1. A method for validating compliance of an implementation of a process with a specification of said process, comprising the steps of:
modeling said process as a directed acyclic graph having nodes and edges that connect said nodes, wherein said nodes represent stages of said process, and said edges represent transitions between said stages;
defining a coverage model for said graph that includes correct traversal paths and erroneous traversal paths therein;
defining a set of test cases for said implementation according to said coverage model;
executing said implementation using said set of test cases;
observing that one of said erroneous traversal paths was followed in said step of executing; and
responsively to said step of observing, concluding that said implementation comprises a misinterpretation of said specification.
2. The method according to claim 1, further comprising the steps of:
introducing false nodes and false edges into said graph that represent new transitions between said stages and correspond respectively to external misinterpretations of said specification, thereby defining false traversal paths that extend through said false nodes via said false edges;
determining than one of said false traversal paths was followed in said step of executing; and
responsively to said step of determining, concluding that said implementation comprises one of said external misinterpretations.
3. The method according to claim 2, wherein in said coverage model a first correct traversal path and a second erroneous traversal path extend from one of said nodes via different edges, and wherein defining a set of test cases comprises the steps of:
formulating at least one test case of said set of test cases as a constraint satisfaction problem, wherein outcomes at a terminal node of said graph of said one test case differ when calculated according to said first correct traversal path and when calculated according to said second erroneous traversal path; and
solving said constraint satisfaction problem to determine inputs for said one test case.
4. The method according to claim 2, wherein said step of introducing false nodes and false edges is performed at least partially automatically.
5. The method according to claim 2, further comprising the step of defining a coverage metric applicable to said graph.
6. The method according to claim 5, wherein said coverage metric measures coverage of said correct traversal paths and said erroneous traversal paths and said false traversal paths of said graph.
7. The method according to claim 5, wherein said coverage metric measures coverage of said edges and said false edges of said graph.
8. The method according to claim 1, wherein said process comprises behavior of instructions of a processor instruction set architecture.
9. A computer software product for validating compliance of an implementation of a process with a specification of said process, including a tangible computer-readable medium in which computer program instructions are stored, which instructions, when read by a computer, cause the computer to:
model said process as a directed acyclic graph having nodes and edges that connect said nodes, wherein said nodes represent stages of said process, and said edges represent transitions between said stages;
define a coverage model for said graph that includes correct traversal paths and erroneous traversal paths therein;
define a set of test cases for said implementation according to said coverage model;
execute said implementation using said set of test cases; and
responsively to an observation that one of said erroneous traversal paths was followed in an execution of said implementation conclude that said implementation comprises a misinterpretation of said specification.
10. The computer software product according to claim 9, wherein said computer is further instructed to:
introduce false nodes and false edges into said graph that represent new transitions between said stages and correspond respectively to external misinterpretations of said specification, thereby defining false traversal paths that extend through said false nodes via said false edges;
determine than one of said false traversal paths was followed in said execution of said implementation; and
thereafter conclude that said implementation comprises one of said external misinterpretations.
11. The computer software product according to claim 10, wherein in said coverage model a first correct traversal path and a second erroneous traversal path extend from one of said nodes via different edges, and wherein said computer is further instructed to define said set of test cases by:
formulating at least one test case of said set of test cases as a constraint satisfaction problem, wherein outcomes at a terminal node of said graph of said one test case differ when calculated according to said first correct traversal path and when calculated according to said second erroneous traversal path; and
solving said constraint satisfaction problem to determine inputs for said one test case.
12. The computer software product according to claim 10, wherein said computer is further instructed to define a coverage metric applicable to said graph.
13. The computer software product according to claim 12, wherein said coverage metric measures coverage of said correct traversal paths and said erroneous traversal paths and said false traversal paths of said graph.
14. A system for validating compliance of an implementation of a process with a specification of said process, comprising:
a processor;
a memory, accessible to said processor;
said processor executing programs that are stored in said memory, said processor operative to:
model said process as a directed acyclic graph having nodes and edges that connect said nodes, wherein said nodes represent stages of said process, and said edges represent transitions between said stages;
define a coverage model for said graph that includes correct traversal paths and erroneous traversal paths therein;
define a set of test cases for said implementation according to said coverage model;
execute said implementation using said set of test cases; and
responsively to an observation that one of said erroneous traversal paths was followed in an execution of said implementation conclude that said implementation comprises a misinterpretation of said specification.
15. The system according to claim 14, wherein said processor is operative to:
introduce false nodes and false edges into said graph that represent new transitions between said stages and correspond respectively to external misinterpretations of said specification, thereby defining false traversal paths that extend through said false nodes via said false edges;
determine than one of said false traversal paths was followed in said execution of said implementation; and
thereafter conclude that said implementation comprises one of said external misinterpretations.
16. The system according to claim 15, wherein in said coverage model a first correct traversal path and a second erroneous traversal path extend from one of said nodes via different edges, and wherein said processor is operative to define said set of test cases by:
formulating at least one test case of said set of test cases as a constraint satisfaction problem, wherein outcomes of said one test case at a terminal node of said graph differ when calculated according to said first correct traversal path and when calculated according to said second erroneous traversal path; and
solving said constraint satisfaction problem to determine inputs for said one test case.
17. The system according to claim 15, wherein said processor is operative to define a coverage metric applicable to said graph.
18. The system according to claim 17, wherein said coverage metric measures coverage of said correct traversal paths and said erroneous traversal paths and said false traversal paths of said graph.
19. The system according to claim 17, wherein said coverage metric measures coverage of said edges and said false edges of said graph.
20. The system according to claim 16, wherein said process comprises behavior of instructions of a processor instruction set architecture.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A light amplification optical fiber having a core portion, and not less than one layer of clad portion surrounding an outer circumference of the core portion, erbium ions being doped to the core portion, comprising at least one kind of rare earth element ions further doped to the core portion which are other than the erbium ions, and which have ion radius of not lower than 70% and not higher than 130% of that of the erbium ions.
2. A light amplification optical fiber according to claim 1, wherein aluminum is doped to the core portion.
3. A light amplification optical fiber according to claim 2, wherein the number of ions of the aluminum doped to the core portion is not less than 6 times as large as a total ion number of the rare earth element contained in the core portion.
4. A light amplification optical fiber according to claim 1, wherein phosphorus is doped to the core portion.
5. A light amplification optical fiber according to claim 1, wherein a substance reducing a refractive index of pure quartz is doped to the core portion.
6. A light amplification optical fiber according to claim 5, wherein the substance reducing a refractive index of pure quarts is fluorine.
7. A light amplification optical fiber according to claim 1, wherein germanium is doped to the core portion.
8. A light amplification optical fiber according to claim 1, wherein germanium is not substantially doped to the core portion.
9. A light amplification optical fiber according to claim 1, wherein a substance increasing a refractive index of pure quartz is doped to at least a part of the clad portion.
10. A light amplification optical fiber according to claim 9, wherein the substance increasing a refractive index of pure quartz is at least one of germanium, phosphorus and aluminum.
11. A light amplification optical fiber according to claim 1, wherein the concentration of the erbium doped to the core portion is set to as high as over 1000 wtppm.
12. A light amplification optical fiber according to claim 11, wherein the concentration of the erbium doped to the core portion is set to as high as 2000 wtppm level.
13. A light amplification optical fiber according to claim 1, wherein the rare earth element, which is other than erbium, doped to the core portion is an element selected from the group of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb and Lu.
14. A light amplification optical fiber according to claim 1, wherein a relative refractive index difference of the core portion with respect to the clad layer on the immediately outer side of the core portion is smaller than 1.0%.
15. A light amplifier having a light amplification optical fiber adapted to amplify an optical signal, comprising the light amplification optical fiber, which is defined in any one of claims 1-14, as the light amplification optical fiber.