SBVR16 — SBVR issue - Need verb concept to support "local closure"

Disposition: Resolved
OMG Issue No: ????
Title: Need business-oriented verb concepts to support "local closure"
Source:
Mark H. Linehan, IBM Research
Summary:
Clause 10.1.1.3 has an extensive discussion of "Open/Closed World Semantics". In particular, the penultimate paragraph near the bottom of page 94 of version 1.0 of the specification says:
"For any given schema, the business might have complete knowledge about some parts and incomplete knowledge about other parts. So in practice, a mixture of open and closed world assumptions may apply. We use the term “local closure” (or “relative closure”) for the application of the closed world assumption to just some parts of the overall schema. One might assume open world semantics by default, and then apply local closure to specific parts as desired; or alternatively, assume closed world semantics by default and then apply “local openness.” We adopt the former approach as it seems more realistic when modeling real business domains."

In SBVR 1.0, local closure is supported by the verb concepts "fact type is internally closed in conceptual schema" and "concept is closed in conceptual schema" in clause 8.5. The resolution of issue 13138 moves clause 8.5 to clause 10, thus making these verb concepts no longer available in the normative specification or in the clause 15 supporting documents. The result is that the specification no longer supports the semantics mentioned in the quote given above. This issue requests that similar functionality be added to clause 11.

The original clause 8.5 verb concepts used designations that are not meaningful to business people. The resolution of this issue should adopt business-oriented terminology. Discussions have identified at least four possible approaches:

1. A verb concept "set is completely known", meaning that the semantic community knows all the elements of the set. This would be particularly useful when applied to a set as the extension of a concept.
2. A verb concept "concept has completely known extension". Similar to the above, but applying specifically to the extension of concepts.
3. A verb concept such as "semantic community completely knows concept".
4. Building on the concept "communication concept" in clause 11.2.2.3 to define closure with respect to an information record.

Example use cases for local closure include the following:

Example 1

This example is about a concept called order that includes a list of line items, where each line item has a quantity, a catalog id, etc. A minimal vocabulary is shown here, just enough to illustrate the example.

order
Definition: A customer request for one or more products and a promise to pay the total cost of the order.
line item
Definition: Details about an order for a particular product.
quantity
Definition: positive integer that is the number of units of the product that is desired by the customer
catalog id
Definition: text that identifies the product desired by the customer
line item has quantity
Necessity: Each line item has exactly one quantity.
line item has catalog id
Necessity: Each line item has exactly one catalog id.
order includes line item
Necessity: Each order includes at least one line item.
"order includes line item" is internally closed in the business xx conceptual schema

The "internally closed" fact says that the business knows all the line items that are included in each order: there are no other line items. Consider a rule such as "Each order must be shipped within 24 hours if the order does not include a line item that has quantity greater than 100." As described in clause 10.1.1.3, this rule makes no sense with the default SBVR "open world" semantics because under those semantics, the business cannot know that no "line item that has quantity greater than 100".

Example 2

Consider a business that has a vocabulary about employees. The business considers it knows all its employees; there are no employees that it does not know.

employee
Definition: person that works for the business

Under SBVR's default open world semantics, the glossary entry given above is insufficient because it does not capture the business sense that it knows all its employees. To accomplish that, the vocabulary needs the following:
"employee" is closed in the business xx conceptual schema

Example 3

Continuing example 2, suppose the business needs concepts relating to employee names and work phone numbers:

employee name
Definition: text that identifies an employee
work phone number
Definition: number used to phone an employee at work

The business requires that it knows the employee name of each employee because the government requires this information on tax and employment reports. So the employee name is authoritative.

The business knows that, in practice, it does not know the work phone number of each employee. These change too often to keep up with.

SBVR needs verb concepts to express the idea that the employee name is reliably know, but the work phone number is not reliably known.

Resolution:
Revised Text:
Disposition: