=Paper=
{{Paper
|id=Vol-149/paper-9
|storemode=property
|title=A Service Control Method Using Semantic Constraint on Context Interpretation
|pdfUrl=https://ceur-ws.org/Vol-149/paper09.pdf
|volume=Vol-149
|dblpUrl=https://dblp.org/rec/conf/ubipcmm/MaedaTK05
}}
==A Service Control Method Using Semantic Constraint on Context Interpretation==
https://ceur-ws.org/Vol-149/paper09.pdf
Jun Maeda, Masaaki Takase, and Mitsuaki Kakemizu 58
A Service Control Method Using Semantic
Constraint on Context Interpretation
Jun Maeda, Masaaki Takase, and Mitsuaki Kakemizu
interpretation" in this paper. The context interpretation is
Abstract— When constructing a personalized context-aware performed by deriving related information about the service
service system, much work is required to develop the service control necessary to achieve the objective from the context. So
control programs that provide services in various personalized far, context interpretation processing is usually realized by the
contexts. Then, a common control system that interprets the
context and dynamically generates various service execution
following method 1.
methods is necessary. A platform that generates service execution
methods by combining context interpretation information is Method 1 (individual application processing)
proposed. The semantic constraint is introduced as a part of the
service definition. It generates appropriate service execution In this method, each application program performs context
methods by specifying how to use the context and it also improves interpretation. The typical processing sequence is as follows:
processing performance. (1) the application registers trigger information in the platform;
(2) the platform calls the application when the context matches
Index Terms— context-aware, context interpretation, service the trigger information; (3) the application generates the service
control, service definition
execution method by interpreting the context; and (4) service
control action is performed according to the service execution
I. INTRODUCTION method. Existing platforms such as the CASC (Context-aware
service control) system [3]-[4] are designed with such a
I n the age of ubiquitous and personal services, context-aware
services [1]-[2] that provide suitable services for individual
processing style, however this method requires a variety of
context interpretation programs in the application program
user's situations (context) are expected. Context-aware service because of various personalized contexts. As a result, the
control platforms [3]-[6] have been developed as basic facilities problem of the expanding application program development
for such as acquisition, sharing and use of the context. To emerges. Fig. 1 shows an example of the application program
provide a context-aware service, a service execution method interpreting context using method 1. While it is the case that the
that achieves the user's objective under the precondition of context interpretation is performed in the platform, if
context is necessary. The service execution methods are information on the service execution method for an individual
described in the application programs on the platform, however service is provided by the application, this is classified as
because the service execution methods differ according to the method 1.
context even if the user's objective of the service is the same, it
if Context1 derives information A by relation R4
is necessary to consider various contexts in the application {
programs, and much work is required for the program if Information A derives service objective D by relation R2
development. It therefore becomes necessary for the service A service execution method is found.
execution methods to be generated dynamically. This research if Information A derives service objective E by relation R3
A service execution method is found.
aims to develop a function to reactively generate personalized }
service execution methods based on the context as a higher if Context1 derives information B by relation R1
layer function of the context-aware service control platforms. {
if Information B derives service objective D by relation R2
A service execution method is found.
II. PROBLEM if Information B derives service objective E by relation R3
A service execution method is found.
The function to generate the service execution method from }
the context and the user's objective is termed "context if Context1 derives information C by relation R11
if Information C derives service objective D by relation R2
A service execution method is found.
if Context1 derives information L by relation R11
Jun Maeda is with Fujitsu Limited, Kawasaki, 211-8588 Japan (e-mail:
if Information L derives service objective M by relation R5
maeda.jun@jp.fujitsu.com).
A service execution method is found.
Masaaki Takase is with Fujitsu Limited, Kawasaki, 211-8588 Japan (e-mail:
masaaki.takase@jp.fujitsu.com).
Mitsuaki Kakemizu is with Fujitsu Limited, Kawasaki, 211-8588 Japan Fig. 1. Context interpretation program by Method 1
(e-mail: kake@jp.fujitsu.com).
ubiPCMM 2005 59
It is essential that the platform generates service execution objective. In Fig. 2, for instance, context interpretation
method for personalized context-aware services. We then information "There is an air-conditioner A in room R2" can be
adopted the following method 2. combined with context interpretation information "The room
next to room R1 is room R2" through "room R2" as essential
Method 2 (common processing) information. However, if the semantic constraint for the
This method performs context interpretation by common objective "file opening" specifies "derive information about IT
processing. The processing sequence is as follows: (1) the equipment," "air-conditioner A" does not satisfy the semantic
application registers trigger information in the platform; (2) the constraint and this context interpretation information is not
platform generates the service execution method by selected. This method generates semantically appropriate
interpreting the context; and (3) the platform calls applications service execution methods, and reduces context interpretation
that control service action according to the service execution processing by eliminating the search process for meaningless
method. service execution methods.
A platform that constructs a user profile to be used by Fig. 3 shows the entire mechanism. The following describes
applications was proposed [5]. In this system, the control of the explanations of each part, details of context interpretation
individual services is performed by the application program processing and discussions about the proposed method.
(method 1), but the platform performs a part of context
interpretation that does not depend on individual services. If Precondition context Semantic constraint Service Objective
this idea is expanded for the entire context interpretation, the Service Category 1
Precondition
Category of Category Obj
definition → Relation → derived →…
service execution method can be constructed from the context. context
information
This is performed by looking for the "story" that reaches the matching matching matching matching matching
service objective by combining context interpretation Input
→ Relation → Output
Category 1 Category X
information (various information derived from the context) Context
interpretattion Context interpretation information
entity
with the context. Fig. 2 shows a sample of context
interpretation.
A mechanism that enables flexible and efficient context Context
interpretation is required. It is also necessary to make service Category 1: Value 1 Category X: Value X … … Category Obj:
Value Obj
development simple. Category 2: Value 2
Description of
relation between …
…
Context Context interpretation information Service Value1 and ValueX
Objective
Personal computer P Service execution method
The user is in room Room R2 is next to Personal computer P Software S
has software S to
R1. room R1. is in room R2.
show file F.
opens file F. Fig. 3. Service control mechanism using semantic constraint
The user requests to
show the content of
file F. A. Context
Service execution method
The context is information that shows various situations of
Fig. 2. A sample of context interpretation the real world. The context includes information supplied by
sensors or information providers, etc. Information that a user
III. PROPOSED CONTEXT-AWARE SERVICE CONTROL METHOD enters from a personal terminal (parameters for specific service,
and personal information such as location of user, age, hobbies,
We designed a context interpretation mechanism as follows. etc.) is also included in the context. The context is represented
1) It is necessary that the mechanism be able to generate diverse by category (type of information) and value. The following are
service execution methods to provide services by flexible examples of context: "User's location: conference room,"
means. Essential information that is in the context or the "Time: ten o'clock," "Document name specified by user:
context interpretation information is then used to combine the document_1" and "User's address: Tokyo".
context interpretation information. For instance, essential
B. Context interpretation information
information items in Fig. 2 are user's location R1, room R2,
personal computer P and so on. This method deals with every This information gives the interpretation of the context and is
item of context interpretation information that has a possibility provided from the context interpretation entities. When the
of being combined, then it can generate varied service context interpretation entity receives an input value that
execution methods. belongs to a specific category, it then outputs a value that
belongs to a specific category and context interpretation
2) It is not that the related context interpretation information is information according to semantic relations between the input
simply combined with the context, but the context and output defined for each entity. For instance, a context
interpretation information suitable for the service objective interpretation entity receives the input value "User's location:
should be combined. The semantic constraint then selects the R1," then outputs the value "Room: R2," and context
context interpretation information suitable for the service interpretation information "Room R2 exists on the same floor
Jun Maeda, Masaaki Takase, and Mitsuaki Kakemizu 60
as R1" according to a semantic relation "Existing on the same context interpretation information is combined by repeating
floor." this process (next context interpretation entity receives a value
that matches the output value of the previous entity). If output
C. Service definition of a context interpretation entity matches the category
The service definition consists of the precondition context, described as a service objective, a set of combined context
the service objective, and the semantic constraint. This interpretation information becomes a service execution method.
describes "What action is performed (service objective) by This describes, for instance, "Run software S on personal
using which information (precondition context) and how such computer P which is in the room next to user's location to
information is used (semantic constraint)." Service objective achieve the service objective that file F is shown". Generated
describes the category that shows the service action such as service execution method is reliable in terms of semantic
"Document edit" and "Air-conditioning control." Precondition appropriateness for the service objective by satisfying semantic
context describes the category of the information used in the constraint.
service such as "User's location" and "User specified Context interpretation also can be personalized according to
document." Semantic constraint is provided for each the situations like user's location or behavior. The following is
precondition context. This defines the scope of the semantic one method.
relation between the precondition context and the context 1) Context interpretation entities are classified into groups,
interpretation information that it is combined with, and the such as general, specific field, district, office and home.
scope of category which that derived value belongs to in the 2) Groups suitable for the user's situation are selected and used
context interpretation processing. Similarly, it defines the for context interpretation.
constraint of context interpretation information combined with
This provides services by context interpretation suitable for a
derived information. Semantic constraint of the precondition
user's situation and efficient processing by eliminating
context not used to derive any information is indicated as
unnecessary context interpretation information. For instance,
"Direct use".
users at different locations can use services peculiar to each
Examples of semantic constraint are shown below. place by selecting the context interpretation entity group for
each district, and the processing becomes efficient by not using
1) Precondition context: User's location -> Relation: Existing in context interpretation information for other districts.
same place -> Derived information: Equipment.
2) Precondition context: User's location -> Relation: Existing in E. Effect of proposed method: efficient context
same place -> Derived information: Personal computer. interpretation
3) Precondition context: User's location -> Relation: Existing The amount of processing becomes enormous to find every
on the same floor -> Derived information: Place -> Relation: possible service execution method when the context amount
Existing in same place -> Derived information: Equipment. and the interpretation information increase. Fig. 4 shows the
4) Precondition context: User's location -> Relation: Attribute context interpretation processing by the platform
-> Derived information: Temperature. corresponding to the application program in Fig. 1. As shown
5) Precondition context: User specified document name -> in Fig. 4, the context interpretation result includes a lot of
Relation: Direct use. meaningless service execution methods, because there are
many context interpretations which are not relevant for the
A hierarchical structure is used for representing relations in service objective.
different abstraction levels, from general relations to specific This unnecessary context interpretation processing is
relations. Similarly, the categories of derived information use a reduced by semantic constraint. That is, because context
hierarchical structure. interpretation entities that are not consistent with semantic
constraint are not invoked, meaningless combinations of
D. Context interpretation processing context interpretation information provided by those entities
In context interpretation processing, the present context is are omitted. In Fig. 4, "X" shows the points where context
first compared with the precondition context that is described in interpretation information is not combined.
the service definitions registered for each user, and if the
F. Effect of proposed method: simple service development
precondition context of a service definition matches the present
context, the definition is activated. The context interpretation The service definition method using semantic constraint
information is then combined based on the activated service enables the development of services more simply and easily
definition using graph search processing. than method 1 because it is not necessary to describe a detailed
Combining context interpretation information is performed context interpretation procedure. Semantic constraint uses
as follows. First the context interpretation entity that receives a hierarchical representations of relations and categories of
value belonging to a category that matches the precondition derived information as shown in Fig. 4. This enables service
context and is consistent with semantic constraint is invoked. definitions to be described with the necessary abstraction level
Context interpretation information provided from the context from the user's viewpoint. Context interpretation generates
interpretation entity is combined with the context. More various service execution methods suitable for the context
ubiPCMM 2005 61
using the graph search algorithm within the scope of a specified something used for the service) and their personal requests are
abstraction level, thus the amount of description necessary to derived from each entity that provides those items of
define the service is significantly reduced compared with the information. Conflict resolution entities then decide the
description for the application program in method 1. The appropriate action (resource control) by considering other
service definition described in Fig. 4 is equivalent to the people’s requests. The conflict can be resolved by combining
application program in Fig. 1. those entities with the service execution method in context
On the other hand, if detailed relations and categories are interpretation processing. Since the processes of conflict
specified in the semantic constraint, it is also possible that the resolution depend on every detail of conflict, it is required to
service definition describes a precise procedure similar to provide corresponding conflict resolution entities.
method 1.
Context Service Objective
The service definition composed from service objective, Request-user: Conflict resolution
entity
precondition context and semantic constraint seems to be close Req-u
Location: Appliance: Control- Appliance-
to the ideas considered when the designers develop new L1 A1 information:
C1
control:
Appliance control
services. Request-x: entity
Req1
Person-x:
Information A is related Service Objective D is related (relation R2) to information A.
Context1 (relation R4) to Context1.
Pa
Service Objective E is related (relation R3) to information A. Person-y: Request-y:
Pb Req2
Information K is related (relation R9) to information A. Fig. 5. Conflict resolution
Information J is related (relation R10) to information A.
Information B is related Service Objective D is related (relation R2) to information B.
IV. CONCLUSION
(relation R1) to Context1.
Service Objective E is related (relation R3) to information B. A context-aware service provides customized services for
Information J is related (relation R10) to information B.
each user according to the dynamically changing personalized
Information C is related
(relation R11) to Context1. Service Objective D is related (relation R2) to information C.
context. This paper proposes a basic mechanism for a
context-aware service control platform. The fundamental idea
Information D is related (relation R9) to information C.
Information L is related
(relation R11) to Context1.
is to generate an appropriate service execution method using
Service Objective M is related (relation R5) to information L.
the service definition represented by the service objective,
Information G is related
(relation R7) to Context1. precondition context and semantic constraint, together with the
Information F is related context interpretation processing that derives the required
(relation R7) to Context1.
action from the precondition context based on semantic
Service definition constraint. This method can efficiently generate a service
Precondition context Semantic constraint Service Objective
Context 1
Context 1→Relation R11 → Category L → Relation R5→ Category M
Category M execution method suitable for the context. We hope to apply
this method to the actual environment and to verify it.
Relation hierarchy Category hierarchy This research is the result of contract research on
"Ubiquitous network control and management technologies"
for the Ministry of Internal Affairs and Communications.
L M N O P
R11 R12 R13 R14 R15 A B C D E F GH I J K
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R4 R5 R6 R7 R8 R9 R10
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