Ontology based interface design and control methodology for collaborative product development

Abstract

Interfaces between subsystems in collaborative product development projects are presently defined by interface control documents. This paper presents a computer aided methodology for defining and controlling subsystem interfaces. Interfaces are considered as interconnections between subsystem ports. Ports are specified by using an ontology that ensures consistency of interface definitions among different design teams. Every port that is based on the ontology is eventually defined by a set of attributes that are derived from its form and function. Interfaces between ports are formed when ports are mated. The essence of port mating is described by logical information that is expressed in two forms. First, a set of requirements are defined for an individual port to ensure that it functions properly. Second, connectivity rules are expressed between ports to guarantee that they integrate correctly. A software architecture that operates on port information and controls the status of subsystem interfaces during collaboration is described. A piece of software is implemented based on the proposed architecture and its functionality is demonstrated by two examples. The examples show how the software can be used to replace interface control documents and support collaboration. The software allows designers to load subsystem descriptions from a shared repository and connect them together by defining connectivity rules. The software reports errors to designers when port requirements or connectivity rules are violated.

Introduction

An interface refers to any logical or physical relationship required to integrate the boundaries between systems or between systems and their environment. Here, the word ‘system’ refers to a set of interoperable elements compatible with each other in form, fit and function to achieve a specific outcome [1]. Interfaces can be regarded as places where the boundaries of two subsystems come together. The places of intended interactions among subsystems are called ports [2].

Interface control is the process of identifying all functional and physical characteristics of interacting entities from different organizations, and of ensuring that proposed changes to these characteristics are assessed and approved before implementation [3]. Interface definition and control is an indispensable part of a systems engineering process. It usually occurs after the conceptual design phase. The more carefully subsystem interactions are defined in these early phases, the more likely it is that products are delivered on time with fewer design errors [4].

Interfaces between subsystems in collaborative engineering design projects are defined by interface control documents (ICD). Documenting agreements and committing to them is a crucial means of preventing design conflicts. The purpose of an ICD is to guarantee that subsystems designed by different engineering agencies are compatible. An ICD specifies what is required to correctly connect subsystems in an overall product.

Use of ICDs is particularly helpful when a product is composed of subsystems that are described by different models, e.g., mechanical, electrical, hydraulic, etc. In such a situation, it is very difficult (if not impossible) to have a product representation that includes all such miscellaneous subsystems and defines the interfaces between them. In these cases, ICDs can be supplied as separate documents that describe the interfaces among subsystems.

An important consequence of using ICDs during collaborative product development is that ICDs make projects document driven. This naturally has some drawbacks since the form of ICDs differ substantially from one organization to another. There are standards for the format of ICDs in certain domains, such as aircraft stores [5], but there is no universal standard for the content and form of ICDs. The common practice of using natural language, technical drawings, graphs, etc. to create ICDs leads to ambiguities in the presence of diversely different terminologies. This not only makes the interface control process manual and time consuming, but also makes it difficult to find common interfaces for reuse. These difficulties can be alleviated by using a computer aided interface control methodology in which interface information is given in formal machine readable form.

This paper proposes a computer assisted methodology for interface design and control. The main entities in this methodology are a port ontology that explicitly specifies port related concepts, and interface rule sets that describe how these ports are related in a product development project. The ontology provides a common vocabulary for interface definitions; so, it helps to overcome the lack of commonality in interface terminologies and improves information sharing among agents. When all collaborating agents commit to a shared ontology, the interface specifications provided by them are consistent and can be managed by software tools. The rule sets are also essential components of a computer aided interface control process because ICDs actually define the logic for using and connecting subsystems in a product development process. This work can be regarded as a foundational step toward making a standard model for computer aided interface design and control.