Activity
Activity. In the formal PSL ontology, the notion of activity is a basic construct, which corresponds intuitively to a kind of (manufacturing or processing) activity. In PSL, an activity may have associated occurrences, which correspond intuitively to individual instances or executions of the activity. (We note that in PSL an activity is not a class or type with occurrences as members; rather, an activity is an object, and occurrences are related to this object by the binary predicate occurrence_of.) The occurrences of an activity may impact fluents (which provide an abstract representation of the "real world"). In FLOWS, with each service there is an associated activity (called the "service activity" of that service). The service activity may specify aspects of the internal process flow of the service, and also aspects of the messaging interface of that service to other services.
Channel
Channel. In FLOWS, a channel is a formal conceptual object, which corresponds intuitively to a repository and conduit for messages. The FLOWS notion of channel is quite primitive, and under various restrictions can be used to model the form of channel or message-passing as found in web services standards, including WSDL, BPEL, WS-Choreography, WSMO, and also as found in several research investigations, including process algrebras.
FLOWS
First-order Logic Ontology for Web Services. FLOWS, also known as SWSO-FOL, is the first-order logic version of the Semantic Web Services Ontology. FLOWS is an extension of the PSL-OuterCore ontology, to incorporate the fundamental aspects of (web and other electronic) services, including service descriptors, the service activity, and the service grounding.
Fluent
Fluent. In FLOWS, following PSL and the situation calculii, a fluent is a first-order logic term or predicate whose value may vary over time. In a first-order model of a FLOWS theory, this being a model of PSL-OuterCore, time is represented as a discrete linear sequence of timees, and fluents has a value for each time in this sequence.
Grounding
Grounding. The SWSO concepts for describing service activities, and the instantiations of these concepts that describe a particular service activity, are abstract specifications, in the sense that they do not specify the details of particular message formats, transport protocols, and network addresses by which a Web service is accessed.  The role of the grounding is to provide these more concrete details.  A substantial portion of the grounding can be acheived by mapping SWSO concepts into corresponding WSDL constructs. (Additional grounding, e.g., of some process-related aspects of SWSO, might be acheived using other standards, such as BPEL.)
Message
Message. In FLOWS, a message is a formal conceptual object, which corresponds intuitively to a single message that is created by a service occurrence, and read by zero or more service occurrences. The FLOWS notion of message is quite primitive, and under various restrictions can be used to model the form of messages as found in web services standards, including WSDL (1.0 and 2.0), BPEL, WS-Choreography, WSMO, and also as found in several research investigations. A message has a payload, which corresponds intuitively to the body or contents of the message. In FLOWS emphasis is placed on the knowledge that is gained by a service occurrence when reading a message with a given payload (and the knowledge needed to create that message.
Occurrence
Occurence (of a service). In FLOWS, a service S has an associated FLOWS activity A (which generalizes the notion of PSL activity). An occurrence of S is formally a PSL occurrence of the activity A. Intuitively, this occurrence corresponds to an instance or execution (from start to finish) of the activity A, i.e., of the process associated with service S. As in PSL, an occurrence has a starting time time and an ending time.
PSL
Process Specification Language. The Process Specification Language (PSL) is a formally axiomatized ontology [Gruninger03a, Gruninger03b] that has been standardized as ISO 18629. PSL provides a layered, extensible ontology for specifying properties of processes. The most basic PSL constructs are embodied in PSL-Core; and PSL-OuterCore incorporates several extensions of PSL-Core that includes several useful constructs. (An overview of concepts in PSL that are relevant to FLOWS is given in Section 6 of the Semantic Web Services Ontology document.)
QName
Qualified name. A pair (URI, local-name). The URI represents a namespace and local-name represents a name used in an XML document, such as a tag name or an attribute name. In XML, QNames are syntactically represented as prefix:local-name, where prefix is a macro that expands into a concrete URI. See Namespaces in XML for more details.
ROWS
Rules Ontology for Web Services. ROWS, also known as SWSO-Rules, is the rules-based version of the Semantic Web Services Ontology. ROWS is created by a relatively straight-forward, almost faithful, transformation of FLOWS, the First-order Logic Ontology for Web Services. As with FLOWS, ROWS incorporates fundamental aspects of (web and other electronic) services, including service descriptors, the service activity, and the service grounding. ROWS enables a rules-based specification of a family of services, including both the underlying ontology and the domain-specific aspects.
Service
(Formal) Service. In FLOWS, a service is a conceptual object, that corresponds intuitively to a web service (or other electronically accessible service). Through binary predicates a service is associated with various service descriptors (a.k.a. non-functional properties) such as Service Name, Service Author, Service URL, etc.; an activity (in the sense of PSL) which specifies intuitively the process model associated with the service; and a grounding.
Service contract
Describes an agreement between the service requester and service provider, detailing requirements on a service occurrence or family of service occurrences.
Service descriptor
Service Descriptor. This is one of several non-functional properties associated with services. The Service Descriptors include Service Name, Service Author, Service Contract Information, Service Contributor, Service Description, Service URL, Service Identifier, Service Version, Service Release Date, Service Language, Service Trust, Service Subject, Service Reliability, and Service Cost.
Service offer description
Describes an abstract service (i.e. not a concrete instance of the service) provided by a service provider agent.
Service requirement description
Describes an abstract service required by a service requester agent, in the context of service discovery, service brokering, or negotiation.
sQName
Serialized QName. A serialized QName is a shorthand representation of a URI. It is a macro that expands into a full-blown URI. sQNames are not QNames: the former are URIs, while the latter are pairs (URI, local-name). Serialized QNames were originally introduced in RDF as a notation for shortening URI representation. Unfortunately, RDF introduced confusion by adopting the term QName for something that is different from QNames used in XML. To add to the confusion, RDF uses the syntax for sQNames that is identical to XML's syntax for QNames. SWSL distinguishes between QNames and sQNames, and uses the syntax prefix#local-name for the latter. Such an sQName expands into a full URI by concatenating the value of prefix with local-name.
URI
Universal Resource Identifier. A symbol used to locate resources on the Web. URIs are defined by IETF. See Uniform Resource Identifiers (URI): Generic Syntax for more details. Within the IETF standards the notion of URI is an extension and refinement of the notions of Uniform Resource Locator (URL) and Relative Uniform Resource Locators.