[904] | 1 | <!-- ******************************************************** --> |
---|
| 2 | <!-- --> |
---|
| 3 | <!-- [History] --> |
---|
| 4 | <!-- Converted to DocBook: Katsuya Amako, Aug-2006 --> |
---|
| 5 | <!-- Changed by: Katsuya Amako, 4-Aug-1998 --> |
---|
| 6 | <!-- Changed by: Michel MAIRE, 3-Aug-1998 --> |
---|
| 7 | <!-- Changed by: Katsuya Amako, 30-Nov-1998 --> |
---|
| 8 | <!-- Changed by: Dennis Wright, 20-Nov-2001 --> |
---|
| 9 | <!-- Proof read by: Joe Chuma, 28-Jun-1999 --> |
---|
| 10 | <!-- --> |
---|
| 11 | <!-- ******************************************************** --> |
---|
| 12 | |
---|
| 13 | |
---|
| 14 | <!-- ******************* Section (Level#1) ****************** --> |
---|
| 15 | <sect1 id="sect.ClassCate"> |
---|
| 16 | <title> |
---|
| 17 | Class Categories and Domains |
---|
| 18 | </title> |
---|
| 19 | |
---|
| 20 | <!-- ******************* Section (Level#2) ****************** --> |
---|
| 21 | <sect2 id="sect.ClassCate.WhatIsClassCate"> |
---|
| 22 | <title> |
---|
| 23 | What is a class category? |
---|
| 24 | </title> |
---|
| 25 | |
---|
| 26 | <para> |
---|
| 27 | In the design of a large software system such as Geant4, it is |
---|
| 28 | essential to partition it into smaller logical units. This makes |
---|
| 29 | the design well organized and easier to develop. Once the logical |
---|
| 30 | units are defined independent to each other as much as possible, |
---|
| 31 | they can be developed in parallel without serious interference. |
---|
| 32 | </para> |
---|
| 33 | |
---|
| 34 | <para> |
---|
| 35 | In object-oriented analysis and design methodology by Grady Booch |
---|
| 36 | <citation> |
---|
| 37 | <xref linkend="biblio.booch1994" endterm="biblio.booch1994.abbrev" /> |
---|
| 38 | </citation> |
---|
| 39 | , class categories are used to |
---|
| 40 | create logical units. They are defined as "clusters of classes that |
---|
| 41 | are themselves cohesive, but are loosely coupled relative to other |
---|
| 42 | clusters." This means that a class category contains classes which |
---|
| 43 | have a close relationship (for example, the "has-a" relation). |
---|
| 44 | However, relationships between classes which belong to different |
---|
| 45 | class categories are weak, i.e., only limitted classes of these |
---|
| 46 | have "uses" relations. The class categories and their relations are |
---|
| 47 | presented by a class category diagram. The class category diagram |
---|
| 48 | designed for Geant4 is shown in the figure below. Each box in the |
---|
| 49 | figure represents a class category, and a "uses" relation by a |
---|
| 50 | straight line. The circle at an end of a straight line means the |
---|
| 51 | class category which has this circle uses the other category. |
---|
| 52 | |
---|
| 53 | <figure id="fig.G4ClassCategory"> |
---|
| 54 | <title> |
---|
| 55 | Geant4 class categories |
---|
| 56 | </title> |
---|
| 57 | |
---|
| 58 | <mediaobject> |
---|
| 59 | <imageobject role="fo"> |
---|
[921] | 60 | <imagedata fileref="./AllResources/Fundamentals/classCategory.jpg" |
---|
| 61 | format="JPG" contentwidth="7.0cm" align="center" /> |
---|
[904] | 62 | </imageobject> |
---|
| 63 | <imageobject role="html"> |
---|
[921] | 64 | <imagedata fileref="./AllResources/Fundamentals/classCategory.jpg" |
---|
| 65 | format="JPG" align="center" /> |
---|
[904] | 66 | </imageobject> |
---|
| 67 | </mediaobject> |
---|
| 68 | </figure> |
---|
| 69 | </para> |
---|
| 70 | |
---|
| 71 | <para> |
---|
| 72 | The file organization of the Geant4 codes follows basically the |
---|
| 73 | structure of this class cateogory. This <emphasis>User's Manual</emphasis> |
---|
| 74 | is also organized according to class categories. |
---|
| 75 | </para> |
---|
| 76 | |
---|
| 77 | <para> |
---|
| 78 | In the development and maintenance of Geant4, one software team |
---|
| 79 | will be assigned to a class category. This team will have a |
---|
| 80 | responsibility to develop and maintain all classes belonging to the |
---|
| 81 | class category. |
---|
| 82 | </para> |
---|
| 83 | |
---|
| 84 | </sect2> |
---|
| 85 | |
---|
| 86 | |
---|
| 87 | <!-- ******************* Section (Level#2) ****************** --> |
---|
| 88 | <sect2 id="sect.ClassCate.ClassCateInGeant4"> |
---|
| 89 | <title> |
---|
| 90 | Class categories in Geant4 |
---|
| 91 | </title> |
---|
| 92 | |
---|
| 93 | <para> |
---|
| 94 | The following is a brief summary of the role of each class category |
---|
| 95 | in Geant4. |
---|
| 96 | |
---|
| 97 | <orderedlist spacing="compact"> |
---|
| 98 | <listitem><para><emphasis role="bold">Run and Event</emphasis> |
---|
| 99 | <para>These are categories related to the generation of events, |
---|
| 100 | interfaces to event generators, and any secondary particles |
---|
| 101 | produced. Their roles are principally to provide particles to be |
---|
| 102 | tracked to the Tracking Management. |
---|
| 103 | </para> |
---|
| 104 | </para></listitem> |
---|
| 105 | <listitem><para><emphasis role="bold">Tracking and Track</emphasis> |
---|
| 106 | <para>These are categories related to propagating a particle by |
---|
| 107 | analyzing the factors limiting the step and applying the relevant |
---|
| 108 | physics processes. The important aspect of the design was that a |
---|
| 109 | generalized Geant4 physics process (or interaction) could perform |
---|
| 110 | actions, along a tracking step, either localized in space, or in |
---|
| 111 | time, or distributed in space and time (and all the possible |
---|
| 112 | combinations that could be built from these cases). |
---|
| 113 | </para> |
---|
| 114 | </para></listitem> |
---|
| 115 | <listitem><para><emphasis role="bold">Geometry and Magnetic Field</emphasis> |
---|
| 116 | <para>These categories manage the geometrical definition of a detector |
---|
| 117 | (solid modeling) and the computation of distances to solids (also |
---|
| 118 | in a magnetic field). The Geant4 geometry solid modeler is based on |
---|
| 119 | the ISO STEP standard and it is fully compliant with it, in order |
---|
| 120 | to allow in future the exchange of geometrical information with CAD |
---|
| 121 | systems. A key feature of the Geant4 geometry is that the volume |
---|
| 122 | definitions are independent of the solid representation. By this |
---|
| 123 | abstract interface for the G4 solids, the tracking component works |
---|
| 124 | identically for various representations. The treatment of the |
---|
| 125 | propagation in the presence of fields has been provided within |
---|
| 126 | specified accuracy. An OO design allows us to exchange different |
---|
| 127 | numerical algorithms and/or different fields (not only B-field), |
---|
| 128 | without affecting any other component of the toolkit. |
---|
| 129 | </para> |
---|
| 130 | </para></listitem> |
---|
| 131 | <listitem><para><emphasis role="bold">Particle Definition and Matter</emphasis> |
---|
| 132 | <para>These two categories manage the the definition of materials and |
---|
| 133 | particles. |
---|
| 134 | </para> |
---|
| 135 | </para></listitem> |
---|
| 136 | <listitem><para><emphasis role="bold">Physics</emphasis> |
---|
| 137 | <para>This category manages all physics processes participating in the |
---|
| 138 | interactions of particles in matter. The abstract interface of |
---|
| 139 | physics processes allows multiple implementations of physics models |
---|
| 140 | per interaction or per channel. Models can be selected by energy |
---|
| 141 | range, particle type, material, etc. Data encapsulation and |
---|
| 142 | polymorphism make it possible to give transparent access to the |
---|
| 143 | cross sections (independently of the choice of reading from an |
---|
| 144 | ascii file, or of interpolating from a tabulated set, or of |
---|
| 145 | computing analytically from a formula). Electromagnetic and |
---|
| 146 | hadronic physics were handled in a uniform way in such a design, |
---|
| 147 | opening up the physics to the users. |
---|
| 148 | </para> |
---|
| 149 | </para></listitem> |
---|
| 150 | <listitem><para><emphasis role="bold">Hits and Digitization</emphasis> |
---|
| 151 | <para>These two categories manage the creation of hits and their use |
---|
| 152 | for the digitization phase. The basic design and implementation of |
---|
| 153 | the Hits and Digi had been realized, and also several prototypes, |
---|
| 154 | test cases and scenarios had been developed before the |
---|
| 155 | alpha-release. Volumes (not necessarily the ones used by the |
---|
| 156 | tracking) are aggregated in sensitive detectors, while hits |
---|
| 157 | collections represent the logical read out of the detector. |
---|
| 158 | Different ways of creating and managing hits collections had been |
---|
| 159 | delivered and tested, notably for both single hits and calorimetry |
---|
| 160 | hits types. In all cases, hits collections had been successfully |
---|
| 161 | stored into and retrieved from an Object Data Base Management |
---|
| 162 | System. |
---|
| 163 | </para> |
---|
| 164 | </para></listitem> |
---|
| 165 | <listitem><para><emphasis role="bold">Visualization</emphasis> |
---|
| 166 | <para>This manages the visualization of solids, trajectories and hits, |
---|
| 167 | and interacts with underlying graphical libraries (the |
---|
| 168 | Visualization class category). The basic and most frequently used |
---|
| 169 | graphics functionality had been implemented already by the |
---|
| 170 | alpha-release. The OO design of the visualization component allowed |
---|
[905] | 171 | us to develop several drivers independently, such as for OpenGL, Qt and |
---|
[904] | 172 | OpenInventor (for X11 and Windows), DAWN, Postscript (via DAWN) and |
---|
| 173 | VRML. |
---|
| 174 | </para> |
---|
| 175 | </para></listitem> |
---|
| 176 | <listitem><para><emphasis role="bold">Interfaces</emphasis> |
---|
| 177 | <para>This category handles the production of the graphical user |
---|
| 178 | interface (GUI) and the interactions with external software |
---|
| 179 | (OODBMS, reconstruction etc.). |
---|
| 180 | </para> |
---|
| 181 | </para></listitem> |
---|
| 182 | </orderedlist> |
---|
| 183 | </para> |
---|
| 184 | |
---|
| 185 | |
---|
| 186 | </sect2> |
---|
| 187 | </sect1> |
---|