Y. LABROU. SEMANTICS FOR AN AGENT COMMUNICATION LANGUAGE. PHD THESIS DISSERTATION SUBMISSION, UNIVERSITY OF MARYLAND GRADUATE SCHOOL, BALTIMORE, SEPTEMBER, 1996.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....use KRAFT s Common Command and Query Language (CCQL) CCQL conveys necessary information such as the nature of the message (for example, a query or a response) a unique message identifier, the source of the message and its destination. The commands are based on a subset of those used in KQML [2] [11]. Once a query has been converted to the internal KRAFT format, the next task is to determine where resources exist which can help to answer the query. This over arching view of the network is the role of a facilitator. The facilitator maintains a knowledge base of resource capabilities , and of ....

Yannis Labrou. Semantics for an Agent Communication language. PhD Thesis, Baltimore, Maryland, 1996. 8

....approach, so called agent s mental structures (e.g. beliefs, desires and intentions) are used to model conversations and to define a formal semantics of speech acts. In the first system that was based on these notions, speech acts were planned like non communicative actions [9] It was used by [19] and [20] to define a formal semantics of KQML. However, this semantics has been criticized for not being verifiable because one cannot verify whether the agents behavior matches their private mental states [12] 5] An alternative to the mental approach was proposed by [29] under the name of ....

Labrou, Y. Semantics for an agent communication language, Ph.D. Thesis, University of Maryland, USA, 1997.

.... filtering programs [40] to agents that monitor the state of the stock market and detect trends in stock prices, to intelligent web search agents [21] to the digital battlefield where agent technology closely monitors and merges information gathered from multiple heterogeneous information sources [1, 35, 36, 52, 61]. More recently, we have seen an increase in the number of agents that automatically interact with one another. Such agents can negotiate with each other, participate in auctions, make group consensus decisions, and the like [34, 60, 46, 32] In previous work [2, 20, 19] Eiter et al. have ....

Y. Labrou and T. Finin. Semantics for an Agent Communication Language. In International Workshop on Agent Theories, Architectures, and Languages, pages 199--203, Providence, RI, 1997.

....and share knowledge. Even though technically the communication takes place by messages over a network that uses a low level protocol, on a conceptual level agents do not exchange messages, but they maintain conversations based on its purposes. The specification of an ACL comprises of three levels [15]: An Interaction Protocol An Interaction Language A Language for representing Shared Beliefs Each agent s interaction protocol is a conversation pattern that governs its interaction with other agents and allows to structure the communication. The interaction language is the medium through ....

Y. Labrou. Semantics for an Agent Communication Language. Ph.D. Thesis, University of Maryland, 1996.

....In general, the KQML specification was ambiguous on other key points; it was often necessary to go to the KQML community for guidance on proper usage. As of this writing, an updated KQML specification including a formal semantics for the language is soon to see print, and is eagerly awaited [22]. On a more positive note, we have found ODBC and JDBC to provide true portability that significantly simplified our implementation of a generic resource agent. For example, even though the resource agent could run on Solaris and Windows NT platforms, but not on Sun OS (where Java is not ....

Y. Labrou, "Semantics for an Agent Communication Language", Ph.D. Dissertation, CSEE department, University of Maryland, Baltimore County, September 1996.

....of this speech act in terms of the intentional stance, i.e. mental attitudes in terms of beliefs, desires and intentions. In both cases, the meaning is specified using a semantic condition, sometimes called the sincerity condition, saying that an agent actually believes what it communicates [21, 9]. As pointed out by Pitt [24] this condition is not valid in many open (and semi open) agent societies. Similar objections can be made for the other levels of linguistic interaction. In fact, we argue that the consequences of the non benevolence assumption and the openness of the Internet are ....

Labrou, Y. and Finin, T.: Semantics for an Agent Communication Language. In: Singh, M., Rao, A., and Wooldridge M. (eds.): Intelligent Agents IV, Springer, 1998.

.... filtering programs [62] to agents that monitor the state of the stock market and detect trends in stock prices, to intelligent web search agents [33] to the digital battlefield where agent technology closely monitors and merges information gathered from multiple heterogeneous information sources [4, 56, 57, 94, 103]. In the long run, a platform to support the creation and deployment of multiple software agents will need to inter operate with a wide variety of custom made, as well as legacy software sources. Any definition Def of what it takes for a software package S (in any programming language) to be ....

....a message is physically sent off) this buffer. We will assume that the agent has the following functions that are integral in managing this message box. Note that over the years, we expect a wide variety of messaging languages to be developed (examples of such messaging languages include KQML [57] at a high level, and remote procedure calls at a much lower level) In order to provide maximal flexibility, we will merely specify below, the core interface functions available on the msgbox type. Note that this set of functions may be augmented by the addition of other functions on an agent ....

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Y. Labrou and T. Finin. Semantics for an Agent Communication Language. In Wooldridge and Jennings [107], pages 199--203.

....coordination medium is the ACL, while the coordination laws are expressed through the finite state machine that describes the protocol. 4. COORDINATION THROUGH THE SEMANTICS OF ACLS ACLs have long been criticized for their lack of formal semantics. A formal semantics for KQML have been proposed [15] and when FIPA chose to define its own ACL it also introduced a formal semantics. FIPA borrowed such a semantics from Sadek s ARCOL [26] Anyway, the debate on an accepted semantics for ACLs is far from concluded and researchers find no agreement on this topic beyond that a formal semantics is ....

Y. Labrou and T. Finin. Semantics for an agent communication language. Lecture Notes in Computer Science, 1365:209--214, 1998.

....with low level header information, including a timestamp and network information. The body of the message consists of two nested protocols: the outer protocol is the Constraint Command and Query Language (CCQL) which is a specialised subset of the Knowledge Query and Manipulation Language (KQML) [10]. Nested within the CCQL message is its content, expressed in the Constraint Interchange Format (CIF) In the current implementation, KRAFT messages are syntactically Prolog term structures. An example message is shown in Figure 2. The outermost kraft msg structure contains a context clause ....

Y. Labrou, Semantics for an Agent Communication Language, PhD Thesis, University of Maryland, Baltimore MD, USA, 1996.

....of other agents, and form cooperative alliances; as KRAFT is concerned with the fusion of knowledge from available on line sources, these features were seen as being of great value. The design of KRAFT is consistent with several emerging agent standards, notably the de facto KQML standard [17] and the de jure FIPA standard [4] Agents are peers; any agent can communicate with any other agent with which it is acquainted. Agents become acquainted by registering their identity, network location, and an advertisement of their knowledge processing capabilities with a specific type of agent ....

....information including a timestamp and network information. 6 The body of the message consists of two nested protocols: the outer protocol is the agent communication language CCQL (Constraint Command and Query Language) which is a subset of the Knowledge Query and Manipulation Language (KQML) [17]. Nested within the CCQL message is its content, expressed in the CIF protocol (Constraint Interchange Format) a superset of the CoLan constraint language shown in Section 2. Syntactically, KRAFT messages are implemented as Prolog term structures. An example message is shown below. The ....

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Y. Labrou. Semantics for an Agent Communication Language. PhD thesis, University of Maryland, Baltimore MD, USA, 1996.

....each message with low level header information including a timestamp and network information. The body of the message consists of two nested protocols: the outer protocol is the agent communication language CCQL (Constraint Command and Query Language) which is a slightly modified subset of KQML [6]. 1 Nested within the CCQL message is its content, expressed in the CIF protocol (Constraint Interchange Format) CCQL deviates from the 1997 specification of KQML as follows: the default syntax is Prolog term structures, rather than LISP, and constraints from 1st vendor s product catalogue ....

....reply with : id(18) ontology : shared, language : cif, content : the advertisement message format allows multiple advertisements to be carried in the body of a single message. However, no new performatives are introduced, and interactions follow the conversation rules specified in [6]. such that name(vendor(d) Storage Inc and type(d) Zip at least 1 p in ports(host pc(d) to have type(p) USB ] Use of Prolog term structures is chiefly for convenience, as most of the current knowledge processing components in the KRAFT implementation are written in Prolog. ....

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Y. Labrou. Semantics for an Agent Communication Language. PhD thesis, University of Maryland, Baltimore MD, USA, 1996.

....section 5 we discuss some future developments and expectations. We conclude the paper in section 6. 2 Agent communication A first attempt to produce an ACL that was both standard and general came out of the DARPA knowledge sharing initiative. The Knowledge Query and Manipulation Language (KQML)[8] was originally devised as a means for exchanging information between heterogeneous knowledge systems. However, because of the generality of its high level primitives and its message orientated structure, KQML also functions well as language for agent communication. KQML is the most widely ....

....KQML agents were very weak, and the resultant semantics of KQML messages were fairly permissive. As is now well know, this permissiveness allowed wide latitude in KQML implementations, and the proliferation of different and incompatible KQML dialects. Labrou s second generation semantics for KQML ([8]) struck a clever compromise between KQML s original virtual knowledge base theory of agency and a BDI style theory, but at the cost of introducing modal operators back in the semantic theory, with the associated computability issues. 2 Certain special classes of acts, parallel to the explicit ....

Labrou, Y. Semantics for an agent communication language, Ph.D. thesis, University of Maryland, USA, 1997.

....Since the functionality that has to be implemented for KQML is very similar to that of FIPA, we think that it will not be much e ort to o er both communication languages in the future. 3. 2 The Knowledge Query and Manipulation Language The Knowledge Query and Manipulation Language (KQML) FMF92, Lab96] is a communication language for software agents which supports the exchange of information about the (virtual) knowledge bases of the agents. KQML is both a message format and a message handling protocol to support shared knowledge in a multi agent system. KQML is based on the speech act theory ....

....to perform in communication with each other. Thus, KQML messages do not solely communicate sentences in some language, but rather communicate an attitude about the content of the message. KQML performatives can be modeled as actions which change the cognitive states of agents. According to [Lab96] cognitive states can be speci ed using the predicates know, want, intend, and bel which describe the knowledge, goals, intentions, and beliefs of agents. With these predicates, the semantics of KQML performatives can be formally speci ed in terms of preconditions and postconditions describing ....

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Yannis Labrou. Semantics for an Agent Communication Language. PhD thesis, University of Maryland, Baltimore County, 1996.

....a machine is on) The ACL actually used should not much matter; however, there is a specific, and to the point of this paper, quite relevant way in which FLBC and KQML differ how each treats a response to a message. This difference applies to the version described in (DARPA 1993) but not in Labrou (Labrou 1996). As I have previously argued (Moore 1998a, p. 216) information about discourse structure should not define a speech act. If we were to go down this path, agents might need, in addition to reply, acts for reply request (if a message is replying to a question but is asking for more information) ....

Labrou, Y. 1996. Semantics for an Agent Communication Language. Ph.D. Dissertation, University of Maryland, Computer Science and Electrical Engineering Department.

....is on the combination of data and constraints. KRAFT also builds upon the work of the Knowledge Sharing Effort (KSE) 6] in that some of the KSE facilitation and brokerage methods are employed, along with a subset of the 1997 Knowledge Query and Manipulation Language (KQML) specification [7]. Unlike the KSE work, however, which attempted to support agents communicating in a diverse range of knowledge representation languages (with attendant translational problems) KRAFT takes the view that constraints are a good compromise between expressivity and tractability. 1.2Overview of ....

....with low level header information including a timestamp and network information. The body of the message consists of two nested protocols the outer one is the agent communication language CCQL (Constraint, Command and Query Language) which is a subset of the 1997 specification of the KQML [7]. Nested within the CCQL message is its content, expressed in the CIF protocol (constraint interchange format) Figure 2 shows the anatomy of a KRAFT message and will be useful in understanding the message sequences presented for illustration purposes in the following sections of this paper. ....

Labrou Y: `Semantics for an agent communication language', PhD thesis, University of Maryland Graduate School. Baltimore, Maryland (September 1996).

....in these standards is aimed to ensure that information received by an agent can be interpreted in the same way as it is intended by the sending agent. Communication standards have been studied extensively and are applied on a large scale for a variety of purposes (e.g. Lee and Malone, 1990; Labrou, 1996). In this article we focus on heterogeneity between (domain) ontologies and leave languages, and protocols. Setting ontological standards is a logical approach in ensuring adequate communication between a group of agents. Once the ontology standard has been set al..l agents are able to share the ....

Labrou, Y. (1996). Semantics for an Agent Communication Language, PhD thesis, University of Maryland, Baltimore, MD, USA.

....and knowledge reuse. KQML is a language based on speech acts, such as tell , ask , and deny , which describe the nature of a message without reference to its content. Agents communicate application specific information embedded in general, higher level KQML messages. A comprehensive semantics [4] for KQML outlines protocols for agent conversation. Additionally, most implementations provide facilities for message handling, agent naming and resource brokering. Problems of software mobility, communication, and autonomy have not been neglected within the Tcl community. Existing Tcl based ....

Yannis Labrou. Semantics for an Agent Communication Language. PhD thesis, University of Maryland Baltimore County, 1996.

....of other agents, and form cooperative alliances; as KRAFT is concerned with the fusion of knowledge from available on line sources, these features were seen as being of great value. The design of KRAFT is consistent with several emerging agent standards, notably the de facto KQML standard [11] and the de jure FIPA standard [6] Agents are peers; any agent can communicate with any other agent with which it is acquainted. Agents become acquainted by registering their identity, network location, and an advertisement of their knowledge processing capabilities with a specific type of agent ....

....header information including a timestamp and network information. The body of the message consists of two nested protocols: the outer protocol is the agent communication language CCQL (Constraint Command and Query Language) which is a subset of the Knowledge Query and Manipulation Language (KQML) [11]. Nested within the CCQL message is its content, expressed in the CIF protocol (Con straint Interchange Format) a superset of the CoLan constraint language shown in Section 1. Syntactically, KRAFT messages are implemented as Prolog term structures. An example message is shown below. The ....

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Y. Labrou, Semantics for an Agent Communication Language, PhD Thesis, University of Maryland, Baltimore MD, USA, 1996.

....information services in order to facilitate communication. An agent communicates verbally with other agents: actively by sending, and passively by receiving, typed messages. 7 5 The above realization of communication acts is based on the built in pvm send of PVM Prolog. 6 See, e.g. [Lab96]. 7 In addition, there may be non verbal forms of communication, e.g. by means of perception. Messages may be sent over network links, or via specific radio links, or, similar to human communication, by means of audio signals. The transport mechanism is not part of the communication model of ....

Y. Labrou. Semantics for an Agent Communication Language. PhD thesis, University of Maryland Graduate School, 1996.

....The run time system provides a high performance agent engine that executes these agent programs. Agents constructed using AgentBuilder communicate using the Knowledge Query and Manipulation Language (KQML) Finin, et al., 1994a; Finin, et al., 1994b; Finin, et al., 1994c; Labrou et al., 1994; Labrou, 1996] and support the performatives defined for KQML (described later in this paper) In addition, AgentBuilder allows the developer to define new interagent communications commands that suit his particular needs. The AgentBuilder toolkit and the run time engine are implemented using the Java ....

....systems engaged in cooperative problem solving. This language, originally developed as part of a DARPA Knowledge Sharing initiative, is becoming a de facto standard for interagent communications languages [Finin, et al., 1994a; Finin, et al., 1994b; Finin, et al., 1994c; Labrou et al., 1994; Labrou, 1996]. A KQML message consists of a performative, the content of the message, and a set of optional arguments. The performative specifies an assertion or a query used for examining or changing a Virtual Knowledge Base (VKB) in the remote agent. Table 2 provides a listing of the defined performatives ....

Labrou, Y., (1996). "Semantics for an agent communication language," in Computer Science and Electrical Engineering Department. Baltimore, MD: University of Maryland Graduate School, pp. 116.

....each glossary provider proposes and decides upon a set of terms and explanations to send back to the AC. Glossary terms Adapted glossary Glossary provider registration Components in the IS renders the glossary. Time) Runtime Setup Prereq. for Runtime 18 interactions dynamically. Labrou (1997) introduces the concept of conversations as a means for controlling threads of interactions between agents speaking KQML 3 (Finin, Labrou, Mayfield, 1997) Examples of conversations implemented in Prolog as definite clause grammars, complete with constraining clauses, are presented. However, ....

Labrou, Y. (1997). Semantics for an Agent Communication Language. Unpublished Ph.D., University of Maryland Graduate School, Baltimore, Maryland.

....acts based languages. 2 1. 1 Agents and Concurrency A general framework to deal with these issues should be able to integrate achievements and results from many diverse research areas, ranging from philosophical studies on human communication [11, 36] and the design of agent languages in AI [12, 27, 25, 35], to the development of parallel and distributed programming languages [1, 7, 8, 9, 43] and the theory of concurrency [23, 28, 30] In fact, on the one hand, a collection of agents will often include humans performing some of the tasks; thus, it is essential that a communication language for ....

....symbol level requirements which need to be obeyed to support these agent level approaches. For example, whether the transport level is characterised by synchronous or asynchronous mechanisms or whether it makes use of blocking or non blocking primitives. Only the last revised specification of KQML [25] suggests a set of requirements that every KQML implementation should conform, but the rationale behind them is not discussed. Our approach is based on the translation of the asynchronous version of KL ACL into a process algebra. This allows us to have a more rigorous understanding of the mapping ....

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Y. Labrou. Semantics for an Agent Communication Language. PhD thesis, University of Maryland, Baltimora, Maryland, USA, September 1996.

.... state of the stock market and detect trends in stock prices, intelligent web search agents (Etzioni and Weld 1994) digital battlefield agents that monitor and merge information gathered from multiple heterogeneous information sources (Arens, Chee, Hsu, and Knoblock 1993; Labrou and Finin 1994; Labrou and Finin 1997; Subrahmanian 1994; Wiederhold 1993) More recently, we have seen an increase in the number of agents that automatically interact with one another. Such agents can negotiate with each other, participate in auctions, make group consensus decisions, and the like (Kraus 1997; Rosenschein and Zlotkin ....

Labrou, Y. and T. Finin (1997). Semantics for an Agent Communication Language. In International Workshop on Agent Theories, Architectures, and Languages, Providence, RI, pp. 199--203.

....by the agents in the system. Naturally, a key piece in this picture is the need for the agent system to be able to coordinate the execution of these complex tasks via the messages between agents. Proposed agent communication language (ACL) standards include FIPA [4] and various flavors of KQML [3, 6, 7]. These proposals are oriented towards speech act theory. Speech acts are utterances that perform some action or request some specification. An ACL message is a representation of a speech act, and thus provides guidelines as to the interpretation of its contents. This facilitates openness by ....

Y. Labrou. Semantics for an Agent Communication Language. PhD thesis, University of Maryland at Baltimore County, September 1996.

....object world, thus its use in an agent based system will restrict the agents interactions to remote procedure calls. Interactions between agents often take a more complex form encompassing a series of method exchanges. Within the agent community, agent communication languages such as kqml [9] attempt to define how an agent advertisement should look. For example, kqml defines an advertise performative that allows an agent to advertise its capabilities in terms of the kqml performatives it is able to accept. Thus, an advertise performative has (one or more) nested performative(s) that ....

....with that signature. The orb looks through its list of interface descriptions and matches the signature to some method in some object s idl description, and returns the matched object. The requesting object can then invoke the method on the matched object. Different agent communication languages [9, 4] have developed special messages to send to a facilitator agent such as a matchmaker. kqml defines advertise, broker and recommend messages, which allow an agent to advertise its services, and ask about other agents services. In these messages, the service is described in terms of a second kqml ....

Y. Labrou. Semantics for an Agent Communication Language. PhD thesis, University of Maryland at Baltimore County, Sep 1996.

....of other agents, and form cooperative alliances; as KRAFT is concerned with the fusion of knowledge from available on line sources, these features were seen as being of great value. The design of KRAFT is consistent with several emerging agent standards, notably the de facto KQML standard [Labrou, 1996] and the de jure FIPA standard. Agents are peers; any agent can communicate with any other agent with which it is acquainted. Agents become acquainted by registering their identity, network location, and an advertisement of their knowledge processing capabilities with a specific type of agent ....

....header information including a timestamp and network information. The body of the message consists of two nested protocols: the outer protocol is the agent communication language CCQL (Constraint Command and Query Language) which is a subset of the Knowledge Query and Manipulation Language (KQML) [Labrou, 1996]. Nested within the CCQL message is its content, expressed in the CIF protocol (Constraint Interchange Format) It is worth noting that, syntactically, KRAFT messages are implemented as Prolog term structures. This is chiefly for convenience, as most of the knowledge processing components are ....

[Article contains additional citation context not shown here]

Labrou, Y. 1996. Semantics for an Agent Communication Language, PhD Thesis, University of Maryland, Baltimore MD, USA.

....in terms of the core set and added to the language. The semantics of the newly added operators are defined to be the compositional result of the component core operators in its definition. This type of semantics stands in contrast to the operational semantics proposed for KQML by Finin and Labrou [8, 9]. Since KQML s operators are defined independently, it is not possible to determine the exact relationship between a pair of operators. Hence neither the language implementor nor the language user is given guidance about how the operators should fit together. The language used to express the ....

Y. Labrou. Semantics for an Agent Communication Language. PhD thesis, University of Maryland, Baltimore County (UMBC), 1996.

....(1994) Agent K language is an attempt to build a hybrid that extends AGENT 0 to use KQML for communication. 27. One well known tool that has been used to construct such vocabularies is Ontolingua (Gruber 1992a, 1992b) 28. Recent efforts to provide a semantic foundation for KQML are described in Labrou (1996) and Labrou and Finin (1994) Another more general approach to agent language semantics is currently under development by Smith and Cohen (1995) 29. Such a strategy parallels the approach of Rosenschein, who designed a compiler that generates finite state machines whose internal states can be ....

Labrou, Y. 1996. Semantics for an Agent Communication Language. Ph.D. diss., Dept. of Computer Science, University of Maryland at Baltimore County.

....with the retrieval of data objects, the focus of KRAFT is on the combination of data and constraints. KRAFT also builds upon the work of the Knowledge Sharing Effort [6] in that some of the KSE facilitation and brokerage methods are employed, along with a subset of the 1997 KQML specification[7]. Unlike the KSE work, however, which attempted to support agents communicating in a diverse range of knowledge representation languages (with attendant translational problems) KRAFT takes the view that constraints are a good compromise between expressivity and tractability. Overview of the ....

....a timestamp and network information. The body of the message consists of two nested protocols: the outer one is the agent communication language CCQL (Constraint, Command and Query Language) which is a subset of the 1997 specification of the Knowledge Query and Manipulation Language (KQML) [7]. Nested within the CCQL message is its content, expressed in the CIF protocol (Constraint Interchange Format) Figure 2 shows the anatomy of a KRAFT message and will be useful in understanding the message sequences presented for illustration purposes in the following sections of this paper. ....

Yannis Labrou. 1996 (September). Semantics for an Agent Communication Language. PhD thesis. University of Maryland Graduate School. Baltimore, Maryland 21228--5398.

.... filtering programs [38] to agents that monitor the state of the stock market and detect trends in stock prices, to intelligent web search agents [18] to the digital battlefield where agent technology closely monitors and merges information gathered from multiple heterogeneous information sources [1, 32, 33, 50, 59]. More recently, we have seen an increase in the number of agents that automatically interact with one another. Such agents can negotiate with each other, participate in auctions, make group consensus decisions, and the like [31, 58, 44, 29] In previous work [2, 17, 16] Eiter et al. have ....

Y. Labrou and T. Finin. Semantics for an Agent Communication Language. In International Workshop on Agent Theories, Architectures, and Languages, pages 199--203, Providence, RI, 1997.

.... in natural language [1] This description was unsatisfactory because different users of the language were unsure of the precise meaning of the communication primitives, leading to an inability of their agents to interact The most recent specification of the language included a formal semantics [2], and it is this description of KQML that provides the basis for this report. Knowledge and data Interchange Ask queries Tell data or knowledge to a peer; reply to queries from a peer Advertise capabilities to a peer Invoke side effect operations on a peer Subscribe to services of a peer ....

.... These are defined in KQML by preconditions in the performative semantics (Section 4) Finally, the perlocutionary effects of a KQML speech act are defined by postconditions in the performative semantics (Section 4) 3 KQML Specification This section is based on the most recent KQML definition [2] rather than the original specification document [1] KQML assumes the following properties of the underlying message transport layer: 1 In practice, the application programmer has a significant responsibility in ensuring that the policy conditions are enforced. ffl Any agent may send a ....

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Yannis Labrou. Semantics for an Agent Communication Language. PhD thesis, University of Maryland, Baltimore MD, USA, September 1996.

....should use when issuing a reply. A reply to this message will include the field :in reply to Q42 . Table 1 lists the communication requirements of agents, and cross references these with KQML peformatives that meet the needs. The performatives are as defined in the 1996 KQML specification [3]. The KQML specification defines valid conversations (sequences of messages) A common conversation instance involves a customer agent using the recommend one performative to ask a Broker Agent to put the customer in touch with a supplier agent. The broker obliges, and then drops out of the ....

Yannis Labrou. Semantics for an Agent Communication Language. PhD Thesis, Baltimore, Maryland, 1996.

....di#er, even if structurally the states would be the same. In particular, conversations must distinguish the di#erent types of correct and error end states. Correct : The finite state automaton must admit only the message exchanges that are correct and no others. We note that, for instance, (Labrou 1996) contains some automata that do not follow this rule. Robust to errors : To be robust to errors, the conversation policy must allow error information to be passed at any time. It must have a locally generated error state and a remotely generated error state, as the response to each is di#erent. ....

....an ask conversation if a proposal is accepted. The D state of the negotiation, entered on accepting the proposal, becomes also the I state (begin state) of the ask conversation. A second example is shown for a standby conversation that leads into a stream all, similar to the one described in (Labrou 1996). The following guidelines are appropriate for a conversation that can have another conversation appended to it: The conversation must have a unique terminating state indicating success in the first conversation. The conversations that are to be concatenated must be represented in the ....

Labrou, Y. 1996. Semantics for an Agent Communication Language. Ph.D. Dissertation, UMBC.

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Yannis Labrou. Semantics for an Agent Communication Language. PhD thesis, University of Maryland, Baltimore County, August 1996.

....services. 3.2 Semantics During its first few years of use, KQML existed with only an informal semantic description. Critics identified this as one of its shortcomings [9] During the past few years, researchers have put forth several e#orts to provide a formal semantics. In other works [23] [22] [27] Labrou and Finin provide the semantics of KQML in terms of preconditions, postconditions, and completion conditions for each performative. Assuming a sender A and a receiver B, preconditions indicate the necessary states for an agent to send a performative, Pre(A) and for the receiver to ....

....them through the network using a lower level network protocol. Identical syntaxes guarantee that this infrastructure will be the same regardless of the choice of ACL. These encouraging thoughts do not apply to the semantics of the two languages. Following the KQML semantics described elsewhere, [22] [25] we can see that semantically the two languages di#er at the level of what constitutes the semantic description: preconditions, postconditions, and completion conditions for KQML; feasibility preconditions and rational e#ect for FIPA ACL. They also di#er at the level of the choice and ....

[Article contains additional citation context not shown here]

Yannis Labrou. Semantics for an Agent Communication Language.PhDthesis, University of Maryland, Baltimore County, August 1996.

No context found.

Y. Labrou and T. Finin, "Semantics for an Agent Communication Language," Agent Theories, Architectures and Languages IV,

....agent sends a message, it has expectations about how the recipient will respond to the message. Those expectations are not encoded in the message itself; a higher level structure must be used to encode them. The need for such conversation policies is increasingly recognized by the KQML community [23, 24, 25, 26], and has been formally recognized in the latest FIPA draft standard [16, 12] It is common in KQML based systems to provide a message handler that examines the message performative to determine what action to take in response to the message. Such a method for handling incoming messages is ....

....(PDT) Lin et al. 28] and Cost et al. 9] demonstrate the use of Colored Petri Nets, and Moore [33] applies state charts. Parunak [37] employs Dooley Graphs. Bradshaw [5] introduces the notion of a conversation suite as a collection of commonly used conversations known by many agents. Labrou [23] uses definite clause grammars to specify conversations. While each of these works makes contributions to our general understanding of conversations, more work must be done in getting agents to share and use conversations. 3.4 Defining CommonAgent Services via Conversations A significant ....

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Y. Labrou. Semantics for an Agent Communication Language. PhD thesis, University of Maryland Baltimore County, 1996.

.... to conversations, Nodine and Unruh #Nodine Unruh 1997#, who use conversation speci#cations to enforce correct conversational behavior by agents, Bradshaw #Bradshaw 1996#, who introduces the notion of a conversation suite as a collection of commonly used conversations known by many agents, and Labrou #Labrou 1996#, who uses de#nite clause grammars to specify conversations. While each of these makes contributions to our general understanding of conversations, none show how descriptions of conversations might be shared by agents and used directly by them in implementing conversations. De#ning common agent ....

....threads based on their ID #the value of the reply with #eld#. This directs their assignment to ongoing conversations when possible. If no such assignment can be made, a new conversation appropriate to the message is started. Conversations Based largely on the work of Labrou and Finin #Labrou 1996; Labrou Finin 1997# regarding a semantics for KQML, wehave created protocols, which describe the correct interactions for various performatives and subsequent messages. The protocol for ask one, for example, speci#es among other things that a reply must be a tell, untell, deny, sorry or error. ....

Labrou, Y. 1996. Semantics for an Agent Communication Language. Ph.D. Dissertation, Universityof Maryland Baltimore County.

....Transducers (PDT) Lin et al. 32] and Cost et al. 9] demonstrate the use of CPNs, and Moore [36] applies state charts. Parunak [38] introduces Dooley Graphs. Bradshaw [4] introduces the notion of a conversation suite as a collection of commonly used conversations known by many agents. Labrou [30] uses definite clause grammars to specify conversations. While each of these works makes contributions to our general understanding of conversations, more work needs to be done to facilitate the sharing and use of conversation policies by agents. 2.4 Defining Common Agent Services via ....

....the machine. CPNs make it possible to formalize much of the extra model extensions of DFAs. To make this concrete, we take the example of a standard JDFA representation of a KQML Register conversation (see Figure 1) and reformulate it as a CPN. Note that this simplified Register deviates from the [30] specification, in that it includes a positive acknowledgment, but does not provide for a subsequent unregister event. The graphic depiction of this JDFA specification can be seen in Figure 2. Conversation Template Convention: Initial and accepting states all caps, other states ....

[Article contains additional citation context not shown here]

Yannis Labrou. Semantics for an Agent Communication Language. PhD thesis, University of Maryland Baltimore County, 1996.

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Y. LABROU. SEMANTICS FOR AN AGENT COMMUNICATION LANGUAGE. PHD THESIS DISSERTATION SUBMISSION, UNIVERSITY OF MARYLAND GRADUATE SCHOOL, BALTIMORE, SEPTEMBER, 1996.

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Y. Labrou, T. Finin, Semantics for an agent communication language, in: M. Wooldridge, A. Rao, M. Singh (Eds.), Intelligent Agents IV: Agent Theories, Architectures and Languages, in: Lecture Notes Comput. Sci., vol. 1365, Springer, Berlin, 1998, pp. 209--215.

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Y. LABROU. SEMANTICS FOR AN AGENT COMMUNICATION LANGUAGE. PHD THESIS DISSERTATION SUBMISSION, UNIVERSITY OF MARYLAND GRADUATE SCHOOL, BALTIMORE, SEPTEMBER, 1996.

No context found.

Y. Labrou and T. Finin. Semantics for an Agent Communication Language. In Intl. Workshop on Agent Theories, Architectures, and Languages, pages 199-203, Providence, RI, 1997.

No context found.

Yannis Labrou. Semantics for an Agent Communication Language. PhD thesis, University of Maryland Baltimore County, 1996.

No context found.

Yannis Labrou. Semantics for an Agent Communication Language. PhD thesis, University of Maryland Baltimore County, 1996.

No context found.

Y. Labrou and T. Finin. Semantics for an Agent Communication Language. In Intl. Workshop on Agent Theories, Architectures, and Languages, pages 199--203, Providence, RI, 1997.

No context found.

Y. Labrou. Semantics for an Agent Communication Language. PhD thesis, UMBC, Sep 1996.

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LABROU, Y and FININ, T. Semantics for an Agent Communication Language. Computer science department, UMBC, MD, 1996.

No context found.

Y. Labrou and T. Finin. Semantics for an Agent Communication Language. In Intl. Workshop on Agent Theories, Architectures, and Languages, pages 199--203, Providence, RI, 1997.

No context found.

Y. Labrou, Y Semantics for an Agent Communication Language. PhD Dissertation Thesis. University of Maryland, Baltimore County, USA, 1996.

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