1. WS-Topics Peter Niblett OASIS TC Face/Face meeting
11/27/2018

2. Information space taxonomy
WS-Topics
Information space taxonomy
Mechanism to organize and categorize things which can subscribed to
Topics have metadata, and a naming scheme. They are grouped into TopicSpaces
Three TopicExpressions used to identify topic(s)
Simple
ConcreteTopicPath
FullTopicPath
XML document for describing topic metadata
11/27/2018

3. What are topics for?
Used by a subscriber to identify the subject area it wishes to cover in a subscription
A Producer/Broker delivers only delivers if notification if the list of topics associated with the subscription intersects with the list of topics associated with the message
Used to identify the set of subjects that a given Producer/Broker deals in
Useful information for a prospective publisher or subscriber
A producer may support only one topic
Can be associated with metadata, e.g.
Notification message schema
Semantic information
Could be used as part of an access control scheme
11/27/2018

4. Topic Naming
In order to avoid name collisions between different users, each Topic is assigned to an XML Namespace. The set of Topics in a given Namespace is called a TopicSpace.
A producer can use its own unique TopicSpace (essentially its topic names are scoped to it), or it can share a TopicSpace with other producers
E.g. a TopicSpace containing topics specific to a particular application domain
A TopicSpace could be defined by a third party, such as a standards organisation.
Topics can be named using simple QNames, or can have structured (hierarchical) names.
TopicSpace:TopicName
TopicSpace:Namepart1/Namepart2
11/27/2018

5. Topic Hierarchies
tns:T1
tns:T4 T2 T3 T5 T6
Topic Space: “
Topics can be organised into hierarchies – each topic can have 0+ child topics
Child topic names must be unique within each parent, to allow path-like names
Reasons for a hierarchy
Manageability (e.g. access control)
Simplifies multiple-topic selection (wildcarding)
Note: A child topic is a distinct topic from its parent
subscribing to a parent does not imply subscribing to its children
11/27/2018

6. Topic Sets and Topic Spaces
Producer
or Broker
Topics property
Topic Set {
ts1:T1,
ts1:T1/T2,
ts2:T4/T6 }
TopicSpace 2 T4 T5 T6
11/27/2018

7. ConcreteTopicPathExpression
Topic Expressions
Simple
QName
e.g. tns:MyTopic
Root topics only
ConcreteTopicPathExpression
Path expression with a Namespace
e.g. tns:/t1/t2/t3
FullTopicPathExpression
Path Expression with XPATH wildcarding, e.g.
tns:t1/* all children of t1
tns:t1//* all descendents of t1
tns:t1//. t1 + all its descendents
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8. Alias Topics
tns:T1 T2 T3
tns:T4 T5 T6
is alias for
Topic Space: “
The Topic Space document includes the capability to define Topic aliases
This formalises the equivalence of two different topic expressions
- in this example subscribing to T4/T6 is equivalent to subscribing to T1/T3
A NotificationBroker is free to perform its own topic transforms, even if the
Source and target of the transforms are not formal aliases.
11/27/2018

9. TopicSpace document
The TopicSpace document is a mechanism for describing topic metadata
Topic names, hierarchy and aliases
Message Schemas associated with the Topics
Open/Closed content model
A producer/broker is required to conform to the definitions in the TopicSpace documents that define its Topics
WS-Notification does not specify the way that a producer/broker obtains this information
It is not a ResourceProperty of a producer or broker
TopicSpace1 T1 T2 T3
11/27/2018

10. Topic Space document <?xml version="1.0" encoding="UTF-8"?>
<wstop:topicSpace name="TopicSpaceExample1"
targetNamespace="
xmlns:tns="
xmlns:xyz="
xmlns:wstop=" >
<wstop:topic name="t1">
<wstop:topic name="t2" messageTypes="xyz:m1 tns:m2"/>
<wstop:topic name="t3" messageTypes="xyz:m3"/>
</wstop:topic>
<wstop:topic name="t4">
<wstop:topic name="t5" messageTypes="tns:m3"/>
<wstop:topic name="t6">
<wstop:AliasRef dialect=“…/concreteTopicPath" >
tns:t1/t3
</wstop:AliasRef>
</wstop:topicSpace>
11/27/2018

11. A Topic’s metadata can describe its content as open
Open content
A Topic’s metadata can describe its content as open
This means that users may, if they wish, dynamically define additional child topics of that topic
For example a broker may accept publications on new child topics (but is not required to)
There is no formal metadata for such topics
Ad-hoc topic space
This is a special TopicSpace whose content is entirely open
11/27/2018

12. Topics Summary Method of categorising Notifications
Each Topic is associated with one or more MessageSchemas
Grouped into namespaces which have URIs
Topics may be defined by an individual publisher, or by a 3rd party (e.g. a standards organisation)
Allow a potential subscriber to understand the notification capabilities of a Publisher/Broker that is has just discovered.
Facilitate interoperation with Topic-based IT pub/sub systems (e.g. JMS)
Convenient attachment point for access control
Subscriber provides a TopicPathExpression to indicate Topic(s) of interest
Matching on a Topic name is usually more efficient than matching against general message content.
Simple Topic Path Expression is just a single Topic Name
A simple NotificationSource may support only one Topic
More complex NotificationSources may permit wildcard expressions
11/27/2018