Semantics. Expressions reduce according to a call-by-value strategy, for which we define evaluation contexts thus:
Semantics. SECA comes with four semantics, for different purposes. The standard xxxxx- tics defines how programs are executed. The energy-aware semantics addition- ally traces the energy consumption during program execution in a skyline. The symbolic execution semantics executes all possible paths through a program. The energy-aware symbolic execution semantics traces all possible skylines a program can produce. The focus of this paper is the last one; the others are formally defined in a technical report [19]. Below, we will informally discuss the energy-aware semantics, as it is a useful foundation to understand the energy- aware symbolic execution semantics.
Semantics. This section discusses the semantics of the flow language and the way to integrate it with Event-B. In particular we show how to reason about flow and machine consistency in the terms of machine properties rather than flow or machine traces. But first we use the traces semantics to formally integrate flows with Event-B. The following defines the traces of a flow expression. traces(jskip) = {()} bj j n traces(jstart) = {(jstart)} traces( stop) = {s | n ∈ N ∧ s ≤ ( stop) } b {( )} traces(ei.a) traces(p; q) traces(p|q) traces(∗(p)) traces(pǁEq) ≤ = ei.a b {s z | s z ∈ traces(p) ∧ z = ( stop)}∪ = ^ ^ j {s^t | s^z ∈ traces(p) ∧ t ∈ traces(q) ∧ z =ƒ (jstop)} b = traces(p) ∪ traces(q) b | ∗ = traces(p (p; (p))) =b {S(sǁEt | s ∈ traces(p) ∧ t ∈ traces(q)} Here s t states that trace s is a prefix of trace t; α(x) is an alphabet of x (set of all events occurring in x). The parallel composition operator is defined as a collection of possible event interleavings:
Semantics. The semantics of the language of agreements L is based on a possible worlds model We rst de ne a class of models M De nition M hW i is a tuple associating the possible multi agent world states W a function that assigns truth values to formulae and an acces sibility relation associated to programs W Wx Wx Wxn with xi Agents is the set of tuples representing the possible multi agent worlds or states where each multi agent state is a tuple of individual agent states Wxi is used to denote the set of possible worlds from xi s perspective W is a function that assigns to formulae the set of multi agent worlds in which they hold Now focusing on the actions performed by agents within a multi agent system we de ne the set of paths along which the state of the multi agent system may pass This set of paths is used to de ne our notion of commitment i e what it means for an agent to be bound to uphold an agreement see constraints " in table De nition The set of possible paths starting at state along which the multi agent system may pass Paths is de xxx as and s t i i g The precedence relation p is de xxx for multi agent states along a path p as i p j i i j p is similarly de xxx We say that i p Paths such that p For our purposes the class of models of L that we are interested in are those that satisfy constraints " see table To determine whether some action or action sequence has actually been performed the history of what actions have been performed and by what agents must be recorded in each state Therefore as each state has a unique history state transitions must be strictly diverging C so we have a branching struc ture of states For our purposes we require that the action that has just been done is recorded within each state C and that actions never fail i e the e ects of an action hold whenever it has just been done C C means that agreements involving an action that must be done may be true only in those states from which there is at least one course of action leading to the performance of that action In other words agents cannot agree on the performance of impossible actions C is the obvious constraint for conjuncts of such agree ments Note that we do not restrict agreements con cerning rights in this way The reason for this is that it is not necessary for rights to be exercised This may C if a and b then and a b C Done x a i W and ax C if Done x a then E a
Semantics. Figure 3 defines the semantic domains and the inference rules for a big-step evaluation judgment of the form x, R, W € H; u; e ‹→ Hj; uj; v ∈ R W R W This judgment declares that given a variable environment ρ and indexed collections and of read and write permissions, the expression e transforms the initial heap H to the final xxxx Xx and returns value v. Furthermore, it threads a time stamp u, uj Stamp that is incremented at each property write operation and at each permit expression. The permission collections and are indexed by the time stamps of the heaps for which the permissions were granted. The time stamp of a permission uniquely identifies different executions of permit expressions and determines their relative order with respect to heap modifications. ∈ M M A value v Val is either a reference or a closure consisting of an environment and a lambda expression. The representation of a reference is a pair of a heap address A and a collection of access paths, indexed by time stamps. The collection records all permitted access paths that have been traversed during evaluation so far to obtain this reference value. The indexing is again used for marking modifications with time stamps. This representation is dictated by the design choice of path dependency (see Sec. 2.1). A heap maps a location to an object and an object maps a property name to a pair of a time stamp and a value. The time stamp indicates the time of the write operation that last assigned the property. It is required to implement the “sticky update” from Sec. 2.4. x, R, W € H; u; e0 ‹→ H ; u ; (ρ , λx.e) ρ, R, W € Hj; uj; e1 ‹→ Hjj; ujj; v1 ρj[x ›→ v1], R, W € Hjj; ujj; e ‹→ Hjjj; ujjj; v x, R, W € H; u; e0(e1) ‹→ Hjjj; ujjj; v NEW A ∈/ dom(H) ρ, R, W € H; u; new ‹→ H[A ›→ ∅]; u; (A, ∅) PUT x, R, W € H; u; e1 ‹→ Hj; uj; (A, M) x, R, W € Hj; uj; e2 ‹→ Hjj; ujj; v W €chk M.p Hjjj = Hjj[A ›→ Hjj(A)[p ›→ (ujj, v)]] x, R, W € H; u; e1.p := e2 ‹→ Hjjj; ujj + 1; v GET x, R, W € H; u; e ‹→ Hj; uj; (A, M) R €chk M.p < x, R, W € H; u; e.p ‹→ Hj; uj; M.p Hj(A)(p) PERMIT ρj, R[u ›→ Lr ], W[u ›→ Lw ] € H; u + 1; e ‹→ Hj; uj; v ρj = ρ[x ›→ ρ(x) a [u ›→ ε]] x, R, W € H; u; permit x : Lr, Lw in e ‹→ Hj; uj; v
Semantics. From the semantic viewpoint a major objective is a clear semantic dissemination of all measured and calculated values for the integration into the VIM. In order to achieve this goal, the Collaborative Semantic Vocabulary Creation Cycle (CSVCC) will be introduced. (1) The CSVCC five-step plan helps to systematically collect the required data for the controlled semantic declaration of values, (2) provides common understanding of data to all participants (users, developers, experts, and doctors, (3) maintain the quality of the controlled vocabulary at a high level. The PRECIOUS vocabulary collection phase currently utilises an online vocabulary management system for collecting parameter definitions from PRECIOUS partners (see Figure 21).
Semantics check permission ∀u ∈ dom(P) ∩ dom(M) : M(u) ∈ P(u) P ▶M M Fig. 3. Checking permissions. ( ❽M (u, v) := (l, M u N ) if v = (l, N ) 8>N (u') if u' ∈ dom(N ) v if v ∈/ Ref (M ❽ N )(u') := <M(u') if u' ∈ dom(M)\dom(N ) ∧ u < u' > u undefined if u' ∈ dom(M)\dom(N ) ∧ u ≥ u' (M(u).p if u ∈ dom(M)M :undefined if u' ∈/ dom(M) ∪ dom(N ) ( .p)(u) := undefined if u ∈/ dom(M) Fig. 4. Auxiliary definitions. R ▶ M M .p checks the read permission for these paths extended with property ❽u
Semantics. To provide semantics for syntactical constructs, we need to describe their meanings in terms of some well-known semantic domain. This implies describing syntactical elements in terms of a formal, mathematical framework (denotational approach), a set of logical rules (axiomatic approach), or a set of rules for execution on an abstract machine (operational approach).
Semantics. The study of semantics discusses the connection between conventional meaning and words. An intriguing question to ask is: What can semantics tell us about the word “prayer”? Certainly, background analysis of this concept and its semantic qualities would appear to answer questions posed in this thesis. However, there is an important nuance between a semantic study of the word “prayer” and a qualitative linguistic study of the concept of prayer. Most simply put, a semantic study is much narrower than a qualitative linguistic study. Although the concept of prayer includes all the denotations of the word “prayer,” all the semantic meanings of the word “prayer” do not completely explain the concept of prayer. The semantics of the concept of prayer include semantic patterns of words that occur in prayer. Crucially, the word “prayer” need not actually occur during prayer. Understanding the meaning of a word in one language is not enough to understand the concept across languages and cultures. Exhibit F: Different conceptions of prayer in different languages.63 There are categories of concepts that are represented by the different words for prayer in different languages. However, no one set of these semantic manifestations contains all of the concepts that make up the “universal” concept of prayer. This thesis hypothesizes that there exists a concept of prayer that is relatively consistent and stable across cultures and languages. This concept manifests itself in language, and the ways that it does so may differ from culture to culture. The English word “prayer” brings to mind a set of concepts, many of which are part of the larger concept of prayer, but might not accurately represent how a greater population of humanity views it. Therefore, a semantic examination of the word “prayer” would only yield a subset of relevant concepts. Relevant are the semantic trends that occur across the languages and cultures examined in this study sample. 63This exhibit is meant to simplify the difference highlighted between conceptions of prayer. In reality, this graphic would be much more complicated with the smaller circles overlapping with each other to exemplify the concentration of concepts that each word shares across languages. For instance, there are likely overlapping concepts between “prayer” and oracíon, but the purpose of the graphic is to show that neither of them separately can adequately explain larger concept of prayer. One of the strongest semantic trends is the ...
Semantics. AVCConfig – SHALL contain sufficient sequenceParameterSetNALUnit and pictureParameterSetNALUnit entries to describe the configurations of all samples referenced by the current track fragment. Note: AVCDecoderConfigurationRecord contains a table of each unique Sequence Parameter Set NAL unit and Picture Parameter Set NAL unit referenced by AVC Slice NAL Units contained in samples in this track fragment. As defined in [ISOAVC] Section 5.2.4.1.2 semantics: • sequenceParameterSetNALUnit contains a SPS NAL Unit, as specified in [H264]. SPSs shall occur in order of ascending parameter set identifier with gaps being allowed. • pictureParameterSetNALUnit contains a PPS NAL Unit, as specified in [H264]. PPSs shall occur in order of ascending parameter set identifier with gaps being allowed.
