Assembly
It is the product which is manufactured in the Plant.  It need not be the Finished goods which are shipped to ultimate customer.  The intermediate product which are manufactured in the plant can also be an assembly (it could rather be called as Sub-Assembly).

Component
These are basically materials which are used for manufacturing the assembly.  These components could be raw materials, consumables, by-products etc.

Valid Parent/Component Relationships
The following table lists valid components for each parent item type.

Valid Component Attributes and Bill Types
Each bill of material can have many components. For each component, you specify attributes, such as operation sequence, item sequence, usage quantity, yield, supply type, supply subinventory and locator, and others. Most of the attributes are applicable for all the components except below

1. Standrad items dont use Planning Percent, Mutually Exclusive Options, Optional Flag
2. Optional Flag and Mutually Exclusive Options are only available for Model and Option class.
Example: The front wheel of tractor is of differnt size compared to the rear wheel. So while making the BOM of tracor we 'll create a Option class as Wheel and the BOM of wheel 'll contain two types of wheel which 'll be optional and can be mutually exclusive.

While making the BOM of an option class/Model we can use the optional checkbox in OM tab (for any kind of component) and if those components are again Option class/Model then we can make them mutually exclusive.

3. For Planning components Item, Item Sequence, Effective Date Range & Planning Percent are required. rest are not mandatory

Phantom
Its an WIP Supply type.  The WIP Supply type is attached to items in item master in WIP tab but while creating BOM for an assembly the WIP supply type for the components and subassembly can be changed and need not required to be same as specified in Item master.

A phantom assembly is a non-stocked assembly that lets you group together material needed to produce a subassembly. When you create a bill of material for a parent item, you can specify whether a component is a phantom. One bill of material can represent a phantom subassembly for one parent item, and a stocked subassembly for another parent item.

• Oracle Work in Process explodes through a phantom subassembly to the components as if the components were tied directly to the parent assembly. You can define routing for phantoms assemblies the same way as other assemblies. Work in Process ignores phantom assembly routings when you define a job or repetitive schedule.
• You can compute manufacturing and cumulative lead times for phantom assemblies that have routings. If you do not want to offset the components of a phantom assembly in the planning process, exclude the phantom item from the lead time calculations.
• In general, phantom assemblies behave like normal assemblies when they represent a top level assembly, such as when you master schedule them or manufacture them using a discrete job. As a subassembly, however, they lose their identity as distinct assemblies and are a collection of their components. The components of the phantom subassembly are included on the job and on the pick list of the job-not the phantom itself.
• When model or option class bills are components to another bill of material, the component supply type is phantom.

Primary & Alternate Bill

A primary bill is a list of the components you most frequently use to build a product. An alternate bill is another list of components for the same basic assembly. The primary bill is the default for rolling up costs, defining a job, and calculating cumulative item lead times.

Use alternate bills to account for manufacturing variations that produce the same assembly, by specifying the parent item number and an alternate name when you create a bill. You cannot enter new revisions for alternate bills of material.

• You must define a primary bill before you define an alternate. A primary bill can have many alternate bills. Any bill of material type can have an alternate.
• Oracle Master Scheduling/MRP uses the primary bill to plan your material. Oracle Order Management uses the primary bill for model and option class products to list available options.
• When you build an item, roll up costs, and perform other functions that use bills of material, you can specify whether to use the primary bill (the default) or an alternate bill. You can also use engineering change orders to control changes to primary and alternate bills of material.
• You can use an alternate to define an engineering bill or routing. The alternate used as a prototype variation from the primary manufacturing bill that produces essentially the same assembly.
• Bills and routings can share alternate labels. If you create an alternate bill with the same label as an alternate routing, components are assigned to operations on the alternate routing. If there is no routing with the same alternate label, components are assigned to operations on the primary routing.

Item and Routing Revisions
You can define any number of revisions for the item and any number of routing revisions for an item's routing.
Important: Item revisions and routing revisions function alike and are discussed together below. However, item revisions and routing revisions are two distinct pieces of information. They are created and maintained separately and have no influence over each other.

• Assign each revision a unique three character alphanumeric revision identifier (such as A, B, B1, and so on) and a revision date. Revisions are sorted according to ASCII rules.
• Each revision must be greater than the previous revision. Therefore, you cannot use revision 10 after revision 9 because, according to ASCII sorting, 10 precedes 9.
• Use letters and/or numbers to label revisions. Letters are always upper case and numbers may include decimals. To ensure that revisions sort properly (according to ASCII sorting rules), decimals should always be followed by a number. Therefore, valid revisions can include: A, B, 1, 2, A1, B1, 1A, 1B, 0.0, 0.1, A.0, A.1, and so on. When you create an item or a routing, the beginning revision defaults to the value for Starting Revision in the Organization Parameters window.
• When you create or update a bill of material or routing, you can choose to create a new revision or modify an existing revision. When adding new revisions, you should be sure that the revision date you enter does not overlap with other existing revision dates. Revisions are time-stamped, so you can determine the latest revision for multiple revisions defined on the same date. New revision numbers must be greater than the revision number of the currently effective revision.
• Different versions of a bill of material or routing can be defined within the same revision. You can change component information for bills or operation information for routings without modifying the revision.

For example, assume that you defined an initial revision A on 18-AUG and made a change on 20-AUG without creating a new revision. If you make another change on 22-AUG, you can create a new revision B, effective 22-AUG. There are now three different versions of the item: revision A of 18-AUG, revision A of 20-AUG, and revision B of 22-AUG.

Access Control by Item Type
Control access to bills of material by item type using the following profile options:

•  BOM: Standard Item Access
•  BOM: Planning Item Access
•  BOM: Model Item Access (also controls access to option class items)

Each profile option can have either a Yes or No value. A Yes value indicates that you can create and update bills for the associated item type. For example, you might specify No at the site level for BOM: Standard Item Access profile to restrict access for creating standard bills. But you might specify Yes for BOM: Planning Item Access profile option at the user level for specific engineers so they can update engineering bills of material for planning items.

Note: Profiles are ignored in query mode. A user with no access to any type of item can query all types of bills.