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| It is aimed to be as the final version for the official HeKatE project (grant). | It is aimed to be as the final version for the official HeKatE project (grant). | ||
| + | //Please put bigger remarks/discussusion, to the [[hekatedev:xtt2|XTT2 development page]]// | ||
| ===== Introduction ===== | ===== Introduction ===== | ||
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| In contrast to traditional rulebases design approaches allowing for a //flat// (single-level) set of rules (e.g. using the Rete-based inference engines) XTT introduces an explicit //structure// in the rulebase, by introducing: | In contrast to traditional rulebases design approaches allowing for a //flat// (single-level) set of rules (e.g. using the Rete-based inference engines) XTT introduces an explicit //structure// in the rulebase, by introducing: | ||
| - | * //tables//, used to represent groups of rules working in the same context and hence having similar structure of preconditions, | + | * //tables//, used to represent groups of rules working in the same context (having similar structure of preconditions), |
| * //intertable links//, used to provide explicit specification of inference control, namely switching between tables, that allow for decision-tree like structure. | * //intertable links//, used to provide explicit specification of inference control, namely switching between tables, that allow for decision-tree like structure. | ||
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| XTT is a formal method based on an expressive logical calculus called //Attributive Logic// (or //Attribute Logic//). | XTT is a formal method based on an expressive logical calculus called //Attributive Logic// (or //Attribute Logic//). | ||
| - | |||
| ==== History and Related Documents ==== | ==== History and Related Documents ==== | ||
| FIXME | FIXME | ||
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| However, in the future the ARD+ shall be replaced by more advanced methods. | However, in the future the ARD+ shall be replaced by more advanced methods. | ||
| - | Basing on the above experiences, the current version of XTT known as XTT^2 has been proposed for the HeKatE project by Grzegorz J. Nalepa and Antoni Ligęza in 2008. | + | Based on the above experiences, the current version of XTT known as XTT^2 has been proposed for the HeKatE project by Grzegorz J. Nalepa and Antoni Ligęza in 2008. |
| XTT^2 uses ALSV(FD) (//Attributive Logic with Set Variables over Finite Domains//) as the formal foundation. | XTT^2 uses ALSV(FD) (//Attributive Logic with Set Variables over Finite Domains//) as the formal foundation. | ||
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| ==== XTT Constraints ==== | ==== XTT Constraints ==== | ||
| - | Rule prototypes these hint for XTT tables: | + | Rule prototypes provide hints for XTT tables: |
| * structure -> what attributes are in the condidtion and conclusion | * structure -> what attributes are in the condidtion and conclusion | ||
| * state changes in conclusion -> in the value modification only attributes present in the given table may be used | * state changes in conclusion -> in the value modification only attributes present in the given table may be used | ||
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| See [[hekate:xtt2#Inference]] for more details. | See [[hekate:xtt2#Inference]] for more details. | ||
| - | |||
| ==== Rule RHS ==== | ==== Rule RHS ==== | ||
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| The rule RHS can contain: | The rule RHS can contain: | ||
| - | * state changes, that is attribute values modifications (with use of retract/assert), possibly with use of any predefined predicates/functions etc. for now we assume all the results are explicitly represented in state! | + | * state changes, that is attribute values modifications (with use of retract/assert, FIXME by iw: there is no assert/retract anymore, assuming that attributes can be multivalued, there are only set operations, an assert is represented as a sum: assert(A(1)) <=> A = A u {1}), possibly with use of any predefined predicates/functions etc. for now we assume all the results are explicitly represented in state! |
| * external actions execution, that do not change attribute values, thus do not change the system state; these include output values definition and export, | * external actions execution, that do not change attribute values, thus do not change the system state; these include output values definition and export, | ||
| * link that specifies inference control (e.g. a switch/case or a loop), | * link that specifies inference control (e.g. a switch/case or a loop), | ||
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| A table provides a //visual// representation of rules, as below. | A table provides a //visual// representation of rules, as below. | ||
| - | {{xttp-table-new.png|XTT table new format}} | + | {{xttp-table-new.png|XTT table new format}} FIXME |
| Rules in the table are interpreted one by one in a given way (see [[hekate:xtt2#Inference]]), this is the Table Inference. | Rules in the table are interpreted one by one in a given way (see [[hekate:xtt2#Inference]]), this is the Table Inference. | ||
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| * //rule-table// (r2t) a given rule in a given table when fired, transfers control to another table, meaning the inference starts at the first rule of the destination table. This is considered the //default// for XTT^2. | * //rule-table// (r2t) a given rule in a given table when fired, transfers control to another table, meaning the inference starts at the first rule of the destination table. This is considered the //default// for XTT^2. | ||
| * //rule-rule// (r2r) a given rule in a given table when fired, transfers control to another rule in another table, or possibly //the same table// (inside table link. | * //rule-rule// (r2r) a given rule in a given table when fired, transfers control to another rule in another table, or possibly //the same table// (inside table link. | ||
| + | |||
| + | FIXME: iw: I'm still not convinced about rule-rule links, any advantages? There are some disadvantages though, ie: if we change the rule firing order (let's say bottom-up instead of top-down,) rule-rule links can screw us really bad. Having rule-table links only forces designer to come up with well designed conditions. So, because there are some doubts I would recommend not implementing it for time being at all. | ||
| ++++More on intertable links| | ++++More on intertable links| | ||
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| (See the discussion at the [[hekatedev:xtt2#Branching]] page.) | (See the discussion at the [[hekatedev:xtt2#Branching]] page.) | ||
| + | |||
| + | //A temporary semi-parallel solution//: | ||
| + | ARD introduces partial order in tables, | ||
| + | tables can be fired in any way, | ||
| + | as long as this contstraint holds. | ||
| + | |||
| + | FIXME: iw: not really there might be more than one table with input attributes (or ro, rw) in the condition parts, it might be not doable to infer which table should be run first. | ||
| + | There might be an algorithm implemented which finds an order of execution (which table to start with), but any conditions using a N/D value can screw it. | ||
| + | I'd suggest choosing an entry table, the one that the inference process starts with, explicitly. | ||
| ==== Interpreter Scenarios ==== | ==== Interpreter Scenarios ==== | ||
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| * communication (comm) (S <-> E) | * communication (comm) (S <-> E) | ||
| Arrows indicate the System/Environment interaction. | Arrows indicate the System/Environment interaction. | ||
| + | |||
| + | FIXME: iw: what's happened to ''ro, rw, wo, state'' classes? | ||
| Discuss ideas here: [[hekatedev:xtt2#Attribute Classes]]. | Discuss ideas here: [[hekatedev:xtt2#Attribute Classes]]. | ||
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| ===== HeKatE Meta Representation ===== | ===== HeKatE Meta Representation ===== | ||
| - | |||
| - | FIXME ALi | ||
| The following textual algebraic representation is provided. | The following textual algebraic representation is provided. | ||
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| Fact: | Fact: | ||
| - | FIXME ALi | + | |
| - | Here - sorry; I am not sure about the idea -- do not understand. Explanations necessary. | + | |
| ===== XTT Analysis ===== | ===== XTT Analysis ===== | ||
