reflect the fact that the proposed model is

a generalisation of existing content models whose

primary purpose was to provide an integrated view

of the individual content models implemented by

Magnolia and Alfresco.

Instantiations are used to demonstrate feasibility

and are aimed to prove that an artefact can be im-

plemented and executed in a working system (Hev-

ner et al., 2004). The instantiation of the proposed

model was in the form of a JSR-170 node type defi-

nition implemented in Jackrabbit to facilitate storage

and retrieval of content in the Generalised Reposi-

tory (Section 4.3).

3.4 Artefact Evaluation

The evaluation of the proposed model was con-

ducted in two steps: (1) It was tested if the node

structures extracted from the simple website in

Magnolia and Alfresco can be transformed to the

generalised content structure, and fully restored

when transforming back to each source repository.

(2) It was tested if the content structures of the sim-

ple website created in Magnolia and Alfresco could

be interchangeably transformed in both directions

between the two systems using Jackrabbit as the

Generalised Repository in between.

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If Step (1) proved successful then the approach

towards the Generalised Content Model was vali-

dated for Magnolia and Alfresco (Section 5.1). If

Steps (1) and (2) proved successful then the pro-

posed model would also facilitate migration between

the selected systems (Section 5.2).

3.5 Reflection

Reflection typically is involved in the final step of

design science research (Arnott, 2006; Hevner et al.,

2004). For this research project, the chosen research

design and the artefact design processes were criti-

cally reviewed. As a result, refinements of the pro-

posed model and its instantiation were identified to

indicate further research directions (Section 6).

4 ARTEFACT DEVELOPMENT

In this section, the artefact development process is

reported in three parts. The first part summarises the

findings of the initial simple website experiment.

The second part describes the Generalised Content

Model that was proposed based on the findings of

the initial experiment. The third part reports on im-

portant design decisions for the instantiation of the

proposed model.

4.1 Experiment Findings

The simple website experiment allowed the re-

searcher to identify substantial differences between

the content models implemented by Magnolia and

Alfresco. With Magnolia, node types are defined in

a rather abstract manner and therefore lack explicit

agreement on how content is structured in the re-

pository. Even worse is the fact that with different

templates the actual content was sometimes stored

with different properties. Also, the Community Edi-

tion used for the investigation did not implement a

particular metadata standard. Even though only the

out-of-the-box node type definitions were used for

the investigation, many websites created using Mag-

nolia may be based on exactly these default node

type definitions, and the identified problems make

migration of content from and to Magnolia difficult.

With Alfresco, on the contrary, there is a rather

explicit agreement on how content is structured in

the repository, which is primarily due to the exten-

sive use of mixin node types. With Dublin Core, a

widely-used metadata standard is partially imple-

mented in Alfresco; however, the system did not

make use of the respective elements when the simple

website was created and associated with metadata.

4.2 Proposed Model

Based on the findings of the simple website experi-

ment, the Generalised Content Model as illustrated

in Figure 3 was proposed.

Figure 3: Proposed Generalised Content Model.

The relations between the different components

in Figure 3 can be described as follows: (1) With the

exception of the root container, each Content unit

always has a container. (2) Depending on the cho-

sen level of granularity, each Content unit can con-

tain finer grained units. Together, these relations

make for a hierarchy of Content units, typically re-

ferred to as the content structure. (3) Each Content

unit is always associated with a Type. The Type

makes for an explicit agreement on the content

structure. (4) Each Content unit is assigned to at

least one Template. Templates are used to transform

content from one form into another. Each form en-

riches the Content unit with format; however, the

format must have no impact on the content structure.

(5) Each Content unit is described by a set of Meta-

data elements. It is good practice to implement exist-

ing metadata models such as the Dublin Core Meta-

data Standard. (6) Each Content unit can have multi-

ple relations to each Identity that participates in the

management of the content lifecycle. The two inves-

tigated CMS implementations both assign at least

the creator with each Content unit.

The proposed model is not necessarily an alter-

native to the separate models proposed by Grossnik-

laus et al. (2002). Rather, it is attempted to integrate

the relationships between content, type, structure,

and format into a unified view of the content model.

Päivärinta et al. (2005) require the content model to

support content lifecycles and metadata. Metadata is

clearly an essential part of the proposed model but

content lifecycles may need further integration.

Päivärinta et al. (2005) also emphasise the need for

corporate taxonomy; however, the researcher argues

that corporate taxonomy can be supported with

MIGRATION BETWEEN CONTENT MANAGEMENT SYSTEMS - Exploiting the JSR-170 Content Repository

Standard

243

metadata provided that a taxonomy of metadata ele-

ments can be established.

4.3 Instantiation of Proposed Model

The instantiation of the proposed model is a node

type definition for JSR-170 compliant repositories. It

was implemented and validated with Jackrabbit.

Mixin node types were first defined to establish

the difference between nodes storing content and

metadata in the repository as well as to allow for a

hierarchical structure of content units and a taxon-

omy of metadata elements. The use of mixin node

types yields the advantage that nodes storing actual

content can inherit from any particular primary node

type but will still be marked as either content or

metadata, simply by adding one of the proposed

mixin node types. As a result, the generalised node

types can be integrated with existing node type defi-

nitions more easily.

Simple primary node types for the storage of the

actual content were then proposed as a generalisa-

tion of the individual node types implemented by

Magnolia and Alfresco. As far as metadata is con-

cerned, the Dublin Core simple metadata element set

was implemented since it was sufficient to describe

the content of the simple website; however, no par-

ticular standard is inherent to the proposed model.

5 ARTEFACT EVALUATION

In this section, the results of the artefact evaluation

processes are presented in two parts. The first part

concentrates on the simple repository transforma-

tions that were defined to validate the proposed

model for Magnolia and Alfresco. The second part

reports on the exchanges of the simple website be-

tween the two systems in both directions.

5.1 Repository Transformations

Four distinct transformation processes between

Magnolia, Alfresco, and the Generalised Repository

were differentiated: (1) from Magnolia to the Gener-

alised Repository, (2) from the Generalised Reposi-

tory to Magnolia, (3) from the Generalised Reposi-

tory to Alfresco, and (4) from Alfresco to the Gener-

alised Repository. In all four cases the Generalised

Repository was Jackrabbit (Figure 4). Simple trans-

formation processes based on JSR-170 were defined

for the exchange of the simple website between each

repository.

Figure 4: The repository transformation processes between

Magnolia, Alfresco, and Jackrabbit.

Processes (2) and (4) were, in fact, inverse trans-

formations of Processes (1) and (3), respectively;

however, exceptions had to be made because with

Magnolia’s templates the content was sometimes

stored with different properties and, for Alfresco, the

implemented mixin node types had to be fully re-

stored as part of Process (4).

The distinct repository transformations were im-

plemented in separate Java classes and, while the

crucial steps involved in the repository transforma-

tion processes were logged, were exercised as fol-

lows: The simple website was transformed through

Process (1) and fully restored through Process (2),

i.e. without substantial loss of information. As a

result, the proposed model was validated for Magno-

lia. The same was shown for Processes (3) and (4),

respectively, so that the proposed model was also

validated for Alfresco.

5.2 Migration of the Simple Website

Final experiments exercised the following composi-

tions of repository transformations: (i) from Magno-

lia to the Generalised Repository and from the Gen-

eralised Repository to Alfresco, and (ii) from Al-

fresco to the Generalised Repository and from the

Generalised Repository to Magnolia. Again, the

Generalised Repository was Jackrabbit in both cases

(Figure 4). Hence, running Composition (i) demon-

strated migration from Magnolia to Alfresco; run-

ning Composition (ii) demonstrated migration from

Alfresco to Magnolia, using Jackrabbit as the inter-

mediator in both cases.

The correct display of the simple website after

executing Compositions (i) and (ii) together with the

visualisation of the exported node structures and the

repository transformation protocols provided strong

evidence that the simple website was effectively

exchanged between Magnolia and Alfresco in both

directions. As a result, the initial hypothesis, that the

Generalised Content Model can resolve individual

differences between the selected systems and there-

fore facilitate migration of content between them,

was accepted.

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6 REFLECTION

Design science is research into building artefacts

that address “important unsolved problems in unique

or innovative ways” (Hevner et al., 2004, p. 81). The

artefact at the core of this research is a model-based

approach towards the migration of content between

two CMS based on JSR-170. It is unique and inno-

vative because, to the knowledge of the researcher,

no similar approach has been presented.

In the initial phase of the artefact development,

the two content models implemented by Magnolia

and Alfresco were studied. An important step was to

extract and scrutinize the different node type defini-

tions implemented by the two selected systems. As

there was no documentation of the node type defini-

tions available, some of the findings of the simple

website experiment had to be tentatively explained

and may need further clarification. Therefore, the

researcher wishes to emphasise the need for a docu-

mentation of content models, where CMS develop-

ers may explain and justify their design decisions.

The design of the proposed model was based

primarily on the most essential commonalities and

differences between Magnolia and Alfresco as iden-

tified in the simple website experiment. Hence, the

researcher notes critically that the proposed model is

an approach towards a Generalised Content Model

rather than the Generalised Content Model, and still

is only based on Magnolia and Alfresco.

7 CONCLUSIONS

Content management systems (CMS) have evolved

in diverse ways due to the lack of sufficient stan-

dards. Only recently, with the JSR-170 content re-

pository standard, an ongoing effort to standardise

CMS can be observed. The reported research project

was designed to investigate migration of content

between two of the most popular open-source CMS

supporting JSR-170, namely Magnolia and Alfresco.

An initial experiment where the same simple

website was created using each of the selected sys-

tems found incompatible content structures due to

differences in the content models implemented by

Magnolia and Alfresco. To resolve these differences,

the Generalised Content Model was proposed as an

integration of both content models, and implemented

in Jackrabbit, the JSR-170 reference implementa-

tion. Simple transformation methods were then de-

fined to transform the content structures between

Magnolia, Alfresco, and Jackrabbit. Final experi-

ments provided evidence that the simple website

could effectively be exchanged between the selected

CMS in both directions using Jackrabbit as an in-

termediator.

The research project showed that many individ-

ual differences between CMS can be traced back to

the lack of a common content model. The relations

between content, type, structure, format, and meta-

data need to be clearly defined to allow for the de-

sign of a common content model. With the chosen

approach, the researcher was able to resolve individ-

ual differences between the content models imple-

mented by Magnolia and Alfresco, and as a result

enabled migration of a simple website between the

two systems in both directions. This research may

therefore be regarded as a starting point to define

methods for automation of migrations between CMS

based on JSR-170 in the absence of a common con-

tent model. However, the researcher believes that

this research is also a blue print for a method to de-

sign and evaluate a content model that may become

standard across CMS implementations.

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