IDEF0

Introduction to IDEF0 Modeling

Dr. James P. Davis Knowledge Based Silicon Corporation EDA&T Conference - August 1995

Overview of IDEF0 Methodology

Activities: -- Interview business experts -- Author the IDEF0 model -- Distribute model for review -- Validate model against business -- Approve the model

Roles: -- Domain experts -- Business analyst (model "author") -- Librarian -- Model "readers" (peer/team reviewers) -- Technical Review Committee (QA)

© Copyright 1995 Knowledge Based Silicon Corporation

08/27/98

Enterprise Modeling Using IDEF0 -- Create description of enterprise for the purpose of gaining understanding, and of being able to answer questions about the enterprise. -- Used to describe enterprise and its environment prior to, or in conjunction with, defining requirements. -- Used to precisely define boundaries of system (i.e., what is in and out of scope for the project under consideration). -- Model the enterprise from a particular "viewpoint", or perspective, so as to keep the activity focused on the goal of effort and on pertinent characteristics of interest in enterprise. -- Create a description of the enterprise with a single subject, single purpose (exemplified by questions to be answered about the enterprise), and single viewpoint. -- Note that, during Project “scoping” activity, the viewpoint is most likely that of looking at the enterprise from the standpoint of the client-server application to be deployed in the enterprise.

© Copyright 1995 Knowledge Based Silicon Corporation

08/27/98

Overview of IDEF0 Notation 1. The IDEF0 notation consists of BOXes, representing Activities in the system or enterprise, and ARROWs, describing relationships between activities. 2. Characteristics of Activity Boxes: -- represent key activities of the enterprise, from the selected viewpoint -- are named using "active" verbs or verb phrases -- are decomposed into groups of lower-level activities -- grouped by no more than 6 activities to a single level in model -- numbered in sequence in a given level, according to "dominance": - influence one activity has over others in level - dominance based on (1) first in sequence, or (2) most influential 3. Characteristics of Arrows: -- represent collections of things ("artifacts") -- named using nouns or noun phrases -- connect activities together, and connect them to interfaces -- arrows clasified into following categories: - inputs (I), outputs (O), controls (C), mechanisms (M)

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08/27/98

Overview of IDEF0 Notation Inputs: transformed by Activity into outputs

Controls: dictate & constrain under what conditions transformations occur

C1: New/modified product C2: New/modified machine I1: New/updated product data I2: New/updated machine data

Update Master Tables

O1: Products O2: Machines

M1: Crew Member

Mechanisms: describe how the activity is to be carried out (resource, process, etc.)

© Copyright 1995 Knowledge Based Silicon Corporation

Outputs: created as a result of activity transformations.

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Characteristics of IDEF0 Activities New/modified product?

New/updated product data New/updated machine data

New/modified machine? Shift start? Shift end? Master Table Mgmt Workflow

Products Machines

Crew Supervisor

Modified machine settings

Roll data

Production Shift/Crew Workflow

Department data Start of day Un-entered shift data available

Shift Crew, Tolerances

Performance Adjustment Workflow

VAX data Upload Workflow

Crew Supervisor

Uploaded VAX data

Decomposition: Taking an activity and diving into it in order to define its internal structure and organization into related subactivities. The "parent" is decomposed into "children" activities and interactions.

Clerical Staff

Supervisor security Product data collected

Selection by date range

Run Prod Historical Reports

Crew Supervisor

proper work authorization Modify Machine Processes

Product performance report

Modified machine settings

Crew Member

© Copyright 1995 Knowledge Based Silicon Corporation

Sequencing: Grouping activities at a given level, using arrows to tie them together, forming the activity sequences giving detail of the parent activity. Activities precede and follow one another.

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Characteristics of IDEF0 Arrows - Fan-out & Split A2 A1

If no labels on branches, it's assumed to be whole collection.

artifact1

A3

Arrow label before the branch to name the output collection.

Arrow flows: collection of entities or artifacts, serving as inputs, outputs, controls and mechanisms for activities. Fan-out: an output collection is routed to multiple inputs of other activities.

artifact2

A2 A1

artifact1

If different label on some of branches, then output collection is being split.

Arrow label before the branch to name the output collection.

A3 Any unlabeled routes are assumed to be same collection as that prior to split. artifact2

A2 A1

artifact1

Arrow label before the branch to name the output collection.

If different label on all branches, then output collection is a disjoint or overlapping split. artifact3

A3

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Split: an output collection is divided up in some manner, directing some of output collection of artifacts to a different destination. The labeled artifacts are a subset of total entering the branch. Disjoint or overlapping split collections: When all branches are labeled, it implies split into disjoint or overlapping subsets from the original collection.

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Characteristics of IDEF0 Arrows - Fan-in & Join A2 If no labels on branches, it's assumed to be whole collection fanning-in from multiple activities. (This is unusual).

artifact1

A1

Arrow label after the join to name the collection (input, control, mechanism).

A3

Fan-in: collections of things are flowing into a single collection, to be used as input, control or mechanism. The collection is the same on both sides of the joining arrow junction.

artifact2

A2 If labels on some branches, it's assumed to be a subset of whole collection fanning-in. (This is also unusual).

artifact1

A1

Arrow label after the join to name the collection (input, control, mechanism).

A3

artifact2

A2 If labels on all branches, it's assumed to be a join of multiple collections into a single collection. (This is most common.)

A3

artifact1 artifact3

A1

Join: an output collection is aggregated up in some manner, directing a combined collection of artifacts from multiple sources to a single destination. The labeled arrows are a subset of total resulting from the join.

Arrow label after the join to name the collection (input, control, mechanism).

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08/27/98

Characteristics of IDEF0 Arrows - Interconnect There are different relationships between activities implied by interconnect patterns.

A1 A2

Output to input: output of one activity becomes input to box of lesser dominance. Output to control: output of one box directly constrains a box of lesser dominance. Implies tight coupling of activities.

A1 A2

I2

I1

O1

A2 M1

A1

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Output to mechanism: output of one activity becomes means by which another activity gets done. Implies a strong sequencing relationship.

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Characteristics of IDEF0 Arrows - Feedback Loops In addition to feed-forward relationships (outputs affect activities of lesser dominance), there are feedbacks into the model affecting activities of greater dominance.

A1 A2

Feedback to input: output of one activity is input to box of greater dominance. Implies iteration, error correction, rework. A1

Feedback to control: output of one box directly constrains a box of greater dominance.

A2

A2 I1

A1 M1

© Copyright 1995 Knowledge Based Silicon Corporation

O1

Feedback to mechanism: output of one activity becomes means by which more dominant activity gets done. Only occurs in tandem with iteration of feedback to input.

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Characteristics of IDEF0 Diagrams 1. Context Diagram: defined the top-level of enterprise being modeled using IDEF0. It delineates the boundaries of the portion of the enterprise under consideration, and is defined for the viewpoint. 2. C-numbers: chronological numbering scheme for diagrams, and includes author's initials + diagram version number (e.g., JD001). This is method for version control of individual IDEF0 diagrams. 3. Node numbers: means for identifying and tracking individual activities in the model. Provides a means for associating activity boxes in a parent diagram with the diagram and activity components of children (e.g., EPR/A12, indicates EPR project, activity 1, sub-activity 2 of the decomposed top-level diagram). 4. ICOM codes: Input, Control, Output, Mechanism number scheme, so as to track these relationships through the levels of hierarchy, as they cross the boundary from current level off the page. 5. Tunneling: In order to reduce the amount of detail that either gets pushed down or carried up in the decomposition hierarchy, you can have arrows in the diagram that aren't associated with arrows in next level above or below. © Copyright 1995 Knowledge Based Silicon Corporation

08/27/98