More ch3 + header

en/chap03.tex

@@ -191,8 +191,85 @@ possibility.)
 
 \section{Annotations}
 
-\XXX{scoping, annotator creation, advantages of storing data in annotations and
+Once a TopologyV3 is obtained, it may be annotated. An Annotator may create an
-not vertices. Annotator protocol and posibility of export. Various uses of annotators: enhancing, analysis, visualisation. heapq}
+Annotation, which is then stored as a part of an AnnotatedTopology. We now
+explore design of these objects in detail.
+
+An Annotation is essentially only a holder for any \uv{tags} that are to be
+attached to the topology. These are represented by a dictionary holding
+annotations for Vertices, another dictionary for annotating Edges, and a single
+field allowing the attachment of a tag to the entire Topology. The keys of the
+dictionaries are VertexIDs and Edges, respectively.
+
+The Annotation can only attach one tag to each vertex and edge, but there are
+little restrictions of what the tag is allowed to be. The intention is to allow
+Annotators to provide any useful data they can collect. However, we think that
+our AnnotatedTopologies could be utilised in other projects, so the Annotation
+objects ought to be easy to serialise into JSON or other formats.
+
+Annotations do not need to take other Annotations into account, because
+AnnotatedTopology stores Annotations from different Annotators separately.
+
+The Annotators are a tiny bit more interesting. While these objects are
+basically a wrapper around the \verb|annotate()| method, which takes an
+AnnotatedTopology and returns an Annotation, there are few twists to it.
+
+First, an Annotator object is intended to be created by the respective
+AnnotatedTopology in order for it to keep track of all the Annotators. To
+describe an Annotator, an AnnotatorID is used, which is a re-creatable and
+hashable recipe for creating that Annotator. It is also used as a handle to
+reference and scope the resulting Annotation. The AnnotatorID is a pair of the
+type object of the particular Annotator, and an optional hashable parameter,
+which is passed to the Annotator's initialiser.
+
+Second, an Annotator might require another Annotator to have already run. We
+make this possible by allowing Annotators to request another Annotator to be
+run by the AnnotatedTopology (provided the AnnotatorID), as long as there is
+not a dependency cycle. This is the recommended method of implementing
+dependencies of Annotators.
+
+Furthermore, an Annotator can be declared to be idempotent. This affects what
+happens when the same Annotator is invoked on the same Topology in the same way
+(that is, using the same AnnotatorID) multiple times. For idempotent
+Annotators, we know that their output will not change, so the Annotator is not
+really run. For non-idempotent Annotators, the previous Annotation is removed
+and the Annotator is run again.
+
+Annotators may not alter the AnnotatedTopology in any way. They are only
+allowed to return an Annotation, which will be added to the AnnotatedTopology.
+As with frozen Topologies, this is not enforced by the code.
+
+Annotators may be used for various tasks, including but not limited to
+performing analysis of the Topology, enhancing it with additional data (e.g.
+ping response times from other system), or specifying parameters for
+visualisation. As a part of Birdvisu itself, we ship several anotators:
+TopologyDifference outputs the differences between the reference and current
+Topology, and ShortestPathTree marks the edges of the shortest path DAG.
+
+The last important object related to annotation is the AnnotatedTopology. It
+serves as a coordinator for running Annotators. It does two main things:
+detects dependency cycles between Annotators, and keeps the Annotations.
+
+The Annotations in the AnnotatedTopology are stored in a dictionary indexed by
+the respective AnnotatorID. For vertices and edges, only sets of AnnotatorIDs
+are stored. This way, both iterating Annotations for a Vertex or Edge and
+examining individual Annotations is fast. Also, our approach isolates unrelated
+Annotations by putting them into different scopes by AnnotatorID.
+
+However, by using the Annotator's type in AnnotatorID, this design enforces a
+rather tight coupling between Annotators and users of Annotations, because the
+consumers of Annotations need to understand the precise format of the
+particular Annotation. This could be solved by implementing support for
+\uv{interface-annotators}, so that various Annotators may provide Annotations
+in a commonly understood format.\footnote{Preliminary work on implementing this
+approach is present in the \texttt{ann\_interfaces} branch, but the interaction of
+implementers of the same interface is not decided yet.}
+
+AnnotatedTopology does not expose a way to delete old Annotations. While we do
+not expect this to cause big memory leaks, in case it does, an LRU-like
+strategy might be employed to tame the memory usage. Also, the Annotators could
+be run dynamically when the Annotation is requested, but our current approach
+does not need this functionality, so it is not implemented at the moment.
 
 \section{Visualisation}
 

en/header.tex

@@ -86,17 +86,20 @@
 % An optional dedication: you can thank whomever you wish (your supervisor,
 % consultant, a person who lent the software, etc.)
 \def\Dedication{%
-Dedication.
+I would like to thank my friends, colleagues and family for nudging and convincing me enough to finish my studies.
+
+Naturally, I would also like to thank my supervisor Martin Mareš, for being hopeful and patient and for teaching me many useful skills.
+
+Last, but not least, I want to thank You, my dear reader, because right now You are making sure this thesis was worth writing.
 }
 
-% Abstract (recommended length around 80-200 words; this is not a copy of your thesis assignment!)
 \def\Abstract{%
 Abstract. \X{Recommended length around 80--200 words. This is not a~copy of your thesis assignment!}
 }
 
 % 3 to 5 keywords (recommended), each enclosed in curly braces
 \def\Keywords{%
-{key} {words} \X{usually 3 to~5 key words or phrases}
+{OSPF} {network visualisation} {BIRD} {routing}
 }
 
 %% The hyperref package for clickable links in PDF and also for storing