The TINA Service Composition Architecture
A Position Paper
The issue of software composition has received some exposure in the literature
and in the market place of late, but the issue of service composition has
received little attention. The TINA Consortium of telecommunications-related
companies has examined the area in the context of developing an architecture
for the delivery of new telecommunications services. The results
of this research are encouraging and point to opportunites for the rapid
deployment of new and innovative services.
There has been some encouraging, if slow, progress in the area of software
composition--the construction of software applications from domain-related
components [Nier95], [Sun96] but hitherto there has been little attention
paid in the literature to service composition. By service composition,
we mean the creation of a new services by the combination of existing service
components or service sessions. For example, it might be desirable
to temporarily merge two separate teleconference sessions or it might be
desirable to combine the appropriate audio and video components of a movie
before delivering the combination to a customer. The TINA Consortium
has developed a composition architecture as part of its Service Architecture
[TINA96] which we present here.
TINA is a consortium of over 40 companies including public network operators,
telecommunications equipment suppliers, and telecommunications research
organisations whose mission is "...to define and validate a consistent
and open architecture for distributed telecommunications software applications".
The TINA architecture is composed of four main parts:
The key concepts in the service architecture are those of a session (a
temporal relationship between components), a business model consisting
of consumers, retailers, brokers, third-party providers, and network providers;
and service components including service supports objects, session endpoints,
and user applications.
a distributed service architecture that specifies a business model, a session
model, service components, and service composition;
a network resource architecture that specifies the underlying connectivity
a computing architecture that specifies the distributed processing environment
(DPE) required to support service delivery, and
a management architecture to provide overall network and systems administration
3. TINA Service Composition
The TINA Service Architecture recognises two forms of service composition:
dynamic composition that can be accomplished at runtime and entailing the
ad hoc merging of services and static composition essentially that of service
creation. In both cases a number of supporting services will be required
including identification services (naming and name resolution), visibility
services (browsing and type-resolution), and management services (accounting,
security, and fault-management).
3.1. Composition Models
The TINA Service Architecture recognises three primary models for service
Parallel Model: all the individual service interfaces of the constituent
services are available to the user;
Serial Model: only the service interfaces of the primary service
are directly available to the user--access to the service interfaces of
the secondary service(s) is mediated by the primary service;
Component Model: a service is composed of service components (special
resources, content, or service logic) rather than service sessions.
3.2. Support Services
In order to make composition possible, a number of support services need
to be made available. Most of these services would normally be made
available through the DPE, but additional services (especially in the case
of static composition) may be required.
Identification of services, service components, and composite services
will require a dynamically extensible naming model that supports intra-
and inter-domain naming of types and instances. Name-resolution services
will also be required to locate services and service components.
Any extensible form of composition, whether dynamic or static, will require
some form of discovery service. Trading services typically provided by
a DPE for machine processing may be sufficient but, likely, browsing services
providing informal information for human consumption will also be required.
3.3. Management Services
An important part of the overall TINA strategy is concerned with management
and administration of TINA services. TINA management requirements
are normally couched in terms of FCAPS (Fault, Configuration, Accounting,
Performance, and Security) and service composition calls on three of these:
Accounting: billing models, subscription models, and
Security: authorisation, delegation of authority, privacy, and
security violations; and
Fault: QoS agreements, best-effort or all-or- nothing, recovery, fault
reporting, and critical service nomination.
The TINA Service Architecture assumes that the implementation of dynamic
service composition will largely rely on the services of the DPE defined
in the Computing Architecture although it is noted that scripting languages
could address behavioural composition. Static service composition
will mainly be supported by the compositional notation of the TINA Object
Definition Language--a super-set of the OMG IDL [OMG95].
The TINA service composition architecture is valuable in fostering an understanding
of the requirements, impacts, and opportunities of service composition;
it will go a long way in helping to reach the goal of rapid deployment
of new telecommunication services. However, it offers only rudimentary
support for the formal specification of service composition either from
a structural or behavioural standpoint. Formalisms for object and
functional composition can be found in the literature [Spiv89], [ISO92]
but these are generally pitched at a fine level of granularity and generally
in the context of programming rather than service delivery. However,
we are encouraged by the popularity of component toolkits such as JavaBeans
and scripting languages such as Perl and believe that such developments
can help in the rapid deployment of new telecommunication services.
[TINA96] Telecommunications Information Networking Architecture
Consortium (TINA-C). Service Architecture, Version 5.0, 1996. (Available
[Nier95] Nierstrasz, O and Meijler, T. D., Research Directions
in Software Composition. ACM Comput. Surv. (27)2, June 1995.
[Sun96] Hamilton, G. (Ed) JavaBeans. Sun Microsystems, 1996.
[OMG95] Object Management Group. The Common Object Request
Broker: Architecture and Specification. 1995
[Spiv89] J.M. Spivey, The Z Notation: A Reference Manual. Prentice-Hall
[ISO92] International Organization for Standardization and International
Electrotechnical Commission. Information Technology | Open Systems Interconnection
| Management Information Services | Structure of Management Information
| Part 4: Guidelines for the Definition of Managed Objects. International
Standard ISO/IEC 10165-4 : 1992.