Towards a Digital Content Services Design Based on ... - CiteSeerX

Towards a Digital Content Services Design Based on Triple Space David de Francisco1 , Noelia Pérez1, Doug Foxvog2, Andreas Harth2 , Daniel Martin3 , Daniel Wutke3 , Martin Murth4 , and Elena Paslaru Bontas Simperl5 1

Telef´ onica Investigaci´ on y Desarrollo {ddf268,npc}@tid.es 2 DERI, National University of Ireland, Galway {doug.foxvog,andreas.harth}@deri.org 3 University of Stuttgart {daniel.martin,daniel.wutke}@iaas.uni-stuttgart.de 4 Vienna University of Technology [email protected] 5 Free University of Berlin [email protected]

Abstract. Digital Asset Management is an emerging business for telecommunication companies, especially when applied to the entertainment market. Current implementations try to overcome the integration needs from each actor participating in the business processes by using Enterprise Application Integration. Triple Space is a space-based communication infrastructure which provides semantic mediation between actors involved in a dialogue. This paper presents a Digital Asset Management use case in which Triple Space will be applied to fulfill the inherent needs of this business domain through the use of this new semantic communication paradigm. Keywords: Triple Space, Digital Asset Management, Enterprise Application Integration, Space-based Computing.

1

Introduction

Digital content constitutes an important commercialization resource1 . The Internet, and more specifically the Web, have enabled content providers to distribute content on a world-wide scale with very little cost, since content is distributed digitally. With the appearance of new wireless and mobile technologies, additional ways of consuming content have become available. For digital content, 1

See figures in http://www.naa.org/technews/tn981112/editorial.html

W. Abramowicz (Ed.): BIS 2007, LNCS 4439, pp. 163–179, 2007. c Springer-Verlag Berlin Heidelberg 2007

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the full workflow can be carried out online, from offering content, browsing catalogs, delivery of goods, to final payment. This enables a vendor to get huge cost-savings by using the Internet (or mobile Internet) as a distribution channel for digital content. For telecommunication companies such as Telefónica2 , digital asset management and digital content distribution offers a large business market. Telecommunication providers can offer services based on digital content, primarily delivering content to end users by providing network communication infrastructure plus value-added services in the digital asset management domain. Telecommunication providers can leverage their existing bandwidth services, both in fixed and mobile networks, and offer distribution channels from providers of digital content to end users. New services must be designed and created in very short amounts of time to satisfy possible market needs as soon as possible. This paper examines a specific scenario in the Digital Asset Management arena. The intent is to supplement a sports news site, which is offered to customers of DSL lines free of charge, with multimedia content (audio and video) as a premium, paid-for service. To be able to quickly put together such service offerings, companies require methods to partially or fully automate the service creation process. This paper makes the following contributions: – It describes a scenario in the area of Digital Asset Management which deals with creating new service offerings based on integrating offerings of multiple partners into one coherent end-user service offering. – It presents a software architecture based on Triple Spaces (Triple Space Communication) which enables the companies involved to implement a system which is able to fulfill the use case. The remainder of this paper is organized as follows: Section 2.1 presents the Digital Asset Management (DAM) business domain. Section 2.2 describes the use case in detail. Section 2.3 shows possible architectures rooted in traditional Enterprise Application Information (EAI) techniques. Section 3.1 presents the Triple Space paradigm, which will be used in the use case to provide benefits pointed out in Sect. 3.2. Section 3.3 presents a high level architecture to realize the use case. Section 4 summarises the paper and presents conclusions.

2

Digital Asset Management (DAM)

Digital Asset Management (DAM), also known as Multimedia Asset Management (MAM), has the aim of organizing, protecting and distributing digital multimedia content in an efficient way, with the aim of improving business industries based on multimedia [1].

2

http://www.telefonica.com/home eng.shtml

Towards a Digital Content Services Design Based on Triple Space

2.1

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DAM Business Domain

Within the DAM business domain many actors interact collaboratively to engage in e-commerce with multimedia content. This paper follows the eTOM e-business reference model [10] – the most widely accepted standard for business practices in the telecommunications industry – to identify the actors relevant to the DAM business domain. A service provider provides content services to final clients by storing a catalogue of proffered media content which it offers through a service portal. All the billing processes, customer care, user management, and user security issues are performed by or subcontracted out by the service provider. This service provider needs media content to provide these content services. A content provider is a supplier which owns media content and wants to trade with it. In order to address the unauthorized copying issue, a service provider needs to use a Digital Rights Management (DRM) system [6]. A DRM provider provides security functions such as privacy, integrity, or authentication which are especially suited for multimedia content [20]. The DRM provider plays the role of a complementary provider in the eTOM business reference model. The service provider needs to distribute the selected content in a secure way to the final clients that purchased it. The content distributor is an intermediary that not only provides the client access to the media content, possibly using different communication networks; it might also sell value-added services to the content provider, providing storage and bandwidth functionalities. Mobility, security, quality of service, rights management and interoperability are key features offered by a service provider supplier. For that reason it is necessary for all the business processes related to DAM environments to be easily adaptable and configurable so that new business possibilities can become available in a fast and effective way. The DAM challenge is to provide agile and seamless interaction between these actors, apart from bridging different proprietary multimedia environments – the so-called content ecosystems in DAM domains – integrating DRM technologies [15]. Due to the inherent heterogeneity of actors, content, and services involved in a content service design, multiple transactions are usually held between service provider and different suppliers. These transactions should be held in parallel to save time and be maintained in a transparent way, so that service providers need not know which vendor is able to provide the content and services they need. To manage this heterogeneity all the actors involved should agree on a common communication language. Communication between these actors should be reliable and ensure confidentiality since business data from different enterprises is being dealt with. Messages in such communications would derive from the service definition and should be easily accessed by actors involved in the content service due to the frequent modifications made to content services. These desired features of a content services design system are illustrated in concrete scenarios below.

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Fig. 1. UML use case diagram

2.2

Definition of the Use Cases

In order to develop an improved communication model for content services design, a concrete working flow for a complete DAM business scenario has been defined as a use case. A content service is modeled as a structure of the components that comprise and uniquely define it: the content provided by this service, access policies defined for this content, and distribution mechanisms employed to provide this content to final users. As depicted in Fig. 1, content offering and contracting will be considered in the final use case. However, only service contracting will be considered initially. Service offering is considered redundant since business interactions are basically the same than content offering.


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In this use case, Terra Sports is a Telefónica-dependant website which offers sports news for free to users who have contracted Telefónica DSL services. These news feeds present a brief summary from sports newspapers and give the users a general overview of the main news about sports events over the previous week. Given that Terra users are very interested in sports-related material, Terra has decided to provide its users with a premium sport news service “Terra Total Sports”. This premium service will consist of selected multimedia content from different content providers which complements the free textual content.

Fig. 2. Service Creation Flow

In the design phase of this service, Terra will define all requirements for offering this service and check if any existing services are already registered and ready in its system to which the task may be subcontracted (as shown in Fig. 2). The use case assumes no similar service is available and Terra has to negotiate the purchase of the required contents and services. In order to get the desired content, Terra will query digital content catalogues stored already available in a data store for a service that already exists and fulfills all requirements. The most natural way to identify this service is to describe its content request which is done by using associative addressing (“template”

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mechanism). This request defines desired features of the content, like the kind of content you are interested in, the format or the quality. When a suitable content is found, a negotiation with the registered owner for each desired set of media content will be started until terms - including a price - are agreed. After that, Terra will send the content provider an order request, which may be amended by Terra in case its needs change. Once an order has been processed and delivered, the content provider will send an invoice to Terra to finish the transaction.

Fig. 3. content and service negotiation flow

The whole process presented in Fig. 3 will be repeated for other services needed by Terra including distribution, and DRM services hiring. This negotiation proccess ends when Terra has all the contents, access policies and distribution channels that needs to run the service, the ones Terra lacked when the service design started. After the combined services supplied are assembled, the content service would be registered in a service register inside the data store as shown in Fig. 2 making it available to be offered to final clients. In order to integrate both data and communication flow between these actors current DAM solutions use EAI technology. 2.3

State of the Art in EAI Technology

The primary goal of EAI technology can be described as the “unrestricted sharing of data and business processes among any connected applications and data sources in the enterprise” [18]. In this context the term “business process” refers


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to a sequence of activities to be carried out to reach a well defined goal, which can be either a material product or a piece of information [17]. Business processes – even inside an enterprise – are usualy not realized using a single monolithic application, but involve multiple independent applications from different vendors, based on different platforms which need to be glued together. Such applications are naturally heterogeneous, autonomous, distributed, and immutable; they have their own data and process models, are designed to run independently, operate on local data stores and have limited adaptability to an overall IT infrastructure because they don’t provide a formal description for their interfaces[4]. Their integration towards a feasible support for the execution of business processes within and among enterprises comprises three different aspects: communication infrastructure, common message formats and protocols, and agreed-upon data semantics. Each of these three dimensions are elaborated below. Communication Infrastructure. Reliable messaging over message-oriented middleware (MOM) is the state-of-the-art communication infrastructure technology for EAI [12]. There are two major forms of message-based application integration: the point-to-point and the broker/bus-based integration. Point-to-Point Integration describes the simplest possible form of integration. Each component directly communicates with each other component, requiring O(n2 ) message transformations for n participating applications. The messaging middleware directly passes the messages to the target application, without necessitating intermediary components as in the hub and spoke or bus-based styles (see below). Point-to-point integration architectures thus have severe drawbacks with respect to scalability and maintenance. Broker/Bus-based Integration was explicitly conceived to cope with these problems (see Figure 4). This integration style extends MOM with message routing and transformation functionality [12]. The key benefit is the introduction of a target application-independent, neutral message format (e.g., EDIFACT [3]) so as to reduce the number of required message transformations from O(n2 ) to O(n).

Fig. 4. Common Forms of Message-based Application Integration

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Common Message Format. Traditional EAI solutions stipulate a common data format to avoid syntax transformation between heterogeneous data formats and syntaxes. There is a whole range of possible data formats and standards to chose from for this purpose. The most widely used Electronic Data Interchange (EDI) systems are EDIFACT (a UN recommendation predominant in Europe) and its U.S. counterpart X.12. Both systems were originally based on ASCII data formats, but now have XML serializations as well. Numerous newer systems based on native XML have been created with RosettaNet and ebXML being two of the most popular. The challenge with XML-based formats is that merging of messages requires a priori schema knowledge and custom-built XSL transformations. Knowledge of the applied schemas is particularly problematic when operating in open environments such as the Web, which are characterized by heterogeneous data formats and vocabularies. We have chosen to use the EDIFACT system for messaging since it is the most commonly used EDI system in Europe and has a lot of experience with the message types which we need. Agreed-upon Data Semantics. While EDIFACT – as a neutral, applicationindependent schema for business data – provides a standardized container for exchanging information between communication partners, it does not describe the semantics of the information encapsulated in the messages in a machineunderstandable way. Due to the lack of this description, mediation between different representations of the message payload is necessary. For example, the IMD segment in the EDIFACT request for the REQOTE (request for quote) message3 allows the description of “products or services that cannot be fully identified by a product code or article number” partially or totally using plain text. Use case partners that do not know each other typically would not share a common understanding of plain text terms used in this segment. Ontologies, controlled vocabularies that formally describe a business domain in terms of domain-specific concepts and the relations between them, provide a widely-accepted instrument to cope with this problem [8]. References to commonly agreed ontological concepts can to be transmitted alongside the message payload, enriching the semantics of the original textual descriptions. If multiple ontologies for the same domain are available, their joint usage can be achieved via user-defined mediators, in form of formal ontology mapping languages or custom code [13,21]. With the help of ontologies and ontology mapping methods, an EAI system is capable of automatically transforming between different representations of the same meaning.

3

Realization of the Use Cases

This section introduces Triple Spaces, a coordination middleware for the Semantic Web. We motivate the major benefits of this novel technology against related 3

http://www.unece.org/trade/untdid/d06b/trmd/reqote c.htm


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solutions in the field of EAI and demonstrate its relevance to the realization of the use cases defined in Sect. 2.2. 3.1

Triple Spaces – A Semantic Coordination Infrastructure

The primary objective of Triple Spaces is providing a novel, highly scalable, semantically-enhanced type of communication middleware for the next generation Web applications, which integrates principles of three core technologies: coordination systems, the Semantic Web, and Web services [9]. In the following we briefly introduce these technologies and their role in the context of a Triple Space infrastructure (cf. Fig. 5).

Fig. 5. Triple Space

Coordination Systems. The coordination language Linda [11] has its origins in parallel computing and was developed as a means to inject the capability of concurrent programming into sequential programming languages. It consists of coordination operations (the coordination primitives) and a shared data space (the Tuple Space) which contains data (the tuples). The Tuple Space is a shared data space which acts as an associative memory for a group of agents. A tuple is an ordered list of typed fields. The coordination primitives are a small yet elegant set of operations that permit agents to emit a tuple into the Tuple Space (operation out ) or associatively retrieve tuples from the Tuple Space either removing those tuples from the space (operation in) or not (operation rd ). Retrieval is governed by matching rules. Tuples are matched against a template, which is a tuple which contains both literals and typed variables. The basic matching rule requires that the template and the tuple are of the same length, that the field types are the same and that the value of literal fields are identical. Given the tuple (“N70241”,EUR,22.14) - three fields containing a string, a pre-defined type (here, currency codes) and a float - it will match the template (“N70241”,?currency,?amount) and bind to the variables currency and amount

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the values EUR and 22.14 respectively. The retrieval operations are blocking, i.e. they return results only when a matching tuple is found. As identified by [5], core features of the Linda model of coordination have been mentioned as attractive for programming open distributed applications such as those encountered in the EAI field: – The model uncouples interacting processes both in space and in time. In other words, the producer of a tuple and the consumer of that tuple do not need to know one another’s location nor need they exist concurrently. – The model permits associative addressing, i.e., the data is accessed in terms of the kind of data that is requested, rather than which specific data is referenced. – The model supports asynchrony and concurrency as an intrinsic part of the tuplespace abstraction. – The model separates the coordination implementation from characteristics of the host implementation environment. Web Services. The aforementioned features are highly relevant for the field of Web services as well. As pointed out in [14], current Web services technology depends largely on synchronous communication links between information producers and consumers. As a matter of fact, instead of following the “persistently publish and read” paradigm of the Web, traditional Web services establish a tightly coupled communication cycle, most frequently using a synchronous HTTP transaction to transmit data. URIs, which are meant as unique and persistent identifiers for resources on the Web, are used only for the identification of the participants, whereas the information is not identifiable, but hidden in the exchanged messages. These flaws motivate the choice of a space-based communication paradigm. Semantic Web. The Semantic Web [19] extends the Web with machineprocessable semantic data. The representation of knowledge in a machine-readable manner through ontologies and open standards (RDF(S),OWL) on the Web is a powerful basis for the integration of heterogeneous data. While ontologies are envisioned as means for a shared knowledge understanding, it is unrealistic to expect that, in the decentralized distributed environment of the Web, different users will use the same vocabularies for annotating their data. The usage of various ontologies on the Web requires the definition of semantic matchings describing explicit relationships between terms in different ontologies. However this data integration is solved only at the data level. At the network level, metadata (semantic annotations of data), ontologies, and matches between ontologies are distributed across the network generally without explicit connections to one another. For integration to take place, current approaches assume that an author explicitly defines his own matching procedure or is able to discover existing data sources and the corresponding matches/mappings. Tuple spaces are an applicable model for the Semantic Web because they realize global places where information can be published and persistently stored just as in the Web architecture.


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Combining the Three Technologies. In order to apply the Linda-based coordination paradigm to the requirements of the Semantic Web and Semantic Web services we need to re-design the underlying data model and the associated coordination primitives. Tuples should contain data which is expressed using formal knowledge representation languages typical of the Semantic Web (RDF(S), OWL, WSML, etc.) and referenced using URIs and namespaces. The coordination model needs to be revised in order to provide methods for using the virtual shared space according to common Web interaction patterns. These topics are addressed in the context of the EU STReP project TripCom4 . The primary objective of the project is the realization of a highly-scalable, semantics-aware communication infrastructure according to principles of tuple space computing. The emerging system will be tailored to solve the challenging integration problems encountered in areas such as eHealth, Semantic Web Services or EAI. The architecture of this paradigm will be the subject of a publication in the near future. To summarize, employing Triple Spaces for integrating enterprise applications promises to provide the following benefits [14]: – Homogeneous coordination model: Triple Spaces provide a flexible coordination model which can be used to describe and realize robust, recoverable business processes, ad-hoc workflows, and collaborative work. – Schema autonomy: By adopting Semantic Web technologies to describe the meaning of data, a number of heterogeneity issues typically arising in EAI environments can be solved, e.g. data schema mediation, business process mediation, and goal-based Web service discovery. – Referential decoupling: Communication parties in EAI environments do not have to know each other explicitly. – Temporal decoupling: Information providers can publish data at any time, even if some or all interested consumers are disconnected from the system. – Spatial decoupling: Information always resides on a virtual space and neither information providers nor information consumers need to know its physical location. Once published, data becomes independent from the EAI system which originated it. 3.2

Benefits of the Space-Based Approach in the DAM Scenario

The technology used to realize the DAM scenario presented in Sect. 2.2 needs to satisfy a series of core requirements: – It needs to be able to cope with an arbitrarily high number of previously unknown and loosely connected parties originating from different administrative domains. – It needs to integrate heterogeneous message and data formats, requiring mediation between communication partners. The integration should be performed according to a broker/bus-based approach so as to reduce the number of message and data transformations (see Sect. 2.3). 4

http://www.tripcom.org

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– The technology should support the non-destructive consumption of data. This means that the application data should be persistently stored so that it is accessible to other communication partners as well. – It should support a reliable publish-subscribe style communication, with partners using message templates to describe the content of the messages they want to receive. – It should include feasible instruments for the management of the access rights of the communicating business parties to the published information. This holds for the authentication mechanisms for both information providers and consumers. – The integration infrastructure should ensure the security of the communication among the participants and with external applications. State-of-the-art EAI technology – mostly Web services on top of messageoriented middleware solutions as outlined in Sect. 2.3 – shows a number of shortcomings in providing a platform for integrating the parties involved in the use case scenario and fulfilling the aforementioned requirements. While current MOM products offer reliable communication based on the paradigm of publication and subscription, they lack scalability in terms of the number of interacting partners [2] and do not provide straightforward support for non-destructive consumption of messages or feasible means for content-based data access. Furthermore, mediation between communication parties is limited to syntactic message and data transformation methods like XSLT, which primarily rely on simple text comparisons, rather than comparing the underlying concepts. For instance a field named “price” may or may not include VAT in the schemas of the data to be integrated, but a potential mismatch would not be identified at the syntactic level. These drawbacks are explicitly addressed by a Triple Space-based integration platform. The data mediation functionality of the Triple Spaces allows different suppliers and service providers to have a common understanding of both the business terms of the transactions being negotiated, and the products and services mentioned in the transactions. This is achieved using semantic technologies, in particular formal ontologies and automatic mediation services. We differentiate between two ontology levels. The first ontology level includes an ontology for electronic business transactions, based on EDIFACT standards. The ontology defines the format of the messages exchanged between the actors involved in the DAM use cases in a machine-understandable manner. A second level is concerned with an ontology that models the business domain, in this case DAM-specific contents and services. Using the semantic mediation capabilities of the Triple Space, a common data schema for both suppliers and service providers can be automatically generated, thus allowing communicating parties to preserve their local autonomy with respect to the schemes used to store and manage the exchanged information. The usage of semantic technologies in this context further enables actors to perform reasoning and semantic validation tasks within the


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business transaction process, which leads to more accurate results in discovering content and services than pure syntactic matching mechanisms. A second core feature of Triple Space technology is its reliable transport mechanism for Web services [16], which is an essential requirement for the electronic business transactions in our scenario. This communication is dynamic, allowing ad-hoc relationships between business parties, which can join or exit a negotiation depending on the satisfaction of business rules, verified by the Triple Space using semantic mediation. This behavior is highly desired within a DAM area, in which the inherent dynamism of the business domain results in frequent availability and functionality changes of content and services. From a technical perspective, the implementation of the use cases using Triple Spaces follows the publish-subscribe paradigm. Message consumers express their interest in messages by describing their content, rather than listening on certain topics. This is an important difference between this and related state-of-theart approaches. In existing Enterprise Integration Architectures [12] based on MOM and/or Web services [22] messages are pushed to certain destinations – identified by e.g. queue or topic names. This means that an endpoint reference has to be explicitly specified as destination of a message and exchanged before the actual message exchange is carried on. By contrast message publication in Triple Spaces can be done without knowing the receiver of a message because data is simply published to a space not addressing a communication partner directly. This is necessary when dealing with DAM business processes becausee service providers may not know the suppliers of media content andd services in advance. In the space-based approach, message receivers pull messages from the space by describing their content. This interaction paradigm greatly simplifies ad-hoc communication between previously unconnected parties because communicating partners do not need to share any a priori information about each other. In the DAM context suppliers prefer to offer their content or services to potentially interested service providers. This requires a mechanism that enables multiple, non-destructive consumption of messages. In the Triple Space-based approach, this is achieved by persistently storing messages that represent a supplier’s content and service descriptions in the space, thus enabling all interested parties to non-destructively retrieve them (read operation) in a way similar to broadcast communication. In turn, service providers need to be able to retrieve information about already existing content offers in order to provide the services they are designing. Order, time, and publisher of this information are irrelevant. Current MOM solutions typically deliver messages in FIFO or priority order. In terms of the DAM scenario this would require each service provider to locally store all content offers and keep them up to date. By contrast, space-based technology offers persistent storage of these messages, classifying the information of each message according to the its content’s semantics, not depending on its publication time or sender. Using such storage policies, the middleware is able to implement random access and advanced query mechanisms to retrieve relevant information for each service provider.

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D. de Francisco et al. Table 1. Benefits of applying Triple Space Computing

REQUIREMENTS MOM TRIPLE SPACE Arbitrary number of communicating parties + Semantically-aware data and message mediation + Non-destructive consumption of data + Reliable publish-subscribe + + Associative (content-based) addressing + Access rights management product-specific + Security of communication product-specific +

To summarize, it can be said that existing data and communication integration technologies can not fulfill the requirements of the business domain and the associated use cases to a satisfactory extent. By comparison, Triple Space computing offers interesting advantages that are worth further investigation (cf. Table 1). The next section elaborates on a possible high-level architecture of a space-based approach to digital asset management. 3.3

High-Level Architecture

The integration model will be a bus-based architecture which will be implemented using Triple Space architecture which will be based on Web services standards. In order to benefit from Triple Space semantic mediation, these Web services from each actor will be semantically enriched by using two ontology levels, which stand for the two EAI levels performed by the Triple Space in this use case. As shown in Fig. 6, a domain ontology is needed to define the semantics of the business domain (DAM) to assist performing data integration and a negotiation ontology is needed to integrate messages exchanged by actors when negotiating transactions. This second ontology will be based on the EDIFACT standard. All semantically enriched supplier Web services will access the Triple Space for offering their products and services (only media content for our simplified prototype) by publishing their service descriptions (offers) into a service catalogue managed by the Triple Space. New offers from different content providers with their own content catalogue format can be integrated to provide a common perspective of available content to service providers. Semantic Web services using WSMO [7] from both service providers and suppliers of any type will be able to negotiate purchases of content and services by using Triple Space as a space-based message mediator. These negotiations, performed by EDIFACT message exchange, will be temporally stored inside the tuple space of the Triple Space. Once all negotiations are successfully ended and the service provider has all the components needed to exploit the service being designed, the Triple Space will store the service settings inside the service register. This register will allow other service providers to search for existing services


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Fig. 6. High level architecture

similar to those they are designing and subcontract them without having to own additional infrastructure; thus allowing reuse of digital content services.

4

Conclusion

Digital asset management is an emerging business for telecommunication companies, especially when applied to the entertainment market. This paper analyzes a typical use case in this field from a business and technological perspective. Triple Space computing is introduced as a novel middleware technology and an explanation is provided for how such an approach can cope with the integration needs of the communicating partners at data and application levels. TripCom activities in the EAI area aim at demonstrating the capacity of Triple Space computing to address the DAM scenario. Space-based middleware is a feasible alternative to traditional solutions to Enterprise Application Integration, since it allows agents to publish and retrieve information in an uncoupled manner in terms of space and time. By extending tuple spaces with Semantic Web technology, applications are able to store and exchange machine-understandable information in a decentralized and distributed manner, while taking advantage of powerful coordination mechanisms. This combination provides a new level of integration of the highly heterogeneous data and message formats exchanged in a DAM scenario.

Acknowledgements This work is supported by EU funding under the TripCom project (FP6 027324).

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