computer operating system built on top of open source linux kernel

... iPhone App The web browser built into the iPhone is one of the most advanced browsers on the market. Features such as CSS transi- tions and animation were part of the iPhone Mobile Safari web browser ... although jQTouch is built using HTML5 standards on top of the jQuery framework, it has not been optimized to run on all devices. For instance, response time on Windows Phone 7 has not been ... 3.16. Location Aware Solutions The final plug-in leverages the geolocation features built into the phone to present the longitude and latitude of your current position. This one will take a little...

Ngày tải lên: 29/04/2014, 15:25

Ngày tải lên: 18/10/2014, 15:30

Ngày tải lên: 29/10/2014, 13:42

... safely deploy Linux in a mission critical environment.” (otn.oracle.com/tech /linux) HP: “HP is hosting a number of open source software projects that run on various HP systems.” (opensource.hp.com) Apple: ... difficult to estimate the size of open source software in- dustry”. Pure open source companies are tiny and many of them are pri- vately held. However, the popularity of open source is significant and practically ... for both systems and applications FROM PROPRIETARY TO OPEN ã 18 Operating system: BSD*, Linux* , Solaris, Windows Server software: Apache*, Microsoft IIS, SunONE, Zope* Database: Microsoft SQL,...

Ngày tải lên: 07/03/2014, 11:20

... general. In this chapter, we report on the results of a continuing study of the effort and motivations of individuals to contributing to the creation of Free /Open Source software. We used a Web-based ... engineer- ing, of organizations and organizing, of the software industry, and of software as a component of contemporary society. JF, BF, SAH, and KRL phenomenon. Starting with the collapse of the Berlin ... Software Development 79 4 Standing in Front of the Open Source Steamroller 81 Robert L. Glass 5 Has Open Source Software a Future? 93 Brian Fitzgerald 6 Open Source Software Development: Future or Fad?...

Ngày tải lên: 11/06/2014, 15:25

Ngày tải lên: 18/10/2014, 15:30

... context switching and scheduling. One of the goals of Mach is to provide an extensible kernel basis upon which operating system environments such as UNIX can be built. Emulation of UNIX-like system ... exception of the hardware validation, all of these steps are implemented in a machine-independent fashion. 17 8.2. Copy -On- Reference Task Migration One of the thorniest problems of task migration ... experimental addition. A production version of Mach is in use on over 200 workstations and large timesharing systems within the CMU Department of Computer Science. It is also being used on dozens of machines...

Ngày tải lên: 12/09/2012, 15:05

... evaluation and description of distributed systems characterized by sequen- tiality, concurrency, synchronization, among others. Specifi- cally, the GSPN [8] is one of the several extension of standard PNs ... transitions were supposed to have constant probability of firing. However, there is a strong correlation between the operating conditions of power systems and the probability of harmful events. To consider ... produce different consequences depending on the power system state. In conclusion, the reliability of protection schemes, understood as the union of dependability and security, and its dependency on the system...

Ngày tải lên: 03/01/2014, 19:35

... function of subsystem ; is the number of components in subsystem i ; i n i M is the number of possible states of subsystem i . is the performance of subsystem i ; is the corresponding ... function of the system; is the number of subsystems in the system; N sys M is the number of possible states of the system; s G is the performance of the system; s q is the corresponding ... multi-state system theory. II. P ROBLEM F ORMATION The power system is composed of eight identical batteries. A branch c onsists of two batteries connected in series, and the system consists of...

Ngày tải lên: 03/01/2014, 19:38

... 267.66 cm -1 of the deformation mode and 802.5 cm -1 of covalent bonds W – O, there is only one clear modification, comparing to Raman spectra of film on thinner ITO layers. The only difference ... crystalline phase of WO 3 . The Raman peak at 256.6 cm -1 indicates the deformation vibration of O – W – O bond and 600 – 900 cm -1 region relates to stretching vibrations of W – O bonds [24]. The ... Gaussian function. This information gives us exact evaluation of the existence of different phases in our films. 3. Results and discussion 3.1. The effect of the thickness of ITO layer on XRD spectrum...

Ngày tải lên: 13/02/2014, 03:20

... collapse. Pulmonary function tests Specifics of pulmonary function testing in an older population The application of conventional quality control standards to objective assessment of pulmonary function ... index de- scribes the relationship between force of contraction (Pdi/Pdi max ) and duration of contraction (ratio of inspiratory time to total respiratory cycle duration [TI/TTOT]) and is related ... Quality control of spirometry in the elderly. The S.A.R.A. study. SAlute Respiration nell’Anziano = Respiratory aging of the respiratory system 481 Aging of the Respiratory System: Impact on Pulmonary Function...

Ngày tải lên: 05/03/2014, 21:20

... conformational states. Open conformation of WtDSD is shown in dark grey while the closed conformation of SeMetDSD is shown in light grey. The small domains are related by a residual rotation of 15°. ... for the cofactor under crystallization conditions. Interestingly, unexpected conformational differences were observed between the two struc- tures. The WtDSD was in an open conformation while ... reac- tions catalysed include the transfer of amino group, decarboxylation, inter-conversion of l- and d-amino acids and removal or replacement of chemical groups at a, b or c positions [1]. Functionally,...

Ngày tải lên: 28/03/2014, 22:20

... Figure 5: Acquiring the Virtual Relations PKCONT and HEMIC window for questions and answers. When the DBE uses the mouse to select one of the items from the three menus, a set of questions appears in the question-answering area at the bottom of the display, to which he can then respond. One of the general principles of acquisition is evident from this display, namely, that the acqui sition is centered upon the relations and fields in the database, because this is the information most familiar to the DBE. The answers to each question can affect the lexicon, the conceptual schema, and the database schema. The DBE need not be aware of exactly why TEAM poses the questions it does—all he has to do is answer them correctly. Even the entries displayed in the word menu owe their presence to questions about the database. The DBE volunteers entries to this menu only in the case of verb acquisition, to supply an adjective corresponding to some noun already in TEAM’s lexicon, or to enter a synonym for some lexicon-resident word. The DBE is assumed not to have any knowledge of formal linguistics or of natural-language processing methods. He is assumed, however, to know some general facts about English—for example, what proper nouns, verbs, plurals, and tense are, but nothing more detailed than that. If more sophisticated linguistic information is required, as in the case of verb acquisition, TEAM proceeds by asking questions about sample sentences, allowing the DBE to rely on his intuition as a native speaker, and extracting the information it needs from his responses. Virtual relations are specified iconically. The left side of Figure 5 shows the acquisi tion of a virtual relation that identifies the continent (PKCONT-CONTINENT, derived from WORLDC-CONTINENT) of a peak (PKCONT-NAME, from PEAK-NAME) by performing a database join on the PEAK-COUNTRY and WORLDC-CONTINENT fields. Similarly, the right side of Figure 5 shows the acquisition of the virtual relation that encodes the hemisphere (HEMIC-HEMI) of a country (HEMIC.NAME) by joining on the WORLDC-CONTINENT and CONT-NAME fields. If he wishes, the DBE can change previous answers. Incremental updates are possible because most of the methods for updating the various TEAM structures (lexicon, schemata) were devised to undo the effects of previous answers before the effects of new answers could be asserted. Help information is always available to assist the DBE when he is unsure how to answer a question. Selecting the question text with the mouse produces a more elaborate description of the information TEAM is trying to elicit, usually accompanied by pertinent examples. Finally, the acquisition component keeps track of what information remains to be supplied before TEAM has the minimum it needs to handle queries. The DBE does not have to determine himself how much information is sufficient; all he has to do is to perceive that no acquisition window indicates remaining unanswered questions. Of course, the DBE can always provide information beyond the minimum—for example, by supplying additional verbs, derived adjectives, or synonyms. — 20 — ... schema;7, hence, the choice of logical form indirectly affects the design of those components of the system and determines, in part, the information the DBE must supply. The logical form employed by TEAM is first-order logic extended by certain intensional and higher-order operators and augmented with special quantifiers for definite determiners and inter rogative determiners. Much research has been done to devise appropriate logical forms for many kinds of sentences Moor8l], but that investigation lies beyond the scope of this article. 2.3 What Information Is Acquired 2.3.1 The Lexicon The lexicon is a repository of the information about each word that is necessary for morphological, syntactic, and semantic analysis. There are two classes of lexical items: closed and open. Closed classes (e.g., pronouns, conjunctions, and determiners) contain only a finite, usually small number of lexical items. Typically, these words have complex and specialized grammatical functions, along with at least some] fixed meanings that are independent of the domain. They are likely to occur with high frequency in queries to almost any database. Open classes (e.g., nouns, verbs, adjectives) are much larger and the meanings of their members tend to vary, depending on the particular database and domain. Therefore, most closed-class words are built into the initial TEAM lexicon, while open- class words are acquired for each domain separately. However, there are a number of open- class words, such as those corresponding to concepts in the initial conceptual schema (see Section 2.3.2) and words for common units of measure (e.g., “meter”, “pound”), that are so broadly applicable to so many database domains that they are included in the initial lexicon as well. Lexical entries include those for the names of file subjects (i.e., the entities about which some relation contains information—e.g., peaks for PEAK, and countries for WORLDC in the sample database illustrated in Figure 1.3), field names, and field values. In addition, the DBE can supply adjectives and verbs, as well as synonyms for words already acquired (see Section 2.4). Associated with every lexical entry is syntactic and semantic information for each of its senses. Syntactic information consists of its primary category (e.g., noun, verb, or adjective), subcategory (e.g., count, unit, or mass for nouns; object types for verbs), and morphology. Semantic information depends on the syntactic category. The entry for each noun includes the sort(s) or individual(s) in the conceptual schema (Section 2.3.2) to which that noun can refer. Entries for adjectives and verbs include the conceptual predicate to which they refer, plus information about how the various syntactic constituents of a sentence map onto arguments of the predicate. Scalar adjectives (e.g., “high”) also include an indication of direction on the scale (plus or minus). 2.3.2 Conceptual Schema The conceptual schema contains information about the objects, properties, and relations in the domain of the database. It includes sets of individuals, predicates, constraints on the arguments of predicates, and the information needed for certain pragmatic processing. The informational content is similar to that commonly encoded in semantic networks, but the apparatus used is more eclectic. The conceptual schema consists of a sort hierarchy and descriptions of various properties of nonsort predicates. The sort hierarchy relates certain monadicj predicates that play a primary role in categorizing individuals. These are called sort predicates (represented here in italics as in PERSON). TEAM was designed with a considerable amount of this conceptual information built in. Figure 3 illustrates 7As noted previously, the specific form depends also on general syntactic, semantic, and pragmatic rules for English that are encoded in the various components of DIALOGIC. — 16 — ... continent of the country. Likewise, the hemisphere in which a country is located can be determined from the continent on which the country is located and the hemisphere of that continent. TEAM allows the DBE to specify virtual relations that convey such additional information. 2 The TEAM System Architecture The design of TEAM reflects several constraints imposed by the demand for transportability; our discussion will emphasize those aspects of the design. The need to decouple the representation of what a user means by a query from the procedure for obtaining that information from the database obviously affected the choice of system components. In addition, the need to separate the domain- dependent knowledge to be acquired for each new database from the domain-independent parts of the system influenced the design of the particular data structures (or “knowledge sources”) selected for encoding the information used by these components. Figure 2 illustrates the major processes of TEAM, the various sources of knowledge they use, and the flow...

Ngày tải lên: 30/03/2014, 22:20

... used to deflect the reading beam very fast. As a result, it is much faster to retrieve information from tracks that are located near the current location of the reading head. We call this a span access capability. The span access capability of optical disks has implications for scheduling algorithms and data structures that are appropriate for optical disks, as well as significant impact on retrieval performance Christodoulakis 87a]. In Christodoulakis 87] we also derive exact analytic cost estimates as well as approximations that are cheaper to evaluate, for the retrieval of records and longer objects such as text, images,voice, and documents (possibly crossing block boundaries) from CAV optical disks. These estimates may be used by query optimizers of traditional or multimedia data bases. Retrieval Performance of CLV Optical Disks Constant Linear Velocity (CLV) optical disks have different characteristics than the CAV optical disks. CLV optical disks vary the rotational speed so that the unit length of the track which is read passes under the reading mechanism in constant time, which is independent of the location of the track. This has implications on the rotational delay cost which, in CLV disks, depends on the track location. This also implies that, in CLV disks, the number of sectors per track varies (outside tracks have more sectors). The latter (variable capacity of a track) has many fundamental implications on selection of data structures that are desirable for CLV optical disks and the parameters of their implementation, for the selection of access paths to be supported for data bases stored on CLV disks, as well as for the retrieval performance and the optimal query processing strategy to be chosen. (These implications are studied in detail in Christodoulakis 87b], in which is shown that these decisions depend on the location of data placement on the disk.) Analytic cost estimates for the performance of retrieval of records and objects from CLV disks are also derived in Christodoulakis 87b]). These estimates may be used by traditional or multimedia query optimizers. It is shown that the optimal query processing strategy depends on the location of files on the CLV disk. This implies that query optimizers may have to maintain information about the location of files on the disk. Estimation of Selectivities in Text In multimedia information systems much of the content specification will be done by specifying a pattern of text words. Queries based on the content of images are difficult to specify, and image access methods are very expensive. Voice content is transformed to text content if a good voice recognition 18 ... A join index captures the semantic links that exist between tuples. If we view the join of two tuples as an arc connecting those tuple identifiers, a join index can represent directed graphs in a very com pact way. Therefore, it will be very useful to optimize graph operations like transitive closure. Let us consider again the PART relation: PART (pname, weight, price, spname) where spname is the name of a subpart (or component part). Assuming that PID and SPID stand for PART tuple identifiers, then we can have two join indices (each clustered on its first attribute) Jl1 (PID, SPID) J12 (SPID, PID) J11 associates a part_id with its subpart_id’s, while J12 associates a subpart_id with its parent part_id. Therefore, Jl1 is well suited for traversals in the part—subpart direction. J12 allows efficient traversals that follow the subpart—part direction. Assuming that a recursive query is mapped into a conceptual query tree of relational algebra operators and transitive closure, the query optimization algorithm discussed in Section 3 still applies. However, the introduction of transitive closure yields a larger solution space, since transitive closure may be permuted with other relational operators (e.g., select and join). The transitive closure operator can be implemented efficiently by a loop of joins, unions, and possibly difference (for cyclic relations). Superior performance is consistently attained when transitive closure is applied using join index rather than the primary copy of the relation Valduriez 86a]. For instance, let us consider the recursive query on the PART relation “list the component parts and their prices for part A”. Figure 3 illustrates the corresponding query tree and a possible processing tree, in which transitive closure (noted IC) is ap plied to the join index. The selection “pname = A” precedes the transitive closure so that only those parts that are (transitively) components of part A are produced. In the PT, the result of the transitive closure on join index JI is a set of pairs (PID of A, PID of a subpart of A). Therefore, an additional join with relation PART is necessary to complete the query. Thus, the most complex part of the query is done on small data structures (selection index, join index). The value of performing the transitive clo sure using join index is to avoid repeated access to relation PART, which is potentially much larger than the join index. pname_IND PART Jl1 (PID, SPID) PART a pname = A a pname = A / PART SPID 1~1 PID ‘IT pname, price ‘~ pname, price Query Tree PT with Join Index Figure 3: Processing of a Recursive Query with Join Index 5. Conclusion Join indices are data structures especially designed to speed up join operations. The incorporation of join indices in a storage model provides the query optimizer with a larger solution space and hence more opportunities for optimization. We have illustrated the use of join indices to optimize non—recur- 15 ... condition of the form: “Name restriction”. The restriction applies to both components whose path-names are Sender.Name and Receiver.Name. The problem is to decide how such a condition is satisfied. There are four possibile interpretations: (1) Name restriction = True if (Sender.Name restriction = True) A (~ (Receiver.Name restriction = True)) (2) Name restriction = True if (Sender.Name restriction = True) A (V (R.eceiver.Name restriction = True)) (3) Name restriction = True if (Sender.Name restriction = True) V (V (Receiver.Name restriction = True)) (4) Name restriction = True if (Sender.Name restriction = True) V (3 (Receiver.Name re8triction = True)) Our system uses the third interpretation, since it is the most general: the answer to query (3) contains the answers to queries (1), (2), and (3). This choice reflects the approach of giving to the user the most general answers, when there are ambiguities in the query. Then, the user, who did not know exactly the types defined in the document base, can refine the the original query specifying exactly the meaning of the query. The four different semantics, in our query language, can be specified explicitly as: (1) Sender.Name restriction and some Receiver.Name restriction (2) Sender.Name restriction and every Receiver.Name restriction (3) Sender.Name restriction or every Receiver.Name restriction (4) Sender.Name restriction or some Receiver.Name restriction In addition to the previous types of conditions, the language must allow conditions on the existence of conceptual components within documents. This allows expressing queries on the conceptual structure of documents. Therefore we have defined the operator “with”. A condition containing the “with” operator has the form: “with component”. This condition expresses the fact that the component whose name (or pathname) is given must be a conceptual component of the documents to be retrieved. To express conditions that require that a conceptual component having name narne~ is contained in a conceptual component having name name,, the path-name name1 * name, is used. The “with” operator is conceptually very important in our query language. While the other operators allow the definition of conditions on data (ie. document instance), the “with” operator allows the definition of conditiou8 on meta-data (ie. document types). An example query that will be used throughout this paper is: find documents where Document.Date > /1/1/1987/ and (*Sender.Name = “Olivetti” or *ProductYresentation contains “Olivetti”) and *Product.Description contains “Personal Computerl” and (*Address.Country = “Italy” or text contains “Italy”) and with *CompanyLogo; It should be noticed that no type is specified for this query. As we will see, one of the tasks associated with Type-Level Processing is to determine the type(s), if any, to which the query applies. 3. Initial Steps in Query Processing The task of query processing consits of several steps, some of which are concerned with query opti mization IBERT87I. In this paper we consider the pre-processing steps, in which some initial activities are performed, such as query parsing and accessing the type catalog. Also during this phase, the query is modified in light of the type hierarchy. 3.1. Parsing The query is parsed by a conventional parser. The parser verifies that...

Ngày tải lên: 30/03/2014, 22:20

... synchronization because of the use of correlators [3]. Due to the limitations in Rake receivers, many researchers shift their research to non-coherent UWB methods. As one of the conventional non-coherent ... spread for GFSK and PPM systems despite the pulse duration of a GFSK system is twice that of a PPM system. We also verify our conclusion using the Matlab code in [22] and these two systems both obtain ... study on performance of an IR-UWB receiver based on energy detection, in IEEE International Conference on WiCOM, Dalian, China, pp. 1–5, 2008 3. N He, C Tepedelenlioglu, Performance analysis of non-coherent...

Ngày tải lên: 18/06/2014, 22:20

... effect of synchronization errors on system performance is analyzed in Section 5. In Section 6, the numerical results are analyzed. In Section 7, the conclusions are stated. 2 System models 2.1 System ... The orthogonality of a GFSK system is achieved in the frequency domain. Although the integration interval and synchronization error also affect performance of a GFSK system, its orthogonality is ... pulse duration. Although the single pulse duration of a GFSK system is twice that of a PPM system, but the values of D are almost the same. Because the multipath components in these two system arrive...

Ngày tải lên: 20/06/2014, 04:20

... system is at most one half of that of a PPM system. But this does not mean that the maximum possible data rate of a G FSK systemisonehalfofthatofaPPMsystem.InUWB channels, the multipath components ... study on performance of an IR-UWB receiver based on energy detection. in IEEE International Conference on WiCOM, Dalian, China 1–5 (2008) 3. N He, C Tepedelenlioglu, Performance analysis of non-coherent ... bandpass filter with notched band for the rejection of 5 GHz WLAN using hexagonal multiple mode resonator. in IEEE International Conference on Communication Control and Technologies, Ramanathapuram,...

Ngày tải lên: 20/06/2014, 21:20

... â2005 Operating System Concepts 7 th Edition, Jan 12, 2005 Four Components of a Computer System Four Components of a Computer System 1.13 Silberschatz, Galvin and Gagne â2005 Operating System Concepts ... Gagne â2005 Operating System Concepts 7 th Edition, Jan 12, 2005 Chapter 1: Introduction Chapter 1: Introduction  What Operating Systems Do  Computer- System Organization  Computer- System Architecture  ... aspects of system z Loads operating system kernel and starts execution 1.4 Silberschatz, Galvin and Gagne â2005 Operating System Concepts 7 th Edition, Jan 12, 2005 What is an Operating System? What...

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Ngày tải lên: 23/07/2014, 23:20