Zicomi Systems Logo
contact us  |  your privacy
Company
Services
Products
Support
Resources
  OMG Standards
OMG Logo
  Have You Heard?
UML Diagrams
Zicomi Systems publishes some UML example diagrams online from the world famous UML dictionary.
more...
Version 2.5 Released
Zicomi Systems is delighted to announce that version 2.5 of Zicomi Mentor is released. With support for UML 2.0 and all thirteen UML diagrams
more...
Zicomi Systems' Director
speaks about the UML at Objects by Design - an informative interview
more...
Partner Programme
Zicom Systems is delighted to announce a new world wide partner programme, become a partner today.
more...
OMG Member
Zicom Systems is made a member of the OMG!
Join Node
Join Node  
A join node is a type of control node that synchronizes a number of incoming flows into a single outgoing flow. Each (and every) incoming control flow must present a control token to the join node before the node can offer a single token to the outgoing flow. If some of the incoming flows are object flows, which carry object (data) tokens, these tokens are all offered to the outgoing flow. A join specification (for complete activities) may be used, which further governs the way that the join will evaluate the arrival of tokens.

This is alternative content.

Explanation

When flows have been divided into a number of concurrent flows by upstream fork nodes they typically need to be re-united (joined) to allow other nodes to receive their necessary inputs; this is achieved by the use of one or more join nodes. A join node has two or more incoming flows, which are synchronized into a single outgoing flow. In normal usage of the join (in intermediate activities) control tokens are required to be present on all incoming flows for the join to offer a single token to the outgoing flow. This is equivalent to a logical 'and' in Boolean logic. If any of the incoming flows have data (object) tokens then the data (or objects) in the tokens are all offered to the outgoing flow. In advanced usage of the join node (in complete activities) a join specification can be used which describes the conditions under which the join will occur. This specification if present overrides the default 'and' condition.

Important Points

All flows regardless of whether they are incoming or outgoing must be either all control flows or all object flows. A join node is a type of control node and therefore can only manage a single type of flow. So all incoming and outgoing flows must all be of a single type: either control flows carrying control tokens, or object flows carrying data or object tokens, but not a mixture of both types of flows.

Related Entries

Fork Node
Fork Node  Paired Element,  Graphically Similar
A fork node is related to a join node as a paired element. A fork node splits flows in an upstream part of an activity, which are subsequently reunited by a join at a point downstream in the activity.
Merge Node
Merge Node  Confused with
A merge node is related to a join node as they both have one or more incoming flows and a single outgoing flow. They have different semantics as a merge is used to unite a number of possible incoming flows only one of which presents a token to the merge, the join reunites concurrent flows where each incoming flow presents a token to the join.
Join (Vertical)
Join (Vertical)  Graphically Similar,  Confused with
A join pseudostate is related to a join node as they have the same appearance. They have different semantics and are used in different diagrams. A join pseudostate reunites transitions in a state diagram whereas a join node reunites flows in an activity or interaction overview diagram. They are both used to model concurrency.

back to the index...
Unified Modeling Language and UML are either registered

trademarks or trademarks of Object Management Group, Inc. in the

United States and/or other countries.