What does “PSL” stand for?

Process Specification Language.

What is the goal of PSL?

One of the goals of PSL are to create a process representation that is common to all manufacturing applications, generic enough to be decoupled from any given application, and robust enough to represent the necessary process information for any given application. Another goal is to address the “runtime” level of processes in a computer-manipulable way, to capture the intended effect of process languages.

Who is the target audience for PSL?

One target audience for PSL is the manufacturers who have a growing need to exchange process information among applications in their company (and among partnering companies). However, vendors would need to develop and incorporate PSL translators in tools that they provide to the manufacturers. Another target audience is process language designers who want to give precise semantics to their languages. Translation to PSL unambiguously defines the exact runtime commitments made by users of a process language.

Is PSL a language?

Yes, but very different from typical process languages. It refers directly to runtime occurrences of process in first order constraints, rather providing a notation or syntax “programming”. For example, a process for assembling a product may occur many times during the life of a factory. PSL refers to each occurrence of assembly separately to enable the user to write temporal constraints on what is the allowable progression of the process. Because of this precision, PSL can unambiguously capture the meaning of typical process languages that are intended for process definition.

How does PSL compare to other process modeling languages (e.g., IDEF0)?

PSL's primary role is not envisioned to be a process modeling language, see question 4. It can be used as an interchange language which would allow manufacturing applications to exchange discrete process data. For example, an IDEF3-based application could use PSL to exchange process models with a Petri net-based application, in the same way that STEP can be used to exchange product models among CAD systems. It can also be used to define the meaning of languages like IDEF3 and Petri Nets. This is due to its unique its underlying, formal ontology of process execution, see question 4. All processes concepts in PSL are formally defined, using the Common Logic Interchange Format (CLIF), To eliminate the ambiguity usually encountered when exchanging information among disparate applications. This ontology provides the backbone that enables and ensures correct translations. PSL can be thought of an ontology for the concepts of process execution.

What is the relationship between PSL and PIF?

Originally, PSL solely focused on manufacturing process information while PIF (the Process Interchange Format) focused on business process information. We quickly found that many of the concepts needed to be represented were exactly the same and that the lines between business and manufacturing were very hazy. Because of this, the PSL and the PIF were merged.

How is PSL standardized?

Who is involved in PSL?

A wide variety of organizations have contributed to PSL. See here for details.

How was the PSL Ontology created?

The PSL Ontology was created by colleagues from all over the world, including representatives from the workflow, manufacturing, business, and military planning communities. Consensus was reached among all of these parties as to the content of the PSL Core concepts and additional work was done to extend these core concepts to model process information in various manufacturing functions.

How is the PSL Ontology organized?

The PSL Ontology is organized as a series of modules, all built upon the PSL Core. The PSL Core is a module which captures the high-level, primitive concepts inherent to process specification. Each module refines the PSL Core, capturing sets of related concepts particular to a specific representational area related to process specification (e.g., resource roles, temporal ordering, etc.). Modules build upon one another, causing the PSL Ontology to resemble a web of modules, all bottoming out at the PSL Core.

What has been accomplished so far with PSL?

All parts of PSL have been standardized, see question 7, and some have associated consistency proofs. PSL has been applied in scheduling, process modeling semantics, process planning, production planning, simulation, project management, workflow, and business process reengineering, see publications.

What are the future plans for PSL?

The future plans of PSL include applying PSL extensions to enterprise and supply chain models to detect inconsistencies between rules and processes, including business-to-business protocols, and web services and choreography. This will leverage previous results in incremental translation of flow models to PSL and extensions for loosely and tightly coupled processes. Theorem provers will be applied to proof-of-concept examples. Also some PSL extensions not yet standardized will be completed, for resources and agents.

How can I find out more?

Check out the PSL web site.