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Show 13 2.5.5 Mneme 1\llneme [17]' is a research prototype that is being deve lop ed at the University of Massac hu sett s, Amhe rst . Tbe i\lln enw s tore provides mechanism s whose policies can lw ch a nged and ex te nd ed . This store is inte nded to be integrated with progranuning lct.ugu ages like Sma\lta ll..:-80 and l\lloclula-:3. i\lln eme bas intern a l ide ntifi e rs for objects in side a fil e . These internal ide ntifi e rs d iT 11 oL 11 secl to name ohj <-'cts frol1l ott ts ide of t he file. In stead , e<Lch fil e b:cts a tabl e wbicb lll a ps external obj ect nam es to internal OIDs. Thus th e exte rnal narne along with t lw i11 ternal OIIJ provid es cllt itt l1111 Ji.ah le JWr s i s t(~ nt OlD to selected obj ecl. s. Tl ti s is hased o tt Llw ass rtmp t io 11 tl"tt few ohjec:ts will need such immu table names. which happ e ns in t he case of a gr aph stru cture. lVl neme prov ides th e notion of ha.nclles to allow a cli ent to amorti ze the lookup cost in a seri es of manipulations of the same object. A handle contains tbe object's identifi er , a pointer to the data part of the object , the size of the object , etc. Applications can also obtain pointe rs to obj ects in buffers , and manipulate objects directl y, IJy j) <'tss ing th e handle int e rfa.ce. Mneme uses files to clus t er obj ects for storage and re tri e val. A file of obj ects 1s se pa ra.t ely nam ed and located within an ove rall di stributed store . Inter-file refer en ces are all owed using forward ers. IVln<~ nw provides the concept of poob which are logical group1ngs of obj ec t s, tmlike files which a re physical groupings. Pools do not span tiles. Each l\lln e rne ohj ecL is associa ted with exact ly one pool , a nd th a t pool determin es t he poli cies like obj ect c reation , obj ect faulting etc. , under which the object is managed. lVl neme provid es se rializability of concurrent reads and writes, leaving more s ttiJtle coucurrency co nt rol to be di ctat ed by tb e appli cation programmer. ln addition , it supports two primitives, mutual e.xclusion and notification. Mutual 1ThP desc ripti on here is based on Mne rne des ign and not on the actual implementation |
